The research summarized in this thesis focuses on synthesizing aldehyde and aldol compounds as substrates and products for the enzyme D-fructose-6-aldolase (FSA). Aldolases are important enzymes for the formation of carbon-carbon bonds in nature. In biological systems, aldol reactions, both cleavage and formation play central roles in sugar metabolism. Aldolases exhibit high degrees of stereoselectivity and can steer the product configurations to a given enantiomeric and diastereomeric form. To become truly useful synthetic tools, the substrate scope of these enzymes needs to become broadened.

In the first project, phenylacetaldehyde derivatives were synthesized for the use as test substrates for E. coli FSA. Different methods were discussed to prepare phenylacetaldehyde derivatives, the addition of a one carbon unit to benzaldehyde derivatives using a homologation reaction was successful and was proven efficient and non-sensitive to the moisture. The analogues were prepared through two steps with 75-80 % yields for both meta- and para-substituted compounds.

The second project focuses on synthesizing aldol compound using FSA enzymes, both wild type and mutated variants selected from library screening, the assay has been successfully used to identify a hit with 10-fold improvement in an R134V/S166G variant. This enzyme produces one out of four possible stereoisomers.

The third project focuses on the synthesis of a range of aldol compounds using two different approaches reductive cross-coupling of aldehydes by SmI₂ or by organocatalysts using cinchonine. Phenylacetaldehydes were reacted with hydroxy-, dihydroxyacetone and hydroxyacetophenone in presence of cinchonine, the reaction was successful with hydroxyacetophenone in moderate yields and 60-99 % de ratio. On the other hand, the aldehydes reacting with methyl- and phenylglyoxal in the presence of SmI₂ resulted in moderate yields and without stereoselectivity.

Polyhydroxylated compounds are building blocks for the synthesis of carbohydrates and other natural products. Their synthesis is mainly achieved by different synthetic versions of aldol-coupling reactions, catalyzed either by organocatalysts, enzymes or metal-organic catalysts. We have investigated the formation of 1,4-substituted 2,3-dihydroxybutan-1-one derivatives from para- and meta-substituted phenylacetaldehydes by three distinctly different strategies. The first involved a direct aldol reaction with hydroxyacetone, dihydroxyacetone or 2-hydroxyacetophenone, catalyzed by the cinchona derivative cinchonine. The second was reductive cross-coupling with methyl or phenyl glyoxal promoted by SmI2 resulting in either 5-substituted 3,4-dihydroxypentan-2-ones or 1,4 bis-phenyl substituted butanones, respectively. Finally, in the third case, aldolase catalysis was employed for synthesis of the corresponding 1,3,4-trihydroxylated pentan-2-one derivatives. The organocatalytic route with cinchonine generated distereomerically enriched syn products (de = 60−99 %), with moderate enantiomeric excesses (ee = 43−56%), but did not produce aldols with either hydroxyacetone or dihydroxyacetone as donor ketones. The SmI2-promoted reductive cross-coupling generated product mixtures with diastereomeric and enantiomeric ratios close to unity. This route allowed for the production of both 1-methyl- and 1-phenylsubstituted 2,3-dihydroxybutanones, at yields between 40−60%. Finally, the biocatalytic approach resulted in enantiopure syn (3R,4S) 1,3,4-trihydroxypentan-2-ones.

Methods for the synthesis of phenylacetaldehydes (oxidation, one-carbon chain extension) were compared by using the synthesis of 4-methoxyphenylacetaldehyde as a model example. Oxidations of 4-methoxyphenylethanol with activated DMSO (Swern oxidation) or manganese dioxide gave unsatisfactory results; whereas oxidation with 2-iodoxybenzoic add (IBX) produced 4-methoxyphenylacetaldehyde in reasonable (75%) yield. However, Wittig-type one-carbon chain extension with methoxymethylene-triphenylphosphine followed by hydrolysis gave an excellent (81% overall) yield of 4-methoxyphenylacetaldehyde from 4-methoxybenzaldehyde (a cheap starting material). This approach was subsequently used to synthesise a set of 10 substituted phenylacetaldehydes in good to excellent yields.

Lipid-based formulations can circumvent the low aqueous solubility of problematic drug compounds and increase their oral absorption. As these formulations are often physically unstable and costly to manufacture, solidification has been suggested as a way to minimize these issues. This study evaluated the physicochemical stability and in vitro performance of lipid-loaded mesoporous magnesium carbonate (MMC) particles with an average pore size of 20 nm. A medium chain lipid was loaded onto the MMC carrier via physical adsorption. A modified in vitro lipolysis setup was then used to study lipid release and digestion with ¹H nuclear magnetic resonance spectroscopy. The lipid loading efficiency with different solidification techniques was also evaluated. The MMC, unlike more commonly used porous silicate carriers, dissolved during the lipolysis assay, providing a rapid release of encapsulated lipids into solution. The digestion of the dispersed lipid-loaded MMC therefore resembled that of a coarse dispersion of the lipid. The stability data demonstrated minor degradation of the lipid within the pores of the MMC particles, but storage for three months did not reveal extensive degradation. To conclude, lipids can be adsorbed onto MMC, creating a solid powder from which the lipid is readily released into the solution during in vitro digestion. The chemical stability of the formulation does however merit further attention.

Due to significant developments in cryogenic probe technology and the easy access to inverse detection pulse programmes (HSQC, HMBC), the sensitivity of nitrogen NMR has lately vastly improved. As a consequence, nitrogen NMR has turned into a useful and commonly available tool for solution studies of molecular structure and properties for small organic compounds likewise biopolymers. The high sensitivity of the nitrogen lone pair to changes in the molecular environment, alterations in intra- and intermolecular interactions, and in molecular conformation along with its wide, up to 1200ppm chemical shift dispersion make nitrogen NMR to an exceptionally sensitive reporter tool. The nitrogen chemical shift has been applied in various fields of chemistry, including for instance the studies of transition metal complexes, chemical reactions such as N-alkylation and N-oxidation, tautomerization, protonation–deprotonation equilibria, hydrogen and halogen bonding, and elucidation of molecular conformation and configuration. The 15N NMR data observed in the investigation of these molecular properties and processes is influenced by the medium it is acquired in. This influence may be due to direct coordination of solvent molecules to transition metal complexes, alteration of tautomerization equilibria, and solvent polarity induced electron density changes of conjugated systems, for example. Thus, the solvent may significantly alter the observed nitrogen NMR shifts. This review aims to provide an overview of solvent effects of practical importance, and discusses selected experimental reports from various subfields of chemistry.

Photolysis of ethyl 3-azido-4,6-difluorobenzoate at room temperature in the presence of oxygen results in the regioselective formation of ethyl 5,7-difluoro-4-azaspiro[2.4]hepta-1,4,6-triene-1-carboxylate, presumably via the corresponding ketenimine intermediate which undergoes a photochemical four-electron electrocyclization followed by a rearrangement. The photorearrangement product was identified by multinuclear solution NMR spectroscopic techniques supported by DFT calculations.

The hexapeptide angiotensin IV (Ang IV) is a metabolite of angiotensin II (Ang II) and plays a central role in the brain. It was reported more than two decades ago that intracerebroventricular injection of Ang IV improved memory and learning in the rat. Several hypotheses have been put forward to explain the positive effects of Ang IV and related analogues on cognition. It has been proposed that the insulin-regulated aminopeptidase (IRAP) is the main target of Ang IV. This paper discusses progress in the discovery of inhibitors of IRAP as potential enhancers of cognitive functions. Very potent inhibitors of the protease have been synthesised, but pharmacokinetic issues (including problems associated with crossing the blood-brain barrier) remain to be solved. The paper also briefly presents an overview of the status in the discovery of inhibitors of ACE and renin, and of AT1R antagonists and AT2R agonists, in order to enable other discovery processes within the RAS system to be compared. The paper focuses on the relationship between binding affinities/inhibition capacity and the structures of the ligands that interact with the target proteins.

Metallo-beta-lactamase (MBL)-producing bacteria resistant to beta-lactam antibiotics are a serious threat to human health. Despite great efforts and important progress in the discovery of MBL inhibitors (MBLIs), there is none in clinical use. Herein, inhibitor complexes of the MBL CcrA were investigated by NMR spectroscopy to provide perspectives on the further development of 2-(triazolylthio)acetamide-type MBLIs. By using the NMR-based chemical shift perturbation (CSP) and direction of CSP methodologies together with molecular docking, the spatial orientation of three compounds in the CcrA active site was investigated (4-6). Inhibitor 6 showed the best binding affinity (K-d approximate to 2.3 +/- 0.3 mu M), followed by 4 (K-d approximate to 11 +/- 11 mu M) and 5 (K-d = 34 +/- 43 mu M), as determined from the experimental NMR data. Based on the acquired knowledge, analogues of other MBLIs (1-3) were designed and evaluated in silico with the purpose of examining a strategy for promoting their interactions with the catalytic zinc ions.

Background: The mechanisms underlying tolerance induction and maintenance in autoimmune arthritis remain elusive. In a mouse model of rheumatoid arthritis, collagen type II (CII)-induced arthritis, we explore the contribution of B cells to antigen-specific tolerance. Methods: To generate expression of the CII-peptide specifically on B-cell major histocompatibility complex type II, lentiviral-based gene therapy including a B-cell-specific Igk promoter was used. Results: Presentation of the CII-peptide on B cells significantly reduced the frequency and severity of arthritis as well as the serum levels of CII -specific IgG antibodies. Further, both frequency and suppressive function of regulatory T cells were increased in tolerized mice. Adoptive transfer of regulatory T cells from tolerized mice to naive mice ameliorated the development of CII-induced arthritis. Conclusion: Our data suggest that endogenous presentation of the CII-peptide on B cells is one of the key contributors to arthritis tolerance induction and maintenance.

The only oral direct thrombin inhibitors that have reached the market, ximelagatran and dabigatran etexilat, are double prodrugs with low bioavailability in humans. We have evaluated an alternative strategy: the preparation of a nonpeptidic, polar direct thrombin inhibitor as a single, macrocyclic esterase-cleavable (acyloxy)alkoxy prodrug. Two homologous prodrugs were synthesized and displayed high solubilities and Caco-2 cell permeabilities, suggesting high absorption from the intestine. In addition, they were rapidly and completely converted to the active zwitterionic thrombin inhibitor in human hepatocytes. Unexpectedly, the most promising prodrug displayed only moderately higher oral bioavailability in rat than the polar direct thrombin inhibitor, most likely due to rapid metabolism in the intestine or the intestinal wall. To the best of our knowledge, this is the first in vivo ADME study of macrocyclic (acyloxy)alkoxy prodrugs, and it remains to be established if the modest increase in bioavailability is a general feature of this category of prodrugs or not.

Substituent effects on the carbon-carbon bonds of hydrocarbons have been a topic of interest within the past seven decades as resultant information would enable one to tune the activity of CC bonds. However, current assessments of the C equivalent to C, C=C, and C-C bond strength of acetylene, ethylene, and ethane as well as their derivatives rely on indirect measures such as bond length and bond dissociation enthalpy. In this work, we introduce a quantitative measure of the intrinsic strength of C equivalent to C, C=C, and C-C bonds for a set of 40 hydrocarbon systems consisting of 3 parent structures, 36 hydrocarbon derivatives involving CF3, CH3, CHO, F, NH2, or OH groups, and a conjugated system, based on vibrational spectroscopy. Local mode force constants k(a)(CC) were computed at the CCSD(T)/cc-pVTZ level of theory for systems 1-32 and 34-40 and CCSD(T)/cc-pVDZ for 33. From k(a)(CC), we derived related bond strength orders BSO n(CC) in order to provide quantitative measures of intrinsic bond strength. Topological electron density and natural population analyses were carried out as to analyze the nature of these bonds and complement bond strength measures. For substituted hydrocarbon systems, we found the strengthening/weakening of the CC bonds occurs as the covalent nature of the bond increases/decreases by means of varying charge delocalizations. Our findings provide new guidelines for desirably modulating C equivalent to C, C=C, and C-C bond strength and for the design of prospective pathways for bond cleavage reactions. [GRAPHICS] .

B cells undergo several rounds of selection to eliminate potentially pathogenic autoreactive clones, but in contrast to T cells, evidence of positive selection of autoreactive B cells remains moot. Using unique tetramers, we traced natural autoreactive B cells (C1-B) specific for a defined triple-helical epitope on collagen type-II (COL2), constituting a sizeable fraction of the physiological B cell repertoire in mice, rats, and humans. Adoptive transfer of C1-B suppressed arthritis independently of IL10, separating them from IL10-secreting regulatory B cells. Single-cell sequencing revealed an antigen processing and presentation signature, including induced expression of CD72 and CCR7 as surface markers. C1-B presented COL2 to T cells and induced the expansion of regulatory T cells in a contact-dependent manner. CD72 blockade impeded this effect suggesting a new downstream suppressor mechanism that regulates antigen-specific T cell tolerization. Thus, our results indicate that autoreactive antigen-specific naive B cells tolerize infiltrating T cells against self-antigens to impede the development of tissue-specific autoimmune inflammation.

A principal challenge in the discovery of proteolysis targeting chimeras (PROTACs) as oral medications is their bioavailability. To facilitate drug design, it is therefore essential to identify the chemical space where orally bioavailable PROTACs are more likely to be situated. To this aim, we extracted structure-bioavailability insights from published data using traditional 2D descriptors, thereby shedding light on their potential and limitations as drug design tools. Subsequently, we describe cuttingedge experimental, computational and hybrid design strategies based on 3D descriptors, which show promise for enhancing the probability of discovering PROTACs with high oral bioavailability.

In this work, we investigate a particular class of carbon nanocones, which we name graphannulenes, and present a generalized Hückel rule (GHR) that predicts the character of their ground state based on simply the three topological indices that uniquely define them. Importantly, this rule applies to both flat and curved systems, encompassing a wide variety of known structures that do not satisfy the “classic” 4n + 2 rule such as coronene, corannulene, and Kekulene. We test this rule at the Hückel level of theory for a large number of systems, including structures that are convex and flat, with a saddle-like geometry, and at the CASSCF level of theory for a selected representative subset. All the performed calculations support the GHR that we propose in this work.

MOLCAS/OpenMolcas is an ab initio electronic structure program providing a large set of computational methods from Hartree-Fock and density functional theory to various implementations of multiconfigurational theory. This article provides a comprehensive overview of the main features of the code, specifically reviewing the use of the code in previously reported chemical applications as well as more recent applications including the calculation of magnetic properties from optimized density matrix renormalization group wave functions.

Superparamagnetic iron oxide nanoparticles (SPIONs) exhibit unique properties for diverse biomedical applications, including drug delivery and diagnostic imaging. Actively targeted SPIONs enhance delivery to diseased sites, reducing side effects and enhancing treatment efficacy. However, development of reproducible functionalization protocols is challenged by the erratic behavior of nanoparticles in suspensions, such as agglomeration and sedimentation. In this study, we develop and systematically optimize a functionalization method to attach the Fc-region of antibodies onto silica coated SPIONs via click chemistry, ensuring controlled ligand orientation on the particle surface. The synthesis and successive modifications of silica coated SPIONs with organic moieties is presented resulting in the final click conjugation with anti-ICAM1 antibodies. These antibodies target ICAM1, upregulated on epithelial cell surfaces during gastrointestinal inflammation. Thermogravimetric analysis and infrared spectroscopy confirm successful SPION functionalization after each modification step. Cell viability assessment indicates no adverse effects of bioconjugated particles. Quantitative elemental analysis reveals significantly higher iron concentration in inflammation-induced Caco-2 cells exposed to ICAM1-modified particles compared to non-conjugated counterparts. Furthermore, laser scanning confocal microscopy of these cells suggests surface interaction and internalization of bioconjugated SPIONs, underscoring their potential for targeted imaging and therapy in inflammatory diseases.

Five new compounds-rhodimer (1), rhodiflavan A (2), rhodiflavan B (3), rhodiflavan C (4), and rhodacarpin (5)-along with 16 known secondary metabolites, were isolated from the CH2Cl2-CH3OH (1:1) extract of the roots of Tephrosia rhodesica. They were identified by NMR spectroscopic, mass spectrometric, X-ray crystallographic, and ECD spectroscopic analyses. The crude extract and the isolated compounds 2-5, 9, 15, and 21 showed activity (100% at 10 mu g and IC50 = 5-15 mu M) against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum.

Proteolysis targeting chimeras (PROTACs) induce intracellular degradation of target proteins. Their bifunctional structure puts degraders in a chemical space where ADME properties often complicate drug discovery. Herein we provide the first structural insight into PROTAC cell permeability obtained by NMR studies of a VHL-based PROTAC (1), which is cell permeable despite having a high molecular weight and polarity and a large number of rotatable bonds. We found that 1 populates elongated and polar conformations in solutions that mimic extra- and intracellular compartments. Conformations were folded and had a smaller polar surface area in chloroform, mimicking a cell membrane interior. Formation of intramolecular and nonclassical hydrogen bonds, π–π interactions, and shielding of amide groups from solvent all facilitate cell permeability by minimization of size and polarity. We conclude that molecular chameleonicity appears to be of major importance for 1 to enter into target cells.

Based on the work done by an electromagnetic field on an atomic or molecular electronic system, a general gauge-invariant formulation of transient absorption spectroscopy is presented within the semiclassical approximation. Avoiding multipole expansions, a computationally viable expression for the spectral response function is derived from the minimal-coupling Hamiltonian of an electronic system interacting with one or more laser pulses described by a source-free, enveloped electromagnetic vector potential. With a fixed-basis expansion of the electronic wave function, the computational cost of simulations of laser-driven electron dynamics beyond the dipole approximation is the same as simulations adopting the dipole approximation. We illustrate the theory by time-dependent configuration interaction and coupled-cluster simulations of core-level absorption and circular dichroism spectra.

Alzheimer's disease (AD) is the most common neurodegenerative disorder. Along with an increasing number of elderly worldwide, it poses a great challenge for the society and health care. Although sporadic AD is the common form of AD, 2-3% of the AD cases are expected to be due to mutations in the fi region of the amyloid precursor protein, which is referred to as autosomal dominant AD (ADAD). These mutations may cause changes in the secondary structure of the amyloid fi fibrils and may alter the fibrillization rate leading to changes in the disease development and could also affect the binding to tracers used in diagnosis. In particular, from some recent clinical studies using PET tracers for detection of fibrillar amyloids, it is evident that in ADAD patients with Arctic mutation no amyloid plaque binding can be detected with the "C Pittsburgh Compound B (C-11-PIB). However, for in vitro conditions, significant binding of H-3-PIB has been reported for the amyloid fibrils carrying the Arctic mutation. The aim of the present study is to investigate if there is any mutation specific binding of commonly used amyloid tracers, namely, florbetaben, florbetapir, FPIB, AZD4694, and AZD2184, by means of molecular modeling techniques. Other than Arctic, ADAD mutations, such as the Dutch, Italian, Iowa, and Flemish mutations, are considered in this study. We report that all tracers except florbetapir show reduced binding affinity toward amyloid beta fibrils with the Arctic mutation when compared to the native type. Moreover, florbetapir is the only tracer that binds to all mutants with increased affinity when compared to the native fibril. The results obtained from these studies could increase the understanding of the structural changes caused by mutation and concomitant changes in the interaction pattern of the PET tracers with the mutated variants, which in turn can be useful in selecting the appropriate tracers for the purpose of diagnosis as well as for designing new tracers with desirable properties.

High-throughput screening has revealed dark chemical matter, a set of drug-like compounds that has never shown bioactivity despite being extensively assayed. If dark molecules are found active at a therapeutic target, their extraordinary selectivity profiles make excellent starting points for drug development. We explored if ligands of therapeutically relevant G-protein-coupled receptors could be discovered by structure-based virtual screening of the dark chemical matter. Molecular docking screens against crystal structures of the A(2A) adenosine and the D-4 dopamine receptors were carried out, and 53 top-ranked molecules were evaluated experimentally. Two ligands of each receptor were discovered, and the most potent had sub-micromolar affinities. Analysis of bioactivity data showed that the ligands lacked activity at hundreds of off-targets, including several that are associated with adverse effects. Our results demonstrate that virtual screening provides an efficient means to mine the dark chemical space, which could contribute to development of drugs with improved safety profiles.

In this thesis molecular interactions between polypeptide conjugates and protein targets were investigated. Polypeptides were derivatized with small organic molecules, peptides and oligonucleotides. New strategies were developed with the aim to increase affinities for proteins of biological interest.

A 42-residue polypeptide (4-C15L8) conjugated to a small organic molecule 3,5-bis[[bis(2-pyridylmethyl)amino]methyl]benzoic acid (PP1), was shown to bind glycogen phosphorylase a (GPa) in the presence of zinc ions. Under the assumption that hydrophobic interactions dominated the binding energy, the hydrophobic residues of 4-C15L8-PP1 were systematically replaced in order to study their contribution to the affinity enhancement. The replacement of the Nle, Ile and Leu residues by Ala amino acids reduced affinities. The introduction of non-natural L-2-aminooctanoic acid (Aoc) residues into the peptide sequence enhanced the binding affinity for GPa. A decreased K_D of 27nM was obtained when Nle5, Ile9 and Leu12 were replaced by Aoc residues, in comparison to the K_D value of 280nM obtained for the unmodified 4-C15L8-PP1. It is evident that there are non-obvious hydrophobic binding sites on the surfaces of proteins that could be identified by introducing the more hydrophobic and conformationally flexible Aoc residues. The downsizing of the 42-mer peptide to an 11-mer and the incorporation of three Aoc residues gave rise to a K_D of 550 nM, comparable to that of  4-C15L8-PP1 suggesting that bioactive peptides can be downsized by the introduction of Aoc.

Aiming to improve in vivo stability, the affinity for human serum albumin (HSA) of hydrophobic, positively and negatively charged polypeptide-PP1 conjugates was evaluated. Increased hydrophobicity due to the introduction of Aoc residues did not significantly increase the affinity for HSA. No binding was observed in the case of the most negatively charged polypeptides whereas the slightly negatively and positively charged polypeptides conjugated to PP1 bound HSA with affinities that increased with the positive charge. It was found that polypeptide-PP1 conjugates target the zinc binding site of the HSA. Affinity enhancement was obtained due to the incorporation of PP1 and increased by charge to charge interactions between the positively charged amino acids of the polypeptide and the negatively charged residues of HSA, in close proximity to the HSA zinc binding site. The survival times of the peptide-PP1 conjugates in human serum were extended as a result of binding to HSA. Zn²⁺ ion chelating agents can be incorporated in potential peptide therapeutics with a short plasma half-life, without increasing their molecular weights.

The affinity for human serum albumin (HSA) of a series of 2–5 kDa peptides covalently linked to 3,5-bis[[bis(2-pyridylmethyl)amino]methyl]benzoic acid, a dipicolyl chelator with micromolar affinity for Zn²⁺, was found by surface plasmon resonance to increase in the presence of 1 μm ZnCl₂ at physiological pH. The dependence on polypeptide hydrophobicity was found to be minor, thus suggesting that the conjugates bound to the metal-binding site and not to the fatty-acid-binding site. The affinity of the conjugates increased strongly with the positive charge of the polypeptides, thus implicating the negatively charged protein surface surrounding the metal-binding site. The survival times of the peptides in human serum were extended as a consequence of stronger binding to HSA, thus suggesting that Zn²⁺-chelating agents might provide a general route to increased survival time of peptides in serum in therapeutic and diagnostic applications without significantly increasing their molecular weights.

A 42-residue polypeptide conjugated to a small-molecule organic ligand capable of targeting the phosphorylated side chain of Ser15 was shown to bind glycogen phosphorylase a (GPa) with a K_D value of 280 nm. The replacement of hydrophobic amino acids by Ala reduced affinities, whereas the incorporation of l-2-aminooctanoic acid (Aoc) increased them. Replacing Nle5, Ile9 and Leu12 by Aoc reduced the K_D value from 280 to 27 nm. “Downsizing” the 42-mer to an undecamer gave rise to an affinity for GPa an order of magnitude lower, but the undecamer in which Nle5, Ile9 and Leu12 were replaced by Aoc showed a K_D value of 550 nm, comparable with that of the parent 42-mer. The use of Aoc residues offers a convenient route to increased affinity in protein recognition as well as a strategy for the “downsizing” of peptides essentially without loss of affinity. The results show that hydrophobic binding sites can be found on protein surfaces by comparing the affinities of polypeptide conjugates in which Aoc residues replace Nle, Ile, Leu or Phe with those of their unmodified counterparts. Polypeptide conjugates thus provide valuable opportunities for the optimization of peptides and small organic compounds in biotechnology and biomedicine.

Photochemical reactions often involve states that are closely coupled due to near degeneracies, for example by proximity to conical intersections. Therefore, a multistate method is used to accurately describe these states; for example, ordinary perturbation theory is replaced by quasidegenerate perturbation theory. Multiconfiguration pair-density functional theory (MC-PDFT) provides an efficient way to approximate the full dynamical correlation energy of strongly correlated systems, and we recently proposed compressed multistate pair-density functional theory (CMS-PDFT) to treat closely coupled states. In the present paper, we report the implementation of analytic gradients for CMS-PDFT in both OpenMolcas and PySCF, and we illustrate the use of these gradients by applying the method to the excited states of formaldehyde and phenol.

We report the synthesis and structural characterization of three crystalline borylated ortho-silylaryl tri­fluoro­methane­sulfonates: 5-(4,4,5,5-tetra­methyl-1,3,2-dioxaborolan-2-yl)-2-(tri­methyl­sil­yl)phenyl tri­fluoro­methane­sulfonate, C₁₆H₂₄BF₃O₅SSi (1a), 4-(4,4,5,5-tetra­methyl-1,3,2-dioxaborolan-2-yl)-2-(tri­methyl­sil­yl)phenyl tri­fluoro­methane­sulfonate, C₁₆H₂₄BF₃O₅SSi (1b), and 2-methyl-4-(4,4,5,5-tetra­methyl-1,3,2-dioxaborolan-2-yl)-6-(tri­methyl­silyl)phen­yl tri­fluoro­methane­sulfonate, C₁₇H₂₆BF₃O₅SSi (2), which are versatile aryne precursors. For all three compounds, the heteroatom substituents are almost coplanar with the central aromatic moiety. C—heteroatom bonding metrics are unexceptional and fall withing the typical range of C—B, C—Si, and C—O single bonds. Despite numerous electronegative sites, only weak inter­molecular inter­actions are observed in the solid state.

In this work we present a new approach to fix the intruder-state problem (ISP) in CASPT2 based on sigma p regularization. The resulting sigma(p)-CASPT2 method is compared to previous techniques, namely, the real and imaginary level shifts, on a theoretical basis and by performing a series of systematic calculations. The analysis is focused on two aspects, the effectiveness of sigma(p)-CASPT2 in removing the ISP and the sensitivity of the approach with respect to the input parameter. We found that sigma p- CASPT2 compares favorably with respect to previous approaches and that different versions, sigma(1)-CASPT2 and sigma(2)-CASPT2, have different potential application domains. This analysis also reveals the unsuitability of the real level shift technique as a general way to avoid the intruder-state problem.

We introduce a new variant of the complete active A space second-order perturbation theory (CASPT2) method that performs similarly to multistate CASPT2 (MS-CASPT2) in regions of the potential energy surface where the electronic states are energetically well separated and is akin to extended MS-CASPT2 (XMS-CASPT2) in case the underlying zeroth-order references are near-degenerate. Our approach follows a recipe analogous to that of XMS-CASPT2 to ensure approximate invariance under unitary transformations of the model states and a dynamic weighting scheme to smoothly interpolate the Fock operator between state-specific and state-average regimes. The resulting extended dynamically weighted CASPT2 (XDW-CASPT2) methodology possesses the most desirable features of both MS-CASPT2 and XMS-CASPT2, that is, the ability to provide accurate transition energies and correctly describe avoided crossings and conical intersections. The reliability of XDW-CASPT2 is assessed on a number of molecular systems. First, we consider the dissociation of lithium fluoride, highlighting the distinctive characteristics of the new approach. Second, the invariance of the theory is investigated by studying the conical intersection of the distorted allene molecule. Finally, the relative accuracy in the calculation of vertical excitation energies is benchmarked on a set of 26 organic compounds. We found that XDW-CASPT2, albeit being only approximately invariant, produces smooth potential energy surfaces around conical intersections and avoided crossings, performing equally well to the strictly invariant XMS-CASPT2 method. The accuracy of vertical transition energies is almost identical to MS-CASPT2, with a mean absolute deviation of 0.01-0.02 eV, in contrast to 0.12 eV for XMS-CASPT2.

Herewith, we propose two new exponents for the recently introduced XDW-CASPT2 method [S. Battaglia and R. Lindh, J. Chem. Theory Comput. 16, 1555-1567 (2020)], which fix one of the largest issues hindering this approach. By using the first-order effective Hamiltonian coupling elements, the weighting scheme implicitly takes into account the symmetry of the states, thereby averaging Fock operators only if the zeroth-order wave functions interact with each other. The use of Hamiltonian couplings also provides a physically sounder approach to quantitate the relative weights; however, it introduces new difficulties when these rapidly die off to zero. The improved XDW-CASPT2 method is critically tested on several systems of photochemical relevance, and it is shown that it succeeds in its original intent of maintaining MS-CASPT2 accuracy for the evaluation of transition energies and at the same time providing smooth potential energy surfaces around near-degenerate points akin to XMS-CASPT2.

The development of small-molecule ligands for biological targets that possess large, featureless or highly polar binding sites is a challenging task. This thesis is focused on a novel lead generation strategy to identify macrocyclic ligands for difficult-to-drug targets, as well as on the relationship between cell permeability and the conformations of macrocycles.

A database of natural products was investigated to compile a set of macrocyclic cores to be used for in silico screening on difficult-to-drug targets. Docking of this set on Keap1, a target considered challenging due to its large and polar binding site, identified the core of the natural product cyclothialidine as a starting point for lead generation. Synthesis and evaluation of a small number of analogues provided a novel macrocyclic Keap1 inhibitor with potency in the low micromolar range that displayed cellular activity. Investigation of the structure-activity relationship of the lead inhibitor identified two positions amenable for optimization. In silico libraries were constructed at both positions using structure-based design to improve the affinity for Keap1. Subsequent synthesis of approximately 100 compounds led to an optimized lead series with potency in the low nanomolar range, providing a 100-fold improvement from the starting point. 

Additionally, the difference in passive cell permeability for a pair of diastereoisomeric macrocycles was rationalized on the basis of differences in their solution-phase conformations, that were determined by NMR spectroscopy. Moreover, for two sets of moderately flexible isomeric macrocycles, it was shown that the molecular descriptors predicted from conformational sampling correlated with cell permeability. This method may find use for prioritization of macrocycles prior to embarking on demanding synthetic routes.

Upregulation of the transcription factor Nrf2 by inhibition of the interaction with its negative regulator Keap1 constitutes an opportunity for the treatment of disease caused by oxidative stress. We report a structurally unique series of nanomolar Keap1 inhibitors obtained from a natural product-derived macrocyclic lead. Initial exploration of the structure-derived macrocyclic lead. Initial exploration of the structure-activity relationship of the lead, followed by structure-guided optimization, resulted in a 100-fold improvement in inhibitory potency. The macrocyclic core of the nanomolar inhibitors positions three pharmacophore units for productive interactions with key residues of Keap1, including R415, R483, and Y572. Ligand optimization resulted in the displacement of a coordinated water molecule from the Keap1 binding site and a significantly altered thermodynamic profile. In addition, minor reorganizations of R415 and R483 were accompanied by major differences in affinity between ligands. This study therefore indicates the importance of accounting both for the hydration and flexibility of the Keap1 binding site when designing high-affinity ligands.

Conformation-dependent 3D descriptors have been shown to provide better predictions of the physicochemical properties of macrocycles than 2D descriptors. However, the computational identification of relevant conformations for macrocycles is nontrivial. Herein, we report that the Caco- 2 cell permeability difference between a pair of diastereomeric macrocycles correlated with their solvent accessible 3D polar surface area and radius of gyration. The descriptors were calculated from the macrocycles’ solution- phase conformational ensembles and independently from ensembles obtained by conformational sampling. Calculation of the two descriptors for three other stereo- and regioisomeric macrocycles also allowed the correct ranking of their cell permeability. Methods for conformational sampling may thus allow ranking of passive permeability for moderatelyflexible macrocycles, thereby contributing to the prioritization of macro- cycles for synthesis in lead optimization.

Lead generation for difficult-to-drug targets that have large, featureless, and highly lipophilic or highly polar and/or flexible binding sites is highly challenging. Here, we describe how cores of macrocyclic natural products can serve as a high-quality in silico screening library that provides leads for difficult-to-drug targets. Two iterative rounds of docking of a carefully selected set of natural-product-derived cores led to the discovery of an uncharged macrocyclic inhibitor of the Keap1-Nrf2 protein- protein interaction, a particularly challenging target due to its highly polar binding site. The inhibitor displays cellular efficacy and is well-positioned for further optimization based on the structure of its complex with Keapl and synthetic access. We believe that our work will spur interest in using macrocyclic cores for in silico-based lead generation and also inspire the design of future macrocycle screening collections.

This paper reports on the evaluation of antiplasmodial, antimicrobial and cytotoxic activities of extracts from eleven plant species traditionally used by some Tanzanian coastal communities for treatment of malaria, microbial infections and related ailments. Crude extracts from selected plant species namely Acacia zanzibarica,  Danais  xanthorrhoea, Diospyros  loureiriana  ssp.  rufescens, Erythrina  sacleuxii, Newtonia paucijuga, Pentas lanceolata, Scorodophloeus fischeri, Stuhlmannia moavi, Tarenna pavettoides, Tessmannia burttii  and  Toussaintia  orientalis  growing  in  Tanzania  were  investigated  using  an  imaging-based  assay (antiplasmodial), well diffusion and microplate dilution methods (antimicrobial) and human embryonic kidney cells (HEK 293) and brine shrimp larvae assays (toxicity). The extracts exhibited activities of varying potencies and cytotoxicity with IC 50 values ranging from 0.45±0.09 to 75.70±24.19 μg/mL against Plasmodium falciparum (3D7 strain), MIC ranging from 0.25 to 2.0 mg/mL (against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans and Cryptococcus neoformans), LC 50 ranging from 0.75 to 1000 μg/mL against brine shrimp larvae (Artemia salina) and IC 50 ranging from 4.02±1.05 to more than 289 μg/mL against HEK 293 cells. The observed bioactivities of some of the investigated plant extracts validate their ethnomedicinal use and are indicative of the presence of bioactive ingredients for further phytochemical investigations.

Diabetic kidney disease is a serious complication of diabetes that can ultimately lead to end-stage renal disease. The pathogenesis of diabetic kidney disease is complex, and fundamental research is still required to provide a better understanding of the driving forces behind it. We report regional metabolic aberrations from an untargeted mass spectrometry imaging study of kidney tissue using an insulinopenic rat model of diabetes. Diabetes was induced by intravenous injection of streptozotocin, and kidneys were harvested 2weeks thereafter. Imaging was performed using nanospray desorption electrospray ionization connected to a high-mass-resolving mass spectrometer. No histopathological changes were observed in the kidney sections; however, mass spectrometry imaging revealed a significant increase in several 18-carbon unsaturated non-esterified fatty acid species and monoacylglycerols. Notably, these 18-carbon acyl chains were also constituents of several increased diacylglycerol species. In addition, a number of short- and long-chain acylcarnitines were found to be accumulated while several amino acids were depleted. This study presents unique regional metabolic data indicating a dysregulated energy metabolism in renal mitochondria as an early response to streptozotocin-induced type I diabetes.

Leupeptin is a naturally occurring inhibitor of various proteases, in particular serine proteases. Following its discovery, the inhibitory properties of several other peptidyl argininals have been studied. The specificity of leupeptin is most likely due to the Leu-Leu-Argininal sequence, and its C-terminal aldehyde group has been suggested to enhance the binding efficiency and to be essential for function. The terminal aldehyde group makes the structure less vulnerable to carboxypeptidases. Here, we investigated whether the inhibitory function of leupeptin toward serine proteases is retained after oxidation or reduction of the aldehyde group. The oxidized form, which corresponds to the natural precursor, was shown to be superior to the reduced form in terms of inhibitory properties. However, the original leupeptin possessed enhanced inhibitory properties as compared with the oxidized form. Based on these results, new synthetic leupeptin analogues, 6-aminohexanoic acid (Ahx)-Phe-Leu-Arg-COOH and Ahx-Leu-Leu-Arg-COOH, were prepared by solid-phase peptide synthesis using the Fmoc strategy. In these analogues, the N-terminal capping acetyl group was replaced with a 6-aminohexanoyl group to allow conjugation. The structures of the modified leupeptin and the synthetic peptides were confirmed by mass spectrometry. Determination of the inhibitory properties against trypsin (IEC 3.4.21.4, Chymotrypsin IEC 3.4.21.1) revealed that these further modified tripeptides were tight binding inhibitors to their target enzyme, similar to the naturally occurring leupeptin, with Ki values generally in the micromolar range. The Ahx-Phe-Leu-Arg-COOH analogue was selected for conjugation to inorganic oxide nanoparticles and agarose gel beads. All conjugates exhibited inhibitory activity in the same range as for the free peptides. 

Understanding the conformational preferences of free ligands in solution is often necessary to rationalize structure–activity relationships in drug discovery. Herein, we examine the conformational behavior of an epimeric pair of side-chain stapled peptides that inhibit the FAD dependent amine oxidase lysine specific demethylase 1 (LSD1). The peptides differ only at a single stereocenter, but display a major difference in binding affinity. Their Raman optical activity (ROA) spectra are most likely dominated by the C-terminus, obscuring the analysis of the epimeric macrocycle. By employing NMR spectroscopy, we show a difference in conformational behavior between the two compounds and that the LSD1 bound conformation of the most potent compound is present to a measurable extent in aqueous solution. In addition, we illustrate that Molecular Dynamics (MD) simulations produce ensembles that include the most important solution conformations, but that it remains problematic to identify relevant conformations with no a priori knowledge from the large conformational pool. Furthermore, this work highlights the importance of understanding the scope and limitations of the available techniques for conducting conformational analyses. It also emphasizes the importance of conformational selection of a flexible ligand in molecular recognition.

The light-induced ultrafast switching between molecular isomers norbornadiene and quadricyclane can reversibly store and release a substantial amount of chemical energy. Prior work observed signatures of ultrafast molecular dynamics in both isomers upon ultraviolet excitation but could not follow the electronic relaxation all the way back to the ground state experimentally. Here we study the electronic relaxation of quadricyclane after exciting in the ultraviolet (201 nanometres) using time-resolved gas-phase extreme ultraviolet photoelectron spectroscopy combined with non-adiabatic molecular dynamics simulations. We identify two competing pathways by which electronically excited quadricyclane molecules relax to the electronic ground state. The fast pathway (<100 femtoseconds) is distinguished by effective coupling to valence electronic states, while the slow pathway involves initial motions across Rydberg states and takes several hundred femtoseconds. Both pathways facilitate interconversion between the two isomers, albeit on different timescales, and we predict that the branching ratio of norbornadiene/quadricyclane products immediately after returning to the electronic ground state is approximately 3:2.

Compressed multistate pair-density functional theory (CMS-PDFT) is a multistate version of multiconfiguration pair-density functional theory that can capture the correct topology of coupled potential energy surfaces (PESs) around conical intersections. In this work, we develop interstate coupling vectors (ISCs) for CMS-PDFT in the OpenMolcas and PySCF/mrh electronic structure packages. Yet, the main focus of this work is using ISCs to calculate minimum-energy conical intersections (MECIs) by CMS-PDFT. This is performed using the projected constrained optimization method in OpenMolcas, which uses ISCs to restrain the iterations to the conical intersection seam. We optimize the S₁/S₀ MECIs for ethylene, butadiene, and benzene and show that CMS-PDFT gives smooth PESs in the vicinities of the MECIs. Furthermore, the CMS-PDFT MECIs are in good agreement with the MECI calculated by the more expensive XMS-CASPT2 method.

Recent literature shows that intramolecular hydrogen bond (IMHB) formation can positively impact upon the triad of permeability, solubility, and potency of drugs and candidates. IMHB modulation can be applied to compounds in any chemical space as a means for discovering drug candidates with both acceptable potency and absorption, distribution, metabolism, and excretion-Tox profiles. Integrating IMHB formation in design of drugs is, therefore, an exciting and timely challenge for modern medicinal chemistry. In this review, we first provide some background about IMHBs from the medicinal chemist's point of view and highlight some IMHB-associated misconceptions. Second, we propose a classification of IMHBs for drug discovery purposes, review the most common in silico tactics to include IMHBs in lead optimization and list some experimental physicochemical descriptors, which quantify the propensity of compounds to form IMHBs. By focusing on the compounds size and the number of IMHBs that can potentially be formed, we also outline the major difficulties encountered when designing compounds based on the inclusion of IMHBs. Finally, we discuss recent case studies illustrating the application of IMHB to optimize cell permeability and physicochemical properties of small molecules, cyclic peptides and macrocycles.

An increasing number of drug discovery programs concern compounds in the beyond rule of 5 (bRo5) chemical space, such as cyclic peptides, macrocycles, and degraders. Recent results show that common paradigms of property-based drug design need revision to be applied to larger and more flexible compounds. A virtual event entitled "Solubility, permeability and physico-chemical properties in the bRo5 chemical space" was organized to provide preliminary guidance on how to make the discovery of oral drugs in the bRo5 space more effective. The four speakers emphasized the importance of the bRo5 space as a source of new oral drugs and provided examples of experimental and computational methods specifically tailored for design and optimization in this chemical space.

Gulf War Illness (GWI) manifests a multitude of symptoms, including neurological and immunological, and approximately a third of the 1990-1991 Gulf War (GW) veterans suffer from it. This study sought to characterize the acute neurochemical (monoamine) and neuroinflammatory profiles of two established GWI animal models and examine the potential modulatory effects of the novel immunotherapeutic Lacto-N-fucopentaose III (LNFPIII). In Model 1, male C57BL/6J mice were treated for 10 days with pyridostigmine bromide (PB) and permethrin (PM). In Model 2, a separate cohort of mice were treated for 14 days with PB and N,N-Diethylmethylbenzamide (DEET), plus corticosterone (CORT) via drinking water on days 8-14 and diisopropylfluorophosphate (DFP) on day 15. LNFPIII was administered concurrently with GWI chemicals treatments. Brain and spleen monoamines and hippocampal inflammatory marker expression were examined by, respectively, HPLC-ECD and qPCR, 6 h post treatment cessation. Serotonergic (5-HT) and dopaminergic (DA) dyshomeostasis caused by GWI chemicals was apparent in multiple brain regions, primarily in the nucleus accumbens (5-HT) and hippocampus (5-FIT, DA) for both models. Splenic levels of 5-HT (both models) and norepinephrine (Model 2) were also disrupted by GWI chemicals. LNFPIII treatment prevented many of the GWI chemicals induced monoamine alterations. Hippocampal inflammatory cytokines were increased in both models, but the magnitude and spread of inflammation was greater in Model 2; LNFPIII was anti-inflammatory, more so in the apparently milder Model 1. Overall, in both models, GWI chemicals led to monoamine disbalance and neuroinflammation. LNFPIII co-treatment prevented many of these disruptions in both models, which is indicative of its promise as a potential GWI therapeutic.

Residual effects of the 1990-1991 Gulf War (GW) still plague veterans 30 years later as Gulf War Illness (GWI). Thought to stem mostly from deployment-related chemical overexposures, GWI is a disease with multiple neurological symptoms with likely immunological underpinnings. Currently, GWI remains untreatable, and the long-term neurological disease manifestation is not characterized fully. The present study sought to expand and evaluate the long-term implications of prior GW chemicals exposure on neurological function 6-8 months post GWI-like symptomatology induction. Additionally, the beneficial effects of delayed treatment with the glycan immunotherapeutic lacto-Nfucopentaose III (LNFPIII) were evaluated. Male C57BL/6J mice underwent a 10-day combinational exposure (i.p.) to GW chemicals, the nerve agent prophylactic pyridostigmine bromide (PB) and the insecticide permethrin (PM; 0.7 and 200 mg/kg, respectively). Beginning 4 months after PB/PM exposure, a subset of the mice were treated twice a week until study completion with LNFPIII. Evaluation of cognition/memory, motor function, and mood was performed beginning 1 month after LNFPIII treatment initiation. Prior exposure to PB/PM produced multiple locomotor, neuromuscular, and sensorimotor deficits across several motor tests. Subtle anxiety-like behavior was also present in PB/PM mice in mood tests. Further, PB/PM-exposed mice learned at a slower rate, mostly during early phases of the learning and memory tests employed. LNFPIII treatment restored or improved many of these behaviors, particularly in motor and cognition/memory domains. Electrophysiology data collected from hippocampal slices 8 months post PB/PM exposure revealed modest aberrations in basal synaptic transmission and long-term potentiation in the dorsal or ventral hippocampus that were improved by LNFPIII treatment. Immunohistochemical analysis of tyrosine hydroxylase (TH), a dopaminergic marker, did not detect major PB/PM effects along the nigrostriatal pathway, but LNFPIII increased striatal TH. Additionally, neuroinflammatory cells were increased in PB/PM mice, an effect reduced by LNFPIII. Collectively, long-term neurobehavioral and neurobiological dysfunction associated with prior PB/PM exposure was characterized; delayed LNFPIII treatment provided multiple behavioral and biological beneficial effects in the context of GWI, highlighting its potential as a GWI therapeutic.

Chemical overexposures and war-related stress during the 1990-1991 Gulf War (GW) are implicated in the persisting pathological symptoms that many GW veterans continue to endure. These symptoms culminate into a disease known as Gulf War Illness (GWI) and affect about a third of the GW veteran population. Currently, comprehensive effective GWI treatment options are unavailable. Here, an established GWI mouse model was utilized to explore the (1) long-term behavioral and neuroinflammatory effects of deployment-related GWI chemicals exposure and (2) ability of the immunotherapeutic lacto-N-fucopentaose III (LNFPIII) to improve deficits when given months after the end of exposure. Male C57BL6/J mice (8-9 weeks old) were administered pyridostigmine bromide (PB) and DEET for 14 days along with corticosterone (CORT; latter 7 days) to emulate wartime stress. On day 15, a single injection of the nerve agent surrogate diisopropylfluorophosphate (DFP) was given. LNFPIII treatment began 7 months post GWI chemicals exposure and continued until study completion. A battery of behavioral tests for assessment of cognition/memory, mood, and motor function in rodents was performed beginning 8 months after exposure termination and was then followed by immunohistochemcal evaluation of neuroinflammation and neurogenesis. Within tests of motor function, prior GWI chemical exposure led to hyperactivity, impaired sensorimotor function, and altered gait. LNFPIII attenuated these motor-related deficits and improved overall grip strength. GWI mice also exhibited more anxiety-like behavior that was reduced by LNFPIII; this was test-specific. Short-term, but not long-term memory, was impaired by prior GWI exposure; LNFPIII improved this measure. In the brains of GWI mice, but not in mice treated with LNFPIII, glial activation was increased. Overall, it appears that months after exposure to GWI chemicals, behavioral deficits and neuroinflammation are present. Many of these deficits were attenuated by LNFPIII when treatment began long after GWI chemical exposure termination, highlighting its therapeutic potential for veterans with GWI.

A series of 172 molecular structures that block the hERG K+ channel were used to develop a classification model where, initially, eight types of PaDEL fingerprints were used for k-nearest neighbor model development. A consensus model constructed using Extended-CDK, PubChem and Substructure count fingerprint-based models was found to be a robust predictor of hERG activity. This consensus model demonstrated sensitivity and specificity values of 0.78 and 0.61 for the internal dataset compounds and 0.63 and 0.54 for the external (PubChem) dataset compounds, respectively. This model has identified the highest number of true positives (i.e. 140) from the PubChem dataset so far, as compared to other published models, and can potentially serve as a basis for the prediction of hERG active compounds. Validating this model against FDA-withdrawn substances indicated that it may even be useful for differentiating between mechanisms underlying QT prolongation.

Three new benzo[b]naphtho[2,1-d]furans, usambarins A–C (1–3), five new 2-phenylnaphthalenes, usambarins D–H (4–8), a new flavan (9), and a new phenyl-1-benzoxepin (10) as well as two known compounds (11 and 12) were isolated from the extract of the stem and roots of Streblus usambarensis (Moraceae). The structures were deduced using NMR spectroscopic and mass spectrometric analyses, and those of compounds 1 and 4 were confirmed by X-ray crystallography. Usambarin D (4) demonstrated moderate antibacterial activity (MIC 9.0 μM) against Bacillus subtilis, while none of the tested compounds were effective against Escherichia coli.

The CH2Cl2/MeOH (1:1) extract of the stems of Tephrosia uniflora yielded the new β-hydroxydihydrochalcone (S)-elatadihydrochalcone-2'-methyl ether (1) along with the three known compounds elongatin (2), (S)-elatadihydrochalcone (3), and tephrosin (4). The structures were elucidated by NMR spectroscopic and mass spectrometric data analyses. Elongatin (2) showed moderate antibacterial activity (EC50 of 25.3 μM and EC90 of 32.8 μM) against the Gram-positive bacterium Bacilus subtilis, and comparable toxicity against the MCF-7 human breast cancer cell line (EC50 of 41.3 μM). Based on the comparison of literature and predicted NMR data with that obtained experimentally, we propose the revision of the structures of three β-hydroxydihydrochalcones to flavanones.

Five known compounds (1–5) were isolated from the extract of Mundulea sericea leaves. Similar investigation of the roots of this plant afforded an additional three known compounds (6–8). The structures were elucidated using NMR spectroscopic and mass spectrometric analyses. The absolute configuration of 1 was established using ECD spectroscopy. In an antiplasmodial activity assay, compound 1 showed good activity with an IC50 of 2.0 μM against chloroquine-resistant W2, and 6.6 μM against the chloroquine-sensitive 3D7 strains of Plasmodium falciparum. Some of the compounds were also tested for antileishmanial activity. Dehydrolupinifolinol (2) and sericetin (5) were active against drug-sensitive Leishmania donovani (MHOM/IN/83/AG83) with IC50 values of 9.0 and 5.0 μM, respectively. In a cytotoxicity assay, lupinifolin (3) showed significant activity on BEAS-2B (IC50 4.9 μM) and HePG2 (IC50 10.8 μM) human cell lines. All the other compounds showed low cytotoxicity (IC50 > 30 μM) against human lung adenocarcinoma cells (A549), human liver cancer cells (HepG2), lung/bronchus cells (epithelial virus transformed) (BEAS-2B) and immortal human hepatocytes (LO2)