Lipophilicity assessement in drug discovery: Experimental and theoretical methods applied to xanthone derivatives

Polyherbal Combinations Used by Traditional Health Practitioners against Mental Illnesses in Bamako, Mali, West Africa

This study explores the traditional knowledge of plants used by traditional health practitioners (THPs) in the treatment of symptoms or syndromes related to mental illnesses in the district of Bamako in Mali, along with the identification of affiliated traditional treating methods. An exploratory and cross-sectional ethnopharmacological survey was conducted in the district of Bamako. The Malian Federation of Associations of Therapists and Herbalists (FEMATH) assisted in the identification and inclusion of the THPs. Data sampling included semi-structured interviews, questionnaires, and in-depth interviews. Quantitative data were evaluated by analysing reports of the use of different medicinal plants and the number of participants. Fifteen THPs belonging to the district of Bamako participated. In total, 43 medicinal plants belonging to 22 plant families were used by the THPs. The most cited plant species was Securidaca longepedunculata (violet tree), followed by Khaya senegalensis (African mahogany) and Boscia integrifolia (rough-leaved shepherds tree). A great number of herbal combinations, preparation methods, and administration routes were used, often with honey as an adjuvant. To our knowledge, this is the first ethnobotanical survey on the use of medicinal plants in the treatment of all types of mental disorders in Bamako.

In vitro and in vivo anticancer activity of novel Rh(III) and Pd(II) complexes with pyrazolopyrimidine derivatives

Six pyrazolopyrimidine rhodium(III) or palladium(II) complexes, [Rh(L1)(H2O)Cl3] (1), [Rh(L2)(CH3OH)Cl3] (2), [Rh(L3)(H2O)Cl3] (3), [Rh2(L4)Cl6]·CH3OH (4), [Rh(L5)(CH3CN)Cl3]·0.5CH3CN (5), and [Pd(L5)Cl2] (6), were synthesized and characterized. These complexes showed high cytotoxicity against six tested cancer cell lines. Most of the complexes showed higher cytotoxicity to T-24 cells in vitro than cisplatin. Mechanism studies indicated that complexes 5 and 6 induced G2/M phase cell cycle arrest through DNA damage, and induced apoptosis via endoplasmic reticulum stress response. In addition, complex 5 also induced cell apoptosis via mitochondrial dysfunction. Complexes 5 and 6 showed low in vivo toxicity and high tumor growth inhibitory activity in mouse tumor models. The inhibitory effect of rhodium complex 5 on tumor growth in vivo was more pronounced than that of palladium complex 6.

An Update on the Anticancer Activity of Xanthone Derivatives: A Review

The annual number of cancer deaths continues increasing every day; thus, it is urgent to search for and find active, selective, and efficient anticancer drugs as soon as possible. Among the available anticancer drugs, almost all of them contain heterocyclic moiety in their chemical structure. Xanthone is a heterocyclic compound with a dibenzo-γ-pyrone framework and well-known to have "privileged structures" for anticancer activities against several cancer cell lines. The wide anticancer activity of xanthones is produced by caspase activation, RNA binding, DNA cross-linking, as well as P-gp, kinase, aromatase, and topoisomerase inhibition. This anticancer activity depends on the type, number, and position of the attached functional groups in the xanthone skeleton. This review discusses the recent advances in the anticancer activity of xanthone derivatives, both from natural products isolation and synthesis methods, as the anticancer agent through in vitro, in vivo, and clinical assays.

Marine and terrestrial endophytic fungi: a mine of bioactive xanthone compounds, recent progress, limitations, and novel applications

Endophytic fungi are a kind of fungi that colonizes living plant tissues presenting a myriad of microbial adaptations that have been developed in such a hidden environment. Owing to its large diversity and particular habituation, they present a golden mine for research in the field of drug discovery. Endophytic fungal communities possess unique biocatalytic machinery that furnishes a myriad of complex natural product scaffolds. Xanthone compounds are examples of endophytic secondary metabolic products with pronounced biological activity to include: antioxidant, antimicrobial, anti-inflammatory, antithrombotic, antiulcer, choleretic, diuretic, and monoamine oxidase inhibiting activity.The current review compiles the recent progress made on the microbiological production of xanthones using fungal endophytes obtained from both marine and terrestrial origins, with comparisons being made among both natural resources. The biosynthesis of xanthones in endophytic fungi is outlined along with its decoding enzymes. Biotransformation reactions reported to be carried out using different endophytic microbial models are also outlined for xanthones structural modification purposes and the production of novel molecules.A promising application of novel computational tools is presented as a future direction for the goal of optimizing microbial xanthones production to include establishing metabolic pathway databases and the in silico analysis of microbial interactions. Metagenomics methods and related bioinformatics platforms are highlighted as unexplored tools for the biodiversity analysis of endophytic microbial communities that are difficult to be cultured.

From Natural Products to New Synthetic Small Molecules: A Journey through the World of Xanthones

This work reviews the contributions of the corresponding author (M.M.M.P.) and her research group to Medicinal Chemistry concerning the isolation from plant and marine sources of xanthone derivatives as well as their synthesis, biological/pharmacological activities, formulation and analytical applications. Although her group activity has been spread over several chemical families with relevance in Medicinal Chemistry, the main focus of the investigation and research has been in the xanthone family. Xanthone derivatives have a variety of activities with great potential for therapeutic applications due to their versatile framework. The group has contributed with several libraries of xanthones derivatives, with a variety of activities such as antitumor, anticoagulant, antiplatelet, anti-inflammatory, antimalarial, antimicrobial, hepatoprotective, antioxidant, and multidrug resistance reversal effects. Besides therapeutic applications, our group has also developed xanthone derivatives with analytical applications as chiral selectors for liquid chromatography and for maritime application as antifouling agents for marine paints. Chemically, it has been challenging to afford green chemistry methods and achieve enantiomeric purity of chiral derivatives. In this review, the structures of the most significant compounds will be presented.

Heterocycles 51: Liphophilicity investigation of some thiazole chalcones and aurones by experimental and theoretical methods

Reversed-phase thin-layer chromatography and reversed-phase high-performance liquid chromatography were used for lipophilicity determination of a library of 30 thiazole chalcones and aurones previously synthetized in our laboratory. The experimental lipophilicity data have been compared with theoretical lipophilicity parameters estimated by various computational methods. Good correlations between the experimental and calculated lipophilicity parameters have been found for both investigated classes of compounds. Correlations between the lipophilicity of the thiazole chalcones and aurones and their antiproliferative activity were discussed. The methodologies and data gathered in this study will contribute to the lipophilicity studies of chalcones and aurones derivatives, two important classes of compounds in medicinal chemistry.

Yicathins B and C and Analogues: Total Synthesis, Lipophilicity and Biological Activities

Natural products have always been an important source of new hits and leads in drug discovery, with the marine environment being regarded as a significant source of novel and exquisite bioactive compounds. Yicathins B and C are two marine-derived xanthones that have shown antibacterial and antifungal activity. Herein, the total synthesis of these yicathins and six novel analogues is reported for the first time. As marine natural products tend to have very lipophilic scaffolds, the lipophilicity of yicathins and their analogues was evaluated in the classical octanol/water system and a biomimetic model-based system. As the xanthonic nucleus is a "privileged structure", other biological activities were evaluated, namely antitumor and anti-inflammatory activities. An interesting anti-inflammatory activity was identified for yicathin analogues that paves the way for the design of dual activity (anti-infective and anti-inflammatory) marine-inspired xanthone derivatives.

Recent advances in the synthesis of xanthones and azaxanthones

A useful chemical toolbox for (aza)xanthones from 2012 to 2020 that covers the optimization of known procedures and novel methodologies.

Assessment of lipophilicity of newly synthesized celecoxib analogues using reversed-phase HPLC

BACKGROUND

Lipophilicity is a physicochemical property of an essential importance in medicinal chemistry; therefore, fast and reliable measurement of lipophilicity will affect greatly the drug discovery process.

RESULTS

A series of N-benzenesulfonamide-1H-pyrazoles, oximes and hydrazones as celecoxib analogues was investigated with regard to their retention behavior using reversed-phase high performance liquid chromatography (RP-HPLC). The mobile phases employed for this study consist of a mixture of water and methanol in different proportions. In addition, the stationary phase utilized for this separation was C18 silanized silica gel and using 200 nm as a detection wavelength. The retention behavior of the investigated compounds was determined based on practical determination of log k at different concentrations of methanol (as an organic modifier) in the mobile phase ranging from 60 to 80%. It was observed that the retention of these compounds (expressed as log k) decreased in a linear manner with increasing the concentration of methanol. High correlation coefficients (more than 0.90 in most cases) were obtained for the relationship between the volume fraction of the organic solvent and the retention values represented as log k w. A comparative evaluation was carried out between chromatographically-obtained lipophilicity parameters (represented as lipophilicity chromatographic index log k w or isocratic chromatographic hydrophobicity index, φ 0) and the computationally calculated log P values (miLogP, ALOGP, ACD/Labs and ALOGPs).

CONCLUSION

It was found that a good correlation exists between the experimental and computed log P values. In the future, these results can give a deep insight about the anti-inflammatory and analgesic activity of the newly synthesized compounds.

Chalcone derivatives targeting mitosis: synthesis, evaluation of antitumor activity and lipophilicity

This study describes the synthesis of a series of chalcones, including pyrazole and α,β-epoxide derivatives, and evaluation of their cell growth inhibitory activity in three human tumor cell lines, as well as their lipophilicity using liposomes as a biomimetic membrane model. Structure-activity and structure-lipophilicity relationships were established for the synthetized chalcones. From this work, nine chalcones (3, 5, 9, 11, 15-19) showing suitable drug-like lipophilicity with potent growth inhibitory activity were identified, being the growth inhibitory effect of compounds 15-17 associated with a pronounced antimitotic effect. Compounds 15-17 affected spindle assembly and, as a consequence, arrested cells at metaphase in NCI-H460 cells, culminating in cell death. Amongst the compounds tested, compound 15 exhibited the highest antimitotic activity as revealed by mitotic index calculation. Moreover, 15 was able to enhance chemosensitivity of tumor cells to low doses of paclitaxel in NCI-H460 cells. The results indicate that 15 exerts its antiproliferative activity by affecting microtubules and causing cell death subsequently to a mitotic arrest, and thus has the potential for antitumor activity.

Enantioseparation, recognition mechanisms and binding of xanthones on human serum albumin by liquid chromatography

Aim: To develop a method for enantioseparation of several chiral derivatives of xanthones (CDXs) by LC using a human serum albumin-chiral stationary phase (HSA-CSP) and screening CDX-HSA affinity. Additionally, recognition mechanisms were investigated. Materials & methods: The influence of organic modifier, buffer type, pH and ionic strength of mobile phase, and temperature were explored. The affinity was determined by measuring the retention times and further calculation of bound percentage. Chiral recognition mechanisms were investigated by docking. Results: Enantioselectivity and resolution values ranged from 1.40 to 9.16 and 1.51 to 4.97. Bound percentages ranged from 79.02 to 99.99%. Conclusion: LC systematic study and binding affinity of CDXs on HSA-CSP are presented here for the first time, expanding the applications of HSA-CSP for this class of compounds.

Investigation of lipophilicity and pharmacokinetic properties of 2-(methoxy)phenylpiperazine dopamine D2 ligands

Reversed-phase thin-layer chromatography and micellar thin-layer chromatography were used in order to investigate retention behaviour and to determine lipophilicity of series of 2-(methoxy)phenylpiperazine dopamine D2 ligands with different size, shape and rigidity. The retention mechanism was discussed. The lipophilicity parameters obtained in conventional reversed-phase systems expressed as R_M⁰ and C⁰, as well as R_M values determined in microemulsion reversed-phase systems were correlated with in silico determined lipophilicity values. In silico pharmacokinetic properties of 2-(methoxy)phenylpiperazine dopamine D2 ligands revealed the importance of experimentally determined lipophilicity values besides the molecular weight, on the blood-brain barrier permeability process. Also, the experimentally determined lipophilicity was found as a very important factor in plasma protein binding process of 2-(methoxy)phenylpiperazine dopamine D2 ligands. Besides, the Lipinski's rule of five indicates that examined ligands satisfy the criterion of drug-like molecules. The principal component analysis was performed on the experimentally determined and calculated lipophilicity values as well on the molecular descriptors which describe the pharmacokinetic properties in order to provide basic insights into similarities among the studied ligands.

Lipophilicity as a Central Component of Drug-Like Properties of Chalchones and Flavonoid Derivatives

Lipophilcity is an important physico-chemical parameter that influences membrane transport and binding ability to action. Migration distance following complete elution of compounds was used to calculate different lipophilicity-related parameters. The aim of this study is to show that lipophilicity is a central component of thiazole chalcones and flavonoid derivatives regarding their drug-like properties. Experimental and computational methods were used. This study considers 44 previously synthesized compounds (thiazole chalcones, flavanones, flavones, 3-hydroxyflavones, and their acetylated derivatives). The concerned compounds have shown antitumoral hallmarks and antibacterial activity in vitro. The experimental method used to determine compounds’ lipophilicity was the reverse-phase thin layer chromatography (RP-TLC). Lipophilicity related parameters—isocratic retention factor (R_M), relative lipophily (R_M⁰), slope (b), chromatographic hydrophobic index (φ₀), scores of principal components (PC1/R_M)—were determined based on reverse-phase chromatography results.

Structures, Activities and Drug-Likeness of Anti-Infective Xanthone Derivatives Isolated from the Marine Environment: A Review

Marine organisms represent almost half of total biodiversity and are a very important source of new bioactive substances. Within the varied biological activities found in marine products, their antimicrobial activity is one of the most relevant. Infectious diseases are responsible for high levels of morbidity and mortality and many antimicrobials lose their effectiveness with time due to the development of resistance. These facts justify the high importance of finding new, effective and safe anti-infective agents. Among the variety of biological activities of marine xanthone derivatives, one that must be highlighted is their anti-infective properties. In this work, a literature review of marine xanthones with anti-infective activity, namely antibacterial, antifungal, antiparasitic and antiviral, is presented. Their structures, biological activity, sources and the methods used for bioactivity evaluation are described. The xanthone derivatives are grouped in three sets: xanthones, hydroxanthones and glycosylated derivatives. Moreover, molecular descriptors, biophysico-chemical properties, and pharmacokinetic parameters were calculated, and the chemical space occupied by marine xanthone derivatives is recognized. The chemical space was compared with marketed drugs and framed accordingly to the drug-likeness concept in order to profile the pharmacokinetic of anti-infective marine xanthone derivatives.

Carboxyxanthones: Bioactive Agents and Molecular Scaffold for Synthesis of Analogues and Derivatives

Xanthones represent a structurally diverse group of compounds with a broad range of biological and pharmacological activities, depending on the nature and position of various substituents in the dibenzo-γ-pyrone scaffold. Among the large number of natural and synthetic xanthone derivatives, carboxyxanthones are very interesting bioactive compounds as well as important chemical substrates for molecular modifications to obtain new derivatives. A remarkable example is 5,6-dimethylxanthone-4-acetic acid (DMXAA), a simple carboxyxanthone derivative, originally developed as an anti-tumor agent and the first of its class to enter phase III clinical trials. From DMXAA new bioactive analogues and derivatives were also described. In this review, a literature survey covering the report on carboxyxanthone derivatives is presented, emphasizing their biological activities as well as their application as suitable building blocks to obtain new bioactive derivatives. The data assembled in this review intends to highlight the therapeutic potential of carboxyxanthone derivatives and guide the design for new bioactive xanthone derivatives.

Novel Alkylimidazolium Ionic Liquids as an Antibacterial Alternative to Pathogens of the Skin and Soft Tissue Infections

Keeping in mind the concept of green chemistry, this research aims to synthesize and characterize new ionic liquids (ILs) derived from N-cinnamyl imidazole with different sizes of alkyl chains (1, 6, 8, and 10 carbon atoms), and evaluate their antibacterial activity against Skin and soft tissue infections (SSTIs) causative bacteria. The antibacterial screening was carried out by agar well diffusion and the Minimum Inhibitory Concentration (MIC) and Half Maximum Inhibitory Concentration (IC₅₀) of the different ILs were determined by microdilution in broth, also Molecular dynamics simulations were performed to study the interaction mechanism between ILs and membranes. The MIC value in Gram-positive bacteria showed that as the hydrocarbon chain increases, the MIC value decreases with a dose-dependent effect. Furthermore, Gram-negative bacteria showed high MIC values, which were also evidenced in the antibacterial screening. The molecular dynamics showed an incorporation of the ILs with the longer chain (10 C), corresponding to a passive diffusion towards the membrane surface, for its part, the ILs with the shorter chain due to its lack of hydrophobicity was not incorporated into the bilayer. Finally, the new ILs synthesized could be an alternative for the treatment of Gram-positive bacteria causative of SSTIs.

Modulation of brain ACE and ACE2 may be a promising protective strategy against cerebral ischemia/reperfusion injury: an experimental trial in rats

The brain renin-angiotensin system (RAS) is considered a crucial regulator for physiological homeostasis and disease progression. We evaluated the protective effects of the angiotensin receptor blocker (ARB) telmisartan and the angiotensin-converting enzyme 2 (ACE2) activator xanthenone on experimental cerebral ischemia/reperfusion (I/R) injury. Rats were divided into a sham control, a cerebral I/R control, a standard treatment (nimodipine, 10 mg/kg/day, 15 days, p.o.), three telmisartan treatments (1, 3, and 10 mg/kg/day, 15 days, p.o.), and three xanthenone treatments (0.5, 1, and 2 mg/kg/day, 15 days, s.c.) groups. One hour after the last dose, all rats except the sham control group were exposed to 30-min cerebral ischemia followed by 24-h reperfusion. Brain ACE and ACE2 activities and the apoptotic marker caspase-3 levels were assessed. Glutathione (GSH), malondialdehyde (MDA), and nitric oxide end products (NOx) as oxidative markers and tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and IL-10 as immunological markers were assessed. Histopathological examination and immunohistochemical evaluation of glial fibrillary acidic protein (GFAP) were performed in cerebral cortex and hippocampus sections. Telmisartan and xanthenone in the higher doses restored MDA, NOx, TNF-α, IL-6, caspase-3, ACE, and GFAP back to normal levels and significantly increased GSH, IL-10, and ACE2 compared to I/R control values. Histopathologically, both agents showed mild degenerative changes and necrosis of neurons in cerebral cortex and hippocampus compared with I/R control group. Modulation of brain RAS, either through suppression of the classic ACE pathway or stimulation of its antagonist pathway ACE2, may be a promising strategy against cerebral I/R damage.

Multivariate assessment of azo dyes' biological activity parameters

Lipophilicity as key molecular descriptor of potential biological activity for selected derivatives of azo dyes was determined mathematically, by using relevant software packages and by reversed-phase thin-layer chromatography (RPTLC) on C18 and cyano modified carriers in mixtures of water/n-propanol and water/acetone. The obtained chromatographic parameters, R_M⁰ and m, of the examined azo dyes were correlated with the standard measure of lipophilicity, log P, important pharmacokinetic predictors and selected toxicity parameters applying linear regression analysis. Thereby, good correlations for each applied system were obtained (average correlation coefficient, r, 0.944, 0.885 and 0.919). Also, the correlations between the studied parameters of azo dyes were examined applying two multivariate methods (Cluster Analysis and Principal Component Analysis). It was shown that the polarity of the substituent, and to a lesser extent its electronic effects has the greatest influence on the studied parameters of the azo dyes derivatives. Multivariate methods pointed out the similarity of the chromatographic retention constant, R_M⁰, with the parameters of lipophilicity, unlike the chromatographic parameter m, which exhibits better agreement with the toxicity parameters.

Accessing lipophilicity of drugs with biomimetic models: A comparative study using liposomes and micelles

Lipophilicity is a physicochemical property of crucial importance in drug discovery and drug design. Biomimetic models, such as liposomes and micelles, constitute a valuable tool for the assessment of lipophilicity through the determination of partition coefficients (log K_p). However, the lack of standardization hampers the judgment about which model or method has the best and broadest passive drug permeation predictive capacity. This work provides a comparative analysis between the methodologies based on biomimetic models to determine the partition coefficient (log K_p). For that purpose, a set of reference substances preconized by the Organization for Economic Cooperation and Development (OECD) guidelines was used. The biomimetic models employed were liposomes and micelles composed by 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) and hexadecylphosphocholine (HePC), respectively. Both lipids were used as representative phospholipids of natural membranes. The partition coefficients between biomimetic models and aqueous phases were determined by derivative spectroscopy at physiological conditions (37 °C and pH 7.4). The partition coefficients obtained using biomimetic models are quite different and more reliable than the ones obtained using an octanol/water system. Comparing the performance of the two biomimetic models, micelles revealed to be suitable only for substances with high molar absorption coefficient and log K_p > 3, but in general liposomes are the best model for accessing lipophilicity of drugs. Furthermore, a comparison between experimental data and the partition coefficients determined by the computational method COSMOmic is also provided and discussed. As a final summarizing result, a decision tree is provided in order to guide the selection of a tool for assessing the lipophilicity of drugs.