For the last years, searching new chiral derivatives of xanthones (CDX) with potential pharmacological properties has remained in the area of interest of our group [1,2]. Recently, we have described the ability of CDX to inhibit the growth of different human tumor cell lines [1]. In fact, some of them exhibited interesting dose-dependent growth inhibitory effects on the evaluated cell lines being dependent on the stereochemistry.

Based on this work, herein we describe the synthesis of a new library of promising bioactive analogues, in enantiomerically pure form, with good yields, short reaction times and no racemization. The optimization of the synthetic pathways to obtain the xanthonic derivative used as chemical building block was also described.

The enantiomeric excesses for all synthesized CDX were measured by HPLC on (S,S)-Whelk-O1® chiral stationary phase under polar-organic elution conditions, achieving values higher than 99%.

The evaluation of growth inhibitory activity on human tumor cell lines of the synthesized CDX is in progress.

  

Acknowledgements:

This research was partially supported by the Strategic Funding UID/Multi/04423/2013 and UID/QUI/00062/2013 through national funds provided by FCT – Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the programme PT2020, and the Portuguese NMR Network.

 

References

[1] Fernandes C.; Masawang K.; Tiritan M. E.; Sousa E.; Lima V.; Afonso C.; Bousbaa H.; Sudprasert W.; Pedro M.; Pinto M. M. Bioorgan. Med. Chem. 2014, 22, 1049.

[2] Fernandes, C.; Oliveira, L.; Tiritan, M. E.; Leitao, L.; Pozzi, A.; Noronha-Matos, J. B.; Correia-de-Sá, P.; Pinto, M. M., Eur. J. Med. Chem., 2012, 55, 1.

Typically, about 90% of drug candidates are N-containing, and an even higher amount are O-containing. As a consequence, it is not surprising that alkylation and arylation of groups with nitrogen and oxygen emerge as major reactions to obtain bioactive compounds.¹ Xanthones are a class of O-heterocycles characterized by a dibenzo-γ-pyrone nucleus. This scaffold may be considered a “privileged structure” able of providing useful ligands for several types of receptors and/or enzymes targets by judicious structural modifications.² In our search for potential anticancer drugs we pursuit with a hybridization approach of N-containing xanthones. N-Substitution is typically achieved by one of the following strategies: (i) direct reaction with alkyl-X or aryl-X, (ii) reductive alkylation using an appropriate aldehyde.

Herein, exploiting chemical routes to reach for bioactive N-containing xanthones with will be shared. The synthesis of new xanthone derivatives proceeds by both strategies and the respective strengths and weakness will be presented in a “medchem” perspective. Although chemical route (i) (S_N2 reactions and nucleophilic aromatic substitutions) provided interesting antitumor derivatives,³ the reductive amination (ii) furnished a library of potential p53:MDM2 inhibitors with noticeable advantages such as: high-yield reactions, one-pot conversions, aliphatic amines with low potential to form reactive metabolites.

The use of a variety of (thio)xanthone building blocks, with various substituents, and different reaction conditions allowed us to develop a repertoire of N-transformations, often referred as the “chemist toolbox”.⁴ 

References

1. Carey, J. S.; Laffan, D.; Thomson, C.; Williams, M. T. Org. Biomol. Chem. 2006, 2337–2347.
2. Pinto, M. M. M.; Sousa, M. E.; Nascimento, M. S. J. Curr. Med. Chem. 2005, 12, 2517-2538.
3. Palmeira, A.; Vasconcelos, M. H.; Paiva, A.; Fernandes, M. X.; Pinto, M.; Sousa. E. Biochem. Pharmacol. 2012, 83, 57–68.
4. Roughley, S. D.; Jordan, A. M. J. Med. Chem. 2011, 54, 3451-3479.

 Acknowledgments: This research was partially supported by ERDF through the COMPETE and national funds through FCT, under the project PEst-C/MAR/LA0015/2013.

 

It is well known that plants are important sources for the preparation of natural remedies as they contain many biologically active compounds: in particular, polyphenols, terpenic compounds, organic acids, and vitamins are the most widely occurring groups of phytochemicals. Some endemic species may be used for the production of herbal preparations containing phytochemicals with significant bioactivity, as antioxidant activity and anti-inflammatory capacities, and health benefits: blackberry sprouts and blackcurrant buds are known to contain appreciable levels of bioactive compounds, including flavonols, phenolic acids, monoterpenes, vitamin C, and catechins, with several clinical effects.

The aim of this research was to perform an analytical study of blackcurrant and blackberry bud-preparations, in order to identify and quantify the main biomarkers, obtaining a specific phytochemical fingerprint to evaluate the single botanical class contribution to total phytocomplex and relative bioactivity, using a High Performance Liquid Chromatograph − Diode Array Detector; the same analyses were performed both on the University laboratory and commercial preparations.

Different chromatographic methods were used to determine concentrations of biomolecules in the preparations, allowing for quantification of statistically significant differences in their bioactive compound content both in the case of Ribes nigrum and Rubus ulmifolius.

Chemical, pharmaceutical and environmental knowledge could be a useful tool for obtaining label certifications for the valorization of specific genotypes, with high clinical and pharmaceutical value: this study allowed to develop an effective tool for the natural preparation quality control and bioactivity evaluation through the chemical fingerprinting of bud preparations.

Increasing demands from the pharmaceutical industry for rapid molecular structure determination of pharmaceutical solids has prompted the development of X-ray diffraction and ¹³C CP/MAS NMR data analyses. The solid-state form of the drug can have dramatic impact on the bioavailability, and the regulatory approval for many drugs is given only for the defined polymorph.

The intermolecular interactions are crucial in interpretation of interactions between the biomolecules and macromolecular targets and their analysis can provide essential information about how they occur.

The compounds presented in this report can be considered as the pentamidine analogs, which are of interest because they have potential use as the chemotherapeutics against Pneumocystis pneumonia, as potent NMDA receptor inhibitors or as anticancer and antimicrobial agents.

Impaired wound healing is an important clinical problem in diabetes and results in slow wound healing which may lead to infection, sepsis, gangrene and even amputations. In the present study, polymer (collagen and arginine) based dressings were prepared to be applied as scaffold for the control release of Lupeol (Lu), a triterpeniod that acts as an inflammatory modulator in wound healing. The activity of Lu–loaded polymer matrices to treat wounds in streptozotocin diabetic induced rat was evaluated. There was a delay in wound healing in diabetic rats as compared to non-diabetic rats. The dressing exhibited potent wound healing activity as indication by the wound contraction in the excision wound model. Lu–loaded polymer dressings make faster healing (21% wound area reduction) in the initial phase of wound healing in diabetic rat. Prepared system also significantly reduced inflammatory cytokine expression namely, TNF-α and IL-1β and decreased the inflammatory infiltrate post-wounding. The contents of hydroxyproline and hexosamine also correlated with the observed healing pattern. These findings were supported by the histopathological characteristics of healed wound sections, as greater tissue regeneration, more fibroblasts, and angiogenesis were observed in the Lu–loaded polymer matrices-treated group.  These results suggest that polymer-based dressings can be an effective support for Lupeol release into diabetic wound enhancing the healing process.

Lichens are particular organisms, consisting of a cyanobacterial or/and an algal symbiotic partnership with a fungus. Their secondary metabolites are usually original molecules which are not found in other types of organisms. These substances are of interest for cosmetics and pharmaceutics as a variety of activities have been reported, antibiotic, anti-inflammatory, antioxidant, UV-A and UV-B filters. The standard methods for the extraction of these secondary metabolites proceed through time consuming, heat reflux protocols with volatile organic solvents. The aim of the current study is to develop innovative methods to accelerate (qualitatively and quantitatively) the selective extraction of lichen compounds. After optimization of microwave assisted extraction (MAE), we applied this method on Pseudevernia furfuracea using various ionic liquids (ILS). This extraction was compared to the classical extraction using Volatile Organic Solvents (VOCs). The efficiencies of the extraction methods are evaluated using TLC coupled to a Camag® spectrophotodensitometer and HPLC analysis.

In the current work we studied the interest of a series of 8-substitued 7-hydroxy-4-methylcoumarins as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors. For the best compounds of the series, the IC50 value was determined. This work was based on previous results and is a preliminary screening for further design and synthesis of new derivatives as potential compounds that can modulate enzymatic systems involved in the neurodegenerative diseases.

In the absence of X-ray data, the exploration of compound binding modes continues to be a challenging task. For structure-based design, specific features of active sites in different targets play a major role in rationalizing ligand binding characteristics. For example, dibasic compounds have been reported as potent inhibitors of various trypsin-like serine proteases, the active sites of which contain several binding pockets that can be targeted by cationic moieties. This results in several possible orientations within the active site, complicating the binding mode prediction of such compounds by docking tools. Therefore, we introduced symmetry in bi- and tribasic compounds to reduce conformational space in docking calculations and to simplify binding mode selection by limiting the number of possible pocket occupations. Asymmetric bisbenzamidines were used as starting points for a multistage and structure-guided optimization. A series of 24 final compounds with either two or three benzamidine substructures was ultimately synthesized and evaluated as inhibitors of five serine proteases, leading to potent symmetric inhibitors for the pharmaceutical drug targets matriptase, matriptase-2, thrombin and factor Xa. This study underlines the relevance of ligand symmetry for chemical biology.

A new series of oxadiazole analogues were synthesized starting from 2-aminopyridine. The compounds were characterized by infrared (IR), nuclear magnetic resonance (NMR) and mass spectral analyses followed by their antiproliferative and antimicrobial activities. Three compounds were tested for in vitro antiproliferative activity against NCI-60 human cell lines of nine different panels including leukemia, non-small lung cancer, colon cancer, CNS cancer, melanoma, ovarian cancer, renal cancer, prostate cancer, and breast cancer according to the National Cancer Institute (NCI US) Protocol at 10 µM. The compounds N-{[5-(4-Chlorophenyl)-1,3,4-oxadiazol-2-yl]methyl}pyridin-2-amine (5c), N-{[5-(4-Methoxyphenyl)-1,3,4-oxadiazol-2-yl]methyl}pyridin-2-amine (5f) and N-{[5-(4-Methoxyphenyl)-1,3,4-oxadiazol-2-yl]methyl}pyridin-2-amine (5g) showed anticancer with higher selectivity towards HOP-92 (Non-Small Cell Lung Cancer) and showed percent growth inhibition of 34.14, 35.29 and 31.59 at 10 µM concentration in single dose assay. N-{[5-(4-Fluorophenyl)-1,3,4-oxadiazol-2-yl]methyl}pyridin-2-amine (5b) showed maximum antibacterial activity with minimum inhibitory concentration (MIC) of 4-8 µg/mL, while N-{[5-(4-Methoxyphenyl)-1,3,4-oxadiazol-2-yl]methyl}pyridin-2-amine (5f) showed maximum antifungal activity with MIC 4 µg/mL.

Testing for HIV drug resistance is essential to the care of HIV-infected patients. Although direct phenotypic resistance assays are highly reliable, the current recombinant virus-based method is costly and time-consuming. Here, we report a novel fluorometric assay for phenotypic differentiation of drug-resistant mutants of human immunodeficiency virus-I protease (HIV-PR) which uses enzymatic and peptide-specific fluorescence (FL) reactions and high-performance liquid chromatography (HPLC) of three HIV-PR substrates. This assay enables the use of non-purified enzyme sources and multiple substrates for the enzymatic reaction. In this study, susceptibility of HIV mutations to drugs was evaluated by selective formation of three FL products after the enzymatic HIV-PR reaction. This proof-of-concept study indicates that the present HPLC-FL method could be an alternative to current phenotypic assays for the evaluation of HIV drug resistance.