The steadily increasing of the resistance of human pathogens to multiple antimicrobials over the last decade is alarming and a serious threat to public health.[1] While the emergence of multidrug resistance has been associated with misuse and abuse of antimicrobials, the number of available effective agents is decreasing as novel compounds arriving into the market are scarce.[2,3]

Tetraazamacrocycles are versatile and readily tunable molecules with potential for the development of derivatives having enhanced antimicrobial activity. Our recent work led to the identification of cyclam derivatives as a potential novel class of compounds that represents a breakthrough in the field of new antibacterial drugs.[4]

[1] WHO. Antimicrobial Resistance: Global Report on Surveillance 2014; Geneva, 2014

[2] Bax, R.; Mullan N.; Verhoef, J., Int. J. Antimicrob. Agents 2000, 16, 51-59

[3] Norrby, S. R.; Nord, C. E.; Finch, R., Lancet Infect. Dis. 2005, 5, 115-119

[4] Alves, L. G.; Pinheiro, P. F.; Feliciano, J. R.; Leitão, J. H.; Martins, A. M., Int. J. Antimicrob. Agents 2017, 49, 646-649

In the present work, molecular docking analyses of few thiazolidinediones into the catalytic domain of protein PPAR-gamma is reported for the discovery of antidiabetic agents. Protein PPARgamma is involved in carbohydrate and fat metabolism hence it will be a useful target for treating type-2 diabetes. With this view, mapping of ligand binding domain of protein PPAR-gamma was carried out using online server such as uniport; pharmacophoric points using co-crystal rosiglitazone were studied. Molecular docking of thiazolidine-2,4-diones was carried out using Vlife MDS suite. Binding energy and interactions such as hydrogen bond, Vander Wall pi stacking and hydrophobic interactions, which happened between ligands and the protein, have been studied. Compounds exhibiting strong affinity and interactions in the pocket where rosiglitazone binds will be taken for wet laboratory synthesis.

Antimicrobial resistance is one of the most pressing health issues of our days. The marine environment has proven to be a very rich source of diverse natural products with broad-spectra of biologically activities being a very helpful resource in the search for novel antimicrobial compounds. These structurally distinct molecules are revealing promising biological activities against a very large number of drug-resistant pathogenic bacteria and fungi, catching marine natural products attention in the discovery of new antimicrobial agents. Inspired by antimicrobial lichen xanthones [1] and fungi-derived alkaloids, two series of marine natural products mimics were prepared. The synthesized compounds were evaluated for their antimicrobial activity. Both series produced interesting compounds active against E. faecalis (ATCC 29212 and 29213) and S. aureus (ATCC 29213) with some synthetic alkaloids being active against a MRSA strain. Some revealed a potent fungistatic and fungicidal activity against dermatophytes clinical strains (T. rubrum, M. canis, and E. floccosum). These results highlight the potential of marine natural products as a source of new antimicrobial agents to revert resistance.

[1] D. I. S. P. Resende, P. Pereira-Terra, Â. S. Inácio, P. M. Costa, E. Pinto, E. Sousa, M. M. M. Pinto. Lichen Xanthones as Models for New Antifungal Agents. Molecules 2018, 23, 2617; doi:10.3390/molecules23102617

Acknowledgments: This work was partially supported through national funds provided by FCT/MCTES—Foundation for Science and Technology from the Ministry of Science, Technology, and Higher Education (PIDDAC) and the European Regional Development Fund (ERDF) through the COMPETE—Programa Operacional Factores de Competitividade (POFC) programme, under the Strategic Funding UID/Multi/04423/2013, the projects POCI-01-0145-FEDER-028736 and POCI-01-0145-FEDER-016790 (PTDC/MAR-BIO/4694/2014; 3599-PPCDT) in the framework of the programme PT2020, as well as by the project INNOVMAR—Innovation and Sustainability in the Management and Exploitation of Marine Resources (reference NORTE-01-0145-FEDER-000035, within Research Line NOVELMAR), supported by North Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). Solida Long thanks Erasmus Mundus Action 2 (LOTUS+, LP15DF0205) for full PhD scholarship. Diana I. S. P. Resende also acknowledge for her grant (NOVELMAR/BPD_2/2016-019) and Patrícia Pereira-Terra for her grant (NOVELMAR/BPD/2017/012).

Currently, one of the most urgent threats is antimicrobial resistance, which leads to the inefficacy of drugs in therapeutics, and can arise from several reasons, being the overexpression of efflux pumps one of them. These pumps are ubiquitous in bacteria, and their overexpression allows bacteria to develop multidrug resistance, through the extrusion of antimicrobial drugs. They can be divided into five families, being the resistance-nodulation-division (RND) family and the major facilitator superfamily (MFS) the most relevant. Efforts have been put towards a selective, efficient efflux pump inhibitor (EPI), and although some progress has been achieved, in the therapeutic scenario no EPIs have been approved.¹

Our group has experience in molecular docking and synthesis of aminated thioxanthones with modulatory activity in the mammal efflux pump P-glycoprotein (P-gp), which is also useful in the detoxification of xenobiotics.^2,3 Taking this into account, the aim of this work was the design of a virtual library of approximately 1.000 aminated (thio)xanthones, the performance of docking studies in bacterial efflux pumps whose crystal structure has been elucidated and available in the Protein Data Bank and in a model of the human P-gp. For the docking studies bacterial efflux pumps chosen were both from the RND family: AcrB, from the AcrAB-TolC efflux system,⁴ and MexB, from the MexAB-OprM efflux system.⁵

The compounds that will be selected for synthesis are the ones that virtually displayed good scores for the bacterial referred efflux pumps and lower scores for P-gp, since this would mean that, in vivo, these compounds would efficiently reduce antimicrobial resistance while not interfering with human detoxification pathways.

Acknowledgements: This research was developed under Project No. POCI-01-0145-FEDER-028736, co-financed by COMPETE 2020, Portugal 2020 and the European Union through the ERDF, and by FCT through national funds.

References:

1. Durães, F.; Pinto, M.; Sousa, E., Medicinal Chemistry Updates on Bacterial Efflux Pump Modulators. Curr Med Chem 2018, Feb 9. doi: 10.2174/0929867325666180209142612.
2. Palmeira, A.; Vasconcelos, M. H.; Paiva, A.; Fernandes, M. X.; Pinto, M.; Sousa, E., Dual inhibitors of P-glycoprotein and tumor cell growth: (re)discovering thioxanthones. Biochem Pharmacol 2012, 83 (1), 57-68.
3. Palmeira, A.; Rodrigues, F.; Sousa, E.; Pinto, M.; Vasconcelos, M. H.; Fernandes, M. X., New uses for old drugs: pharmacophore-based screening for the discovery of P-glycoprotein inhibitors. Chem Biol Drug Des 2011, 78 (1), 57-72.
4. Yu, E. W.; Aires, J. R.; McDermott, G.; Nikaido, H., A periplasmic drug-binding site of the AcrB multidrug efflux pump: a crystallographic and site-directed mutagenesis study. J Bacteriol 2005, 187 (19), 6804-15.
5. Sennhauser, G.; Bukowska, M. A.; Briand, C.; Grutter, M. G., Crystal structure of the multidrug exporter MexB from Pseudomonas aeruginosa. Journal of molecular biology 2009, 389 (1), 134-45.

Ethnopharmacological relevance: Cuscuta reflexa Roxb. belonging to the family Convolvulaceae, known as dodder is an Indian traditional medicinal plant with claims of antibacterial, antiproliferative, anti-inflammatory properties in literature.

Aim of the study: Present study was designed to investigate the protective effect of extracts of Cuscuta reflexa Roxb. against adjuvant induced arthritis.

Materials and methods: Arthritis was induced by intradermal injection of 0.1 ml of a 0.4% Complete Freund’s adjuvant. Arthritic rats were treated with methanol and aqueous extract of Cuscuta reflexa Roxb. MECR & AECR (300 mg/kg body weight, p.o.) respectively from the beginning of the study. Diclofenac sodium (10 mg/kg body weight, p.o.) was used as standard treatment. Protection against arthritis was investigated using various parameters like paw thickness, changes in whole body weight, weight of spleen and thymus, pain in inflammation by using thermal stimulus, radiological and histological analysis of the joint and serum levels of biochemical markers and inflammatory mediators (TNF-α and IL-6). Methanol extract of Cuscuta reflexa Roxb. (MECR) was fractionalized and its fraction was subjected to IR and LC/MS analysis.

Results: Treatment of arthritic rats with methanol and aqueous extracts of Cuscuta reflexa Roxb. significantly protected the animals from the arthritic changes as compared to the arthritic control group. Elevated levels of inflammatory cytokines (TNF-α and IL-6), lipid peroxidation and other biochemical and pathological changes associated with arthritis were normalized by the treatment of MECR and AECR which was also evident from the radiological and histological analysis of the joints. Pain associated with arthritis was significantly inhibited by Cuscuta reflexa Roxb..IR and LC-MS analysis of fraction isolated from MECR was identified as Quercetin.

Conclusion: Results suggest significant antiinflammatory and antiarthritic effects produced by MECR and AECR. Cuscuta reflexa Roxb. may serve as a candidate with strong potential to be useful in arthritis.

Lady's bedstraw (Galium verum L.) are often used in the traditional medicine of the Balkan countries. In previous studies it has been shown that the main components of G. verum extracts, phenols and flavonoids are in the form of heterosides with different saccharides. Also, different types of terpenes, which are the main components of essential oil, are present. In this study, we wanted to identify the optimal conditions for the extraction of phenolic compounds from G. verum. For extraction we used methanol, 96% ethanol and 70% ethanol at five time intervals (15, 30, 60, 90 and 120 minutes). Extraction was carried out in conical flasks, on a shaker, at room temperature (25°C). The total phenolic content in the extracts was determined spectrophotometrically, using the standard method with the Folin–Ciocalteu reagent, and the results were expressed as gallic acid equivalents (GAE – mg of gallic acid/g of crude extract). The total phenolic content when 70% ethanol was used were 33.36±1.94, 64.06±1.51, 112.36±3.23, 141.40±3.06 and 142.77±3.28 GAE in 15, 30, 60, 90 and 120 minute respectively. We used historical data design (HDD) in Design Expert 7.0 software to identify optimal extraction conditions. ANOVA analysis showed that there is a statistically significant difference in the amount of extracted phenols in between all time intervals except between 90 and 120 minutes. The results of the optimization analysis showed that the highest yield of total phenols (145.78 GAE) was obtained using 70% ethanol as a solvent in a time of 107.03 minutes (desirability level = 0.996), while the lowest yield was obtained using methanol as a solvent. Equation of model when 70% ethanol is used as a solvent is: Total phenols = 0.26 + 2.30 ∗time + 4.74^−3 ∗ time^2 − 3.70^−5 ∗ time^3. The experimental values agreed with those predicted, thus indicating suitability of the model employed and the success of HDD in optimizing the extraction conditions.

Liquidambar formosana (also known as maple) is a tall deciduous tree widely distributed in various regions of the South of the Qinling Mountains and Huaihe River in China, and also found in Northern Vietnam, Laos and South Korea. L. formosana is a famous ornamental plant for leaves are green in spring and summer, and red in autumn. Different plant parts of L. formosana, such as leaf, fruit, bark, and resin, are proved to be treasures as natural medicinal plant resources [1]. Among the bioactive constituents, several diterpenoid acids of the abietane family have been identified. Abietic acid (1) occurs in plants of the genus Abies and is the first member of a class of plant metabolites, the abietane-type diterpenoids. They are characterized by a tricyclic ring system and have shown a wide range of chemical diversity and biological activity.[2,3] Medicinal chemists have studied derivatives of two readily available materials such as dehydroabietic acid (2) and dehydroabietylamine (3, DHAA).[3] To date, there is only one commercial drug, Ecabet® [ecabet sodium (4)], based on abietanes, which is used for the treatment of reflux esophagitis and peptic ulcer disease. Ferruginol (5) exhibits anticancer effects in human ovarian cancer and inhibition of cancer cell migration. Recent studies of sugiol (6) demonstrated in vivo antitumor activity in DU145 prostate xenografts. These biological reports and the simultaneous isolation, (in 2014) by Hua and co-workers, of the new abietane liquiditerpenoic acid A (7), a sugiol analogue, from the resin of Liquidambar formosana [4] and from Pinus massoniana,[5] by Kuo and co-workers named independently as abietopinoic acid, prompted us to synthesize it and study its biological properties along with some analogues.

References

[1] Ouyang, X. L.; Yi, S.; Lu, H. Y.; Wu, S. M.; Zhao, H. Q. Eur. J. Med. Plants 2016, 17, 1-11.

[2] For a review on this topic, see: González, M. A. Nat. Prod. Rep. 2015, 32, 684-704.

[3] For a review on this topic, see: González, M. A. Eur. J. Med. Chem. 2014, 87, 834-842.

[4] Shang, H.-J.; Li, D.-Y.; Wang, W.-J.; Li, Z.-L.; Hua, H.-M. Nat. Prod. Res. 2014, 28, 1-6.

[5] Mohamed, H. A.; Hsieh, C.-L.; Hsu, C.; Kuo, C.-C.; Kuo, Y.-H. Helv. Chim. Acta 2014, 97, 1146-1151.

Ethnopharmacological knowledge provides useful information for experimental pharmacological studies. Based on this knowledge, this study was aimed at isolating the bioactive compound in Senecio serratuloides which is used in treating hypertension in Eastern Cape Province of South Africa. Senecio serratuloides was serially extracted using hexane, dichloromethane, ethyl acetate and methanol. The fractions were tested for their phytochemical constituents, antioxidant capacity and antihypertensive properties. Methanol fraction was subjected to thin layer and column chromatography for isolation of bioactive compound whose acute antihypertensive effects was determined. Ethyl acetate and methanol fractions had more phytochemicals, better antioxidant capacity and significantly (p<0.001) prevented increase in systolic and diastolic blood pressure. The bioactive compound (Estran-3-one, 17-(acetyloxy)-2-methyl-, (2à,5à,17á)-) isolated from the methanol fraction significantly prevented increase in blood pressure from the first to the fourth hour after treatment. Senecio serratuloides is a potential source of lead compounds for treating hypertension.

Acacia auriculiformis Benth. is an evergreen shrub traditionally used as a remedy in the cure of itching, aches, allergy, rheumatism, and sore eyes. But recently, this shrub has been explored for antidiabetic activity. Here in this work, we have attempted to evaluate various leaves extracts of Acacia auriculiformis Benth. for α-glucosidase assay and α-amylase assay and thereafter the bioactive ethyl acetate leaves extract was subjected to GC-MS analysis. The in vitro antidiabetic evaluation showed promising results. The % inhibition of ethyl acetate leaves extract in the α-glucosidase assay and the α-amylase assay was found be 94.259% and 95.259% respectively, at a concentration of 10 μg/ml. The LC-MS results revealed the presence of phenolic compounds (phenol, 2,4-bis(1,1-dimethylethyl); 2,4-Ditert-butylphenol) and various esters (hexadecanoic acid, methyl ester; 1,2-benzenedicarboxylic acid, butyl octyl ester; hexadecanoic acid, 2,3 bis[(trimethylsilyl)oxy]propyl ester). Those compounds could be responsible for the desired antidiabetic activity.

Over several years, xanthone derivatives have been the core of several studies, essentially due their wide range of biological and pharmacological activities [1]. Recently, chiral derivatives of xanthones (CDXs) have come to arouse great interest considering enantioselectivity studies associated with biological activities [2,3] as well as selectors for chiral stationary phases (CSPs) in liquid chromatography (LC) [4,5].

From the perspective of Medicinal Chemistry, some CDXs synthetized by our group revealed interesting biological activities [2,3]. Besides the potential as new drugs, CDXs afford promising LC enantioresolution results [6].

In a continuation of our study, new enantiomerically pure CDXs were synthetized for biological activity evaluation as well as selectors for new CSPs, confirming that CDXs have important applications not only in the field of Medicinal Chemistry but also for analytical applications.

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 and ERDF, in the framework of PT2020, by projects PTDC/MAR-BIO/4694/2014 (reference POCI-01-0145-FEDER-016790; Project 3599-PPCDT), and project No. POCI-01-0145-FEDER-028736, co-financed by COMPETE 2020, Portugal 2020 and the European Union through the ERDF, and by FCT through national funds, as well as by the Portuguese NMR Network, and CHIRALXANT-CESPU-2018.

[1] Shagufta, A.I. Eur. J. Med. Chem., 2016, 116, 267-280.

[2] Fernandes, C. et al. Bioorg. Med. Chem. 2014, 22, 1049-1062.

[3] Fernandes, C. et al. Pharmaceuticals, 2017, 10, 50, doi:10.3390/ph10020050.

[4] Phyo, Y.Z. et al. Molecules, 2018, 23, 142, doi:10.3390/molecules23010142.

[5] Carraro, M.L. et al. Chirality, 2017, 1–10

[6] Fernandes, C. et al. Chirality, 2017, 29(8),430-442.