Antitubercular constituents from Premna odorata Blanco

ETHNOPHARMACOLOGICAL RELEVANCE

Premna odorata Blanco (Lamiaceae) is a medicinal plant traditionally used in Albay Province, in southeastern Luzon, Philippines to treat tuberculosis. This study aimed to determine the antitubercular property of the crude extract and sub-extracts of the leaves, and to isolate the bioactive principles from the active fractions.

MATERIALS AND METHODS

Through extraction, solvent polarity-based fractionation and silica gel chromatography purification of the DCM sub-extract, compound mixtures from the bioactive fractions were isolated and screened for their in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv using the colorimetric Microplate Alamar Blue assay (MABA).

RESULTS

The crude methanolic extract and sub-extracts showed poor inhibitory activity against Mycobacterium tuberculosis H37Rv (MIC≥128µg/mL). However, increased inhibitory potency was observed for fractions eluted from the DCM sub-extract (MIC=54 to 120µg/mL). Further purification of the most active fraction (MIC=54µg/mL) led to the isolation of a 1-heneicosyl formate (1), 4:1 mixture of β-sitosterol (2), stigmasterol (3) and diosmetin (4), which were identified through GC-MS analysis (with dereplication) and NMR experiments. The MIC of compound 1 was 8µg/mL.

CONCLUSIONS

The results of this study provide scientific basis for the traditional use of Premna odorata as treatment for tuberculosis.

Studies on molecular properties prediction, antitubercular and antimicrobial activities of novel quinoline based pyrimidine motifs

In the present study, a series of 3-((6-(2,6-dichloroquinolin-3-yl)-4-aryl-1,6-dihydro-pyrimidin-2-yl)thio)propanenitriles 5a-o were synthesized and subjected to molecular properties prediction and drug-likeness model score by Molinspiration property calculation toolkit and MolSoft software, respectively. Compound 5m (4-OCH3) was found to be maximum drug-likeness model score (0.42). Among the screened compounds, 5m showed the most promising antitubercular activity with MIC of 0.20 μg/mL, while compounds 5g, 5k and 5m displayed broad spectrum antibacterial activity against all the bacterial strains. Moreover, compound 5k was found to be the most potent antifungal agent. Further, the results of preliminary MTT cytotoxicity studies on HeLa cells suggested that potent antimicrobial activity of 5g, 5k and 5m was escorted by low cytotoxicity.

Discovery of novel bis-oxazolidinone compounds as potential potent and selective antitubercular agents

A variety of new mono-oxazolidinone molecules by modifying the C-ring of Linezolid, a marketed antibiotic for MRSA, were synthesized and tested for their in vitro antibacterial activities against several Staphylococcus aureus, Mycobacterium smegmatis and two Gram-negative bacteria strains (Escherichia coli and Pseudomonas aeruginosa). Among them, compounds 4-7 displayed moderate antimicrobial activities. After development of a second oxazolidinone ring in the western part of the mono-oxazolidinone compounds 4-7 by a ring closure reaction with N,N'-carbonyldiimidazole (CDI), we found thus obtained bis-oxazolidinone compounds 22-25 possess excellently inhibitory activities against H37Rv but poor or no effects on other test bacteria. Among them, bis-oxazolidinone compound 22 and 24 are the most potent two compounds with a same MIC value of 0.125μg/mL against H37Rv virulent strain. Compound 22 also exhibited extremely low cytotoxicity on monkey kidney Vero cells with a selective index (IC50/MIC) over 40,000, which suggested bis-oxazolidinone compound 22 is a promising lead compound for subsequent investigation in search of new antitubercular agents.

QSAR and Molecular Docking Studies of Oxadiazole-Ligated Pyrrole Derivatives as Enoyl-ACP (CoA) Reductase Inhibitors

A quantitative structure-activity relationship model was developed on a series of compounds containing oxadiazole-ligated pyrrole pharmacophore to identify key structural fragments required for anti-tubercular activity. Two-dimensional (2D) and three-dimensional (3D) QSAR studies were performed using multiple linear regression (MLR) analysis and k-nearest neighbour molecular field analysis (kNN-MFA), respectively. The developed QSAR models were found to be statistically significant with respect to training, cross-validation, and external validation. New chemical entities (NCEs) were designed based on the results of the 2D- and 3D-QSAR. NCEs were subjected to Lipinski’s screen to ensure the drug-like pharmacokinetic profile of the designed compounds in order to improve their bioavailability. Also, the binding ability of the NCEs with enoyl-ACP (CoA) reductase was assessed by docking.