Anti-tubercular agents from Ammannia baccifera (Linn.)
摘要:
Ammannia baccifera is an important component of various traditional Chinese herbal formulations. The samples of A. baccifera were extracted with methanol and the methanolic extract was successively fractionated with n-hexane, chloroform and n-butanol. The serial chromatographic separation of chloroform and n-butanol fractions resulted in the isolation and characterization of betulinic acid (1), 4-hydroxy-alpha-tetralone (2), tetralone-4-O-beta-D-glucopyranoside (3) and ellagic acid (4). Further, the compound 2 was chemically modified into its five semi-synthetic acyl and aryl derivatives (2A-2E) namely; 4-O-m-anisoyl-alpha-tetralone (2A), 4-O-benzoyl-alpha-tetralone (2B), 4-O-palmitoyl-alpha-tetralone (2C), 4-O-(3,4,5-trimethoxybenzoyl)-alpha-tetralone (2D) and 4-O-myricitoyl-alpha-tetralone (2E). The tetralone group compounds 2, 3 and semi-synthetic derivatives 2A-2E were evaluated for their in vitro anti-tubercular activity against Mycobacterium tuberculosis H37Rv by BACTEC-460 radiometric susceptibility assay. The compounds 2 and 2E have shown significant anti-tubercular activity (MIC 50 mu g/ml) while 2B was moderate active (MIC 100 mu g/ml) against the pathogen. The results of SAR study indicated that substitutions in alpha hydroxyl group of 4-hydroxy-alpha-tetralone either retards or have no increasement in in vitro anti-tubercular potential.
4-Hydroxy-<i>α</i>-Tetralone and its Derivative as Drug Resistance Reversal Agents in Multi Drug Resistant<i>E</i><i>scherichia coli</i>
作者:Gaurav R. Dwivedi、Harish C. Upadhyay、Dharmendra K. Yadav、Vigyasa Singh、Santosh K. Srivastava、Feroz Khan、Nandan S. Darmwal、Mahendra P. Darokar
DOI:10.1111/cbdd.12263
日期:2014.4
The purpose of present investigation was to understand the drug resistance reversal mechanism of 4‐hydroxy‐α‐tetralone (1) isolated from Ammannia spp. along with its semi‐synthetic derivatives (1a–1e) using multidrug resistant Escherichia coli (MDREC). The test compounds did not show significant antibacterial activity of their own, but in combination, they reduced the minimum inhibitory concentration (MIC) of tetracycline (TET). In time kill assay, compound 1 and its derivative 1e in combination with TET reduced the cell viability in concentration dependent manner. Compounds 1 and 1e were also able to reduce the mutation prevention concentration of TET. Both compounds showed inhibition of ATP dependent efflux pumps. In real time polymerase chain reaction (RT‐PCR) study, compounds 1 and 1e alone and in combination with TET showed significant down expression of efflux pump gene (yojI) encoding multidrug ATP binding cassettes (ABC) transporter protein. Molecular mechanism was also supported by the in silico docking studies, which revealed significant binding affinity of compounds 1 and 1e with YojI. This study confirms that compound 1 and its derivative 1e are ABC efflux pump inhibitors which may be the basis for development of antibacterial combinations for the management of MDR infections from inexpensive natural product.