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DOI: 10.1055/s-0035-1545204
Anti-vancomycin-resistant Enterococcus faecium and E. faecalis activities of (-)-gossypol and derivatives from Thespesia garckeana
The roots extract of Thespesia garckeana yielded three sesquiterpenoids, (-)-gossypol (1), (-)-6-methoxygossypol (2) and (+)-6, 6′-dimethoxygossypol (3), and the stem bark afforded E-docosyl 3-(3, 4-dihydroxyphenyl) acrylate, stigmasterol and betulinic acid. Their structures were determined by full spectral analysis. Compound 1 showed potent antibacterial activity against vancomycin-resistant Enterococcus faecium (VRE) with IC50/MIC/MBC values of 0.89/2.50/10.00 µg/mL, whereas vancomycin was found to be inactive. The mono and di-methoxylated derivatives of 1 (i.e., 2 and 3) were less active with respective IC50/MIC/MBC values of 1.45/2.50/5.00 µg/mL and 3.35/10.00/10.00 µg/mL, respectively, against this microbe. Compound 2 was more potent than the standard drug against low level VRE strain with IC50/MIC/MBC values of 2.31/5.00/5.00 µg/mL (vs 2.45/10.00/> 20 µg/mL for vancomycin). Both 1 and 2 also showed good inhibition of C. glabrata (IC50 0.38 and 1.58 µg/mL) but were weakly active against methicillin-resistant S. aureus (IC50 4.66 µg/mL, 9.22 µg/mL).