Anthocleistenolide B, a New Secoiridoid from Anthocleista liebrechtsiana De Wild & T. Durand

Drug resistance due to the extensive abuse and over-use of antibiotics has become an increasingly serious problem and researchers started to use plants as an alternative source of new antibiotics. The aim of the present study was to assess the antimicrobial properties of secondary metabolites isolated from A. liebrechtsiana. A new secoiridoid derivative, anthocleistenolide B (1), along with three known compounds, the monoterpene diol, djalonenol (2), the xanthone O-glycoside, decussatin 1-O-β-D-glucopyranoside and the fatty acid, dotriacontanoic acid (4) was isolated from the leaves and bark of this plant. Their structures were elucidated by extensive analysis of spectroscopic (1D and 2D NMR) and mass spectrometric data. The isolated compounds were screened for their antimicrobial properties against five strains of bacteria (two gram positive: Staphylococcus aureus 29213, Enterococcus faecalis ATCC 25922 and three gram negative: Escherichia coli ATCC51299, Proteus mirabilis (isolate), and Pseudomonas aeruginosa QC76110), but all were inactive.