A new antibacterial diarylpropanoid and other constituents from Lannea velutina A. Rich (Anacardiaceae) and their chemotaxonomic significance

Phytochemical investigation of the methanol extracts from the stem bark and leaves of Lannea velutina afforded a new diarylpropanoid (1) and eighteen previously described compounds from other plants. They included eleven flavonoids (2–12), three triterpenoids (13–15), three steroids (16–18) and one sugar (19). The structure of compound 1 was established by analysis of its spectroscopic and spectrometric data. All the isolated compounds are here reported for the first time from L. velutina species while only compounds 3, 6, 8, 10, 13–16 and 18 were previously reported from the genus Lannea. The extracts, fractions, and compounds were subjected to in vitro antibacterial assays against one Gram-positive (Enterococcus faecalis ATCC 29212) and three Gram-negative (Escherichia coli ATCC 8739, Salmonella Typhi ATCC 6539 and Pseudomonas aeruginosa 4C 76110) bacteria. The MeOH extract from the stem bark, its chromatographic fraction C and the EtOAc partitioned leaves extract showed significant activity against the growth of E. faecalis, E. coli and P. aeruginosa (16 ≤ MIC ≤64 μg/mL). Lannepoxide (1) inhibition activities were 16 ≤ MIC ≤128 μg/mL against the four bacterial strains. The findings demonstrated the chemotaxonomic significance of the isolated compounds and their potential as antimicrobial agents.