Inhibitory antibacterial activity of two novel dihydroxy fatty acids and other constituents from the stem bark of Trichilia gilgiana Harms (Meliaceae)

Abstract

Two novel dihydroxy-fatty acids, gilgianic acid (1), phenylgilgianic acid (2) together with four known compounds: ß-sitosterol (3), stigmasterol (4), sitosterol-3-O-ß-D-glycoside (5) and lupeol (6) were isolated from the stem bark of Trichilia gilgiana. The structures of compounds 1–6 were elucidated based on spectroscopic (1 D and 2 D NMR) and HR-ESI-MS data as well as comparison with relevant literature data. This study reports for the first time the isolation of fatty acids from the genus Trichilia. Compounds 3–6 had already been isolated from trichilia genus. The crude extract and compounds 1–5 were tested for their inhibitory effect against a panel of bacterial strains using the microdilution technique with ampicillin, nalidixic acid and streptomycin as standard drugs. The crude extract and the tested compounds were found to exhibit significant activity against Bacillus subtilis and Klebsiella aerogenes with a MIC value of 2.3 µg/mL. Compounds 3 and 5 were also found to be active against Enterococcus faecalis with a MIC value of 2.3 µg/mL.