Chemical constituents and antimicrobial activity of the aerial part of Solanum betaceum Cav. (Solanaceae)

A new saponin namely diosgeninoside (25 R-spirost-5-en-3-O-[β-_D-glucopyranosyl (1→2) - β-_D-glucuronic acid]) and a new fatty acid betacic acid: (Z)-8(S*),9(S*),10(R*)-trihydroxy-11-octadecenoic acid together with six known compounds: N-trans-coumaroyl tyramine, ergosta-7,22-dien-3β,5α,6β-triol, β-sitosterol, and β-sitosterol-3-O-β-_D-glucopyranoside, L-threitol and soya-cerebroside I were isolated from the methanolic extract of Solanum betaceum. The structures were elucidated by interpretation of their 1D and 2D NMR spectra and spectrometric data. The methanolic extract, the EtOAc and n-BuOH fractions, and several isolated compounds were tested for antibacterial activity against four bacteria (Staphylococcus aureus; Staphylococcus epidermidis; Escherichia coli; and Pseudomonas aeruginosa). The methanolic extract and the EtOAc fraction showed moderate activity against Staphylococcus aureus and Pseudomonas aeruginosa with MIC value of 128 µg/mL. Compound 1 showed moderate activity against Staphylococcus aureus with MIC value of 64 µg/mL.