Antimicrobial and in silico studies of the triterpenoids of Dichapetalum albidum

Here we report a new polyhydroxylated triterpene, 20,60,21a-trihydroxyfriedelan-3-one (4) isolated from the root and stem bark of Dichapetalum albidum A. Chev (Dichapetalaceae), along with six known triterpenoids (1-3, 5, 6, 8), sitosterol-30-O-D-glucopyranoside (9), a dipeptide (7), and a tyramine derivative of coumaric acid (10). Friedelan-3-one (2) showed an antimicrobial activity (IC50) of 11.40 & mu;g/mL against Bacillus cereus, while friedelan-3a-ol (1) gave an IC50 of 13.07 & mu;g/ mL against Staphylococcus aureus with ampicillin reference standard of 19.52 & mu;g/mL and 0.30 & mu;g/ mL respectively. 30-Acetyl tormentic acid (5) showed an IC50 of 12.50 & mu;g/mL against Trypanosoma brucei brucei and sitosterol-30-O-D-glucopyranoside (9) showed an IC50 of 5.06 & mu;g/mL against Leishmania donovani with respective reference standards of IC50 5.02 & mu;g/mL for suramin and IC50 0.27 & mu;g/mL for amphotericin B. Molecular docking of the isolated compounds on the enzyme glucose-6-phosphate dehydrogenase (G6PDH) suggested 30-acetyl tormentic acid (5) and sitosterol-30-O-D-glucopyranoside (9) as plausible inhibitors of the enzyme in accordance with the experimental biological results observed.