Antimicrobial triterpenes from the stem bark of Crossopteryx febrifuga

Phytochemical investigation of the stem bark extract of Crossopteryx febrifuga resulted in the isolation of epimeric mixtures of 3β-urs-12,20(30)-diene-27,28-dioic acid and 18-epi-3β-urs-12,20(30)-diene-27,28-dioic acid (1), as well as: 3β-D-glucopyranosylurs-12,20(30)-diene-27,28-dioic acid and 18-epi-3β-D-glucopyranosylurs-12,20(30)-diene-27,28-dioic acid (2), together with some known compounds such as the monoglyceride of palmitic acid, as well as β-sitosterol and its glucoside. The structures of the isolated compounds were determined by application of spectroscopic methods. The MeOH extract and compounds 1 and 2 were examined for antimicrobial activity in in vitro assays against bacteria (Enterobacter aerogenes ATCC13048, Escherichia coli ATCC8739, Klebsiella pneumoniae ATCC11296, Staphylococcus aureus) and fungi (Candida parapsilosis, Candida albicans ATCC 9002 and Cryptococcus neoformans IP 90526). The tested samples showed selective activities. The antibacterial and antifungal activities of compound 2 (MIC=8-64 μg/mL) were in some cases equal to or even higher than those of the respective reference drugs chloramphenicol (MIC=16- 64 μg/mL) and nystatin (MIC=128-256 μg/mL).