Antimicrobial diterpenoids and triterpenoids from the stem bark of Croton macrostachys

Abstract

Antimicrobial-guided fractionation of the EtOAc extract of the stem bark of Croton macrostachys afforded five known compounds including two lupane triterpenoids, lupeol (1) and betulin (2), and three clerodane diterpenoids, floridolide A (3), hardwickic acid (4) and 12-oxo-hardwickic acid (5). Their structures were elucidated on the basis of spectral studies and comparison with published data. The EtOAc extract and compounds 1, 2, 4 and 5 were evaluated for their antibacterial and antifungal activities by macro-dilution method. The extract displayed significant antibacterial and antifungal activities (MIC = 31.25-1000 µg/ml). Betulin (2) and 12-oxo-hardwickic acid (5) were the most active compounds (MIC = 7.81-500 µg/ml). The most sensitive microorganisms were Staphylococcus aureus ATCC 25922 for bacteria and two Candida species, Candida albicans ATCC 24433 and Candida krusei ATCC 6258, for fungi. The isolation of these active antibacterial and antifungal principles supports the use of C. macrostachys in traditional medicine for the treatment of microbial infections