New bioactive triterpenoids and antimalarial activity of Diospyros rubra Lec.

The first investigation of the chemical constituents and bioactivities of Diospyros rubra Lec. is reported. D. rubra extracts were screened for antimicrobial, antimalarial and cytotoxic activities. They were only shown to be active antimalarials. The extracts with good antimalarial activity were isolated and extensively purified to give lupeol (1), lupenone (2), betulin (3), lupeol acetate (4), 28-O-acetylbetulin (5), β-sitosteryl-3-O-β-D-glucopyranoside (6) and a mixture of β-sitosterol and stigmasterol. Some of the isolates were tested for antimicrobial and cytotoxic actions. Betulin (3) displayed antimicrobial activity against Streptococcus pyogenes with a minimum inhibitory concentration (MIC) of 85 μg/mL. Interestingly, bioactive fractions all selectively exerted some antimicrobial activity against Corynebacterium diphtheriae NCTC 10356 with the MIC range of 64-256 μg/mL. The study provides data to support the medicinal importance of the D. rubra.