Four pentacyclic triterpenoids with antifungal and antibacterial activity from Curtisia dentata (Burm.f) C.A. Sm. leaves

Ethnopharmacological relevanceCurtisia dentata is used in southern Africa to treat various diseases of bacterial and fungal origin in humans and animals to such a degree that the species is vulnerable and declining [Dold, A.R., Cocks, M.L., 2001. Traditional veterinary medicine in the Alice district of the Eastern Cape Province, South Africa. South African Journal of Science 97, 375–379]. Preliminary studies indicated good activity against Candida albicans.Aim of the studyThe phytochemistry and antimicrobial activity of this plant species has not been extensively investigated, and a closer examination of the compounds responsible for antimicrobial activity was warranted.Materials and methodsBroth microdilution assay and bioautography were used to evaluate antibacterial and antifungal activity in Curtisia dentata leaf extracts and fractions. Bioassay-directed fractionation using column chromatography yielded four compounds characterised by spectroscopic methods.ResultsLupeol (1), betulinic acid (2), ursolic acid (3) and 2α-hydroxyursolic acid (4) were isolated from Curtisia dentata leaves. Betulinic acid, ursolic acid and 2α-hydroxyursolic acid appreciably inhibited fungal growth with MIC values ranging from 8 to 63 μg/mL.ConclusionsThe isolation of four antibacterial and antifungal triterpenoids is reported for the first time from Curtisia dentata. This study provides information on the antimicrobial compounds of this species, as well as a preliminary rationale for the use in traditional South African medicine.