Isolation and antimicrobial activities of a novel discolornolide and other compounds from Monanthotaxis discolor

Abstract

Characterisation of a novel discolornolide (1) isolated from a first time investigation of Monanthotaxis discolor is described. Other 6 known compounds, karatavin (2), N-acetylanonaine (3), quercetin-3-O-arabinose (4), stigmasterol (5), a mixture of stigmasterol and β-sitosterol (6) and octahydro-5-isopropyl-3-methyl-2-methyleneazulene-8,8-diol (7) isolated are also reported. The structures were established by spectroscopic methods. Citotoxicities and antimicrobial activities of the compounds and crude extracts are also reported whereby compound 1 showed in vitro antifungal activity against Candida albicans and Aspergilus niger at concentrations of 0.13 and 0.17 mg/ml with zones of inhibitions of 7.0 and 5.5 mm respectively. The compound also showed cyitotoxic activity in the brine shrimp test with LC₅₀ of 5.88 μg/ml. - Compound 4 exhibited antibacterial activity against E. coli and S. aureus. The compound also exhibited cytotoxic activities in the brine shrimp test with LC₅₀ of 24.73 μg/mL. The crude extracts exhibited varying citotoxic and in vitro antimicrobial activities.

Keywords: Antimicrobial; Monanthotaxis; Tanzania; cytotoxicity; discolornolide.