Antimutagenic constituents from Monanthotaxis caffra (Sond.) Verdc.

Objectives Monanthotaxis caffra (Sond.) Verdc. (Annonaceae) has been reported to possess antitumoural properties. Preliminary screening showed that the crude methanolic leaf extract had strong antimutagenic effects against aflatoxin B 1 ‐induced mutagenicity. The aim of this study was to isolate and evaluate the antimutagenic properties of the active constituents from M. caffra . Methods Different chromatographic, spectroscopic and spectrometric techniques were used for the isolation and identification of the antimutagenic constituents. The antimutagenic effect of the extract and compounds was evaluated using Ames, Vitotox and Comet assays. Key findings Bioassay‐guided fractionation of the methanolic leaf extract yielded two antimutagenic compounds identified as (+)‐crotepoxide and 5,6‐diacetoxy1‐benzoyloxymethyl‐1,3‐cyclohexadiene. Crotepoxide had strong antimutagenicity in the Vitotox assay with an IC 50 value of 131 μg/ml. 5,6‐Diacetoxy‐1‐benzoyloxymethyl‐1,3‐cyclohexadiene showed strong antimutagenic activity in the Ames assay with an IC 50 value of 348.9 μg/plate and no antimutagenic activity in the Vitotox test. Furthermore, the compound was able to inhibit, block or prevent biotransformation of aflatoxin B 1 by repressing the proteins involved in transcription. Conclusions Crotepoxide and 5,6‐diacetoxy‐1‐benzoyloxymethyl‐1,3‐cyclohexadiene have the potential to mitigate the risks arising from consumption of aflatoxin B 1 ‐contaminated food and feed.