Bioassay-guided isolation and structure elucidation of cytotoxic stilbenes and flavonols from the leaves of Macaranga barteri

Bioassay-guided fractionation of the leaves of Macaranga barteri collected from Nigeria led to the isolation of three previously undescribed cytotoxic stilbenes, macabartebenes A–C (1–3), together with six known compounds including prenylated stilbenes: vedelianin (4), schweinfurthin G (5), and mappain (7), prenylated flavonols: 8-prenylkaempferol (6), and broussoflavonol F (8), and the geranylated flavonol, isomacarangin (9). The cytotoxicity of the compounds was evaluated against four human cancer cell lines, with vinblastine as the positive control and DMSO vehicle as the negative control. Vedelianin (IC50 = 0.32–0.54 μM) displayed the greatest antiproliferative activity across the panel of cancer cell lines amongst the compounds, while macabartebene A (IC50 = 0.60–0.79 μM) was the most potent of the previously unreported compounds. The compounds displayed varying selectivity towards the cancer cell lines compared to the normal human prostate cell line. The findings of this study revealed that M. barteri leaves contain several cytotoxic compounds. [Display omitted]