Cytotoxic ent-abietane diterpenoids, banyangmbolides A-E, from the leaves of Suregada occidentalis

The chemical investigation of a leaf extract from a herbarium specimen of Suregada occidentalis collected in Banyang Mbo Wildlife Sanctuary, Southwest Region, Cameroon, yielded five undescribed ent-abietane diterpenoids, banyangmbolides A-E, (1–5), and four known diterpenoids, gelomulides A (6), B (7), D (8) and O (9). The structures of the isolated compounds were determined using NMR, IR, ECD and HRESIMS. Compounds 5, 7 and 8, showed 48–55% inhibition at 200 μM against FM-55-M1 human melanoma cells.