Novel bioactive clerodane diterpenoids from the leaves and twigs of Casearia sylvestris

Fractionation of a methanol extract of the leaves and twigs of Casearia sylvestris, as directed by activity against KB cell cytotoxicity, led to the isolation of three novel clerodane diterpenoids, casearvestrins A?C (1?3). The structures of 1?3 were deduced from one- and two-dimensional NMR experiments, including relative stereochemical assignments based on ROESY correlations and COSY coupling constants. All three compounds displayed promising bioactivity, both in cytotoxicity assays against a panel of tumor cell lines and in antifungal assays via the growth inhibition of Aspergillus niger in a disk diffusion assay.