Clerodane diterpenoids from Croton crassifolius.

Seven new clerodane diterpenoids (1-7) were isolated from roots of Croton crassifolius, along with six known compounds. The structures were elucidated by extensive spectroscopic methods (IR, UV, HRESIMS, 1D NMR, and 2D NMR), and the structures of 1, 3, 4, and 7 were confirmed by single-crystal X-ray diffraction analyses. Compounds 1-13 were evaluated for in vitro antiviral activity against herpes simplex virus type 1 using the cytopathic effect reduction assay.