Two novel diterpenes from the stems and leaves of tropical seagrass in the South China sea.

Two novel diterpenes Enhoidin A () and Enhoidin B () featuring an unusual gibberellane skeleton were isolated from the stems and leaves of . Their structures were elucidated on the basis of spectroscopic analysis including 1D and 2D NMR techniques and HR-ESI-MS. This is the first time that this type of lactone ring between C-18 and C-20 has been found among gibberellanes from the tropical seagrasses. Evaluation of the all compounds for cytotoxicity against four human cancer cell lines (MCF-7, HCT-116, HepG-2 and HeLa), and showed moderate cytotoxic activities.