Cytotoxicity of diterpenes from Premna schimperi and Premna oligotricha. 
The cytotoxicity of two diterpenes from Premna schimperi and Premna oligotricha (Verbenaceae) was studied using the MTT assay.  Their cytotoxic activity against three human (HeLa, SK.N.SH, and ECV 304) and two murine (L929 and RAW 264.7) carcinoma cell lines varied between 1.5 to 35 micrograms/ml and was comparable with azauridine and chlorambucil.