Anti-tumour clerodane-type diterpenes from Mitrephora thorelii.

Bioassay-guided fractionation of the crude extract of Mitrephora thorelii (Annonaceae) led to the isolation of two clerodane-type diterpenes. Their structures were characterised on the basis of spectroscopic methods as 6alpha,16,18-trihydroxycleroda-3(4),13(14)-dien-15,16-olide (1) and 16-hydroxycleroda-3(4),13(14)-dien-15,16-olide (2). Compound 1 is a new compound. Compounds 1 and 2 exhibited inhibitory activity against the proliferation of human hepatoma BEL-7402 cells in vitro. Compound 2 also showed an in vivo anti-tumour effect against the growth of hepatoma H22 in mice.