A new ent -clerodane diterpenoid from Crassocephalum bauchiense Huch. (Asteraceae)

A phytochemical investigation of the whole plant of Crassocephalum bauchiense Huch. resulted in the isolation of a new clerodane diterpenoid, ent -2β,18,19-trihydroxycleroda-3,13-dien-16,15-olide ( 1 ), together with two known flavonoids 3′,5-dihydroxy-4′,5′,6,7,8-pentamethoxyflavone ( 2 ) and 4′,5-dihydroxy-3′,5′,6,7,8-pentamethoxyflavone ( 3 ). The compounds were tested against the chloroquine-sensitive 3D7 strain of Plasmodium falciparum.

Compound 2 showed weak activity (IC 50 = 10.1 g/mL) whilst compounds 1 and 3 were inactive. The structures of the compounds were elucidated by using detailed spectral analyses, especially 1 H and 13 C NMR, 1 H– 1 H COSY, NOESY, HMBC and HR-ESI-MS.