A chloroform extract of Vernonia amygdalina Del. was found to show significant inhibitory activity in vitro against cells derived from human carcinoma of the nasopharynx (KB) carried in tissue culture. The isolation and structural elucidation are reported of vernodalin (1) and vernomygdin (8), two new cytotoxic sesquiterpene lactones. Mass spectrometry indicated a C19H20O7 molecular formula for vernodalin. Acidic hydrolysis in methanol gave methanol adduct 2, identical with the methanol adduct of vernolepin. An additional interrelation with vernolepin (5) was effected by conversion of vernodalin to hexahydrovernolepin isobutyrate (4). Elemental analysis and mass spectrometry indicated a C19H25O7 molecular formula for vernomygdin (8). Its structure and relationship to vernolide (7) was established by catalytic hydrogenation to tetrahydrovernolide (9). © 1969, American Chemical Society. All rights reserved.
