New trichothecenes isolated from Holarrhena floribunda

Bioassay-guided fractionation of an extract of Holarrhena floribunda stem, has led to the isolation of the new trichothecenes, 8-dihydrotrichothecinol A (1), loukacinol A (2), and loukacinol B (3), and the known compounds, tr ichothecolone (4), trichothecin (5), trichothecinol A (6), rosenonolactone (7), 6 beta-hydroxyrosenonolactone (8), and rosololactone (9). The structur es were determined by spectral and chemical methods, and absolute configura tions were established by a modified Horeau's method using HPLC. Compounds 1 and 6 exhibited significant cytotoxicity against several human tumor cell lines, whereas compound 8 showed moderate and weak antileishmanial activit y toward extracellular and intracellular Leishmania donovani, respectively.