Clerodendrins from Clerodendron trichotomum and their feeding stimulant activity for the turnip sawfly

Adults of the turnip sawfly, Athalia rosae ruficornis, are stimulated to fe ed pharmacophagously on the leaves of Clerodendron trichotomum by bitter ne o-clerodane diterpenoids contained in glandular organs on the leaf surface. Four new neo-clerodane analogues; clerodendrins E, F, G and H, were isolat ed from leaf surface extracts of C. trichotomem. clerodendrins E, F and G w ere characterized as analogues of clerodendrin A, in which the acyl moiety at the C-3 beta position was replaced by 2-acetoxy-2-methylpropanoyl, 2,3-d iacetoxy-2-methylbutanoyl and 2-methylbutanoyl moieties, respectively. Cler odendrin H was shown to be the 7,8-dihydro-derivative of F. Of the seven cl erodendrins (A-H) isolated from C. trichotomum, only the 7,8-dihydro analog ues (clerodendrins B, D and H) exhibited distinct feeding stimulant activit y to adults of the turnip sawfly. (C) 1998 Published by Elsevier Science Lt d. All rights reserved.