The root back of Melia toosendan afforded four new limonoids with a C-
19/C-29 bridged acetal structure, together with two known limonoids, 1
2 alpha-hydroxyamoorastatone and its 12-acetate, The new compounds wer
e elucidated as 1-O-acetyltrichilin H and 29-O-substituted amoorastato
ne derivatives, named neoazedarachins A, B and D, by spectroscopic and
chemical means, Their antifeedant activity was also studied.