Alkaloidal and other constituents from the root bark of Clausena excavata

Ten new carbazole alkaloids, clausine-M, -N, -O, -P, -Q, -R, -S, -U, -V and clausenatine-A, together with 39 known compounds were isolated and identified from the acetone extract of the root bark of Clausena excavata. Their structures have been elucidated by spectroscopic analyses. This is the first report of a decarboxylated carbazole alkaloid from a natural source. The presence of a C23-skeleton carbazole alkaloid in a plant of Clausena genus is also reported for the first time.