Synthesis and in vitro anticancer studies of novel C-2 arylidene congeners of lantadenes.

The antitumor pentacyclic triterpenoids, Lantadene A (1) and B (2) were isolated from the leaves of weed Lantana camara L. (Verbenaceae) and were structurally transformed to bioactive intermediates 3-6. The Claisen-Schmidt reaction of 22β-hydroxy-3-oxoolean-12-en-28-oic acid (5) with requisite aldehydes afforded 2-arylidene-22β-hydroxy-3-oxoolean-12-en-28-oic acids (7-16). The compounds were evaluated for their in-vitro anticancer activity by National Cancer Institute (NCI), USA and some of these compounds showed marked cytotoxicity in micromolar range. The mean graph midpoint (MG_MID) value of compound 3 (MG_MID -5.69) was higher than standard drug cisplatin (MG_MID -5.66) while comparable in case of compound 12 (MG_MID -5.52). The NCI's COMPARE molecular mechanistic analysis showed that these compounds were in significant correlations with activity patterns of mechanistic set of compounds (PCC ≥ 0.60).