Triterpenoids from the fruits of Azadirachta indica (Meliaceae).

Four new triterpenoids, indicalilacols A-D (1-4), were isolated from the MeOH extract of the fruits of Azadirachta indica, including a new 19(10→9β)abeo-tirucallane derivative, two new tirucallane-type triterpenoids, and a new euphane-type triterpenoid, along with three known tirucallane-type triterpenoids. Their structures were elucidated on the basis of spectroscopic analyses. The absolute configuration of 2 was elucidated by the chemical conversion of 2 into 21-oxo-melianodiol 24,25-acetonide. Compounds 2, 6-8 exhibited moderate cytotoxicity against three human cancer cell lines, including multidrug-resistant (MDR) cancer cells (KB-C2). Although compound 5 was not cytotoxic against any of the tested cancer cell lines, 5 showed cytotoxicity against KB-C2 cells in the presence of 2.5 μM colchicine, suggesting that 5 might have an MDR-reversal effect.