Cytotoxic triterpenoids from Azadirachta indica.

Two new tirucallane triterpenoids, 24,25-epoxy-3 β-hydroxy-20-oxo-7-tirucallene (1) and 22,23;24,25-diepoxy-3 β-hydroxy-7-tirucallene (2), and a new tetranortriterpenoid, 4 α-hydroperoxy-6- O-acetylnimbandiol (3), along with eight known compounds, were isolated from the branches and leaves of Azadirachta indica. Their structures were elucidated through spectroscopic and chemical methods. The cytotoxic assay showed that the abundant constituent nimbolide (8) had obvious cytotoxic activities against HL-60, SMMC7721, A549, MCF-7, and SW-480 cell lines, with IC₅₀ values of 0.8 ± 0.1, 2.2 ± 0.2, 1.9 ± 1.3, 4.5 ± 1.1, and 2.3 ± 0.1 µM, respectively.