Cytotoxic triterpenoids and steroids from the bark of Melia azedarach.

Two new triterpenoids (1, 2) and two new steroids (3, 4) along with twelve related known compounds (5-16) were isolated from the bark of Melia azedarach. The new structures were elucidated by means of spectroscopic methods and molecular modeling studies and found to be 21,24-cycloeupha-7-ene-3 β,16 β,21 α,25-tetrol (1), 3 β-acetoxy-12 β-hydroxy-eupha-7,24-dien-21,16 β-olide (2), 29-hydroperoxy-stigmasta-7,24(28) E-dien-3 β-ol (3), and 24 ξ-hydroperoxy-24-vinyl-lathosterol (4). All isolated compounds were tested for their cytotoxic activity against three human cancer cell lines (A549, H460, HGC27) using the CellTiter Glo™ luminescent cell viability assay. Among them, compounds 2- 4, 24 ξ-hydroperoxy-24-vinyl-cholesterol (6), kulinone (7), meliastatin 3 ( 8), 3-oxo-olean-12-en-28-oic acid (10), and (22 E,24 S)-5 α,8 α-epidioxy-24-methyl-cholesta-6,22-dien-3 β-ol (12) were found to have cytotoxic effects, with IC₅₀ values of 5.6-21.2 µg/mL.