Degraded and oxetane-bearing limonoids from the roots of Melia azedarach

Brine shrimp lethality test (BST)-guided fractionation of a methanol extract of the roots of Melia azedarach resulted in the isolation of two new limonoids, 9 alpha-hydroxy-12 alpha-acetoxyfraxinellone (1) and 7,14-epoxyazedarachin B (2), together with the known compounds, 12 alpha-hydroxyfraxinellone (4), 9 alpha-hydroxyfraxinellone (5), azedarachin B (6), and neoazedarachin B (7). The structures of 1 and 2 were elucidated by analysis of spectroscopic data and comparison of their NMR data with those of the known compounds. Compounds 1, 2 and 47 exhibited significant activity in the BST, in particular, azedarachin B (6) showed remarkable BST activity with an LC50 value of 0.0098 mu M.