New meliacarpin-type (C-seco) and C-ring intact limonoids from the fruits of Melia toosendan.

Toosendansins E-I (1-5), five new limonoids together with nine known limonids(6-14), were isolated and identified from the fruits of Melia toosendan. Their skeletons were belonged to meliacarpins (1 and 2), nimbin (3), and vilasinins (4 and 5). All the isolates were identified using 1D & 2D NMR spectroscopic experiments, and the absolute configurations of 1 and 2 with 1,3-dicinnamoyl moieties were achieved by CD method. Compounds 1 and 4 showed moderate inhibitory activity against osteosarcoma cell line U-2 OS, and compound 4, ohchinolal (12), meliatoxin B1 (13) and 1,12-diacetyltrichichilin B (14) showed obvious reversal activity of multidrug resistance in MCF-7 cell line at 6.25 μM.