New limonoids isolated from the bark of Melia toosendan

Two new limonoids, 12-ethoxynimbolinins G and H (compounds 1 and 2 ), and one known compound, toosendanin (Chuanliansu) (compound 3 ), were isolated from the bark of Melia toosendan. Their structures were elucidated by spectroscopic analysis and X-ray techniques. The absolute configuration of toosendanin ( 3 ) was established by single-crystal X-ray diffraction. Compounds 1-3 were evaluated for their cytotoxicity against five tumor cell lines.