New Structurally Diverse Limonoids from the Seeds of Khaya senegalensis

Twelve new limonoids (khasenegasins O-Z; 1-12) with three different kinds of skeletons, including eight mexicanolides, two gedunins, and two andirobins, together with four known limonoids (13-16) were isolated from the seeds of Khaya senegalensis. Their structures were determined by extensive spectroscopic analyses (HR-ESI-MS, 1D/2D NMR), and the absolute configurations of 1 and 2 were established by the electronic circular dichroism exciton chirality method. Moreover, a new andirobin-type limonoid (12) showed significant neuroprotective activity against glutamate-induced injury in primary rat cerebellar granule neuronal cells with increased viability of 83.3 ± 6.0 % at 10 µM and 80.3 ± 3.2 % at 1 µM.