Isolation of bioactive limonoids from the fruits of Melia azedarach.

Two previously undescribed limonoids, 1-O-benzoyl-3-O-deactylnimbolinin C (1) and a pair of epimers named toosendalactonins A and B (12a and 12b), together with ten known compounds (2-11) were isolated from the fruits of Melia azedarach L. Their structures were determined by extensive spectroscopic methods, including 1D-, 2D-nuclear magnetic resonance, and mass spectrometry. All the isolated compounds were evaluated for their nitric oxide (NO) inhibition in lipopolysaccharide-activated microglia and nerve growth factor (NGF) production in astrocytes. Compounds 1-2 and 5-8 significantly inhibited NO production, which is comparable to the positive control, L-NMMA. Previously undescribed limonoid, compound 12, and two known limonoids, munronin K (3) and 12-O-methyl-1-O-deacetyl-nimbolinin B (4), showed the highest potency to increase the NGF production in C6 astrocytes.