Cytotoxic and apoptosis-inducing activities of limonoids from the seeds of Azadirachta indica (neem).

Thirty-five limonoids, including 15 of the azadiradione type (1-15), five of the gedunin type (16-20), four of the azadirachtin type (21-24), nine of the nimbin type (25-33), and two degraded limonoids (34, 35), isolated from Azadirachta indica seed extracts, were evaluated for their cytotoxic activities against five human cancer cell lines. Seven compounds (3, 6, 7, 16, 18, 28, and 29) exhibited cytotoxic activity against one or more cell lines. Among these compounds, 7-deacetyl-7-benzoylepoxyazadiradione (7), 7-deacetyl-7-benzoylgeduin (18), and 28-deoxonimbolide (28) exhibited potent cytotoxic activity against HL60 leukemia cells with IC(50) values in the range 2.7-3.1 µM. Compounds 7, 18, and 28 induced early apoptosis in HL60 cells, observed by flow cytometry. Western blot analysis showed that compounds 7, 18, and 28 activated caspases-3, -8, and -9 in HL60 cells. This suggested that compounds 7, 18, and 28 induced apoptotic cell death in HL60 cells via both the mitochondrial- and the death receptor-mediated pathways. Futhermore, compound 7 was shown to possess high selective cytotoxicity for leukemia cells since it exhibited only weak cytotoxicity against a normal lymphocyte cell line (RPMI 1788).

Melanogenesis inhibitory, anti-inflammatory, and chemopreventive effects of limonoids from the seeds of Azadirachta indicia A. Juss. (neem).

Thirty-one nortriterpenoids, including 28 limonoids (1-28) and 3 degraded limonoids (29-31), and one diterpenoid (32), were isolated from the seed extract of Azadirachta indica (neem). Among these, six were new compounds and their structures were established to be 15-hydroxyazadiradione (3), 7-benzoyl-17-hydroxynimbocinol (5), 23-deoxyazadironolide (12), limocin E (13), 23-epilimocin E (14), and 7alpha-acetoxy-3-oxoisocopala-1,13-dien-15-oic acid (32). Upon evaluation of compounds 1-32 on the melanogenesis in the B16 melanoma cells, five compounds, 20, 26, 27, 29, and 31, exhibited marked inhibitory effect (74-91% reduction of melanin content at 25 microg/mL) with no or almost no toxicity to the cells. Seven compounds, 1, 6, 9, 10, 18, 20, and 26, on evaluation for their inhibitory effect against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation (1 microg/ear) in mice, exhibited, except for compound 26, marked anti-inflammatory activity (ID(50) values 0.09-0.26 mg/ear). In addition, all of the 32 compounds exhibited moderate or potent inhibitory effects (IC(50) values of 230-501 mol ratio/32 pmol TPA) against the Epstein-Barr virus early antigen (EBV-EA) activation induced by TPA. Furthermore, on evaluation of azadirachtin B (21) for its anti-tumor-initiating activity on the two-stage carcinogenesis of mouse skin tumor induced by peroxynitrite (ONOO-; PN) as an initiator and TPA as a promoter, this exhibited marked inhibitory activity.