No abstract

Six new limonoids, 7-benzoyl-17-epinimbocinol (5), 3-acetyl-7-tigloylnimbidinin (8), 1-isovaleroyl-1-detigloylsalanninolide (15), 2,3-dihydro-3α-methoxynimbolide (16), deacetyl-20,21-epoxy-20,22-dihydro-21-deoxyisonimbinolide (26), and deacetyl-20,21,22,23-tetrahydro-20,22-dihydroxy-21,23-dimethoxynimbin (27), along with 28 known limonoids, 1-4, 6, 7, 9-14, 17-25, and 28-34, and two known flavonoids, 35 and 36, have been isolated from the extracts of bark, leaves, roots, and seeds of Azadirachta indica A. Juss. var. siamensis Valeton (Siamese neem tree; Meliaceae). The structures of the new compounds were elucidated on the basis of extensive spectroscopic analysis and comparison with literature data. All of these compounds were evaluated for their cytotoxic activities against leukemia (HL60), lung (A549), stomach (AZ521), and breast (SK-BR-3) cancer cell lines. Eleven compounds, 1, 2, 4-7, 13, 16, 17, 29, and 30, exhibited potent cytotoxicities against one or more cell lines with IC50 values in the range of 0.1-9.3 μM. Compound 16 induced apoptotic cell death in AZ521 cells upon evaluation of the apoptosis-inducing activity by flow cytometric analysis. Western blot analysis on AZ521 cells revealed that compound 16 activated caspases-3, -8, and -9, while increasing the ratio of Bax/Bcl-2. This suggested that 16 induced apoptosis via both mitochondrial and death receptor pathways in AZ521. In addition, upon evaluation of all compounds against the melanogenesis in B16 melanoma cells induced with α-melanocyte-stimulating hormone (α-MSH), 20 limonoids, i.e., 1-3, 6, 9-11, 18, 19, 21-29, 32, and 34, and two flavonoids, 35 and 36, exhibited melanogenesis-inhibitory activities, with no, or almost no, toxicities to the cells at lower and/or higher concentrations, which were more potent than the reference arbutin, a known melanogenesis inhibitor. Western blot analysis showed that nimbin (18) reduced the protein levels of microphtalmia-associated transcription factor (MITF), tyrosinase, tyrosine-related protein 1 (TRP-1), and TRP-2 mostly in a concentration-dependent manner, indicating that 18 inhibits melanogenesis on a α-MSH-stimulated B16 melanoma cells by, at least in part, inhibiting the expression of MITF, followed by decreasing the expression of tyrosinase, TRP-1, and TRP-2.

Seventeen limonoids (tetranortriterpenoids), 1-17, including three new compounds, i.e., 17-defurano-17-(2,5-dihydro-2-oxofuran-3-yl)-28-deoxonimbolide (14), 17-defurano-17-(2ξ-2,5-dihydro-2-hydroxy-5-oxofuran-3-yl)-28-deoxonimbolide (15), and 17-defurano-17-(5ξ-2,5-dihydro-5-hydroxy-2-oxofuran-3-yl)-2',3'-dehydrosalannol (17), were isolated from an EtOH extract of the leaf of neem (Azadirachta indica). The structures of the new compounds were elucidated on the basis of extensive spectroscopic analyses and comparison with literature. Upon evaluation of the cytotoxic activities of these compounds against leukemia (HL60), lung (A549), stomach (AZ521), and breast (SK-BR-3) cancer cell lines, seven compounds, i.e., 1-3, 12, 13, 15, and 16, exhibited potent cytotoxicities with IC50 values in the range of 0.1-9.9 μM against one or more cell lines. Among these compounds, cytotoxicity of nimonol (1; IC50 2.8 μM) against HL60 cells was demonstrated to be mainly due to the induction of apoptosis by flow cytometry. Western blot analysis suggested that compound 1 induced apoptosis via both the mitochondrial and death receptor-mediated pathways in HL60 cells. In addition, when compounds 1-17 were evaluated for their inhibitory activities against melanogenesis in B16 melanoma cells, induced with α-melanocyte-stimulating hormone (α-MSH), seven compounds, 1, 2, 4-6, 15, and 16, exhibited inhibitory activities with 31-94% reduction of melanin content at 10 μM concentration with no or low toxicity to the cells (82-112% of cell viability at 10 μM). All 17 compounds were further evaluated for their inhibitory effects against the EpsteinBarr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells.

Cytotoxic and Melanogenesis-Inhibitory Activities of Limonoids from the Leaves of Azadirachta indica (Neem). -[isolation, structure elucidation and evaluation of 17 limonoids, including the three novel ones (I), (II), (III), for their cytotoxic activities, their inhibitory activities against melanogenesis in B16 melanoma cells and against the Epstein-Barr virus early antigen]. -(TAKAGI, M.; TACHI, Y.; ZHANG, J.; SHINOZAKI, T.; ISHII, K.; KIKUCHI, T.; UKIYA, M.; BANNO, N.; TOKUDA, H.; AKIHISA*, T.; Chem. Biodiversity 11 (2014) 3, 451-468, http://dx.doi.org/10.1002/cbdv.201300348 ; Coll. Sci. Technol., Nihon Univ., Chiyoda, Tokyo 101, Japan; Eng.) -H. Toeppel 33-203

Background: Artocarpus heterophyllus L. (Jackfruit) has been used traditionally as treatment for inflammation and cancer. The aim of this study was to isolate compounds from A. heterophyllus wood extract and evaluate their biological activities such as anti-tumor promoting effect on Epstein-Barr virus early antigen induction, melanogenesis inhibitory activity on the B16 mouse melanoma 4A5 cell line and cytotoxic activity against three human cancer cell lines (HL60, A549, SK-BR-3). Methods: A. heterophyllus wood was extracted with n-hexane and methanol. The ethyl acetate soluble- fraction separated from the methanol extract was separated and purified with column chromatography to isolate compounds. The structures of isolated compounds were elucidated with spectroscopic methods. These compounds were evaluated for their biological activities. Results: Thirteen known compounds including four prenylflavonoids were isolated from the wood extracts. Nine flavonoids (2, 3, 5-11) exhibited potent anti-tumor promoting activity with IC50 values of 259-296 molar ratio / 32 pmol TPA. Two flavonoids, Norartocarpetin (6) at concentration of 30 μM and cyanomaclurin (11) at the concentration of 100 μM showed melanin content value of 47.6 % and 80.1 %, respectively. Two prenylflavonoids, cudraflavone B (2) and artocarpin (5), showed cytotoxicity against the human cancer cell lines tested. Cudraflavone B (2) showed cytotoxicity against all three human cancer cell lines whereas artocarpin (5) only exhibited cytotoxicity against two out three cell lines testes. The IC50 values were comparable to or better than cisplatin. Conclusion: From the view point of structure activity relationships of the flavonoids isolated, side chains such as prenyl and 3-methyl-1-butenyl moiety were key for their potent biological activities.