title: Cytotoxic and melanogenesis-inhibitory activities of limonoids from the leaves of Azadirachta indica (Neem).
abstract: 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.
authors.affiliation: College of Science and Technology, Nihon University, 1-8-14 Kanda Surugadai, Chiyoda-ku, Tokyo 101-8308, Japan.
authors.forename: Mio
authors.initials: M
authors.lastname: Takagi
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Tachi
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Takuro
authors.initials: T
authors.lastname: Shinozaki
authors.forename: Kenta
authors.initials: K
authors.lastname: Ishii
authors.forename: Takashi
authors.initials: T
authors.lastname: Kikuchi
authors.forename: Motohiko
authors.initials: M
authors.lastname: Ukiya
authors.forename: Norihiro
authors.initials: N
authors.lastname: Banno
authors.forename: Harukuni
authors.initials: H
authors.lastname: Tokuda
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Akihisa
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects; D031601:Azadirachta / Q000737:chemistry* / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D018922:HL-60 Cells; D004854:Herpesvirus 4, Human / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D036701:Limonins / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity*; D008543:Melanins / Q000378:metabolism; D051379:Mice; D008968:Molecular Conformation; D018515:Plant Leaves / Q000737:chemistry / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014775:Virus Activation / Q000187:drug effects; D000521:alpha-MSH / Q000378:metabolism
chemical_list: D000956:Antigens, Viral; D000972:Antineoplastic Agents, Phytogenic; C033305:Epstein-Barr virus early antigen; D036701:Limonins; D008543:Melanins; D000521:alpha-MSH; D013755:Tetradecanoylphorbol Acetate
keywords: Azadirachta indica; Caspase-dependent apoptosis; Cytotoxic activity; Limonoids; Melanogenesis-inhibitory activity; Neem tree