A 50% ethanolic extract (MCS-ext) from seeds of Morinda citrifolia ("noni" seeds) showed more potent in vitro inhibition of elastase and tyrosinase, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity than extracts of M. citrifolia leaves or flesh. Activity-guided fractionation of MCS-ext using in vitro assays led to the isolation of ursolic acid as an active constituent of elastase inhibitory activity. 3,3'-Bisdemethylpinoresinol, americanin A, and quercetin were isolated as active constituents having both tyrosinase inhibitory and radical scavenging activities. Americanin A and quercetin also showed superoxide dismutase (SOD)-like activity. These active compounds were isolated from noni seeds for the first time.

The [3 + 2 + 2] cocyclization of ethyl cyclopropylideneacetate (1a) and terminal alkynes (2) proceeded smoothly in the presence of 10 mol % "Ni(PPh3)2", which was prepared in situ from Ni(cod)2 and PPh3. The high reactivity of 1a, which was induced by the introduction of an electron-withdrawing group, is very important for the progress of this reaction. The cycloheptadiene derivatives were synthesized in highly selective manner in good yields.

In a previous study we found that 50% ethanol extracts of immature fruits of Citrus unshiu (satsuma mandarin) have anti-allergic effects against the Type I, II and IV allergic reactions. However, many adverse interactions between citrus fruit, especially grapefruit juice, and drugs have been reported due to the inhibition of cytochrome P450 (CYP) activities. The purpose of this study was to examine the competitive inhibitory effects of extracts from immature citrus fruit on CYP activity. Extracts were prepared from 12 citrus species or cultivars, and were tested against three kinds of major CYPs, CYP2C9, CYP2D6 and CYP3A4, in human liver microsomes. We also estimated the amounts of flavonoids (narirutin, hesperidin, naringin and neohesperidin) and furanocoumarins (bergapten, 6,7-dihydroxybergamottin and bergamottin) in each extract using HPLC. Citrus paradisi (grapefruit) showed the greatest inhibition of CYP activities, while Citrus unshiu which has an antiallergic effect, showed relatively weak inhibitory effects. Extracts having relatively strong inhibitory effects for CYP3A4 tended to contain higher amounts of naringin, bergamottin and 6,7-dihydroxybergamottin. These results, providing comparative information on the inhibitory effects of citrus extracts on CYP isoforms, suggest that citrus extracts containing high levels of narirutin and hesperidin and lower levels of furanocoumarins such as C. unshiu are favorable as antiallergic functional ingredients.

Melanogenesis stimulated by UV irradiation occurs in plants, microorganisms, and mammalian cells by an enzymatic oxidation process starting with L-tyrosine. Various ingredients for skin-whitening cosmetics are developing to reduce melanogenesis. Tyrosinase catalyzes the oxidation of L-tyrosine to 3,4-dihydroxyphenyl-L-alanine (L-DOPA), followed by the oxidation of L-DOPA to dopaquinone, and oxidative polymerization of several dopaquinone derivatives produces melanin. Thus the tyrosinase inhibitor is one of the candidates for reduction of melanogenesis.1) On the other hand, it has been reported that superoxide dismutase (SOD) is one of the key factors that reduce melanin production caused by UV irradiation.2) Therefore tyrosinase inhibitors with SOD-like activity and/or antioxidant activity may be useful ingredients in the field of skin-whitening cosmetics. During our screening program to find a potential tyrosinase inhibitor from natural resources, we reported several crude drugs, such as Glebnia littoralis F. SCHMIDT, Prunus zippeliana M., Myrica rubra S. et ZUCC., and Arctostaphylos uva-ursi L. SPRENGEL, some of which have been applied to cosmetic beauty preparations. 1,[3][4][5] Recently, the tyrosinase inhibitory activities of the peel of Citrus fruit (Citrus unshiu Markovich) and its flavonoids, such as nobiletin, have been reported. 6,7) As a part of our continuous studies on the biological activities of Citrus species, [8][9][10][11][12] we found that a 50% ethanolic extract (CH-ext) obtained from the unripe fruit of Citrus hassaku HORT ex T. TANAKA, which was collected by thinning out in July, exhibited potent mushroom tyrosinase inhibitory activity. Thinning out the unripe fruit of C. hassaku in July is important for a rich harvest of ripe fruit in December. Thus this study was undertaken to examine whether the unripe fruit of C. hassaku collected in July by thinning can be utilized as a plant resource for skin-whitening cosmetic agents, because, to the best of our knowledge, there is no report on the tyrosinase inhibitory activity of C. hassaku. First, to identify the active component, we carried out activity-guided fractionation of the CH-ext using tyrosinase inhibitory assay. For antioxidant activity, SOD-like and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities of the CH-ext and its flavanone glycosides were also studied. Second, according to the method of Imokawa, 13) we examined the effects of the CH-ext on melanogenesis using cultured murine B16 melanoma cells after exposure to glucosamine. Third, we examined the in vivo preventive effects of the CH-ext against UVB-induced pigmentation of dorsal skin in brownish guinea pigs. 14) MATERIALS AND METHODSReagents Hesperidin, naringin, and neohesperidin were purchased from Sigma-Aldrich Japan (Tokyo, Japan). Narirutin was isolated from fruit of C. unshiu.10) Other chemical and biochemical reagents were of reagent grade and were purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan) and/or Nacalai Tesque, Inc. (Kyoto, Japan)...

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