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)...
The objective of this study was to examine the effects of Morinda citrifolia (noni) extract and its constituents on α-melanocyte stimulating hormone (α-MSH)-stimulated melanogenesis in cultured murine B16 melanoma cells (B16 cells). A 50% ethanolic extract of noni seeds (MCS-ext) showed significant inhibition of melanogenesis with no effect on cell proliferation. MCS-ext was more active than noni leaf and fruit flesh extracts. Activity guided fractionation of MCS-ext led to the isolation of two lignans, 3,3′-bisdemethylpinoresinol (1) and americanin A (2), as active constituents. To elucidate the mechanism of melanogenesis inhibition by the lignans, α-MSH-stimulated B16 cells were treated with 1 (5 μM) and 2 (200 μM). Time-dependent increases of intracellular melanin content and tyrosinase activity, during 24 to 72 h, were inhibited significantly by treatment with the lignans. The activity of 1 was greater than that of 2. Western blot analysis suggested that the lignans inhibited melanogenesis by down regulation of the levels of phosphorylation of p38 mitogenactivated protein kinase, resulting in suppression of tyrosinase expression.Key words Morinda citrifolia; noni seed; B16 melanoma cell; tyrosinase; 3,3′-bisdemethylpinoresinol; americanin A Melanogenesis is a multistage process involving melanin synthesis, melanin transport, and melanosome release. Tyrosinase is one of the key enzymes in the melanin biosynthetic pathway. Abnormal deposition of melanin pigment causes hyperpigmentary disorders, such as melasma, freckles and age spots. Tyrosinase inhibitor is one of the candidates for reduction of melanogenesis. 1,2) In the development of novel and useful cosmetic agents and functional foods, we have continued to research melanin hyperpigmentation inhibitors from natural sources. The fruit, roots, bark and leaves of a tropical tree, Morinda citrifolia L. (Rubiaceae), commonly known as "noni" in Hawaii and Tahiti, have long been used throughout Polynesia as a folk medicine in the treatment of many diseases, e.g. hypertension and diabetes.3) Recently, the noni fruit juice and tea made from noni leaves have been introduced into the functional food market. Noni fruit contains a large number of seed throughout its flesh. During the production of noni fruit juice, these seeds are removed and discarded. Consequently, we have investigated the utility of noni seeds. In a previous paper, 4) we reported the tyrosinase inhibitory activity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of 50% ethanolic extracts of noni seeds, fruit flesh and leaves. A 50% ethanolic extract from noni seeds (MCS-ext) inhibited tyrosinase activity and scavenged the DPPH radical more potently than extracts from the leaves or fruit. Activity-guided fractionation, followed by chromatography of MCS-ext, led to the isolation of 3,3′-bisdemethylpinoresinol (1), americanin A (2) and quercetin (3), as active constituents with both tyrosinase inhibitory and radical scavenging activities. 4) After the publication of our previous pa...
Oral administration of a 50% ethanolic extract (CH-ext) obtained from unripe Citrus hassaku fruits collected in July exhibited a potent dose-dependent inhibition of IgE (immunoglobulin E)-mediated triphasic cutaneous reaction at 1 h [immediate phase response (IPR)], 24 h [late phase response (LPR)] and 8 days [very late phase response (vLPR)] after dinitrofluorobenzene challenge in mice. Naringin, a major flavanone glycoside component of CH-ext, showed a potent dose-dependent inhibition against IPR, LPR and vLPR. Neohesperidin, another major glycoside component of CH-ext, showed an inhibition against vLPR. The effect of CH-ext on type IV allergic reaction was examined by determining inhibitory activity against ear swelling in mice by using the picryl chloride-induced contact dermatitis (PC-CD) model. Oral administration (p.o.) of CH-ext and subcutaneous administration (s.c.) of prednisolone inhibited ear swelling during the induction phase of PC-CD. The inhibitory activities of combinations of CH-ext (p.o.) and prednisolone (s.c.) against PC-CD in mice were more potent than those of CH-ext alone and prednisolone alone, without enhancing the adverse effects. Other combinations of prednisolone (s.c.) and flavanone glycoside (p.o.) components of CH-ext, i.e. naringin and neohesperidin, exerted similar synergistic effects.
<p>The objective of this study was to identify pancreatic lipase inhibitory active ingredients of mango leaves, and to examine a relationship between leaves maturation and pancreatic lipase inhibitory activity. A methanolic extract of old dark green mango leaves (OML-ext) showed a porcine pancreatic lipase inhibitory activity. The pancreatic lipase inhibitory activity of OML-ext was attributable to 3-C-<em>β</em>-D-glucosyl-2,4,4’,6-tetrahydroxybenzophenone (<strong>2</strong>) and mangiferin (<strong>1</strong>). The pancreatic lipase inhibitory activity of young mango leaf extract was superior to that of old leaf extract. It was suggested that the activity is correlated with the content of <strong>2</strong> in these extract. Considering the amounts of leaves obtained from pruning, old dark green leaves may be a reasonable natural resource for the preparation of ingredients with lipase inhibitory activity.</p>
Kaempferia parviflora (KP), a Zingiberaceae plant, is used as a folk medicine in Thailand for the treatment of various symptoms, including general pains, colic gastrointestinal disorders, and male impotence. In this study, the inhibitory activities of KP against xanthine oxidase (XOD) were investigated. The extract of KP rhizomes showed more potent inhibitory activity (38% at 500 m mg/ml) than those of the other Zingiberaceae plants tested. Ten methoxyflavones were isolated from the KP extract as the major chemical components and their chemical structures were elucidated by X-ray crystallography. The structurally confirmed methoxyflavones were subjected to the XOD inhibitory test. Among them, 3,5,7,4,5-pentamethoxyflavone and 3,4,5,7-tetramethoxyflavone showed inhibitory activities (IC 50 of 0.9 and Ͼ4 mM, respectively) and their modes of inhibition are clarified as competitive/non-competitive mixed type. To the best of our knowledge, this is the first report to present the inhibitory activities of KP, 3,5,7,4,5-pentamethoxyflavone and 3,4,5,7-tetramethoxyflavone against XOD.
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