Megumi Masuda

Inhibitory effects of constituents of Morinda citrifolia seeds on elastase and tyrosinase.

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.

Anti-degranulating activity in rat basophil leukemia RBL-2H3 cells of flavanone glycosides and their aglycones in citrus fruits

The anti-degranulating activity of flavonoids present in Citrus fruits was comprehensively evaluated. Among these, hesperetin and naringenin, respectively aglycones of hesperidin and narirutin, showed significant activity. The targets of hesperetin and naringenin were found: hesperetin inhibited phosphorylation of Syk and Akt, while naringenin suppressed the expression of Lyn and inhibited the phosphorylation of Akt. These results suggest that hesperetin and naringenin inhibit degranulation by suppression of pathway signals and reduce the symptoms of allergy by inhibiting phosphorylation of Akt, which leads to the suppression of cytokines. In addition, hesperetin showed inhibitory activity against the degranulation induced by calcium ionophores, indicating that hesperetin exerts its inhibitory activity by stabilizing the membrane structure.

Anti-allergic effect of a combination of Citrus unshiu unripe fruits extract and prednisolone on picryl chloride-induced contact dermatitis in mice

Effect of 50% ethanolic extract of unripe fruits of Citrus unshiu (CU-ext) on type IV allergic reaction was examined by inhibitory activity of ear swelling of picryl chloride-induced contact dermatitis (PC-CD) in mice. Oral administration of CU-ext and subcutaneous administration of prednisolone showed inhibition of ear swelling during both induction and effector phases of PC-CD. The inhibitory activities of combinations of CU-ext (p.o.) and prednisolone (s.c.) during induction phase of PC-CD were more potent than those of CU-ext alone and prednisolone alone. Successive oral administration of hesperidin, a major flavanone glycoside of CU-ext, inhibited ear swelling during induction phase of PC-CD. The inhibitory activities of combinations of hesperidin (p.o.) and prednisolone (s.c.) were more potent than those of hesperidin alone and prednisolone alone. These results indicated that the combinations of prednisolone and CU-ext or hesperidin exerted a synergistic effect.

Study of the Anti-Photoaging Effect of Noni (Morinda citrifolia)

During the aging process, morphological changes in the human skin appear most noticeably in areas of frequent exposure to ultraviolet (UV) light from the sun, such as the face and hands. Chronic UV exposure induces photoaging, characterized by pigmented spots and wrinkles in the skin. Gradual destruction of the ozonosphere has raised photoaging risk. This has led to rapid growth of the anti-photoaging cosmetic market, especially among women with young and fair skin. Sunscreen agents are a first choice for protection against photoaging. However, a certain amount of UV irradiation penetrates skin dermis, and adverse effect may occur with use of these agents. Because of this, a current trend is the development of safer cosmetic ingre‐ dients that effectively inhibit the UV signaling pathways leading to photoaging [1].

Melanin Hyperpigmentation Inhibitors from Natural Resources

In Oriental countries, such as China, Korea and Japan, a female beauty criterion since ancient times has been a face with fair skin, and the admiration of women with young, healthy, bright and fair skin has created a whitening cosmetics market. The color of human skin and hair is determined by a number of factors. Biosynthesis of the melanin pigment, namely melanogenesis, is the most important factor. 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 the melanin pigment causes hyperpigmentary disorders. From natural sources, a number of ingredients with an inhibitory effect on melanin hyperpigmentation have been found, and some of them were developed as cosmetic agents and over the counter (OTC) drugs in Oriental countries. On the other hand, some medicinal chemists have recently paid a lot of attention to inhibitors of melanin production to prevent hyperpigmentary disorders such as melasma, freckles and age spots. To develop novel and useful cosmetic agents, supplements, functional foods and OTC drugs, we have continued to research regulators of melanin production from natural sources since 1980. We describe here our screening strategy and studies on targeted melanin hyperpigmentation inhibitors from natural plant sources, e.g. Umbelliferae, Ericaceae, Rubiaceae, Piperaceae and Rutaceae plants. Interesting findings originating from the screening results are also described.