Shunsuke Naruto

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.

Neosidomycin, a new antibiotic of Streptomyces

A new indole-N-glycoside, neosidomycin (I), is produced by a strain belonging to Streptomyces hygroscopicus. The structure of I has been deduced from physico-chemical data obtained using the natural compound, its derivatives and products of degradation reactions.

Rearrangement reaction of N-halo-s-[(1,2-benzisoxazol-3-yl)methyl]-sulfoximine to the corresponding α-halo sulfoximine

Abstract The first example of the rearrangement reaction of N-halosulfoximine to α-halo sulfoximine is described.

Synthesis and anti-cholinergic activity of aminoalkyl 2-cyclic amino-2-(1,2-benzisoxazol-3-yl)acetates and their quaternary ammonium salts

Abstract A series of aminoalkyl 2-cyclic amino-2-(1,2-benzisoxazol-3-yl)acetates 1 and 2 and their quaternary ammonium derivatives 3 and 4 has been prepared and tested for anti-cholinergic activity. Among these compounds, 1-alkyl-1-methyl-4-[2-cyclic amino-2-(1,2-benzisoxazol-3-yl)acetoxy]piperidinium salts 3 showed potent anti-cholinergic activity in the in vitro studies. The structure—activity relationships of these compounds are discussed.

Novel base-induced reactions of substituted (1,2-benzisoxazol-3-yl)acetates

The reactions of substituted (1,2-benzisoxazol-3-yl) acetates with strong bases are described. The esters (1) and (2) having electron-donating and dialkylamino substituents undergo novel ring transformations on treatment with NaH, ButOK, or MeONa in DMF to afford the 2H-azirines (8) and the 3-iminobenzofurans (18), respectively, while under similar conditions the halogeno esters (3) dimerize to give the ethylenedicarboxylate (24). Treatment of the esters (4)–(7) having electron-withdrawing substituents with NaH in DMF results in the recovery of the starting esters. However, on treatment of the sulphinyl esters (6) with MeONa in methanol, C-S bond cleavage occurs to afford methyl arylsulphinates (27).

Novel rearrangements of N- and α-halogeno derivatives of S-aryl-S[(1,2-benzisoxazol-3-yl)methyl]sulphiximides to the corresponding N-sulphinylimines

The title N-and α-halogno-sulohoximides (1) and (2) undergo base-induced rearrangement reactions to give the correspondingN-sulphinylimines (3), suggesting the intermediacy of a three-membered cyclic sulphoximide (4) with an endocyclic SN moiety.

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.

Novel base-induced ring transformation of 1,2-benzisoxazole-3-acetic acid esters into 2H-azirines or benzofurans

Treatment of α-mono-substituted 1,2-benzisoxazole-3-acetic acid esters (1) with strong bases caused a ring transformation to afford 2H-azirines (2) or 3-imino-2,3-dihydrobenzofurans (3).