Toshio Morikawa

Publications (138) View all

• Article: Flavonol glycosides with lipid accumulation inhibitory activity and simultaneous quantitative analysis of 15 polyphenols and caffeine in the flower buds of Camellia sinensis from different regions by LCMS.

  Toshio Morikawa, Kiyofumi Ninomiya, Sohachiro Miyake, Yoshinobu Miki, Masaki Okamoto, Masayuki Yoshikawa, Osamu Muraoka
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  ABSTRACT: A simultaneous quantitative analytical method for 15 major polyphenols, e.g. five catechins (1-5) and 10 flavonols (6-15), as functional constituents in the extracts of "tea flowers", the flower buds of Camellia sinensis (Theaceae), has been developed. The content of caffeine (16), which showed similar chromatographic behaviour under the analytical conditions, was also determined. To approve the validity of the newly developed protocol, thirteen extracts of the plant's flower buds collected from different regions, i.e. China, Taiwan, Japan and India, were evaluated. The results indicated that the assay was reproducible and precise, and could be readily underutilised for the quality evaluation of tea flowers on the basis of polyphenols' contents. It was noteworthy that the contents of two major constituents, kaempferol 3-O-β-d-glucopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→6)-β-d-glucopyranoside (10) and kaempferol 3-O-β-d-glucopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→6)-β-d-galactopyranoside (11), varied by region where the flower buds were produced. A new flavonol glycoside, chakaflavonoside B (17), which was isolated in the course of this analytical study, was found to show oleic acid-albumin-induced lipid accumulation inhibitory activity.
  Food Chemistry 09/2013; 140(1-2):353-60. · 3.65 Impact Factor
• Article: In silico design, synthesis and evaluation of 3'-O-benzylated analogs of salacinol, a potent α-glucosidase inhibitor isolated from an Ayurvedic traditional medicine "Salacia".

  Genzoh Tanabe, Shinya Nakamura, Nozomi Tsutsui, Gorre Balakishan, Weijia Xie, Satoshi Tsuchiya, Junji Akaki, Toshio Morikawa, Kiyofumi Ninomiya, Isao Nakanishi, Masayuki Yoshikawa, Osamu Muraoka
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  ABSTRACT: With the aid of an in silico method, α-glucosidase inhibitors with far more potent activities than salacinol (1), a potent natural α-glucosidase inhibitor isolated from an Ayurvedic traditional medicine Salacia reticulata, have been developed.
  Chemical Communications 07/2012; 48(69):8646-8. · 6.17 Impact Factor
• Article: Suppressive effects of coumarins from Mammea siamensis on inducible nitric oxide synthase expression in RAW264.7 cells.

  Toshio Morikawa, Mayumi Sueyoshi, Saowanee Chaipech, Hisashi Matsuda, Yukiko Nomura, Mikuko Yabe, Tomoko Matsumoto, Kiyofumi Ninomiya, Masayuki Yoshikawa, Yutana Pongpiriyadacha, Takao Hayakawa, Osamu Muraoka
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  ABSTRACT: A methanol extract of the flowers of Mammea siamensis (Calophyllaceae) was found to inhibit nitric oxide (NO) production in lipopolysaccharide-activated RAW264.7 cells. From the extract, two new geranylated coumarins, mammeasins A (1) and B (2), were isolated together with 17 known compounds including 15 coumarins. The structures of 1 and 2 were determined on the basis of their spectroscopic properties as well as of their chemical evidence. Among the isolates, 1 (IC(50) = 1.8 μM), 2 (6.4 μM), surangins B (3, 5.0 μM), C (4, 6.8 μM), and D (5, 6.2 μM), kayeassamins E (7, 6.1 μM), F (8, 6.0 μM), and G (9, 0.8 μM), mammea A/AD (11, 1.3 μM), and mammea E/BB (16, 7.9 μM) showed NO production inhibitory activity. Compounds 1, 9, and 11 were found to inhibit induction of inducible nitric oxide synthase (iNOS). With regard to mechanism of action of these active constituents (1, 9, and 11), suppression of STAT1 activation is suggested to be mainly involved in their suppression of iNOS induction.
  Bioorganic & medicinal chemistry 07/2012; 20(16):4968-77. · 2.82 Impact Factor
• Article: Promoting the effect of chemical constituents from the flowers of Poacynumhendersonii on adipogenesis in 3T3-L1 cells

  Toshio Morikawa, Katsuya Imura, Sohachiro Miyake, Kiyofumi Ninomiya, Hisashi Matsuda, Chihiro Yamashita, Osamu Muraoka, Takao Hayakawa, Masayuki Yoshikawa
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  ABSTRACT: A novel sugar ester poacynose (1) was isolated from the flowers of Poacynum hendersonii together with 31 known compounds. The structure of 1 was established mainly on the basis of 1D and 2D NMR spectral data. Among the isolates, several constituents, such as kaempferol 3-O-sophoroside (5), picein (16), and 4-hydroxybenzoic acid 4-O-β-d-glucopyranoside (17) moderately promoted adipogenesis of 3T3-L1 cells. In addition, simultaneous quantitative analysis of eight flavonoid constituents from the flower and leaf parts of P. hendersonii was developed. Keywords Poacynum hendersonii –Kaempferol 3-O-sophoroside–Poacynose–Quantitative analysis–Apocynaceae
  Journal of Natural Medicines 04/2012; 66(1):39-48. · 1.39 Impact Factor
• Article: Quantitative analysis of acylated oleanane-type triterpene saponins, chakasaponins I-III and floratheasaponins A-F, in the flower buds of Camellia sinensis from different regional origins.

  Toshio Morikawa, Sohachiro Miyake, Yoshinobu Miki, Kiyofumi Ninomiya, Masayuki Yoshikawa, Osamu Muraoka
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  ABSTRACT: A quantitative analytical method was developed for the determination of acylated oleanane-type triterpene saponins, chakasaponins I-III (1-3) and floratheasaponins A-F (4-9), found in Camellia sinensis (Theaceae). The practical conditions for separation and detection of these saponins were established on an ODS column with methanol containing 5 mM trifluoroacetic acid as a mobile phase, and the detection and quantitation limits of the method were estimated to be 1.1-3.8 and 3.5-12.5 ng, respectively. The relative standard deviation values of intra- and interday precision were lower than 2.35 and 6.12%, respectively, overall mean recoveries of all saponins being 94.7-108.8%, and the correlation coefficients of all the calibration curves showed good linearity within the test ranges. To approve the validity of the protocol, extracts of 13 kinds of C. sinensis collected in China, Taiwan, Japan, and India were evaluated. The results indicated that the assay was reproducible and precise, and could be readily utilized for the quality evaluation of tea flowers. It was noteworthy that the distinct regional difference was observed with respect to the content of chakasaponins and floratheasaponins, more chakasaponins being contained in the extracts of tea flowers from Fujian and Sichuan provinces, China than those from Japan, Taiwan, and India. Optimum conditions for the extraction process were also established.
  Journal of Natural Medicines 02/2012; 66(4):608-13. · 1.39 Impact Factor