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326 results on '"Nonaka, Gen‐ichiro"'

6. Activity-Guided Fractionation of Green Tea Extract with Antiproliferative Activity against Human Stomach Cancer Cells

Author

Kinjo, Junei, Nagao, Tsuneatsu, Tanaka, Takashi, Nonaka, Gen-Ichiro, Okawa, Masafumi, Nohara, Toshihiro, Okabe, Hikaru, Kinjo, Junei, Nagao, Tsuneatsu, Tanaka, Takashi, Nonaka, Gen-Ichiro, Okawa, Masafumi, Nohara, Toshihiro, and Okabe, Hikaru

Abstract

Epidemiological studies have suggested that the consumption of green tea provides protection against stomach cancer. Fractionation of green tea extract, guided by antiproliferative activity against human stomach cancer (MK-1) cells, has resulted in the isolation of six active flavan-3-ols, epicatechin (EC), epigallocatechin (EGC), epigallocatechin gallate (EGCg), gallocatechin (GC), epicatechin gallate (ECg), gallocatechin gallate (GCg), together with inactive glycosides of kaempferol and quercetin. Among the six active flavan-3-ols, EGCg and GCg showed the highest activity, EGC, GC, ECg followed next, and the activity of EC was lowest. These data suggest that the presence of the three adjacent hydroxyl groups (pyrogallol or galloyl group) in the molecule would be a key factor for enhancing the activity. Since reactive oxygen species play an important role in cell death induction, radical scavenging activity was evaluated using the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical. The order of scavenging activity was ECg?EGCg?EGC?GC?EC. The compounds having a galloyl moiety showed more potent activity. The contribution of the pyrogallol moiety in the B-ring to the scavenging activity seemed to be less than that of the galloyl moiety., identifier:Biological & Pharmaceutical Bulletin v.25(9) p.1238-1240, 2002

Published
2020

13. Highly Oxidized Ellagitannins of Carpinus japonicaand Their Oxidation–Reduction Disproportionation

Author

Kojima, Daisetsu, Shimizu, Kengo, Aritake, Kosuke, Era, Manami, Matsuo, Yosuke, Saito, Yoshinori, Tanaka, Takashi, and Nonaka, Gen-ichiro

Abstract

In the research on ellagitannin metabolism, two unique dehydroellagitannins, carpinins E (1) and F (2), bearing dehydrohexahydroxydiphenoyl (DHHDP) and hydrated biscyclohexenetrione dicarboxyl ester (HBCHT) groups, were isolated from young leaves of Carpinus japonica. Upon heating in H2O or treatment with pH 6 buffer at room temperature, 1and 2afforded the reduction product 3, isocarpinin A, with an (R)-hexahydroxydiphenoyl (HHDP) group, suggesting the occurrence of redox disproportionation of the (S)-DHHDP group. This was supported by the increase in production of 3in the pH 6 buffer solution by coexistence of epigallocatechin-3-O-gallate (15), accompanied by oxidation of 15. In contrast, treatment of 1and 2with ascorbic acid yielded 4, carpinin A, with an (S)-HHDP group. Upon heating with ascorbic acid, the HBCHT group was also reduced to an (S)-HHDP group, and 2was converted to 2,3;4,6-bis(S)-HHDP glucose. In leaves of C. japonica, the tannins 1and 2are dominant in young spring leaves, but compounds 3and 4become the major components of tannins in mature leaves. These results suggest that, in ellagitannin biosynthesis, oxidative coupling of the two galloyl groups first generates a DHHDP group, and subsequent reduction of DHHDP esters produces HHDP esters.

Published
2020
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14. Purification of Catechins using Tempe Protein

Author

Kazuyuki Ushijima, Takahi Nozawa, Kanji Ishimaru, Norie Tanaka, and Nonaka Gen-ichiro

Subjects
Chromatography, Chemistry, medicine, Tempe, Food Science, medicine.drug
Published
2001

17. New Phenylpropanoid-Substituted Flavan-3-ols from the Leaves of Castanopsis sclerophylla

Author

Tanaka, Takashi, Huang, Yong-Lin, Matsuo, Yosuke, Kouno, Isao, Li, Dian-Peng, Nonaka, Gen-ichiro, Tanaka, Takashi, Huang, Yong-Lin, Matsuo, Yosuke, Kouno, Isao, Li, Dian-Peng, and Nonaka, Gen-ichiro

Abstract

In the course of a chemotaxonomical study of Chinese Castanopsis species, two previously unknown flavan-3-ols, named sclerophynins A and B, were isolated from the leaves of C. sclerophylla, together with five related known compounds. On the basis of spectroscopic analysis, the new compounds were characterized to be (4S,8R,9S)-4-(3,4-dihydroxyphenyl)-8-(3,4,5-trihydroxyphenyl)- 3,4,9,10-tetrahydro-5,9-dihydroxy-2H,8H-benzo[1,2-b:3,4-b']dipyran-2- one and (4S,7S,8R)-4,8-bis(3,4-dihydroxyphenyl)-3,4,6,7-tetrahydro-5-glucopyranosyloxy- 7-hydroxy-2H,8H-benzo[1,2-b:5,4-b']dipyran-2-one, respectively., HETEROCYCLES, 83(10), pp.2321-2328; 2011

Published
2011

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