2006 Fiscal Year Final Research Report Summary
Accumulation and Metabolism of Antioxidative Flavonoids on Oxidative Stress-Targeted Organs and Expression Mechanism of Their Activity
| Project/Area Number |
16380089
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Food science
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| Research Institution | University of Tokushima |
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Principal Investigator |
TERAO Junji University of Tokushima, Institute of Health Biosciences Graduate School, Professor, 大学院ヘルスバイオサイエンス研究部, 教授 (60093275)
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| Co-Investigator(Kenkyū-buntansha) |
MUROTA Kaeko University of Tokushima, Assistant Professor, 大学院ヘルスバイオサイエンス研究部, 助教 (40294681)
KAWAI Yoshichika University of Tokushima, Assistant Professor, 大学院ヘルスバイオサイエンス研究部, 助教 (50380027)
BANDO Noriko University of Tokushima, Research Associate, 大学院ヘルスバイオサイエンス研究部, 教務員 (40116851)
AZUMA Keiko National Institute for Vegetable and Tea Science, NAFRO Research Head, 野菜茶業研究所, ユニット長 (10355604)
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| Project Period (FY) |
2004 – 2006
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| Keywords | flavonoid / oxidative stress / antioxidant / life style-related disease / blood aorta / high cholesterol / glucuronic acid conjugation / quercetin |
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| Research Abstract |
Numerous in vitro studies have revealed that dietary flavonoids possess diverse biochemical functions related to anti-atherosclerotic effect. Their antioxidant activity should, at least partly, underlies such a wide variety of functions. However, bioavailability of flavonoids has been questioned for long years, as their intestinal absorption seems to be hardly achieved. Furthermore, dietary flavonoids are mostly converted into inactive glucuronide and/or sulfate conjugates before reaching to the target organs. Thus, their inactive metabolites seem to circulate in the body at quite low concentration. Nevertheless, several biological activities of their metabolites were recently reported as similarly to their aglycones. We aimed to clarify the accumulation and metabolism of flavonoids in the target site for exerting their biological effect. Quercetin was selected as a representative of dietary flavonoids from vegetables and quercetin-3-0-D-glucuronide (Q3GA) was synthesized as a typical quercetin metabolite found in circulation. We discovered that quercetin metabolites accumulate in atherosclerotic aorta exclusively. This phenomenon implies that quercetin metabolites are incorporated into the atherosclerotic region and act as complementary antioxidants, when oxidative stress is loaded in the vascular system. This hypothesis is supported by the results that Q3GA was incorporated into macrophage cells and present as Q3GA, quercetin aglycone and its methylated form and that their distribution was modified by stimulating the cells with LPS. This modification is likely to be helpful in increasing biological activity of dietary quercetin. We found that these metabolites circulating in the human blood stream were mostly localized in plasma albumin fraction, indicating that plasma albumin is a carrier for translocation of quercetin metabolites to vascular target.
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