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* Healthcare Research Institute, Wakunaga Pharmaceutical Co., Ltd., Hiroshima 739-1195, Japan and
Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Hiroshima 7398530, Japan
3 To whom correspondence should be addressed. E-mail: ichikawa_m{at}wakunaga.co.jp.
This study used the hydroden peroxide scavenging assay to investigate antioxidant chemical constituents derived and separated from aged garlic extract, a unique garlic extract produced by soaking sliced garlic in an aqueous ethanol solution for >10 mo. Four types of 1, 2, 3, 4-tetrahydro-ß-carboline derivatives (THßCs); 1-methyl-1, 2, 3, 4-tetrahydro-ß-carboline-3-carboxylic acid, and 1-methyl-1, 2, 3, 4-tetrahydro-ß-carboline-1, 3-dicarboxylic acid (MTCdiC), from both diastereoisomers, were isolated and identified by use of liquid chromatographymass spectrometry. All these compounds indicate strong hydrogen peroxide scavenging activities and inhibit 2, 2'-azobis(2-amidinopropane) hydrochlorideinduced lipid peroxidation. Particularly, (1S, 3S)-MTCdiC had the most potent hydrogen peroxide scavenging activity, more than ascorbic acid. The (1R, 3S)- and (1S, 3S)-MTCdiC at 50100 µmol/L and 10100 µmol/L inhibited LPS-induced nitrite production. Interestingly, THßCs were not detected in raw garlic and other processed garlic preparations, but they were generated and increased during the natural aging garlic extraction process. These data suggest that THßCs, which are formed during the natural aging process, are potent antioxidants in aged garlic extract and thus may be useful for the prevention of diseases associated with oxidative damage.
KEY WORDS: aged garlic extract tetrahydro-ß-carboline derivatives Maillard reaction products antioxidant liquid chromatography mass spectrometry
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