Functional substance search of horticultural products and research of the action mechanism of a functional substance

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Dihydropyrazine (DHP) species are included in the Maillard reaction intermediates. The Maillard reaction is thought to play a role in the pathophysiology of aging and diabetes. Thus, DHP may be involved in aging and diabetes related diseases, however, there is little reported the biological and physiological roles of DHPs. Moreover, polyphenolics(POPs) as a secondary metabolite in plant, have various physiological functions and play important roles in human nutrition. By using Escherichia coli mutant strains, we observed that cyclohexyl-DHP exposure strongly reduced the survival rate of a cytosolic sodium dodecyl sulfate (SOD)-deficient strain (sodA sodB), significantly reduced the survival rates of DNA repair-deficient strains (recA and uvrB) and mildly reduced the survival rate of a catalase-deficient strain (katE katG) compared with the survival rate of the wild-type strain. Addition of Cu(2+) enhanced the cell killing ability of cyclohexyl-DHP. The frequency of mutations induced by cyclohexyl-DHP increased dose-dependently in the sodA sodB strain. Moreover, cyclohexyl-DHP elevated the protein carbonyl levels in E caoli. We investigated the suppression of the proliferation of selected human cancer cells by phenolic compounds isolated from sweetpotato leaf. Caffeic acid and di-and tricaffeoylquinic acids dose-dependently depressed cancer cell proliferation, and the difference in sensitivity between caffeoylquinic acid derivatives and each kind of cancer cell was observed. Specifically, 3,4,5-tri-O-caffeoylquinic acid effectively depressed the growth of three kinds of cancer cells, and caffeic acid had an exceptionally higher effect against romyelocytic leukemia cells (HL-60) than other di- and tricaffeoylquinic acids.