phytochemicals Phytochemicals

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Studies about the anti-mutagenic effect of myricetin.

Myricetin helps to reduce damage to DNA through its direct antioxidant activity and by enhancing DNA repair. A study conducted by University College, Cork, Republic of Ireland, found that a preincubation with the flavonoids before hydrogen peroxide exposure significantly protected the DNA of cells [1]. This study investigated the flavonoids myricetin, quercetin and rutin on cell viability, antioxidant enzyme activities, DNA integrity protective against hydrogen peroxide -induced DNA damage on tow different cell lines. They found no effect of the tested phytochemicals on cell viability, catalase or superoxide dismutase activity. But preincubation with the phytochemicals before hydrogen peroxide exposure significantly protected both cell lines against hydrogen peroxide-induced DNA damage.

A study by the UFR des Sciences Pharmaceutiques et Biologiques, Rennes, France, conducted an in-vitro test with liver cells to determine the possible protective action of myricetin on DNA damage, induced by iron [2]. The researchers treated rat hepatocytes with ferric nitrilotriacetate, a toxic iron chelate, in the presence or absence of myricetin. Treatment of the cells with the iron chelate severely increased DNA oxidation and resulted in lipid peroxidation. Simultaneous treatment with myricetin prevented both lipid peroxidation and accumulation of oxidation products in DNA. This study concluded that myricetin might be used in the prevention of liver cancer derived from iron overload pathologies.

Laughton and co-workers of the Department of Biochemistry, University of London King's College, found that myricetin can have pro-oxidant effect under certain condition, and therefore myricetin and maybe many other phytochemicals cannot be classified simplistically as antioxidants [3]. The researchers tested the protective effects of gossypol, quercetin and myricetin on iron-induced lipid peroxidation in rat liver microsomes and found that they greatly accelerated the generation of hydroxyl radicals from hydrogenperoxide in the presence of Fe3+-EDTA. Quercetin and myricetin accelerated bleomycin-dependent DNA damage in the presence of Fe3+.

[1] Protection by the flavonoids myricetin, quercetin, and rutin against hydrogen peroxide-induced DNA damage in Caco-2 and Hep G2 cells. Nutr Cancer. 1999;34(2):160-6.
[2] Repair of iron-induced DNA oxidation by the flavonoid myricetin in primary rat hepatocyte cultures. Free Radic Biol Med. 1999 Jun;26(11-12):1457-66.
[3] Antioxidant and pro-oxidant actions of the plant phenolics quercetin, gossypol and myricetin. Effects on lipid peroxidation, hydroxyl radical generation and bleomycin-dependent damage to DNA. Biochem Pharmacol. 1989 Sep 1;38(17):2859-65.

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