| Summary: | 碩士 === 國立中興大學 === 食品科學系 === 87 === The objectives of this research were to investigate the antioxidative properties of resveratrol (a non-flavonoid phytoalexin), 4-hexylresorcinol (a resorcinol derivatives), and trolox (a hydrophilic analogue of α-tocopherol). The effects of these three compounds on cell viability, oxidative DNA damage and the activities of antioxidative enzymes in human lymphocytes and HepG2 cells induced by hydrogen peroxide were also studied.
Resveratrol, 4-hexylresorcinol and trolox showed no chelating effect on iron (II) and scavenaging effect on superoxide anion and hydrogen peroxide, but their reducing power and the scavenging effects on DPPH radical increased with the increasing concentration. However, these three compounds inhibited the damage of deoxyribose induce by Fe3+-EDTA / ascorbic acid and Fe3+-EDTA / H2O2 / ascorbic acid. This means that the reducing power of these three compounds didn''t cause prooxidative effect, and these three compounds also could inhibit the oxidative damage induced by hydroxyl radical that forward in Fe3+-EDTA / ascorbic acid.
The results indicated that the cell viability of human lymphocytes and HepG2 cells was not affected by resveratrol, trolox and 4-hexylresorcinol. There was no significant difference (P > 0.05) in the production of lipid hydroperoxides in human lymphocytes and HepG2 cells induced with or without hydrogen peroxide (50 mM). All theses three compounds also didn''t affect the production of lipid hydroperoxides in different cells either with or without the treatment of hydrogen peroxide.
The effects of resveratrol, 4-hexylresorcinol and trolox on hydrogen peroxide-mediated oxidative DNA damge in human lymphocytes and HepG2 cells were determined using alkaline single cell gel electrophoresis (the comet assay). Resveratrol, trolox and 4-hexylresorcinol didn''t induce the oxidative DNA damage in human lymphocytes and HepG2 cells at a concentration of 10-100 mM. However, with an increasing concentration, these three compounds inhibited the oxidative DNA damage in human lymphocytes but accelated the oxidative DNA damage in HepG2 cells induced by the 50 mM of hydrogen peroxide. Resveratrol (100 mM), 4-hexylresorcinol (100 mM), trolox (100 mM) and trolox+resveratrol (each of 50 mM) inhibited the oxidative DNA damage in human lymphocytes with 44, 40, 30 and 35 %, respectively. However, they accerlerated the oxidative DNA damage in HepG2 cells with 21.7, 35.7, 10.4 and 23.5 %, respectively.
With the increasing concentration, resveratrol, 4-hexylresorcinol and trolox increased the content of glutathione and the activities of antioxidative enzymes in human lymphocytes. The content of glutathione in human lymphocytes exposed to resveratrol, 4-hexylresorcinol and trolox, was increase 50, 39 and 36 %, respectively, at a concentration of 100 mM. The activities of glutathione peroxidase (GSP) was increased 38.4, 41 and 34 %, respectively while the activities of glutathione reductase (GSR) was increased 20, 9 and 14.6 %, respectively. However, the activity of glutathione S-transferase (GST) in human lymphocytes was only enhanced by resveratrol, and the activity of catalase (CAT) was inhibited by all these three compounds.
In HepG2 cells, the content of glutathione was increased 11.4, 7.2 and 8.7 %, respectively, by resveratrol, 4-hexylresorcinol, and trolox at a concentration of 100 mM. Six-percentage activity of GSR was increased by trolox while resveratrol and trolox inhibited 52 and 11 % of GSR activity, respectively, at a concentration of 100 mM. In addition, 44 and 30 % activity of CAT was inhibited by resveratrol and 4-hexylresorcinol, respectively. Thus, the modulatory effect of these three compounds on antioxidative enzymes varied with different cells.
Based on the results of studies, resveratrol, 4-hexylresorcinol, and trolox could inhibit DNA damage in human lymphocytes. The inhibition of resveratrol, 4-hexylresorcinol, and trolox on oxidative DNA damage in human lymphocytes induced by hydrogen peroxide should be due to the increase of glutathione and the activities of antioxidative enzymes except the catalase. The acceleration of resveratrol, 4-hexylresorcinol, and trolox on hydrogen peroxide mediated DNA damage in HepG2 cells were due to decrease the activities of antioxidative enzymes. Therefore, the antioxidant and prooxidant effects of these three compounds in human lymphocytes and HepG2 cells were due to their antioxidant properties and the abilities on modulating the antioxidative systems in different cells.
Key words： Comet assay, resveratrol, 4-hexylresorcinol, trolox, lymphocyte, HepG2 cells, oxidative DNA damage, antioxidative enzymes
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