Antioxidant activity of green teas in different lipid systems

Abstract

Different commercial green teas from Japan, China, and India, were compared in different lipid systems. Green teas were active antioxidants in bulk corn oil oxidized at 50°C but were prooxidant in the corresponding oil-in-water emulsions. Green teas also were active antioxidants in soybean lecithin liposomes oxidized at 37°C in the presence of cupric acetate as catalyst. At 50°C, however, three of the samples of green tea were active antioxidants in the absence of copper catalyst, and two samples showed prooxidant activity in the presence of copper catalyst. The marked variation in activity among green tea samples may be due partly to differences in their relative partition between phases in different lipid systems. The improved antioxidant activity observed for green teas in lecithin liposomes compared to corn oil emulsions can be explained by the greater affinity of the polar tea catechin gallates for the polar surface of the lecithin bilayers, thus affording better protection against oxidation. Liposomes may thus be appropriate lipid models to evaluate antioxidants for foods containing phospholipids. JAOCS 74, 1309-1315 (1997).

Food antioxidants and phytochemicals: present and future perspectives

“…We observed a concentration-dependent inhibition between 10 and 30 ppm green tea and between 10 and 30 µM catechin [6]. Here also more inhibition of hexanal formation than conjugated diene formation was observed.…”

“…However, these methods do not consider the effects of lipid substrate on antioxidant capacity. Yet, we have found that the relative activities of various natural antioxidants are greatly affected by the type of lipid system used in the assays [3][4][5][6]. To learn about the real effects of antioxidants, it is important therefore to obtain specific chemical information about what products of lipid oxidation are inhibited.…”

Antioxidative gelatin hydrolysate from unicorn leatherjacket skin as affected by prior autolysis

“…For the control (without hydrolysate or trolox), the sharp increase in PV was found within the first 42 h of incubation (P \ 0.05), in which the highest value (138.74 ± 3.64 mg cumene hydroperoxide/L lecithin liposome) was found at 42 h of incubation. Thereafter, the sharp decrease in PV was observed up to 48 h. The sharp decrease in PV after 42 h of incubation was plausibly caused by the decomposition of hydroperoxide to the secondary products (Frankel et al 1997). The system added with NS and SS showed the lower PV than the control throughout 48 h of incubation (P \ 0.05).…”

Effect of methanol extracts of rosemary and olive vegetable water on the stability of olive oil and sunflower oil

“…Recently, consumers show a growing tendency to reject all synthetic additives to foods, including synthetic antioxidants. Thus, there has been an increased interest on the use of natural antioxidants, especially those extracted from herbs, spices and other plant materials (Manganari y Oreopoulou, 1991;Tsuda et al, 1993;Frankel et al, 1997;Chen étal., 1998;Hall et al, 1998). Several substances including alcoholic extracts of different spices, paprika and rosemary, show good antioxidant activity.…”