Antioxidant activity of gallic acid and methyl gallate in triacylglycerols of Kilka fish oil and its oil-in-water emulsion

摘要

The anti-DPPH radical effect as well as anti-peroxide activity of gallic acid, methyl gallate, and α-tocoph-erol in a bulk Kilka fish oil and its oil-in-water emulsion stabilized by soy protein isolate at 55 ℃ were investigated. Gallic acid with the lowest hydrophobicity (log P= -0.28) was found to be the most active antiradical agent (IC_(50)-29.5 μM), followed by methyl gallate (IC_(50) - 38.0 μM, log P=-0.23) and α-tocopherol (IC_(50) =105.3 μM, log P=0.70). The anti-peroxide activity in the bulk oil system decreased in the order of methyl gallate ＞ gallic acid ＞ α-tocopherol. In the emulsion system, methyl gallate still behaved better than gallic acid, but the highest activity belonged to α-tocopherol. Based on the calculation of a number of kinetic parameters, the antioxidants, in general, showed better performances in the bulk oil system than in the emulsion system.