46C-31 |
Antioxidative effects of ginseng compounds on the photosensitized oxidation and autoxidation of linoleic acid in an aqueous system |
H. O. Lee1, S. D. HOWARD1, and D. B. Min. (1) Food Science and Technology, The Ohio State University, 110 Parker Food Science and Technology, 2015 Fyffe Road, Columbus, OH 43210-1007 Many natural substances, including ginseng, are known to contain organic compounds with antioxidant effects. Due to variability in the degree of antioxidant effects, correlation must be made between antioxidant activity and individual organic compounds. The objectives were to identify antioxidants from ginseng and evaluate their antioxidant effectiveness to that of BHT and a-tocopherol in an aqueous system. Ginseng compounds were extracted with a mixture of organic solvents, separated by HPLC, and identified by mass spectroscopy and retention time of standards. Antioxidant effectiveness to photosensitized oxidation was evaluated in an aqueous buffer system containing 0.2 - 2.0 % linoleic acid and 20 ppm riboflavin. Samples were held in a 4000 lux tungsten lamp light box at room temperature for 3 hours. Oxidative stability of each system was determined by the ferric thiocyanate spectrophotometric method (FTM) at 500 nm and by headspace oxygen depletion, measured by gas chromatography. Antioxidant effectiveness to autoxidation was evaluated in an aqueous buffer system containing 0.2 - 2.0 % linoleic acid stored at 37C for 16 hours. FeCl2 and H2O2 were used to catalyze autoxidation. Antioxidant effectiveness to autoxidation was determined by measuring headspace oxygen, by thermal conductivity gas chromatography, and malonaldehyde, by HPLC after reaction with urea. Of the 7 extracted ginseng compounds, 4 showed better antioxidant activity to photosensitized oxidation than a-tocopherol (caffeic acid > kaempferol=vanillic acid > salicylic acid > a-tocopherol > ferulic acid) and all were better than a-tocopherol in autoxidation. Two of the 7 had better antioxidant activity than BHT against autoxidation (kaempferol > maltol=BHT > vanillic acid > saponin > salicylic acid > ferulic acid > a-tocopherol). Caffeic acid showed prooxidant effect possibly due to polymer formation during autoxidaiton. Several compounds extracted from ginseng have antioxidant activity towards both autoxidation and photosensitized oxidation.
Session 46C, Food Chemistry: Lipids, antioxidants and emulsifiers
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