Inhibitory activities of some vitamins on the formation of cholesterol oxidation products in beef patties.
The capacities of 15 vitamins to inhibit the formation of 7α-hydroxycholesterol, 7β-hydroxycholesterol, and 7-ketocholesterol were examined in beef patties. Their inhibitory activities were tested at a concentration of 0.4 mmol in 30 g of beef. Among them, L-ascorbic acid, retinoic acid, and α-(±)-tocopherol were found to exert a potent inhibitory effect (30-50%) on 7-ketocholesterol formation and (~20%) on 7α-hydroxycholesterol and 7β-hydroxycholesterol formations. Pyridoxamine inhibited 7-ketocholesterol formation by 60% with a statistically significant difference (p < 0.05) from that achieved in the control setup. To further elucidate the possible inhibitory mechanism of pyridoxamine against cholesterol oxidation, a chemical model with pyridoxamine added in the cholesterol oxidation system (heated at 140 °C for 240 min in dimethyl sulfoxide) was employed. It was demonstrated that pyridoxamine could directly react with 7-ketocholesterol via the addition reaction. The reaction involved a nucleophilic attack of the free amine group of pyridoxamine on 7-ketocholesterol (an α,β-unsaturated carbonyl compound). This type of reaction was also found to occur in beef patties by chromatographic and spectral analyses.
School of Biological Sciences, The University of Hong Kong , Pokfulam Road, Hong Kong, People's Republic of China.
Daniel
D
Wong
Mingfu
M
Wang
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002417:Cattle; D002784:Cholesterol / Q000737:chemistry*; D006888:Hydroxycholesterols / Q000737:chemistry; D007653:Ketocholesterols / Q000737:chemistry; D008460:Meat / Q000032:analysis*; D010084:Oxidation-Reduction; D014815:Vitamins / Q000494:pharmacology*
D000975:Antioxidants; D006888:Hydroxycholesterols; D007653:Ketocholesterols; D014815:Vitamins; D002784:Cholesterol; C003001:7-ketocholesterol