COMPARISON OF THE ANTIOXIDANT ACTIVITY OF ASPALATHIN WITH THAT OF OTHER PLANT PHENOLS OF ROOIBOS TEA (ASPALATHUS-LINEARIS), ALPHA-TOCOPHEROL, BHT, AND BHA

The antioxidant activity of aspalathin, the major flavonoid of unferme nted rooibos tea, was compared with that of other polyphenols present in rooibos tea, alpha-tocopherol, BHT, and BHA using the beta-carotene bleaching, alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radical sc avenging, and automated Rancimat methods. The phenolic compounds inclu de the flavonoids vitexin, rutin, quercetin, luteolin, isoquercitrin, (+)-catechin, and the phenolic acids protocatechuic acid, caffeic acid , p-hydroxybenzoic acid, p-coumaric acid, ferulic acid, syringic acid, and vanillic acid. (+)-Catechin had the longest induction period acco rding to the Rancimat method, while BHT was the most effective inhibit or of beta-carotene bleaching. Compounds with the highest degree of DP PH radical scavenging and highest rate of scavenging were caffeic acid and aspalathin, respectively. Aspalathin offered less protection agai nst lipid oxidation than BHT and alpha-tocopherol according to the Ran cimat and beta-carotene methods, but it displayed a higher ability to scavenge the DPPH radical.