Antioxidant activity compared anthocyanins

The antioxidant activity of a compound depends upon which free radical or oxidant is used in the assay (Halliwell and Gutteridge, 1995), and a different order of antioxidant activity is therefore to be expected when analyses are performed using different methods. This has been demonstrated by Tsuda et al. (1994) in their study of antioxidative activity of an anthocyanin (cyanidin-3-O-p-D-glucosidc) and an anthocyanidin (cyanidin) in four different lipophilic assay systems. Both compounds had antioxidative activity in all four systems, but the relative activity between them and their activity, compared with Trolox, varied with the method used. Fukumoto and Mazza (2000) reported that antioxidant activity of compounds with similar structures gave the same trends, although not always the same results, when measured by P-carotene bleaching, DPPH and HPLC detection of malonaldehyde formation in linoleic acid emulsion. 

The antioxidant activities of red and white commercial grape juices have been studied using in vitro inhibition of the copper-catalyzed oxidation of human LDL (Frankel et al., 1998). The correlation between total phenols, expressed as GAE, and relative percent of inhibition of LDL oxidation was r = 0.99. In red Concord grape juices, the antioxidant activity was related to the anthocyanin levels. In the white grape juice, the antioxidant activity was associated with the levels of hydrox-ycinnamates (caffeic acid) and flavanols (catechin). When compared at the same level of total phenolics (10 pM GAE), the antioxidant activities of the grape juices were comparable to the antioxidant activities of red wine (Frankel et al., 1995). Laplaud et al. (1997) found protective action of copper-mediated LDL oxidation in aqueous V. myrtillus extracts. On a molar base, the extracts were more efficient than ascorbic acid and BHT in inhibiting LDL oxidation. 

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