Efficiency of DPPH and FRAP assays for estimating antioxidant activity and separation of organic acids and phenolic compounds by liquid chromatography in fresh-cut nectarine

Abstract

Nectarine contain relevant amounts of antioxidants, including hydroxycinnamic acids, flavan-3-ols, flavonols, anthocyanins, procyanidins, and carotenoids. The aim of this research was to compare the efficiency of DPPH and FRAP assays to estimate antioxidant activities contents in nectarine minimally processed. Moreover, separation of organic acids, phenolic compounds and carotenoids were done by HPLC. Nectarine fruits ‘R48’ cv. were hand harvested, with 80% of their reddish coloration. The following treatments were applied: Control; 1% citric acid + 1% calcium chloride as anti-browning (AB) agent; 4 KJ m-2 UV-C radiation; 8 KJ m-2 UV-C; 12 KJ m-2 UV-C ; AB +  95 kPa O2 (High O2); AB + 4 KJ m-2 UV-C + High O2; AB + 8 kJ m-2 UV-C + High O2 and AB + 12 KJ m-2 UV-C + High O2. We determined antioxidant activity to DPPH; antioxidant activity to FRAP; total phenols and HPLC-DAD analyses. In general the DPPH showed higher efficiency of antioxidant concentration in comparison with FRAP in minimally processed nectarines. There was clear trend in phenolic content in fresh-cut nectarine the treatment AB + 8 kJ m-2UV-C + High O2. The 22 minimally processed nectarine phenolic compounds were studied and quantified by HPLC, being detected: Hydroxycinnamates, flavonols, and anthocyanins. These results allow to conclude that the most abundant compounds found in this study of fresh-cut nectarine were chlorogenic acid, caffeic acid and ellagic acid with HPLC chromatograms were recorded at 280 nm, quercentin 3-galactoside, quercetin 3- Xyloside at 340nm and Cyanidin 3- glucoside at 510nm.