Antioxidant activities, phenolic and β-carotene contents of sweet potato genotypes with varying flesh colours

Antioxidant activities (mu mol Trolox equivalent (TE)/g fresh weight) of 19 sweet potato genotypes with distinctive flesh colour (white, cream, yellow, orange and purple) were measured by oxygen radical absorbance capacity (ORAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2'-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS). Total phenolics were measured using the Folin-Ciocalteau method, total anthocyanins by the pH-differential method, and -carotene by HPLC. The total antioxidant activity (hydrophilic + lipophilic ORAC) was highest (27.2 mu mol TE/g fresh weight (fw)) for NC415 (purple-fleshed) and lowest (2.72 mu mol TE/g fw) for Xushu 18 (white-fleshed). The hydrophilic-ORAC values were significantly correlated with the DPPH (R-2 = 0.859) and ABTS (R-2 = 0.761) values. However, the lipophilic-ORAC values were poorly correlated with the beta-carotene contents (R-2 = 0.480). The total phenolic contents (0.011-0.949mg chlorogenic acid equivalent/g fw) were highly correlated with the hydrophilic-ORAC (R-2 = 0.937) and DPPH (R-2 = 0.820) values. Therefore, the total phenolic content can serve as a useful indicator for the antioxidant activities of sweet potatoes. (c) 2006 Elsevier Ltd. All rights reserved.