Major Phenolics in Apple and Their Contribution to the Total Antioxidant Capacity

TLDR

The study quantified the contribution of each phytochemical to the total antioxidant capacity of apples. Major phenolic compounds in six apple cultivars were identified and quantified, and their antioxidant activity was measured by a DPPH radical scavenging assay and expressed as vitamin C equivalent antioxidant capacity (VCEAC). Quercetin, epicatechin, and procyanidin B₂ were the most abundant phenolics and contributed 40.4, 23.1, and 22.1 VCEAC per 100 g of apple, respectively, while vitamin C contributed only 12.8 VCEAC; a strong linear relationship (r² > 0.97) linked phenolic concentrations to total antioxidant capacity, indicating flavonoids dominate apple antioxidant activity. Keywords: apples, free radical, phenolics, vitamin C equivalent antioxidant capacity (VCEAC).

Abstract

The contribution of each phytochemical to the total antioxidant capacity of apples was determined. Major phenolic phytochemicals of six apple cultivars were identified and quantified, and their contributions to total antioxidant activity of apples were determined using a 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging assay and expressed as vitamin C equivalent antioxidant capacity (VCEAC). Average concentrations of major phenolics and vitamin C in six apple cultivars were as follows (mg/100 g of fresh weight of apples): quercetin glycosides, 13.20; procyanidin B2, 9.35; chlorogenic acid, 9.02; epicatechin, 8.65; phloretin glycosides, 5.59; vitamin C, 12.80. A highly linear relationship (r 2 > 0.97) was attained between concentrations and total antioxidant capacity of phenolics and vitamin C. Relative VCEAC values of these compounds were in the order quercetin (3.06) > epicatechin (2.67) > procyanidin B2 (2.36) > phloretin (1.63) > vitamin C (1.00) > chlorogenic acid (0.97). Therefore, the estimated contribution of major phenolics and vitamin C to the total antioxidant capacity of 100 g of fresh apples is as follows: quercetin (40.39 VCEAC) > epicatechin (23.10) > procyanidin B2 (22.07) > vitamin C (12.80) > phloretin (9.11) > chlorogenic acid (8.75). These results indicate that flavonoids such as quercetin, epicatechin, and procyanidin B2 rather than vitamin C contribute significantly to the total antioxidant activity of apples. Keywords: Apples; free radical; phenolics; vitamin C equivalent antioxidant capacity (VCEAC)