Characteristics of Functional Components and Antioxidant Activity of 28 Common Beans

Abstract

Common beans are either white or colored. They contain large amounts of phenolic compounds and other phytochemicals. Polyphenols exhibit high antioxidant activity that promote health by reducing oxidative stress. The objective of this study was to compare the content and composition of polyphenols in 28 common beans and determine the relation between their antioxidant activities and seed coat color. Here, we measured seed coat color by the International Commission in Illumination method, estimated polyphenol content and antioxidant activity by colorimetry, and identified polyphenol compositions by RP-HPLC. The results showed that polyphenol content and antioxidant activity were higher in colored beans than in the white beans. Taisho-Kintoki (red kidney) had the highest polyphenol content (6.12 mg / g seed) and antioxidant activity (21.98 $μ$mol / g seed; 3.75 mg / g seed). There was a high correlation between the total polyphenol content and seed coat redness. There were also high equilateral correlations between antioxidant activity and polyphenol content. Twelve phenolic compounds were identified. Based on their polyphenol compositions synthesized by various enzymes, the 28 common beans were divided into three groups. White beans and several half-spotted beans contained a large amount of catechin-7-O-glucoside with low antioxidant activity. Anthocyanin, procyanidin, and kaempferol-3-O-glucoside constituted significant proportions of the total polyphenol compounds and were positively correlated with antioxidant activity in the colored common beans. These findings are expected to help guide consumers and breeders in the selection of common bean varieties with high antioxidant activity.