Dependence of Sorghum bicolor antioxidant activity on harvest time

Abstract

This study was done to examine the correlation between differential contents of antioxidants and their antioxidative activities in the seeds obtained from two sorghum cultivars (Nampungchal and Hwanggeumchal) according to harvest time post heading, and to understand the properties of the harvested seeds. The seeds were harvested every 5 days from 25-55 days post heading. Length, width, thickness, and morphological properties of the obtained seeds were increased in proportion to the harvest time. The weights per thousand grains, crude fat, and redness (a*) clearly changed depending on the harvest time. The grain weight and fat content showed the highest value at harvest time days 45 (HT 45). The seed coat lightness (L*), crude protein, total polyphenol, flavonoid, and tannin in both cultivars were inversely proportional to the harvest time. In addition, ABTS and DPPH radical scavenging activities were also reduced in inverse proportion to the elapsed harvest time. Antioxidants including polyphenol, flavonoid, and tannin showed positive correlations with the antioxidative activities such as ABTS and DPPH activities, but antioxidants and their activities had no significant correlations between cultivars. We therefore propose that sorghum harvest is performed earlier to improve its antioxidative function.