Fractionation of blue wheat anthocyanin compounds and their contribution to antioxidant properties

Abstract

Demands for anthocyanin-rich foods and supplements are steadily increasing due to their significant roles in human health and food coloration. In the development of blue wheat as a functional food ingredient, dry milling was employed to separate the bran fraction where anthocyanins are concentrated 2.3-fold as compared to whole grain (13.9 mg/100 g). Anthocyanins were then extracted with aqueous ethanol and partially purified into a highly concentrated powder. The total anthocyanin content in the isolated powder as analyzed by high-performance liquid chromatography (HPLC) averaged 3378 mg/100 g and afforded a 243-fold increase in concentration relative to the whole grain product. Four main anthocyanins, delphinidin-3-glucoside (45%), cyanidin-3-glucoside (28%), delphinidin-3-rutinoside (22%), and cyanidin-3-rutinoside (2%), were isolated from the powder using preparative HPLC. Anthocyanin products and compounds were assessed against scavenging of 2,2-diphenyl-1-picryl-hydrazyl and 2,2'-azino-di-(3-ethylbenzthiazoline sulfonate) radicals and inhibition of human low-density lipoprotein cholesterol oxidation. Significant differences in antioxidant capacity were observed with anthocyanin powder and compounds exceeding that of butylated hydroxytoluene, indicating a potential for the development of blue wheat-based natural antioxidants and colorants.