Comparative Metabolic Analysis and Antioxidant Properties of Purple and White Wheat Grains: Implications for Developing Functional Wheat Varieties

Pigmented wheat has garnered attention due to its elevated antioxidant activity. This study aimed to compare the metabolic components and antioxidant properties of purple and white wheat grains. The results revealed that purple wheat exhibited significantly higher levels of total polyphenols, total flavonoids, and antioxidant activity compared to white wheat. Metabolic analysis identified a total of 405 secondary metabolites using three extraction methods: free, acid, and alkali hydrolysis. Notably, there were substantial variations in 90, 80, and 73 secondary metabolites between white and purple wheat under the respective extraction methods. The content of hispidulin-8-C-(2''-O-glucosyl) glucoside, hispidulin-8-C-glucoside, diosmetin-6-C-glucoside, and scoparin decreased across all groups, while the content of peonidin-3-O-glucoside, keracyanin, kuromanin cyanidin-3-O-glucoside, and cyanidin-3-O-(6''-O-malonyl) glucoside increased. These findings suggest that pathways associated with anthocyanin, flavone, and flavonol biosynthesis were influenced. Furthermore, each extraction method revealed distinct secondary metabolites. Acid and alkali hydrolysis up-regulated 16 and 3 metabolites in purple wheat, and 20 and 3 metabolites in white wheat, respectively. Acid and alkaline hydrolysis also identified indole-3-carboxylic acid, vanillic acid, pyridoxine, and other metabolites with antioxidant and antihypertensive effects in both white and purple wheat. This indicates that acid and alkaline hydrolysis can dissociate a greater variety and quantity of differential metabolites. These findings offer valuable insights for breeders seeking to develop wheat varieties with enhanced functional nutrition.