Investigation of flavonoid components and their associated antioxidant capacity in different pigmented rice varieties.

• There was inconsistent results between UPLC and metabolome analysis. • The content and types of flavonoids in black rice (BR) varieties were high. • Different flavonoids have different antioxidant capacities. • Both red rice (RR) and BR were found to possess significant antioxidant capacity. • Quercetin and catechin had peak antioxidant capacity in BR and RR, respectively. Black and red rice are flavonoid-rich and nutritious. However, comprehensive information of flavonoid components in different pigmented rice varieties remain unclear. Here, we analyze the differences in flavonoid components in black, red, and white rice by ultra-high-performance liquid chromatography (UPLC) and metabolome analysis. Cyanidin-3-glucoside (Cy-3-G), peonidin-3-glucoside (Pe-3-G), quercetin, dihydromyricetin, naringin, and taxifolin contents were significantly high in black rice. By contrast, catechin and epicatechin contents were substantial in red rice. Cy-3-G was the main anthocyanin and its content was more than four times that of Pe-3-G in black rice varieties. Trifolin hardly showed specificity and exhibited a high content in all rice varieties. The antioxidant capacity of the red and black rice varieties was significantly higher than that of white rice. Moreover, in black and red rice, quercetin and catechin respectively exhibited the strongest antioxidant capacity and a good contribution toward the total flavonoid content, and mean time, white rice possessed antioxidant capacity main derived from quercetin and trifolin. Besides, the study also found that there was slightly inconsistent results between UPLC and metabolome, because certain components with trace by metabolome were not detected by UPLC, but their combination could play a complementary role in the exploration of metabolic components to confirm the ingredients. [ABSTRACT FROM AUTHOR]