Phenolic composition and antioxidant potential of Indian pigmented rice landraces cultivated under identical agro-climatic conditions

Abstract

Pigmented rice has attracted significant attention from researchers and consumers. Unlike commonly consumed rice, which undergoes extensive polishing that removes the bran and germ, pigmented rice retains these components, distinguishing it from white rice and contain high levels of bioactive compounds. The present study aimed to evaluate black and red rice landraces (n = 17) grown on the same agro-climatic location (Telangana, India), for their free and bound polyphenolic profile and antioxidant potential. HPLC was used to quantify individual polyphenols while antioxidant activity was measured using ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, reducing power (RP), metal chelation (MC) and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) scavenging activity. The rice landraces had a good amount of total phenolics (362–1495 mg GAE/100g), flavonoids (965–1854 mg CE/100g), anthocyanins (4.5–39.7 mg C3G/100g), pro-anthocyanins (82.2–230.6 μg CE/100 mg) and exhibited high antioxidant capacity. A total of 19 individual polyphenols were analyzed, ferulic acid emerged as the predominant phenolic acid detected primarily in the bound fractions of pigmented rice. Pearson's correlation showed a significant relationship between total phenolic content and antioxidant activities (DPPH, FRAP, RP, and ABTS). These findings highlight the role of polyphenols in the antioxidant potential of pigmented rice. Multivariate analysis, including hierarchical cluster analysis (HCA) and principal component analysis (PCA), was used to interpret the heterogeneity of the analyzed characteristics among the pigmented rice landraces. The results of the present study revealed high levels of both free and bound polyphenolic content and antioxidant activity. These findings suggest that such characteristics could play a vital role in selecting the rice landraces for the breeding programs to develop novel rice varieties high in phenolics, anthocyanin, and antioxidant potential.