Contribution of individual phenolics to antioxidant activity and in vitro digestibility of wild rices (Zizania aquatica L.)

- Polyphenols, flavonoids, DPPH, ABTS, digestibility were assessed.
- The main free and bound individual phenolics in wild rices were determined.
- Correlation between total phenolic content and antioxidant activity was linear.
- Total flavonoid content showed positive correlation to antioxidant activity of wild rices.
- Contributions of individual phenolics to antioxidant activity of wild rices were evaluated.

Zizania aquatica L. was analysed for total flavonoids, phenolics and HPLC profile in both free and bound phenolic fractions. The highest content of flavonoids (378-455 mg RE/kg) was detected in bound fractions, while the highest polyphenols content (1061-2988 mg GAE/kg) was determined in free fractions. Additionally, predominant phenolics were identified. To understand the contribution of individual phenolics to an antioxidant activity their mutual correlations were evaluated. Regarding free flavonoids, the main contributors to an antioxidant activity (r > 0.7111) were epigallocatechin, epicatechin and rutin; while epicatechin, quercetin and rutin were the main contributors in bound fractions (r > 0.6868). Concerning free phenolic acids, the main contributors to an antioxidant activity (r > 0.7585) were ferulic, vanillic, ellagic, sinapic and syringic acids; while caffeic, sinapic, syringic, o-coumaric, p-hydroxy benzoic, vanillic, protocatechuic, gallic and cinnamic acids were the main contributors in bound fractions of wild rice (r > 0.6538). Finally, in vitro organic matter and dry matter digestibility were assessed.