# Comparative analysis of the metabolite compositions and antioxidant capacity of waxy and non-waxy black rice (Oryza sativa L.) bran via widely targeted metabolomics

## TL;DR

Non-waxy black rice bran has higher antioxidants and beneficial compounds than waxy rice, making it more valuable for functional foods.

## Contribution

The study identifies specific flavonoid-rich metabolites in non-waxy black rice bran linked to enhanced antioxidant and health-promoting properties.

## Key findings

- Non-waxy black rice bran shows significantly higher antioxidant activity and polyphenol content compared to waxy rice bran.
- UPLC-MS/MS identified 1130 metabolites, with flavonoids and phenolic acids being the most abundant in non-waxy rice bran.
- Differential flavonoids in non-waxy rice are strongly associated with improved functional properties like α-glucosidase inhibition.

## Abstract

Black rice (Oryza sativa L.), valued for its nutritional benefits, was investigated to elucidate metabolite profiles and antioxidant capacity differences between waxy and non-waxy varieties. Eight black rice varieties sourced from diverse Chinese provinces were categorized based on amylose content. Non-waxy varieties demonstrated significantly superior antioxidant capacity, evidenced by elevated levels of DPPH and ABTS radical-scavenging activities, FRAP values, total polyphenol content, and α-glucosidase inhibitory activity. Utilizing UPLC-MS/MS, a total of 1130 secondary metabolites were identified, with flavonoids and phenolic acids constituting prominent classes. Multivariate analysis revealed distinct metabolite profile differences between the waxy and non-waxy groups, particularly in associated metabolic and genetic pathways. The enhanced antioxidant capacity and α-glucosidase inhibitory activity were strongly associated with differential metabolites, notably flavonoids. These findings underscore the potential of non-waxy black rice bran components, particularly flavonoid-rich fractions, for development in functional food applications. .

•Non-waxy black rice bran exhibits significantly higher antioxidant capacity (DPPH, ABTS, FRAP), total polyphenols, and α-glucosidase inhibitory activity compared to waxy bran.•Widely targeted UPLC-MS/MS metabolomics identified 1130 metabolites in black rice bran, with flavonoids and phenolic acids as major classes.•Multivariate and association analyses revealed distinct metabolite profiles between waxy/non-waxy groups and linked the enhanced functional properties in non-waxy bran specifically to differential flavonoids.•Identification of key differential metabolites provides a foundation for targeted development of black rice bran components and breeding improved varieties for functional food applications.

Non-waxy black rice bran exhibits significantly higher antioxidant capacity (DPPH, ABTS, FRAP), total polyphenols, and α-glucosidase inhibitory activity compared to waxy bran.

Widely targeted UPLC-MS/MS metabolomics identified 1130 metabolites in black rice bran, with flavonoids and phenolic acids as major classes.

Multivariate and association analyses revealed distinct metabolite profiles between waxy/non-waxy groups and linked the enhanced functional properties in non-waxy bran specifically to differential flavonoids.

Identification of key differential metabolites provides a foundation for targeted development of black rice bran components and breeding improved varieties for functional food applications.