Exploring antioxidant and bioactive compounds of brown rice, germinated brown rice, and germinated Hang rice varieties

Rice is a staple food crop globally, playing a crucial role in feeding a large portion of the world's population. In addition to its nutritional value, rice contains bioactive compounds with significant biological effects. This study analyzed Gamma-aminobutyric acid (GABA), total phenolic compounds, proteins, and antioxidant properties in 24 rice extract samples, including anthocyanins in various pigmented rice varieties. GABA content ranged from 0.021 to 0.181 mg/g dry weight, with the highest levels in Kam-Noi germinated brown rice. The Folin-Ciocalteu method revealed total phenolic content ranging from 0.008 to 0.074 mg/g, with Mali-Daeng germinated brown rice showing the highest levels. Protein content, measured via Kjeldahl and SDS-PAGE methods, ranged from 6.090 to 8.380%, with Hom-Thung germinated brown rice having the highest protein concentration. Protein molecule sizes varied between 14.40 and over 97.00 kDa. Kam-Noi brown rice had the highest anthocyanin concentration. Antioxidant activity, evaluated through 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferrous ion chelating (FIC), and oxygen radical absorbance capacity (ORAC) assays, showed that Nieow-Daeng germinated Hang rice had the strongest DPPH radical scavenging activity, while Hom-Thung germinated Hang rice chelated Fe2 + effectively, and Hom-Thung brown rice demonstrated the strongest peroxyl radical inhibition. These findings emphasize the presence of bioactive compounds and valuable antioxidant properties in rice.