Purpose: To investigate phenolic levels, phytophenolic profiles and total antioxidant activities of Oryza sativa, unpolished Thai rice.
Methods: Unpolished Thai rice strains of Leum Phua, Klam, Hawm Nil and Black Rose were measured for antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2’-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and ferric reducing antioxidant power (FRAP) methods. Phytophenolic chromatograms were obtained by a high performance liquid chromatography (HPLC) technique. Additionally, phenolic content and anthocyanin pigment were also assayed.
Results: Oryza sativa, unpolished Thai rice strain of Leum Phua showed the highest antioxidant activity. It was also highest in anthocyanin pigment. The strains of Leum Phua, Klam, Hawm Nil and Black Rose showed high levels of phenolic content: 1.36±0.03, 0.78±0.02, 0.61±0.01 and 0.57±0.02 mg gallic acid/ g sample, respectively. Interestingly, phytophenolic chromatogram and anthocyanin pigment levels showed a strong correlation.
Conclusion: Oryza sativa, unpolished Thai rice strain of Leum Phua, has high levels of anthocyanin pigment, phenolic content and antioxidant activity. Its pure phytochemical contents should be further studied for their pharmaceutical benefits.