Comparative Analysis of γ-Oryzanol, β-Glucan, Total Phenolic Content and Antioxidant Activity in Fermented Rice Bran of Different Varieties

Abstract

Rice bran, a by-product derived from processing rice, is a rich source of bioactive compounds. Recent studies have suggested that the fermentation can improve their biological activities. This study aimed to determined the level of γ-oryzanol, β-glucan and total phenol contents of fermented rice bran from 21 Korean varieties, as well as to evaluate their antioxidant activities. We also assessed the validation of the analytical method for determining γ-oryzanol content in fermented rice brans. Among the fermented rice brans, the Haedam rice bran contained the highest level of total phenol content (156.08 mg gallic acid equivalents/g), DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity (71.30%) and ORAC (Oxygen radical absorbance capacity) value (1101.31 μM trolox equivalents/g). Furthermore, the fermented Migwang rice bran showed the highest level of γ-oryzanol content (294.77 ± 6.74 mg/100 g).

Keywords: antioxidant activity; cultivars; fermented; rice bran; γ-oryzanol.

Figure 1

Total γ-oryzanol content. Comparison of non-fermented and fermented rice bran (a); composition of γ-oryzanol species of non-fermented rice bran (b); and fermented rice bran (c).

Figure 2

Linearity and specificity of γ-oryzanol. Calibration curve of γ-oryzanol standard solution (a); HPLC-PDA chromatograms of γ-oryzanol standard (b); non-fermented Haiami rice bran (c); and fermented Haiami rice bran (d).

Figure 3

Linear correlation between the antioxidant activities and bioactive compounds. DPPH radical scavenging activity and the ORAC value (a); DPPH radical scavenging activity and the total phenolic content (b); DPPH radical scavenging activity and the β-glucan content (c); DPPH radical scavenging activity and the γ-oryzanol content (d); ORAC value and total phenolic content (e); ORAC value and the β-glucan content (f); ORAC value and the γ-oryzanol content (g); total phenolic content and the β-glucan content (h); total phenolic content and the γ-oryzanol content (i); and β-glucan content and the γ-oryzanol content (j). All of correlations among the response variables were significant as p < 0.05.

Figure 3

Linear correlation between the antioxidant activities and bioactive compounds. DPPH radical scavenging activity and the ORAC value (a); DPPH radical scavenging activity and the total phenolic content (b); DPPH radical scavenging activity and the β-glucan content (c); DPPH radical scavenging activity and the γ-oryzanol content (d); ORAC value and total phenolic content (e); ORAC value and the β-glucan content (f); ORAC value and the γ-oryzanol content (g); total phenolic content and the β-glucan content (h); total phenolic content and the γ-oryzanol content (i); and β-glucan content and the γ-oryzanol content (j). All of correlations among the response variables were significant as p < 0.05.