Extraction and antioxidant activity of phenolic compounds from wheat bran treated by steam explosion

Purpose: To use response surface methodology to optimize the extraction of the phenolic compounds in wheat bran treated by steam explosion, and to determine the antioxidant activity of the extract obtained. Methods: By using response surface methodology, the effects of extraction time, methanol concentration, liquid/solid and temperature were studied and optimized. 2,2-Diphenyl-1-(2,4,6- trinitrophenyl) hydrazyl (DPPH) radical-scavenging capacity, reducing capacity and 2,2′-Azino-bis(3- ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging capacity were also employed to determine antioxidant activity of the extract. Results: Under the optimal conditions, i.e., extraction time: 120 s, ethanol content: 43 %, liquid/solid: 35:1, temperature: 70°C, the experimental total phenolic yield was 30.464 ± 0.025, which agreed with the predicted value of 31.687. The phenolic compounds showed strong antioxidant activities. At extract concentration of 1 mg/ml, DPPH radical-scavenging activity was 50 %. Although its reducing power (2 - 10 mg/mL) was lower than that of BHA, ABTS radical scavenging of the extract (close to 90 %) was higher than that of BHA at extract concentration > 6 mg/mL. Conclusion: The yield of the phenolic compounds was high and the compounds displayed strong antioxidant capacity, which indicates that the extraction of wheat bran under steam explosion holds high potentials for the food and pharmaceutical industries.