ARTICLE INFO

ABSTRACT

Received 23 May 2018
Revised 01 Jul 2018

Accepted 03 Aug 2018

Recently, the interest towards phenol compounds has progressed. In this study, a response surface methodology (RSM) was applied to predict the optimum conditions for extraction of phenolic from red rice bran. Firstly, the effects of ethanol concentration (20–80%), added acetic acid concentration (0–20%), extraction time (0–6.5 hours), temperature (25–100^oC), number of extraction cycles (1–4) and solid–solvent ratio (1/4–1/10 w/v) on total polyphenolic content (TPC) of red rice bran were found. After that, three parameters such as solvent concentration (48–68%), added acetic acid concentration (10–15%) and extraction time (120–240 min) were able to be optimized using the Box Behnken design (BBD) with a quadratic regression model built by using RSM. The experiment was designed according to 30 runs with 2 blocks; each block consists of 3 central points and 1 replicate. This design was set up for 3 factors to optimise the response in term of TPC extraction. The extracts were analyzed the TPC spectrophotometrically according to the Folin-Ciocalteu colorimetric assay. The optimal extraction conditions were determined as follows: ethanol concentration of 54.5%, added acetic acid concentration of 13.1%, extraction time of 210 min, temperature of 40^oC, 3 cycles of extraction and solid–solvent ratio 1/6 w/v. Using these extraction conditions, the experimental yield of TPC was 2391.1±5.9 mg GAE/100 g dry weight (dw) that was in close significant agreement with predicted value (p < 0.05). The experimental results were fitted to a second order quadratic polynomial model, and they have shown a good fit to the proposed model (R² = 0.99). With these conditions, the antioxidant capacity assayed by 1,1–diphenyl–2–picrylhydrazyl (DPPH) radical–scavenging activity in term of IC50 value of extract was 108.1±2.9 μg dw/mL. The study result indicates the suitability of the developed model and the success of RSM in optimizing the extraction conditions.

KEYWORDS

Antioxidant activity, extraction, phenolic compounds, red rice bran, response surface methodology

Cited as: Tram, P.T.B., Liem, N.T. and Lien, D.T.P., 2018. Optimization of the polyphenolics extraction from red rice bran by response surface methodology. Can Tho University Journal of Science. 54(Special issue: Agriculture): 79-87.