Study on optimization of ultrasonic assisted extraction of phenolic compounds from rye bran

Ultrasonic assisted extraction (UAE) conditions for the extraction of phenolic compounds from rye bran (RB) were optimized by using response surface methodology. The optimal conditions for UAE were; time: 29 min, temperature: 66 degrees C, and solid to solvent ratio: 1:45 (g/mL), which provided a total phenolic content of 245.74 mg GAE/100 g dw. Compared with conventional extraction (CE) technique, UAE resulted in higher yield of total phenolic and flavonoid compounds, whereas only a slight difference was reported in the total flavonol and pmanthocyanidin content. The UAE extract showed higher antioxidant activity in all antioxidant assays (DPPH, FRAP, ABTS, reducing power, and H2O2). The phenolic composition of both extracts was analyzed using HPLC-MS. Resultantly, a significant (p < 0.05) increase in the concentration of phenolic acid was observed when the extraction was accomplished with UAE as compared to CE. Both UAE and CE extracts exhibited in vitro hypoglycemic activities by inhibiting alpha-amylase and alpha-glucosidase enzymes. However, no significant differences (p > 0.05) were observed in the FTIR spectra of UAE and CE treated RB. These finding indicates that UAE increased the yield of phenolic compounds from RB. Furthermore, these phenolic compounds could be used as a potential source of natural antioxidants.