Ultrasound and microwave-assisted extractions as green and efficient approaches to recover anthocyanin from black rice bran

Extraction techniques are one way to separate bioactive compounds from agro-industrial material. Emerging technologies for the extraction of bioactive compounds, such as ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE), are preferable to conventional extraction techniques because they are more efficient, spend less time, and are environmentally friendly. This study compared ultrasound (UAE) and microwave (MAE) assisted extraction techniques to recover anthocyanins from black rice bran. By optimizing using Box Behnken design, for UAE, 83.73% of the total anthocyanins (2.44 mg C3G/g) were recovered, using as parameters temperature 50 degrees C, a frequency 380 W, and a solvent 60:40 (v/v) citric acid 0.1 M:ethanol. For MAE, it was possible to recover 81.44% of the total anthocyanins (2.37 mg C3G/g), using parameters temperature 55 degrees C, citric acid 0.1M:ethanol (50:50, v/v), and a mass of 0.8 g (1:24, g/ml). Both techniques were considered ecologically green by the Green Certificate (A) and excellent methods by EcoScale (scores higher than 75). Anthocyanin-rich extracts did not show cytotoxicity for L292 cells (1000 mu g/mL) and showed cytoprotection (> 92% using 500 mu g/mL) when subjected to oxidative stress with H2O2. Both extracts showed technological potential as a natural dye and as an ingredient of nutraceutical products.