Optimization of anthocyanin extraction from Oxalis tuberosa peel by ultrasound, enzymatic treatment and their combination

Oca Oxalis tuberosa is an Andean tuber with an important concentration of polyphenols and anthocyanins in the peel and flesh of the tuber. To exploit health and antioxidant benefits from these compounds they need to be extracted from the plant. Nowadays ultrasound and enzymatic extractions have demonstrated that they can enhance biocompound recovery over short periods of time and minimal solvent use. Therefore, the aim in this investigation is optimize pH, temperature and time for ultrasound, enzymatic extraction and their combination of anthocyanins from O. tuberosa peel. This peel is rich in carbohydrates (68.29 +/- 0.37%), while starch and hemicellulose are the main constituents in the cell wall. The enzyme-ultrasound combination method showed the best results for obtaining anthocyanins using the following conditions: a 5-value of pH solvent, 30 degrees C temperature and 30 min of time. The concentration of monomeric anthocyanins reaches up to 583.50 +/- 1.87 mg Cyn-3-glu g(- 1), while antioxidant activity using DPPH increases from 806.32 +/- 8.33 to 823.08 +/- 1.98 mg. ET g(- 1) for the extract. When ABTS radical was used the activity increased from 618.83 +/- 1.45 to 657.40 +/- 1.76 mg. ET g(- 1) and in FRAP increased from 334.30 to 360.89 mu mol Eq. Trolox g(- 1). Extracts with a high content of polyphenol and anthocyanin can be used in the food and pharmaceutical industries to prevent degenerative diseases.