Microwave-assisted extraction of phenolic compounds from Sacha Inchi shell: Optimization, physicochemical properties and evaluation of their antioxidant activity

The interest in phenolic compounds has significantly increased in the recent years, due to their multiple health benefits and antioxidant activity. In this study, microwave-assisted extraction (MAE) was applied for extracting phenolics from the Sacha Inchi shell (SI-shell), an underutilized by-product of the SI oil processing. Response surface methodology was used to estimate the optimal operating conditions. A Box-Behnken design was employed to investigate the effects of the microwave power (500, 1000, and 1500 W), ethanol concentration (E30, E60, and E90 %, v/v), and extraction time (60, 90, and 120 s) on the total phenolic content (TPC) and antioxidant capacity (evaluated by means of the FRAP and TEAC assays) of the obtained extracts. Under the optimal extraction conditions (1500 W, E63.0 %, and 110 s) the TPC reached up to 41.97 +/- 1.05 mg gallic acid/g SI-shell, while the FRAP and TEAC values were 374.39 +/- 1.81 and 384.50 +/- 3.55 mu mol Trolox/g SI-shell, respectively. The predominant phenolic compounds found in the extracts were 3,4-dihydroxy-benzaldehyde, hydroxy-4-chromone, and their derivatives. These results indicate that SI-shell is a promissory source of natural compounds with antioxidant activity, and that MAE could be used for their extraction in shorter times compared to the conventional processes.