Optimization of microwave assisted extraction of bioactive compounds from black bean waste and evaluation of its antioxidant and antidiabetic potential in vitro

Legumes processing industries have led to an accumulation of waste as a byproduct which is often discarded. However, this study aimed to use a ‘green technology’ such as microwave-assisted extraction (MAE) to valorize the wastage and assess the functional attributes of black beans (Phaseolus vulgaris L.) hull powder (BBHP). The Box- Behnken design was employed to optimize the response variables of MAE and the process variables were as follows: microwave power (100–600 W), extraction time (2–6 min), and solvent: solid ratio (20:1–50:1 mL/g). For comparative purposes, conventional solvent extraction (CSE) has been considered for extracting bioactive compounds. The black bean extract was obtained by MAE under optimum conditions of microwave power of 334.4 W, solvent: solid ratios of 50:1 mL/g, and an extraction time of 6 min showed the highest yield of bioactive components, with total anthocyanin and phenolic content of 34.14 mg/g and 197.23 mg (GAE)/g, and their antioxidant activities are 91.37 % ABTS and 93.51 % DPPH compared to CSE. Further, an optimized sample of BBHP extracts exhibited the inhibitory effects on the activities of α-amylase 80.41% and α-glucosidase 86.14% respectively. Overall results show that MAE is better than CSE for extraction of functional attributes from black bean waste.