Optimization of microwave-assisted extraction (MAE) of key phenolic compounds from pigeon pea ( Cajanus cajan L.), their characterization, and measurement of their anti-diabetic and cytotoxic potential

The current work aims to optimize and develop a scale-up process design for higher yields of phenolic compounds, as well as propose and validate their antidiabetic and cytotoxic effects when extracted from Cajanus cajan leaves. The optimization procedure included 17 experimental runs using microwave-assisted extraction parameters such as temperature (50–70 °C), power (400–1000 W), and time (15–45 min), and was optimized using response surface methodology for total phenolic content (TPC), total flavonoid content (TFC), total tannin content (TTC), and antioxidant activities like 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) was found to be 52.15 mg GAE/g dw, 25.12 mg QE/g dw, 43.02 mg TAE/g dw, 35.16%, and 43.25 mg TE/g dw, respectively. The optimized values of response variables were achieved at 700 W of power, 60 °C of temperature, and 40 min of processing time. Purification, thin-layer chromatography, fourier transform infrared (FTIR), and liquid chromatography-mass spectrometry (LC-MS) spectral analysis of the plant extract revealed the existence of 18 bioactive phenolic compounds. The in silico investigation found that fifteen out of eighteen bioactive phenolic compounds had strong binding affinities in the range of −4.0 to −8.8 kcal/mol, along with enhanced pharmacokinetic characteristics and a low to moderate level of toxicity. The IC 50 values of in vitro α-amylase and α-glucosidase inhibitory activity were 46.49 ± 2.2 and 59.51 ± 3.57 µg/mL, respectively, indicating a high level of enzymatic inhibition activity. In addition, the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) and chorioallantoic membrane (CAM) tests revealed that cytotoxicity was minimal up to a concentration of 62.5 µg/mL of the extract. The results of this study will open new doors for researchers, scientists, and industrialists in the food and pharmaceutical industries who intend to develop antidiabetic food formulations and antidiabetic drugs as a way for diabetic people to manage their disease and improve their overall health.