Abstract
The bioactive properties of olive leaf extract (OLE) were investigated using various extraction methods, including microwave-assisted extraction (MAE), conventional extraction (CE), and maceration (Mc). Response surface methodology (RSM) was employed to optimize extraction parameters such as microwave power and time. RSM optimization revealed the influence of extraction types, independent variables, and their interactions on yield, total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity (DPPH, ABTS, and CUPRAC assays) of OLE. The coefficient equation models (CEM, P < .01 and P < .0001) demonstrated high reliability (Rexp2:0.75–0.93, Radj2:0.69–0.9), with non-significant lack of fit (P > .05) and significant F values (P < .05). The model coefficients and analysis of variance (MCA) were significant between P < .05 and P < .0001. Watt power was identified as a more significant parameter than time. IC50 (half maximal inhibitory concentration) values for DPPH/ABTS ranged from 8.57 to 14.80 mg/L, with the highest antioxidant activity observed in Mc. TPC and TFC ranged from 85.21 to 169.20 mg GAE/g dry and 1.49 to 111.98 mg Qrc/g dry, respectively, with MAE yielding the highest polyphenol content. LC-MS/MS analysis identified eight major components in OLE, primarily Oleuropein and Quercetin, whose concentrations varied with extraction methods. The optimized conditions for CE (t = 30 min) and MAE (t = 30 min/350 W) were determined with desirabilities of 91.1% and 82.2%, respectively. Overall, extraction method, time, and watt significantly influenced response variables (p < 0.05).