Pretreatment and Optimization of Processing Conditions for Extraction of Oleuropein from Olive Leaves using Central Composite Design

Background: The extraction methods used for isolation of biomolecule from Olive leaves show risk of residual solvent and less extraction efficiency. Hence, there is a need to develop novel techniques to encapsulate the risks headed with extraction process. Objective: The goal was to unravel the effect of novel extraction techniques on the extraction efficiency of Oleuropein from Olea europaea, a major secoiridoid resided in Olive leaf. Materials and Methods: Olive leaves were collected, authenticated, and subjected to proximate, phytochemical analysis to contemplate the source of active moiety. The précised solvent, i.e., water: glycerol (3:1%v/v) was functionalized to depict the influence of independent variable on response using central composite design. For hot blanching, the independent factors selected were treatment temperature (50°C–70°C) and duration of blanching (10–30 min) whereas the observed response is percentage extraction efficiency of Oleuropein. The hot blanched leaves were subjected to extraction by cold maceration, microwave‑assisted extraction (MAE), and ultrasound‑assisted extraction (UAE). The content of Oleuropein was analyzed by high‑performance thin‑layer liquid chromatography. Results: From the design space, the model is stable at a range of 0.002–0.80 which indicates lack of fit is very less and more curvature effects are clearly visualized with P = 5% level of significance. Maximum response was attained at a temperature of 60°C–65°C and duration of 15–20 min. Microstructural changes in leaf were observed through scanning electron microscopy studies. From the study, pretreated leaves followed by UAE result in higher yield of Oleuropein compared to MAE and maceration. Conclusion: Hot blanching technique shows a significant linear upswing in the concentration of Oleuropein when compared to direct extraction techniques. Blanching of Olive leaves causes deactivation of enzymes, and further exposure to ultrasonic waves enhances mass transfer of solvent and promotes the release of Oleuropein.