Optimization of extraction of phenolic compounds from ornamental apple leaf samples

Background: Apple leaves contain various phenolic compounds with antioxidant, anti-inflammatory, and anticancer properties, contributing to the prevention of chronic conditions such as cardiovascular diseases and diabetes. The extraction of these compounds is influenced by different factors including the type of solvent, extraction time, temperature, and sample preparation methods. By optimizing these parameters, the process can achieve higher yields and better preservation of biologically active compounds. Aim: This research aims to optimize phenolic compound extraction from ornamental apples. Methods: 0.25 g lyophilized powder of ornamental apple leaf samples (mixture of 32 cultivars) were weighed (exact weight) and extracted with ethanol using ultrasonic bath. Extraction conditions were optimized using ―Design-Expert® 6.0.8‖ software (―Stat-Ease Inc.‖, Minneapolis, Minnesota, USA). A three-levelthree-factor central composite design using the response surface methodology was employed. The variables optimized were ethanol concentration, extraction time and ultrasonic power, aiming to maximize the yield of phenolic compounds. Total phenolic content was measured by the Folin–Ciocâlteu assay and expressed as mg GAE/g, recalculated for dry weight. Results: Statistical analysis using ANOVA confirmed that the quadratic polynomial model is significant (p=0.0387). The desirability value of the model was 0.979 which confirmed that the selected model is suitable for extraction of phenolic compounds. The lack of fit p value (0.1922) was not significant, also confirming the model's appropriateness. An adequate precision was 6.27 indicating adequate model discrimination. The predicted total phenolic content was 33.35 mg GAE/g. Through mathematical statistical modeling of the extraction optimization of phenolic compounds, the optimized extraction conditions were 70% (v/v) ethanol, extraction time – 60 min., and ultrasonic power – 904 W. These extraction conditions could be suitable for further research on the phenolic compounds of ornamental apple leaf samples.