A multivariate optimization of bioactive compounds extracted from oregano (Origanum vulgare) leaves using pulsed mode sonication

Abstract

In this study, pulsed mode ultrasound assisted extraction (PUAE) was investigated as green technology for the extraction of bioactive compounds from oregano (Origanum vulgare) leaves. A Box–Behnken experimental design (BBD) combined with response surface methodology (RSM) was used to determine the optimum sonication parameters. Solvent concentration and feed to solvent (F:S) ratio were first optimized using single factor experiment, followed by the optimization of three pulsed mode sonication parameters, namely sonication time, amplitude percentage and duty cycle. RSM was used to simultaneously maximize all the four responses viz. total phenolic content (TPC), total flavonoid content (TFC) and antioxidant capacity in terms of gallic acid equivalent antioxidant capacity (GAEAC) and ferric reducing antioxidant power (FRAP). The experimental results were fitted to quadratic models and statistical analysis in terms of multiple regression and analysis of variance (ANOVA) was carried out for each response variable. The optimum values of response variables were obtained at a sonication time of 10 min, using a duty cycle of 0.8 at 80% of sonication amplitude. Multivariate analysis in terms of principal component analysis (PCA) and hierarchical cluster analysis (HCA) was done for better understanding of interactions among the response variables and treatment conditions.