Multivariate optimization of ultrasound-assisted extraction for the determination of phenolic compounds in plums ( Prunus salicina Lindl.) by high-performance liquid chromatography (HPLC)

A high-performance liquid chromatographic (HPLC) method with a diode array detector (DAD) and ultrasound-assisted extraction (UAE) was established to obtain the maximum response for the extraction of phenolic compounds in plums (Prunus salicina Lindl). The effects of solvent relationship (methanol/water) (0 to 100%, v/v) and ultrasound extraction time (5 to 30 min) using a multivariate design and response surface methodology were studied. All of the studied extracted condition models established showed significant effects (p < 0.05). Nevertheless, the determination of common optimum combination for all compounds was complex and a weighted desirability function was applied to maximize the extraction for each analyte. The optimum conditions of extraction were for a period of 30 min. For the solvent optimized conditions (84/16 methanol/water, v/v), the important phenolic compounds selected in the design model according to the concentration range and insignificant lack of fit p-value were extracted, detected, and quantified with a probability of 84% including hydroxycinnamic acids (chlorogenic and neochlorogenic acids), flavonols (quercetin-3-O-rutinoside, kaempferol-3-O-rutinoside, isoharmentin-3-O-rutinoside), and anthocyanins (cyanidin-3-O-glucoside, cyanidin-3-O-rutinoside). The validity and adequacy of the predictive extraction model was checked in plums and no significant differences were detected between the predicted and the actual phenolic contents. The intra-day and inter-day assay repeatabilities for the analysis of real samples were less than 11.5% and 11.7%, respectively. Recovery values between 72.0 and 112% were obtained for all compounds. For all these reasons, the methodology is appropriate for the routine determination of the majority of phenolic compounds in Prunus salicina Lindl.