Enhancing the Extraction of Phenolic Compounds from Juniper Berries Using the Box-Behnken Design

Juniper berry is an important medicinal plant used in pharmaceutical and petrochemical industries thanks to its strong antioxidant potential, which is attributed to the presence of phenolic compounds. In this study, four different solvents, namely, aqueous acetone, aqueous ethanol, aqueous NaOH, and water, were used in the extraction process with a view to optimize and determine the polyphenolic contents in the juniper berry using ultraviolet (UV) spectrophotometry. Many experiments were performed at different solvent concentrations, time, temperature, and liquid–solid ratio. The models to evaluate the effects and the optimum of these variables on the polyphenols extraction using the response surface methodology (RSM) were developed. The predicted values of the polyphenol content of juniper berry were thus highly correlated with costly measured values (SECV = 0.14 and <i>R</i>² = 0.97), and the optimal conditions of extraction were determined for the different solvents. Following the numerical optimization, the maximum predicted polyphenol contents obtained under the optimum extraction conditions are as follows: 17.57% for 58 °C extraction temperature, 78.5 min extraction time, 60% acetone concentration, and 29.8 liquid–solid ratio for the aqueous ethanol extraction; 20.68% for 71.46 °C extraction temperature, 79.2 min extraction time, 21.9% ethanol concentration, and 26.4:1 liquid–solid ratio for the aqueous acetone extraction; 34.51% for 96.4 °C extraction temperature, 37.7 min extraction time, 1.48% NaOH concentration, and 15.2:1 liquid–solid ratio for the aqueous NaOH extraction; and 9.8% was obtained under the optimum extraction conditions of 69 °C extraction temperature, 126 min extraction time, and 23:1 liquid–solid ratio for the water extraction. The GC–MS analysis of the chemical composition of juniper Berry revealed 60 identified components that represent 97.43% of the sample. The predominant fraction was monoterpene representing 80.87% especially for α-pinene (39.12%), β-pinene (12. 68%), and myrcene (12.92%). In the other fraction of sesquiterpene representing 16.54%, the predominant components were β-caryophyllene (4.41%) and germacrene D (4.23%).