Box behnken design for ultrasound extraction of phenolics from Algerian Pistacia Lentiscus L. cake: green approach & bioactivity assessment

In Northern Algeria, Pistacia Lentiscus berries are cold-pressed to extract a valuable oil with medicinal uses. However, after the berries are defatted, the residue (cake) is still underestimated, although it is a rich source of bioactive compounds. This work aimed to optimize the ultrasound-assisted extraction (UAE) of phenolic compounds from Pistacia Lentiscus berries cake (LBC) and to investigate some in vitro biological activities of the rich-phenolic optimized extract. Box Behnken’s design of experiments (BBD) was applied to explore the effect of three independent variables (temperature, duration of extraction, and ethanol in water fraction) at three levels, and then HPLC with a Diode Array Detector was used for analysis of its polyphenol composition. Afterwards, the optimized extract was assessed for its antioxidant and antidiabetic capacities. The validated model confirmed the best operative condition of extraction as 50%, 60 °C, and 86 min for, respectively, the ethanol concentration, temperature, and duration of extraction, and the predicted results were experimentally confirmed. Under these conditions, the obtained extract interestingly showed an IC50 of 61.79 ± 0.40 µg/mL against the free radical ABTS^• versus Trolox as a positive control (IC 50 = 50.67 ± 0.32 µg/mL). Moreover, a promising anti-α-amylase capacity has been shown by the sonicated LBC extract with an IC50 of 99,82 ± 2,03 µg/mL. These in vitro biological activities should be due to the bioactive phenolic composition of the LBC extract. Indeed, twelve phenolic compounds were identified and quantified in the optimized extract, comprising six flavonoids, five phenolic acids, and a phenylethanoid (Tyrosol).