Optimization of ultrasound-assisted extraction of Pistacia lentiscus L. leaves in a green way to obtain the highest content of polyphenols using a response surface methodology

Pistacia lentiscus L. leaves are used in several applications, thanks to their polyphenolic abundance. Different methods are used for the extraction of these compounds. We aimed to optimize the ultrasond-assisted extraction (UAE) of P. lentiscus to obtain higher amounts of polyphenols in a greener way. A Box-Behnken design using temperature (30-50 °C), solvent volume (15-30 mL) and ethanol fraction (30-50 %) was conducted. Galloyl and myricetin derivatives were the most abundant compounds detected (HPLC-DAD-MS analysis). The regression analyses of total polyphenol (TPC), total tannins (TTC), total flavonoids (TFC) and myricitrin contents (MYC) showed good fit of the models. The maximum yields of TPC (51.3 ± 1.8 mg g^-1 DW) and TTC (40.2 ± 1.4 mg g^-1 DW) are obtained using 18 mL of 40 % ethanol at 50 °C. For flavonoids, an extraction with 20 mL of 50 % ethanol at 50 °C predicts the highest content (10.2 ± 0.8 mg g^-1 DW), while 15 mL of 30 % ethanol at 30 ° C results in the maximum of MYC (2.6±0.19 mg g^-1 DW). This greener process decreased in 25 % the percentage of ethanol and in half the time of the usual ethanolic extraction. Therefore, these UAE conditions can be applied to obtain polyphenolic enriched extracts from P. lentiscus leaves, which can be further employed for several industrial purposes.