Optimization of a Green Ultrasound-Assisted Extraction of Different Polyphenols from L. Leaves Using a Response Surface Methodology.

leaves are used in several applications, thanks to their polyphenolic abundance. Thiswork aimed to characterize the polyphenols and to optimize the extraction conditions to shorten the time, decrease the consumption of solvent, and to maximize the yield of different classes of phenolics, which have diverse industrial applications. The variables were optimized by applying a Box-Behnken design. Galloyl and myricetin derivatives were the most abundant compounds, and two new tetragalloyl derivatives were identified by LC-MS/MS. According to the models, the maximum yields of polyphenols (51.3 ± 1.8 mg g DW) and tannins (40.2 ± 1.4 mg g DW) were obtained using 0.12 L g of 40% ethanol at 50 °C. The highest content of flavonoids (10.2 ± 0.8 mg g DW) was obtained using 0.13 L g of 50% ethanol at 50 °C, while 0.1 L g of 30% ethanol at 30 °C resulted in higher amounts of myricitrin (2.6 ± 0.19 mg g DW). Our optimized extraction decreased the ethanolic fraction by 25% and halved the time compared to other methods. These conditions can be applied differently to obtain extracts richer in tannins or flavonoids, which might be employed for various purposes.