Optimization of Pulsed Electric-Field-Based Total Polyphenols’ Extraction from Elaeagnus pungens ‘Limelight’ Leaves Using Hydroethanolic Mixtures

In this study, the use of pulsed electric field (PEF) for the extraction of polyphenols from mature Elaeagnus pungens ‘Limelight’ leaves is discussed. Optimization of the main parameters that affect the extraction process was carried out. More specifically, the composition of the solvent (ethanol, water, and mixtures of the two at a 25% v/v step gradient) and the main PEF-related parameters (i.e., pulse duration, pulse period, and electric field intensity) was optimized. The obtained extracts were examined for their polyphenol content with the Folin–Ciocalteu assay and individual polyphenols were also assessed with high-performance liquid chromatography. The extracts obtained with PEF were compared to the extract compared without PEF, in terms of total polyphenols. According to the results, the optimum extraction parameters were found to be a pulse duration of 10 μs, a pulse period of 1000 μs, and an electric field intensity of 0.85 kV cm−1 after 20 min of extraction. The optimum solvent was found to be the 50% (v/v) ethanol/water mixture. The extract prepared under the optimum conditions was found to contain 58% more polyphenols compared with the extract prepared without PEF. Moreover, an increase of up to 92% was recorded for specific polyphenols. Based on the above, it was evidenced that the examined parameters influenced the recovery of polyphenols, suggesting that such parameters should be also examined in similar studies, in order to maximize the extraction yield of polyphenols.