Integration of pressurized liquid extraction and in-line solid-phase extraction to simultaneously extract and concentrate phenolic compounds from lemon peel (Citrus limon L.).

This work aimed to develop an integrated method to extract and fractionate phenolic compounds from lemon (Citrus limon L.) peel by in-line coupling pressurized liquid extraction and solid-phase extraction (PLE-SPE). The effect of the adsorbent used in the SPE (Sepra™ C18-E, Sepra™ NH, and PoraPak Rxn), the combination of organic extraction-elution solvents (water-ethanol and water-ethyl lactate), extraction temperature (40-80 °C), and extraction water pH (4.0, 6.0, and 7.0) were the investigated variables. The highest yield and separation degree were observed using Sepra™ C18-E and the water-ethanol combination as the extraction solvent-eluent. Higher temperatures led to higher yields but negatively affected the retention of less polar compounds, hesperidin, and narirutin during the extraction step. The lower pH improved the yield of most evaluated compounds; however, it did not improve the adsorbent retention at high temperatures. Thus, the developed PLE-SPE method resulted in higher extraction yields from lemon peel, especially total less polar compounds (20.2100 ± 0,0050 mg/g) and hesperidin (12.8120 ± 0.0006 mg/g) and allowed the separation of polar compounds and less polar compounds in distinct extract fractions. Besides, PLE-SPE resulted in higher yields compared to other extraction methods. The integrated approach allowed obtaining extract fractions with different chemical composition through an environmentally friendly procedure. The research outcomes may be helpful for natural products chemistry, and industrial processes.