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™ NH2, 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.

Recent advances and trends in extraction techniques to recover polyphenols compounds from apple by-products.

Apple is one of the most consumed fruits worldwide and has recognized nutritional properties. Besides being consumed fresh, it is the raw material for several food products, whose production chain generates a considerable amount of by-products that currently have an underestimated use. These by-products are a rich source of chemical compounds with several potential applications. Therefore, new ambitious platforms focused on reusing are needed, targeting a process chain that achieves well-defined products and mitigates waste generation. This review covers an essential part of the apple by-products reuse chain. The apple composition regarding phenolic compounds subclasses is addressed and related to biological activities. The extraction processes to recover apple biocompounds have been revised, and an up-to-date overview of the scientific literature on conventional and emerging extraction techniques adopted over the past decade is reported. Finally, gaps and future trends related to the management of apple by-products are critically presented.

Comprehensive analysis of phenolic compounds from natural products: Integrating sample preparation and analysis.

The comprehensive analysis of phenolic compounds from natural products comprises critical steps, including quantitative extraction, extract preparation, and chromatographic procedure. Performing these steps off-line requires a long time to obtain results, besides being laborious and more error-prone. This work discusses the concept and presents the details of assembling and validating a new system to comprehensively analyze phenolic compounds in natural products. The system is based on a bidimensional separation through the combination of pressurized liquid extraction with in-line solid-phase extraction coupled online with HPLC-PDA. The system proved to be able to perform a bidimensional separation to characterize the sample and ensure quantitative extraction of all detected components using the most appropriate extraction solvent gradient depending on the raw sample analyzed. The 1st dimension separation is achieved by PLE-SPE with a solvent gradient and differential interactions of extracted compounds with the adsorbent. The 2nd dimension presents the HPLC-PDA separation. The extraction/separation process can be monitored in real-time, and kinetic extraction curves for individual compounds can also be obtained to ensure quantitative extraction. Thus, the 2D PLE-SPE × HPLC-PDA may provide fast and precise comprehensive analyses of a large plethora of phenolic compounds, finding relevant applications in the chemical, food, pharmaceutical, and agricultural fields.

Simultaneous extraction and separation of compounds from mate (Ilex paraguariensis) leaves by pressurized liquid extraction coupled with solid-phase extraction and in-line UV detection.

The in-line coupling of the pressurized liquid extraction with a solid-phase adsorbent and a UV-Vis detector for the simultaneous extraction and separation of bioactive compounds from yerba mate (PLE-SPE-UV) was carried out in two stages. In the first stage, water was used as a solvent, while in the second stage, ethanol was used. For the optimization of the method, different adsorbents (Sepra C18-E, Isolute C18-EC, and Strata-X C18), temperatures (40-80 °C), solvent flow-rate (1-3 mL/min), and pH (4.0 and 8.0) were evaluated. By using a UV-Vis detector on-line, it is possible to monitor the process in real-time. The developed method allowed obtaining similar or higher recoveries of all the compounds classes than other methods, such as ultrasound-assisted extraction, stirring, maceration, and pressurized liquid extraction alone, in addition to separating them into fractions. The developed method could be used as sample preparation for the analysis of different compounds classes from mate.