Insights on the Extraction and Analysis of Phenolic Compounds from Citrus Fruits: Green Perspectives and Current Status.

Citrus fruits (CF) are highly consumed worldwide, fresh, processed, or prepared as juices and pies. To illustrate the high economic importance of CF, the global production of these commodities in 2021 was around 98 million tons. CF's composition is considered an excellent source of phenolic compounds (PC) as they have a large amount and variety. Since ancient times, PC has been highlighted to promote several benefits related to oxidative stress disorders, such as chronic diseases and cancer. Recent studies suggest that consuming citrus fruits can prevent some of these diseases. However, due to the complexity of citrus matrices, extracting compounds of interest from these types of samples, and identifying and quantifying them effectively, is not a simple task. In this context, several extractive and analytical proposals have been used. This review discusses current research involving CF, focusing mainly on PC extraction and analysis methods, regarding advantages and disadvantages from the perspective of Green Chemistry.

Extraction of potential bioactive compounds from industrial Tahiti lime (Citrus latifólia Tan.) by-product using pressurized liquids and ultrasound-assisted extraction.

This work evaluated two emerging techniques in extracting phenolic compounds from Tahiti lime pomace - pressurized liquid extraction (PLE) and ultrasound-assisted extraction (UAE). PLE was performed at different temperatures (60 - 110 °C) and times (5 - 40 min), and UAE was carried out varying ultrasound power (160 - 792 W), time (2 - 10 min), and solvent to feed mass ratio (20 - 40 kg solvent/kg dried pomace). Both used ethanol and water (3:1, wt.) as the solvent. The effects of these variables were evaluated on global extraction yield, polyphenols, hesperidin, narirutin yields, and antioxidant capacity. PLE was strongly affected by temperature and extraction time, and the highest temperature (110 °C) provided the best results for global yield, total phenolic, and ORAC, except for hesperidin and narirutin, which were not significative affected by temperature. UAE revealed a weak dependency on power, S/F, and time; however, the lowest power level significantly increased the yields compared to no power application. Thus, P = 480 W, t = 6 min, and S/F = 30 was chosen as the best condition in the UAE in terms of overall extraction yield, total phenolics, specific phenolics, antioxidant capacities, and solvent and energy expenditures. UAE mechanisms were investigated by comparing with heated and stirred maceration, and scanning electron microscopy suggested that total phenolic yield was influenced by mechanisms that only ultrasound can provide. Micrographics confirmed the cavitation effect on Tahiti lime pomace particles' surface. To sum up, PLE resulted in the highest yields and antioxidant capacity, followed by UAE.

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.

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.