In this review, recent advances in the methods of pre-treatment of plant material for the extraction of secondary metabolites with high biological activity are presented. The correct preparation of the material for extraction is as important as the selection of the extraction method. This step should prevent the degradation of bioactive compounds as well as the development of fungi and bacteria. Currently, the methods of preparation are expected to modify the particles of the plant material in such a way that will contribute to the release of bioactive compounds loosely bonded to cell wall polymers. This review presents a wide range of methods of preparing plant material, including drying, freeze-drying, convection drying, microwave vacuum drying, enzymatic processes, and fermentation. The influence of the particular methods on the structure of plant material particles, the level of preserved bioactive compounds, and the possibility of their release during the extraction were highlighted. The plant material pre-treatment techniques used were discussed with respect to the amount of compounds released during extraction as well their application in various industries interested in products with a high content of biologically active compounds, such as the pharmaceutical, cosmetics, and food industries.

The aim of this study was to develop a new comprehensive extraction protocol based on green technology for the enhanced release of polyphenolic compounds from plant cells. In this work, extracts from yerba mate and yellow lupine seed were obtained by using three different extraction techniques: maceration, supercritical fluid extraction with co-solvent (SFE) and enzyme assisted-supercritical fluid extraction with co-solvent (EA-SFE). Several experimental parameters such as time, type of solvent and co-solvent as well as CO₂ flow rate were selected to obtain the highest extraction efficiency. The chemical profiles in the obtained extracts and their biological activity were evaluated. HPLC-MS/MS analysis indicated that the level of phenolic compounds in extracts from yerba mate obtained by EA-SFE was approximately five times higher than for maceration and 3.2 times higher than for SFE. In the case of extracts from yellow lupine seed an approximately 5.6-fold increase was observed in comparison with maceration and SFE with 96% MeOH, and 2.9 times for SFE with 96% EtOH. The developed protocol with a mix of enzymes commonly applied in the agricultural industry significantly raises the efficiency of liberation of secondary metabolites.

To elaborate a complete extraction protocol for the enhanced release of biologically active compounds from plant cells, this study aimed to optimize together the parameters of the supercritical fluid extraction (SFE) process (temperature, pressure, and percentage of cosolvent) and enzymatic treatment of plant material (pH, enzyme concentration, time, and temperature) by response surface methodology (RSM). Medicago sativa L. was selected as a plant material due to its richness in phenolics and flavonoids. HPLC-MS/MS analysis allowed evaluating the content of individual bioactive compounds in obtained extracts. The total content of polyphenolic compounds in the extract obtained after two-step optimization was much higher (546 ± 21 µg/g) than in the extract obtained from non-hydrolyzed material (275 ± 23 µg/g) and in the extract obtained by maceration (162 ± 20 µg/g). Furthermore, it was evidenced that extract with the highest content of polyphenolic compounds can support the cellular antioxidant system both as a free radical scavenger and by stimulating the antioxidant enzyme system.