A Comprehensive Analysis of Diversity, Structure, Biosynthesis and Extraction of Biologically Active Tannins from Various Plant-Based Materials Using Deep Eutectic Solvents.

This paper explores the emerging subject of extracting tannins from various plant sources using deep eutectic solvents (DESs). Tannins are widely used in the food and feed industries as they have outstanding antioxidant qualities and greatly enhance the flavor and nutritional content of a wide range of food products. Organic solvents are frequently used in traditional extraction techniques, which raises questions about their safety for human health and the environment. DESs present a prospective substitute because of their low toxicity, adaptability, and environmental friendliness. The fundamental ideas supporting the application of DESs in the extraction of tannins from a range of plant-based materials frequently used in daily life are all well covered in this paper. Furthermore, this paper covers the impact of extraction parameters on the yield of extracted tannins, as well as possible obstacles and directions for future research in this emerging subject. This includes challenges such as high viscosity, intricated recovery of compounds, thermal degradation, and the occurrence of esterification. An extensive summary of the diversity, structure, biosynthesis, distribution, and roles of tannins in plants is given in this paper. Additionally, this paper thoroughly examines various bioactivities of tannins and their metabolites.

Towards a Greener Approach for Biomass Valorization: Integration of Supercritical Fluid and Deep Eutectic Solvents.

A green and sustainable procedure for obtaining Lavandula stoechas extracts with antioxidant and antimicrobial properties was investigated. Green solvents, supercritical CO2, and natural deep eutectic solvents (NADES) together with ultrasound-assisted extraction were used for the sequential extraction of terpene and polyphenols fractions. After the CO2 extraction of the terpene fraction, the residue material was used in an extraction with different NADES (betaine-ethylene glycol (Bet:EG), betaine-glycerol (Bet:Gly), and glycerol-glucose (Gly:Glu)), intensified with an ultrasound-assisted method (at 30 and 60 °C). In the CO2 extract, the major group of components belonged to oxygenated monoterpenes, while the highest polyphenol content with the dominant rutin (438.93 ± 4.60 µg/mL) was determined in Bet:EG extracts (60 °C). Bet:EG extracts also exhibited the most potent antioxidant activity according to DPPH, ABTS, and FRAP assays. Moreover, Bet:EG extracts showed significant inhibitory activity against Gram-positive and Gram-negative bacteria, with minimum inhibitory activity of 0.781-3.125 and 1.563-6.250 mg·mL-1, respectively. By comparing the polyphenolic content and antioxidant and antimicrobial activities of Bet:EG extracts with extracts obtained with conventional solvents (water and ethanol), the superiority of NADES was determined. The established environmentally friendly procedure unifies the requirements of green and sustainable development and modern pharmacognosy because it combines the use of safe alternative solvents, the absence of solvent waste generation, more rational use of resources, and the attainment of safe and quality extracts.

Comparison of Different Green Extraction Techniques Used for the Extraction of Targeted Flavonoids from Edible Feijoa (Acca sellowiana (O.Berg) Burret) Flowers.

This study aimed to investigate the effect of four green extraction techniques (ultrasound-assisted extraction, UAE; supercritical fluid extraction, SFE; subcritical water extraction, SWE; and extraction using deep eutectic solvents, DES) on the extraction of targeted flavonoids from edible feijoa flowers. The bioactive components in the obtained extracts were quantified by High-Performance Liquid Chromatography-Photodiode Array Detector (HPLC-PDA). Moreover, total polyphenol content and antioxidant activity by DPPH•, ABTS•+, FRAP, and CUPRAC assays were investigated. UAE generally gave the highest yields for isoquercitrin and quercetin content (18.36-25.33 and 10.86-16.13 µg/g), while DES extraction with choline chloride:lactic acid (1:2) and H2O content of 50% gave the highest yield of chrysanthemin (90.81 µg/g). The highest yield of flavone (12.69 mg/g) was obtained with supercritical CO2 at 300 bar. Finally, UAE gave the highest total polyphenol content (ca. 64 mg GAE/g) and antioxidant activity at 70 °C during 30 min with 40% (0.84 mmol TEAC/g and 2.25 mmol Fe2+/g, for ABTS•+ and CUPRAC, respectively) and 60% ethanol-water solution (0.49 mmol TEAC/g and 2.09 mmol Fe2+/g, for DPPH• and FRAP, respectively). The eco-friendly extraction techniques resulted in selective methods capable of extracting targeted bioactive compounds from edible feijoa flowers.

Determination of Suitable Macroporous Resins and Desorbents for Carnosol and Carnosic Acid from Deep Eutectic Solvent Sage (Salvia officinalis) Extract with Assessment of Antiradical and Antibacterial Activity.

In this study, for the first time, the adsorption/desorption characteristics of carnosic acid and carnosol from deep eutectic solvent extract of Salvia officinalis on five macroporous resins (HP20, XAD7HP, XAD16N, HP21, HP2MG) were evaluated. The high adsorption and medium desorption capacities of carnosic acid and carnosol as well as antibacterial and antiradical activity from the extract obtained with choline chloride:lactic acid (1:2) on XAD7HP resin indicated that resin was appropriate. To get the optimal separation process, the influence of factors such as adsorption/desorption time and volume of desorbent was further investigated. The results showed that the extract with high antiradical and antibacterial activity was obtained via adsorption and desorption on XAD7HP resin. The extraction efficiencies of the deep eutectic solvents (DESs) recycled once, twice, and thrice were 97.64% (±0.03%), 93.10% (±0.66%), and 88.94% (±1.15%), respectively, for carnosic acid, and 96.63% (±0.04%), 94.38% (±0.27%), and 91.19% (±0.36%), respectively, for carnosol, relative to the initial solvent efficiency. Based on that, this method is a promising basis for the large-scale preparation of extracts from Salvia officinalis with further application in the pharmaceutical or food industry, especially for maintaining the "green" character of the whole process to obtain the appropriate extract.