Ultrasonic‐assisted and enzymatic‐assisted extraction to recover tannins, flavonoids, and terpenoids from used tea leaves using natural deep eutectic solvents

Abstract

SummaryThe conventional extraction technique using organic solvent was employed to recover bioactive compounds from plants; however, this technique showed low efficiency and caused environmental pollution. Novel extraction techniques such as ultrasound‐assisted extraction (UAE) and enzymatic‐assisted extraction (EAE) combined with natural deep eutectic solvent were developed to overcome this problem. The efficiency of a binary NADES system with sonication was evaluated based on total tannin contents (TTAC), total flavonoid content (TFC), and total terpenoid content (TTC). The NADES system with a molar ratio of acetic acid and glycerol at 2:1 showed the highest TTAC and TFC, while acetic acid and glucose at 2:1 yielded the highest TTC. The impact of UAE and EAE parameters on extraction yield was examined. Combined methods, including ultrasonic‐enzymatic assisted extraction (UEAE), enzymatic‐ultrasonic assisted extraction (EUAE), and simultaneous ultrasonic‐enzymatic assisted extraction (SUEAE), were performed using NADES. UEAE exhibited the highest extraction yield and biological activities. Scanning electron microscopy (SEM) was employed to examine the surface variations of used tea leaves before and after treatment. This study demonstrated that UEAE is a sustainable technique for recovering valuable compounds from used tea leaves.

Extracting bioactive compounds and proteins from Bacopa monnieri using natural deep eutectic solvents

“…These results agreed with Manel Elakremi et al, who used MAE to recover bioactive compounds from Pistacia vera L. leaves [54]. The same trend was also observed by our previous study, which investigated the impact of NADES-based novel extraction techniques on spent tea leaves and Abelmoschus sagittifolius (Kurz) Merr roots [5,47] These findings affirm that UMEAE was shown as an effective technique for destroying plant cell walls.…”

“…The augmentation in the quantity of intra-main chains hydrogen bonds facilitated by the introduction of water grows the interaction between NADES and enzymes. The stability of the enzyme's secondary and tertiary structure is attained within the NADES solvent as a result of the establishment of hydrogen bonds among amino acids, particularly at the enzyme's active site along protein chains [47]. The slight decrease in outcome occurred at 50%, similar to the reasons for sections 3.2.2 and 3.3.3.…”

“…enhancing the solubility of bioactive compounds and proteins in solvents and leading to higher extraction yield [47]. However, the extraction efficiency of phenolics, flavonoids, terpenoids, and proteins declined when increasing molar ratios of L-Gly-Na up to 2:5:1 [44].…”

A Comprehensive Review on Deep Eutectic Solvents and Its Use to Extract Bioactive Compounds of Pharmaceutical Interest

“…The extracts with DESs also presented better results in terms of antimicrobial activity [ 165 , 174 , 179 ], antiproliferative activity in tumour Caco-2 cells and normal human keratinocyte cells [ 180 ], lower toxicity and increased bioavailability of the target compounds when administered to rats [ 181 ], higher antioxidant effects [ 179 ], and higher anti-inflammatory effects, as well as inhibitory effects against α-glucosidase and pancreatic lipase [ 182 ] when compared to the extracts from the traditional solvents. The enhanced biological activity of the DESs extracts can be explained by the higher content of bioactive compounds [ 182 , 183 ]. Duarte et al [ 184 ] studied the effect of extracts rich in polyphenols from a UAE based DES extraction and concluded those extracts showed a large antioxidant activity and a significant effect on the growth of Gram-positive and Gram-negative bacteria.…”

In situ NADES microwave‐mediated extraction of bioactive compounds from Beta vulgaris L. var. rubra waste

“…Synthetic NADES can reproduce this natural behaviour, and their use is emerging in food, cosmetic, and pharmaceutical areas (Hikmawanti et al, 2021). For instance, researchers have used these processes in the extraction of compounds from tea leaves and improving the recovery of the flavonoid compounds for potential nutritional benefits (Vo et al, 2023). Similarly, researchers have used DES to extract compounds from dark chocolate in an ecological extraction manner (Vinci et al, 2023).…”