# Diversity of Potential (Bio)Technological Applications of Amino Acid-Based Ionic Liquids
## 2 Bioapplications of AA ILs: An Overview
### AA ILs as Media for Extraction  
#### 2.7.1 AA ILs as Media for Extraction of Plant Secondary Metabolites  
Compared to classical extraction methods, many studies highlight the numerous advantages of using AA ILs as extraction media, including higher yields of target products, reduced environmental impact in terms of lower CO\({}_{2}\) emissions, and a 3- to 5-fold reduction in energy consumption per unit of product obtained, as well as shortened extraction times and the avoidance or minimization of the use of organic solvents [127,128]. In addition, pretreatment of plant materials with ILs can help break down the rigid cell walls, thereby increasing the efficiency of the extraction process.  
For example, essential oils, scutellarin, and rosmarinic acid were extracted directly from _Perilla frutescens_ leaves by vacuum microwave-assisted rotary hydrodistillation with up to 3-fold higher efficiency in the presence of 10% [Ch][Glu] compared to the heating jacket method using pure water [129]. Similar efficiencies for essential oil extraction were observed with 10% [Ch][Trp], [Ch][Phe], [Ch][Ala], [Ch][Pro], [Ch][His], and [Ch][Tyr]. However, these ILs were 25% to 95% less effective as solvents for rosmarinic acid.  
On the other hand, [Ch][Leu] was used as a component in a K\({}_{3}\)HPO\({}_{4}\)-based aqueous two-phase extraction (ATPE) system for the simultaneous extraction and separation of flavonoids and pectin from mandarin peels [130]. Under optimal conditions, the yield of crude flavonoids was 20%, while the yield of purified pectin was 12.8%.  
Compared to classical extraction methods such as Soxhet extraction, solvent extraction with methanol or chloroform, and microwave extraction, the yield of compounds with antioxidant properties obtained from plants can be significantly increased by ultrasound-assisted extraction in the presence of ILs [131,132,133]. For example, [PERSON] et al. demonstrated the use of TEA salts in the preparation of aqueous extracts from _Lycopodium clavatum_, _Cetraria islandica_, and _Dipsacus fulloun_ using an ultrasound-assisted method [134]. Specifically, the addition of 2.5% (\(w/v\)) [TEA][Thr] increased the amount of isolated polyphenols by 5.5-fold compared to the pure water medium, and the extract exhibited a 2.4-fold higher antioxidant capacity compared to the control [134]. In addition, this method reduced the extraction time, making it more effective for thermosensitive natural compounds. Another significant improvement in the AA IL-assisted isolation of polyphenols was reported by [PERSON] et al. [135]. They developed a new polymeric material with a porous structure based on imidazole-type bicationic (ViIm)2 Cn amino acid-based ILs, which selectively adsorbs tea polyphenols. The [(ViIm)\({}_{2}\)Cn][(L-Pro)\({}_{2}\))] membrane extracts 521 g of tea polyphenols per gram of material, significantly outperforming other adsorption media [135]. In addition, the polyphenols can be easily desorbed with an acid-methanol solution. The membrane was used four times without significant loss of capacity.  
Finally, [PERSON] et al. reported that, compared to Emim-based ILs with classical anions such as Br, BF\({}_{4}\), PF\({}_{6}\), or pure dimethylformamide, those with AA anions such as Ala, Gly, Lys, Phe, and Ser enhanced the distribution of \(\alpha\)-tocopherol in the water-DMF phase [136]. A suitable partition coefficient and adequate extraction capacity for \(\alpha\)-tocopherol mixed with methyl linoleate were achieved in the [Emim][Ala]-DMF-hexane biphasic system. Highseparation selectivity of \(\alpha\)-tocopherol over methyl linoleate (up to 29) was reported under the optimized extraction conditions [136].