Table 2.
Application of DES/NADES in improving solubility of some plant metabolites.
| Plants | Bioactive Compounds | Selected DES/NADES (Molar Ratio in mol/mol); Optimal Conditions |
Conventional Solvents for Comparison | Results | Refs. |
|---|---|---|---|---|---|
| Spent Coffee ground | Chlorogenic acid | Betaine-triethyleneglycol (1:2) and 30% water and matrix-solvent ratio was 1:15 (g/mL) using ultrasonication at 65 °C for 20 min. | 70% methanol | Compared to choline chloride-based NADES and 70% methanol, betaine-triethylene glycol (1:2) was demonstrated to be the most powerful in extracting total chlorogenic acids from spent coffee grounds. | [24] |
| Herba artemisiae scopariae (Artemisia argyi H.Lév. & Vaniot) | Chlorogenic acid | Proline-malic acid (1:1) using pre-treatment with ultrasonic for 30 min followed by continuous stirring for 2 h. | Water and ethanol | In comparison to other NADES and conventional solvents, the chosen NADES with the highest solvation free energy had the best impact for chlorogenic acid extraction. | [25] |
| Blueberry leaves | Chlorogenic acid | Choline chloride-1,3-butanediol (1:2) using negative pressure of −0.07 Pa; solvent-matrix ratio was 17.01 mL/g, at 59.03 °C, for 24.12 min. | - | NPCE was used for extraction The method is efficient for extraction of Chlorogenic acid (NPCE > MAE > HRE > UAE). |
[26] |
| Lonicera Japonica Thunb. | Chlorogenic acid, caffeic acid, 3,4-dicaffeoylquinic acid (3,4-DCQA), 3,5-dicaffeoylquinic acid (3,5-DCQA), and 4,5-dicaffeoylquinic acid (4,5-DCQA) |
Choline chloride-1,3-butanediol (1:6) with 10% water; solvent-matrix ratio was 9 mL/g, at 60 °C for 20 min using MAE. | - | MAE was an efficient method of extracting five phenolic compounds from L. japonica flos (MAE>UAE and HRE). | [27] |
| Curcuma longa L. | Curcuminoids | Citric acid-glucose (1:1) and 15% water; at 50 °C, solvent-matrix ratio was 0.1/10 g/mL, for 30 min with constant stirring. | Ethanol and methanol | Citric-acid-glucose yielded the most curcuminoids, followed by malic acid-glucose (1:1) > ethanol > methanol. Curcumin at 21.18 mg/g, bisdemethoxy curcumin at 16.54 mg/g, and demethoxy curcumin at 15.12 mg/g. | [28] |
| Choline chloride-glycerol (1:1), mechanical stirrer for 24 h. | Methanol and water | The percentage of curcuminoids extracted from three commercial turmeric powders from different suppliers in NADES (0.94–1.26%) was higher than in water (0.06–0.08%). However, it is still lower than methanol (5.05–5.09%). | [29] | ||
| Choline chloride-lactic acid (1:1) and 20% water content; 5% solid loading; at 30 ± 2 °C in 20 min using UAE. | - | The maximum curcuminoids yield was 77.13 mg/g; The solubility of curcuminoids was 13.7 mg/mL. | [30] | ||
| Sucrose-lactic acid-water (1:5:7) 15–20 min, solvent-matrix ratio was 14.5–16.5 mL/0.2 g depending on the NADES using MAE. | 80% methanol | NADES showed a high yield of curcuminoids and antioxidants compared to 80% methanol. | [33] | ||
| Scutellaria baicalensis Georgi | Baicalein, scutellarein, wogonin, and oroxylin A (flavonoid aglycones); baicalin, scutellarin, wogonoside, and oroxyloside (flavonoid glycosides) |
Proline-citric acid (1:1) with 40% water or citric acid-β-alanine (1:1) with 50% water; for 30 min, extract with UAE at room temperature. | 80% methanol and 70% ethanol | The yield of aglycon flavonoids extracted with NADES was 2–6 times that of 80% methanol. However, as compared to aqueous methanol, the number of glycosides extracted with NADES was only 1.5–1.8 times greater. | [34] |
| Peumus boldus Molina | Boldine and phenolics | l-proline-oxalic acid (1:1) with 20% water; 340 rpm, at 50 °C for 50 min. | Methanol and water | The selected NADES was eight times more efficient for extraction of boldine than methanol. No significant differences of TPC in extracts obtained with methanol and NADES. | [32] |
Note: MAE = microwave-assisted extraction; HRE = heat reflux extraction; UAE = ultrasonic-assisted extraction; NPCE = negative pressure cavitation extraction.