Table 4.
Techniques and main results reported in literature for the extraction of phenolic compounds from lemon balm.
| Solvent | Method | Measured Parameters | Main Results | Reference |
|---|---|---|---|---|
| Ethanol (Solid/liquid 1/4–1/10, w/v) |
CSE temperature 0–80 °C, particle size 200–250, 250–315, 315–400 μm |
CA UA OA Extraction yield |
Extraction was governed by internal mass transfer (diffusion coefficients according to Fick’s 2nd low were determined) Yield increased with decreasing particle size and solid-to-liquid ratio. |
[130] |
| Ethanol, methanol, acetone or acetonitrile, all 30% in water Water Ethanol 15–96% Solid/liquid 1/500, w/v |
UAE 10 min | RA CAF |
All 30% mixtures showed similar RA recovery 20% higher than pure water. 30 and 60% ethanol in water showed the highest recovery of both acids. |
[131] |
| Methanol in water 40–80% Solid/liquid 1/20, w/v |
CSE (25–55 °C, extraction time 30–90 min) |
RA | The optimum conditions determined by RSM were methanol concentration 59%, v/v, at 55 °C, for 65 min and gave RA yield 4.6% on dry leaves. | [132] |
| Methanol in water Methanol in water (pH 2.5) Ethanol in water Ethanol on water (pH 2.5) Water Solid/liquid 1/50, 1/100, 1/150, w/v |
CSE, UAE (bath) (25 °C, 5–20 min) |
RA CAF ProtCa |
UAE was more effective than CSE at the same time. RA extraction was slightly higher with acidified mixtures. Methanol 60%, at a solid-to-liquid ratio 1:100, by 3 successive extractions of 10 min each, recovered quantitatively all phenolic acids. | [119] |
| Methanol in water 0–100% Ethanol in water 0–100% Acidification with 0.1–1.0% HCl Solid/liquid 1/40, w/v |
Maceration under stirring (30–1140 min) CSE at boiling point (15–60 min) MAE (50 or 80 °C, 5–30 min) |
RA | MAE gave similar results to conventional methods at shorter time (5 min). More than 5 min in MAE and 15 in CSE caused degradation. Ethanol:water:HCl 70:29:1, v/v/v gave the best results |
[133] |
| Ethanol in water 20–80% | CSE (25–60 °C) |
RA | Highest RA yield at 50% ethanol in water. Increase of temperature caused minor increase in yield that was not significant above 50 °C | [134] |
| Ethanol in water 80% or 50% Solid/liquid 1/10, w/v |
CSE of untreated or SFE treated material (40 °C, extraction time 110 min) |
RA Extraction yield |
Ethanol 50% achieved higher RA yield than 80%. 3 successive extractions were needed to recover RA absorbed in the wet material. SFE pretreatment increased extraction rate and final yield |
[120] |
| Ethanol in water 0–100% Solid/liquid 1/33, w/v |
CSE (30–90 °C, 30–90 min) UAE (probe 100–500 W, 3–45 min at constant temp.: 30–35 °C) MAE (60–180 °C, 3–45 min) |
RA | RSM analysis showed that all studied variables were significant in all methods. UAE gave the highest RA yield (86 mg RA/g dry plan) under the optimum conditions (40% ethanol, 371 W, 33 min). |
[135] |
| Ethanol in water 0, 70, 100% Solid/liquid 1/10, w/v in MAE Successive extractions with hexane, acetone, ethanol, water in UAE |
UAE (probe 20 kHz, 10 min) MAE (under N2, 100 °C, 10 min) Dry extraction by grinding with β-cyclodextrin (1:2, w/w) |
HPLC Extraction yield |
MAE with water showed the highest extraction yield, but with 100% ethanol the highest phenolic and RA recovery was shown. UAE was less efficient and the best phenolic and RA recovery was obtained with ethanol and was enhanced when acetone was used in a previous extraction. Dry extraction was the least efficient. |
[136] |
| Ethanol in water 70%, 96% Solid/liquid 1/10, w/v |
MAE (5–15 min, 25, 40, 60 °C) | TPC | 70% ethanol at 10 min and 60 °C showed the highest TPC recovery | [137] |
| Ethanol Water Solid/liquid 1/20, w/v |
EAE (cellulose, β-xylanase, pectinase, 50 °C, 2 h, pH 5) ASE (150 °C, 20 min) |
TPC LC-MS/MS DPPH TEAC (ABTS) |
ASE showed the highest TPC yield and antioxidant activity with water being more effective than ethanol. EAE with a combination of all enzymes gave better results than non-enzymatic extraction (pH 5). | [127] |
| Water Solid/liquid 1/20, w/v |
CSE (40–100 °C, 5–120 min) | TPC DPPH ABTS |
Optimization by RSM. Temperature and temperature-time interaction were significant. Optimum results at 100 °C for 120 min | [138] |
| Water Solid/liquid 1/10, 1/20, 1/30, w/v |
CSE (97 °C, 5–30 min) UAE (probe at 150 or 240 W, 5–30 min, and constant temp 40 °C) MAE (97 °C, 5–20 min) Maceration (40 °C, 24 h) |
TPC | Phenolics recovery increased as solid-to-liquid decreased. MAE showed the highest TPC recovery (146 mg GAE/g dry plant, at 5 min) and UAE the lowest (106 mg GAE/g dry plant, at 20 min) CSE yield amounted to 120 mg GAE/g dry plant, at 30 min but the extract showed similar DPPH scavenging to MAE. Maceration showed similar results to UAE. |
[139] |
ABTS: 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid radical, ASE: accelerated solvent extraction, CA: carnosic acid, CAF: caffeic acid, CSE: conventional solvent extraction, DPPH: 1,1-diphenyl-2-picrylhydrazyl radical, MAE: microwave assisted extraction, OA: oleanolic acid, ProtCa: protocatechuic acid, RA: rosmarinic acid, SFE: supercritical fluid extraction, TPC: total phenolic content, UA: ursolic acid, UAE: ultrasound assisted extraction.