Table 2.
Influence of extraction conditions in the phenolic content and antioxidant activity of seeds extracts.
| Source | Extraction Conditions | Phenolic Content and Antioxidant Activity | Ref. |
|---|---|---|---|
| CEREALS AND PSEUDOCEREALS | |||
| Black rice (Oryza sativa L.) | Conventional extraction: temperature (10, 30, and 50 °C); time (20, 50 and 80 min); and solid/solvent ratio (1 g/15, 30, and 45 mL) | TPC 1: 520.17 mg GAE 2/100 g; AA 3: 46.5% of DPPH 4 inhibition; optimum conditions: 34.7 °C, 80 min, 1 g/30 mL | [65] |
| Ultrasound: frequency (35 kHz); temperature (30–60°C); pH (2–4); solvent (20–60% ethanol); and time (10–60 min) | TPC: 2124.98 mg GAE/100 g; optimum conditions: 36.0 °C, pH 2.5, 23.8% ethanol, and 22.9 min | [66] | |
| Buckwheat (Fagopyrum esculentum Moench) | Microwave irradiation: time (15 min); solid/solvent ratio (1 g/50 mL); rotation (320 rpm); temperature (23–150 °C); and solvent (0, 50, and 100% ethanol) | TPC: 18.5 mg GAE/g; optimum conditions: 150 °C, 50% ethanol | [67] |
| Chia (Salvia hispanica L.) |
Conventional extraction: solid/solvent ratio (1 g/10 mL); solvent (0, 20, 50, 80, and 100% ethanol); extraction cycles (1–4); and time (1–72 h) | TPC: 42% increase; optimum conditions: 50% ethanol, and 4 cycles of 1 h each | [68] |
| FRUITS | |||
| Cacao bean shell (Theobroma cacao L.) | Pressurized liquid extraction: solid/solvent ratio (1 g/3 mL); pressure (10.35 MPa); time (5, 30; 50 min); and temperature (60–90 °C) | Increasing time and temperature increased the extraction of flavonols (90 °C, 50 min) and antioxidant activity (DPPH and FRAP 5 assays); optimum conditions: 90 °C and 50 min for polyphenols; and 75 °C and 50 min for antioxidant activity | [69] |
| Grape seed (Vitis vinífera L.) |
Ultrasound: frequency (20 kHz); power (150 W); time (15 min); temperature (<30 °C); and solvent (methanol); Soxhlet: temperature (RT 6); time (12 h); solvent (methanol) | TPC: 104.19 mg GAE/g; AA: 109.3 aTocE 7/g for DPPH radical assay; defatted seeds with ultrasound followed by Soxhlet extraction of polyphenols | [70] |
| Microwave irradiation: time (15 min); solid/solvent ratio (1 g/10–50 mL); solvent (10–90% ethanol); time (2-32 min); and temperature (40–60 °C) | TPC: 96.3 mg GAE/g; optimum conditions: 47.2% ethanol, 1 g/45.3 mL, ratio, 4.6 min | [71] | |
| Guarana seed (Paullinia cupana) | Conventional extraction (cold): solid/solvent ratio (1 g/3 g); temperature (25 °C); time (24 h); particle size (25, 125, and 1680 μm); and solvent (0, 50, 65, 80, and 100% ethanol) | Highest TPC was obtained with 1680 μm particles and 50% ethanol solution | [72] |
| Conventional extraction (hot): solid/solvent ratio (1 g/3 g); agitation (48 rpm); temperature (40, 50, and 60 °C); and time (1–6 h) | Highest TPC was obtained after 6 h, no effect of temperature (40–60 °C) | [72] | |
| Enzyme-assisted extraction: solid/solvent ratio (1 g/3 g); time (4 h); agitation (48 rpm); pH (4.8); time (4 h); enzyme (pectinase:celulase, 1:0, 1:1, 0:1); and temperature (40 and 50 °C) | Highest TPC was obtained using pectinase alone 50 °C | [72] | |
| Super-critical CO2: flow (6 mL/min); pressure (100, 200, and 300 bar); temperature (40, 50, and 60 °C); co-solvent (0, 10, 20, 40% of methanol, ethanol, and their 1:1 combination); and time (20, 40, and 60 min) | TPC: 105.76 mg PE 8/g; optimum conditions: 300 bar, 40 °C, 40% of 1:1 ethanol:methanol, and 40 min | [73] | |
| NUTS | |||
| Peanut skin (Arachis hypogaea L.) | Conventional extraction: time (5–150 min); temperature (25–90 °C); and solvent (20–100% ethanol) | TPC: 0.39 g GAE/g; AA: 79.9% of inhibition in the DPPH radical assay and IC50 of 0.26 μg/mL in the ABTS 9 radical assay; optimum conditions: 71.6 °C and 74% ethanol | [74] |
| Sub-critical water: temperature (140, 180 and 220 °C); flow (3, 5, and 7 g/min); and solvent (0, 50 and 95% ethanol) | TPC: 136.9 mg/g; AA: IC50 of 10.5 μg/mL in DPPH radical assay and IC50 of 17.05 μg/mL optimum conditions: 220 °C, 7 g/min, and 60.5% ethanol | [75] | |
| Pistachio (Pistacia vera L.) | Sub-critical water: solid/solvent ratio (1 g/25 mL); pressure (6.9 MPa); flow (4 mL/min); and temperature (110–190 °C) | TPC: 39.5 and 39.4 g/kg at 150 and 170 °C, respectively; AA: ABTS radical (1.18 mmol TE 10/g), DPPH radical (0.84 mmol TE/g) and FRAP (1.20 mmol TE/g) assays at 190 °C | [76] |
| Ultrasound: solid/solvent ratio (1 g/60 mL); and solvent (methanol:water:formic acid; 80:19:1) | TPC of 81.8 g/kg; AA: 0.47, 0.51, and 0.49 mmol TE/g for ABTS, DPPH, and FRAP assays, respectively | [76] | |
| OTHER SOURCES | |||
| Acorn (Quercus spp.) | Eco-friendly extraction: solid/solvent ratio (1 g/50 mL); time (10 min); solvent (water:glycerol:CD; 40–100%:0–60%:1–13%); and temperature (40, 60, and 80 °C) | TPC: 122.2 mg/g; AA: DPPH radical (1209.8 μmol TE/g) and reducing power (555.8 µmol AAE 11/g) assays optimum conditions: water: glycerol: CD 12, 27:60:13 and 80 °C | [77] |
1 TPC: total phenolic content; 2 GAE: gallic acid equivalent; 3 AA: antioxidant activity; 4 DPPH: 2,2-diphenyl-1-picrylhydrazyl; 5 FRAP: ferric reducing ability of plasma; 6 RT: room temperature; 7 aTocE: alpha-tocopherol equivalent; 8 PE: pyrogallol equivalent; 9 ABTS: 2,2’-azino-bis-(3-ethyl-benzothiazoline-6-sulphonic acid); 10 TE: trolox equivalent; 11 AAE: ascorbic acid equivalent; and 12 CD: 2-hydroxypropyl-β-cyclodextrin.