Environmentally Friendly Methods for Flavonoid Extraction from Plant Material: Impact of Their Operating Conditions on Yield and Antioxidant Properties

Table 5

Flavonoid sources and principal parameters and conditions in MWAE.

Plant^a	Solvent^b (concentration)	Conditions during extraction^c	Results^d yield and optimum conditions	Reference
Arbutus unedo L.; M: 1 g; P.S.: —	Ethanol (0–100%)	P: 400 W; TOE: 1.6–45 min; S.C.: —	Y: 81.23 ± 6.34 mg/g; O.C.: 1.6 s, —, 120 ± 10.9°C	[65]
Nectandra grandiflora leaf; M: 5 g; P.S.: —	Ethanol (96%)	P: —; TOE: 30 min; S.C.: 50°C	Y: 123.83 ± 3.60 mg QE/g of dry weight; O.C.: —	[81]
Oryza sativa c.v. (black rice); M: 2 g; P.S.: 0.841 mm	Ethanol (40–70%)	P: —; TOE: 20–60 s; S.C.: sample first was exposed to ultrasound-assisted extraction	Y: 3.04 mg of TFC/100 g; O.C.: 31.1 s, 1 g/40.79 mL, —, —	[96]
Eleocharis dulcis (chestnut peels); M: 2 g; P.S.: —	Ethanol	P: 100–300 W; TOE: 30–180 s; S.C.: sample treated before extraction with enzymatic hydrolysis and 0.1 mol/L of NaH2PO4 with varying pH, enzyme and NaH2PO4 concentration, time, and power	Y: 1.48% of TFC (w/w) for EAUMSE; O.C.: 60 s, 200 W for EAUMSE	[155]
Satureja macrostema; M: 3 g; P.S.: —	Ethanol (0–100%); Water	P: —; TOE: —; S.C.: ultrasound process was accoupled (microwave- and ultrasound-assisted extraction)	Y: 123.88 ± 8.62 mg of TFC/g; O.C.: —	[55]
Theobroma cacao L. (cacao leaves); M: 1–6 g; P.S.: 0.1–0.6 mm	Ethanol (85%)	P: 100–800 W; TOE: 4–35 min; S.C.: —; S.C.: 20–80 mL/g of solvent-to-solid	Y: 80–95%; O.C.: —	[156]
Tomato; M: —; P.S.: —	Ethanol (0–100%)	P: 200 W; TOE: 0–20 min; S.C.: —	Y: 11.7 ± 0.6 mg of TFC/g; O.C.: 2 min, 5 g/L, —, 60°C, ethanol (100%)	[157]
Physalis angulata; M: —; P.S.: 10-mesh sieve	Ethanol (0–100%)	P: 10–30 W; TOE: 30–50 s	Y: 0.86 mg of rutin/L; O.C.: 50 s, 30 mg/L, —, —, 30 W, 50%; Y: 2.43 mg of mangiferin/L; O.C.: 50 s, 20 mg/L, —, —, 10 W, 100%	[158]
Young barley leaves; M: —; P.S.: 40-mesh sieve	Water	P: 0.4–1.32 W per gram; TOE: 4–20 min; S.C.: —	Y: 80.78% as rutin equivalents; O.C.: 11 min, 34.02 mL/g, 1.27 W per gram	[159]
Allium cepa L. (onion peels); M: 1 g; P.S.: 10–100 mm	Methanol (10–100% v/v)	P: 20–50% of 700 W; TOE: 10–20 min; S.C.: 10–60 mL/g	Y: 45.61 mg of TFC/g; O.C.: 15 min, 40 mL/g, 210 W	[160]
Apium graveolens L. (celery); M: 2 g; P.S.: —	Ethanol (50–80%)	P: 300–500 W; TOE: —; S.C.: 10–30 mL/g of solvent-to-solid ratio	Y: —; O.C.: 30 mL/g, 500 W, 75.6% (v/v)	[161]
Periploca forrestii Schltr.; M: 1 g; P.S.: 60-mesh sieve	Ethanol (50–70%)	P: 210–350 W; TOE: 180–240 s; S.C.: 15–25 mL/g, microwave combined with ultrasonic-assisted extraction	Y: 19.86%; O.C.: 209 s, 21.24 mL/g, 274 W	[162]

^aM: mass; P.S: particle size (average) or sieved (no. of meshes). ^bExtraction without solvent (none) using natural moisture. ^cP: power of MW; TOE: time of extraction; S.C.: special conditions. ^dY: yield (expressed as QE: quercetin equivalent; TFC: total flavonoid content); O.C.: optimum conditions (time of extraction, solvent-to-solid ratio, energy, power, temperature, solvent concentration, and particle size).