Table 1.

The principle, advantages and disadvantages of different extraction technology of apigenin.

Extraction method	Extraction principle	Examples	Advantages	Disadvantages	Reference
Organic solvent extraction	Apigenin has high solubility in different organic solvents.	Apigenin has high solubility in different organic solvents.	Mature technology, low equipment cost, simple operation and easy industrialization.	The extraction rate is low, the extraction time is long, the amount of solvent is large, difficult to recover, a variety of organic solvents make the safety risks greatly increased.	(14–19)
Supercritical fluid extraction	A solute in the mixture to be separated in a certain supercritical region near the critical point.	The extraction rate of apigenin was 61.80 μg/g under the condition: 25°C, 8 ~ 14 MPa, 125 s.	High extraction efficiency, high yield, high purity, low energy consumption, shortened extraction time, lower equipment price, cheaper extractant, non-toxic, suitable for recovery.	Higher equipment costs.	(20, 21)
Enzymatic hydrolysis assisted extraction	Specific enzymes are used to degrade or destroy endogenous pectin, glycoprotein, cellulose, etc. In cell walls, cell molds, reduce mass transfer resistance, and promote the dissolution of active ingredients.	Under the condition of enzyme reaction temperature 40°C, time 30 min; and a concentration of 0.4 mg/mL at pH 5.5，the yield of apigenin was 25.3 mg/g.	Mild extraction conditions, favorable for maintaining the activity of apigenin, improving extraction efficiency, improving product purity, and having great development prospects and application potential.	Industrial enzyme preparations are costly.	(22)
Ultrasonic assisted extraction	The multi-stage effects, including cavitation, mechanical, and the thermal effect, increase the frequency and velocity of movement of the extracted components	The recovery rate of apigenin ranging from 72.7 to 89.5% under the conditions by using 1.0 mol/L 1-butyl-3-methylimidazolium methylsulfate ([Bmim][MS]) aqueous solution at pH 1.0 as the extraction solvent; 200 W for 90 min (solid: liquid ratio was 1: 10).	High extraction efficiency, low energy consumption, shortened extraction time, lower equipment price and simple operation.	The equipment is still at the laboratory level, and has not been industrialized.	(23)
Microwave assisted extraction	Under the action of microwave electric field, many substances composed of polar molecules will strongly oscillate, causing rapid generation of a large amount of heat energy, leading to cell rupture	The extraction rate of apigenin was 104 μg/g, the yield was significantly improved compared with conventional extraction method.	High extraction efficiency, low solvent consumption, and high extraction rat.	Microwave has a selective temperature effect on polar substances, so it is required to have a small dielectric constant.	(24)
Ultrasonic-microwave synergistic extraction	Combining ultrasonic vibration and microwave heating to enhance the extraction efficiency	The apigenin yield was over 80%.	Overcome ultrasonic vibration, low noise, large noise, and uneven microwave penetration.	The mass transfer mechanism of ultrasonic-microwave synergistic extraction and the effect on the structure and activity of apigenin are still unclear.	(25)