**3.2 Irradiation time**

Additionally, the extracting solvent is absorbed into the plant sample through diffusion, causing the dissolution of solutes into the solvent until saturation. This solution diffuses to the plant surface through effective diffusion and then transfer to the bulk solution (**Figure 2**). Several forces that include physicochemical relations and interactions can be seen during the process (chemical interactions, driving forces, interstitial diffusion, and dispersion forces), and the strength and persistence of properties can be related to the characteristics of the extraction solvent (polarity, solubility in water, purity, solubilization, and among others) [4].

*Microwave Heating - Electromagnetic Fields Causing Thermal and Non-Thermal Effects*

**3. Essential factors influencing MAE and mechanism of action**

actions of these parameters on the extraction process is paramount.

**3.1 Solvent-to-feed ratio**

**6**

**Figure 2.**

*Pictorial diagram of yield against time in the extraction [14].*

Several studies had been done on optimizing MAE factors to achieve optimal yields from the considered plant samples. The operative parameters influencing MAE include solvent-to-feed ratio, solvent composition, characteristic of the plant sample and its water content, microwave power, irradiation time, stirring effect, microwave energy density, and extraction temperature. These operative parameters determine the efficiency of MAE. Hence, understanding the influences and inter-

The selection of solvent is the most significant factor that affects microwaveassisted extraction. Adequate solvent selection will produce an efficient extraction process. The solubility of the compound of interest, mass transfer kinetics of the process, and solvent penetration that occurs from the interaction between the dielectric effect and sample matrix are inevitable parameters [24, 25]. Chan et al. reported that the selection of extraction solvent depends on the capacity of that solvent to absorb microwave energy [26]. If the solvent has a high dielectric constant and dielectric loss, the solvent capacity to absorb microwave energy will be high [25]. Tatke and Jaiswal reported that solvents such as methanol, ethanol, and water are excellent microwave-absorbing solvents which possess sufficient polarity to be heated up through microwave power [27]. Studies had shown that the addition of a small quantity of water to polar solvent resulted in higher diffusion of water into the cells of the matrix, leading to effective heating and thus facilitating the transport of compounds into the solvent at higher mass transfer rates [24, 26, 28].

The irradiation time is another important factor that affects microwave-assisted extraction. One of the importance of MAE over conventional methods is that the extraction time is very short. The usual time ranges from a few minutes to half an hour depending on the plant matrix so as to avoid possible oxidation and thermal degradation [13, 25, 27]. The irradiation time is affected by the dielectric property of solvent used. Solvents such as ethanol, water, and methanol may heat up rapidly on longer exposure which can result in degradation of thermolabile compounds in the extracts [4, 26]. Increased time of irradiation can improve the recovery yield; nevertheless, the increased yield can decline at prolonged irradiation time [21].

Sometimes, if the extraction will take a longer time, the plant materials are extracted through multiple stages by utilizing consecutive extraction cycle. Here, a new solvent is introduced to the residues, the procedure is then repeated to ensure exhaustion of the plant sample. The use of this process helps higher recovery yield with no excessive heating [26, 31]. The nature of plant sample and solute determines the number of extraction cycles. A study presented that 3 cycles of 7 min were adequate in extracting triterpene saponins from yellow horn through MAE [32]. The optimization MAE to obtain triterpenoids saponins from *Ganoderma atrum* yielded 5 min for each cycle [33].

#### **3.3 Effect of stirring**

Mass transfer processes in the solvent phase are usually enhanced by stirring. The equilibrium between the vapor and aqueous phases is achieved more rapidly. The use of a stirrer in MAE accelerates the extraction process by increasing the dissolution and desorption of bioactive compounds in the sample matrix [13, 27]. Thorough stirring can reduce the drawbacks possess when using a low solvent-tosolid ratio and minimized the mass transfer barrier [13].

#### **3.4 Microwave power and temperature**

Microwave power and temperature are important factors that affect the extraction yield when using MAE. The higher microwave power can lead to an increase in the temperature of the system resulting in the increase of the extraction yield until it becomes insignificant or declines [13, 25, 34]. An increase in temperature can result in solvent power increase because of a drop in surface tension and viscosity, enhancing the solvent to solubilize solutes, improving matrix wetting and penetration [13]. However, Spigno and De Faveri reported that the efficiency of MAE increases with the increase in temperature until an optimum temperature is reached [25]. Microwave power is also related to the quantity of sample and the extraction time required. However, the power provides localized heating in the plant matrix acts as a driving force for MAE to destroy the plant matrix so that the solute can diffuse and dissolve in the solvent. Therefore, increasing the microwave power will generally improve the extraction yield and result in a shorter extraction time [13, 29, 35]. On the other hand, if microwave power is too high, it can result in poor extraction yield leading to the degradation of thermally sensitive compounds in the plant matrix [29]. It is then important to select the appropriate microwave power to reduce the extraction time required to reach the set temperature and avoid a "bumping" phenomenon [13].

#### **3.5 Characteristic of plant sample and its water content**

The characteristic of the plant sample and its water content can influence MAE. The extraction efficiency improves as the contact surface area of the plant sample increases. Moreover, finer samples give room for deeper penetration of microwave irradiation [36]. Nevertheless, too much finest of the plant sample may generate some technical difficulties; hence, filtration or centrifugation is employed in the preparation of the plant samples [27, 37]. During the sample preparation, the grinded sample is homogenized to improve contact between the solvent and the plant matrix. The plant particle sizes mostly fall within 2 and 100 mm [31]. Sometimes, the plant matrix is soaked before extraction to improve the yield; this is known as pre-leaching [37].

Mostly, the recovery of bioactive compounds from the plant matrix tends to increase through its moisture that acts as a solvent. This moisture is heated up, evaporated, causes pressure within the cell, and dispenses the solutes through rupturing of the cell wall; thus, increase the yield of bioactive compounds [38]. An increase in the polarity of solvent causes the addition of water to have a positive influence on microwave-absorbing capability; thus, encourages the heating procedure [26]. Extra water generates hydrolyzation and reduces the oxidation of bioactive compounds.

#### **3.6 Microwave energy density**

There are three heating operational modes employed in the performance evaluation of microwave-assisted extraction [28]. These include the constant-power heating mode, intermittent heating mode, and the constant temperature heating mode. Terigar et al. reported that the constant power heating mode presents the standard practice in the extraction of thermally sensitive active constituents of the plant matrix [35]. It is worthy to note that the microwave power alone does not provide an adequate explanation as to how energy is being absorbed in the extraction of the biological medium. Li et al. therefore studied the interrelationship between the microwave energy density and the extraction yield, it was concluded that for a unit of extracting solvent, microwave energy density is the most important factor affecting the extraction efficiency in a microwave-assisted extraction [39].

Gao et al. reported an accelerated effect on the ionic conduction and dipole rotation which in turn leads to an increase in the extraction yield [40]. This is due to the release of more microwave energy to the biological medium as the microwave power increases. Polar solvents rates of absorption improve with increasing power and ultimately resulting in higher heating and extraction rate [41]. Li et al. in [39] described the energy density of microwave heating as the power per unit quantity of sample under extraction as shown in Eq. (1).

$$Energy\ density\ (W/mL) = \frac{Microwave\ power\ (W)}{Volume\ of\ extracting\ solvent\ (mL)}\tag{1}$$

**Number**

**9**

1.

*Artemisia annua* L.

 **Plant sample**

**Results obtained**

MAE:

Microwave

ratio = 15; Extraction time = 12 min

SFE:

Artemisinin

 (33.2% db)

> Pressure = 30 MPa; solvent = CO2; Solvent/

feed ratio = 6;

time = 2.5 h

Soxhlet:

Artemisinin

 (60.4% db a)

5,8-Dihydroxycoumarin

High yields and selectivity compared to other

[44]

*Microwave-Assisted Extraction of Bioactive Compounds (Review)*

*DOI: http://dx.doi.org/10.5772/intechopen.96092*

extraction methods.

(0.42% db) 5-Hydroxy-8-

glucopyranosylbenzopyranone

 (0.11% db)

5,8-Dihydroxycoumarin

(0.49% db) 5-Hydroxy-8-

glucopyranosylbenzopyranone

 (0.06% db)

5,8-Dihydroxycoumarin

(0.46% db) 5-Hydroxy-8-

glucopyranosylbenzopyranone

 (0.08% db)

Glycyrrhizic

 acid–GA (2.26%)

It recovered a higher yield in reduced time.

 [45]

*O*-β-D-

*O*-β-D-

*O*-β-D-

Solvent oil; S/F = 11.67; T = 35 C; t = 6 h

MAE:

Microwave

used = acetone;

Temperature

time = 15 min; one-step extraction

SFE:

Two-step:

1. Pressure = 35 MPa;

2. Pressure = 25Mpa; Solvent = 20% of ethanol; Extraction

time = 2 h; Flowrate = 0.5 L/min

Soxhlet:

Solvent/feed

Extraction time = 6 h

MAE:

Microwave

Solvent/feed

C; Extraction time = 4 min

Ultrasonic:

Solvent = ethanol; Extraction time = 20.5 h

Soxhlet:

Solvent/feed

 ratio = 10;

Glycyrrhizic

Glycyrrhizic

 acid–GA (2.5%)

 acid–GA (2.26%)

 ratio = 10;

Temperature

 = 85–90 °

 power = 700 W; Solvent = ethanol;

3

 Licorice roots

 ratio = 50; Solvent = acetone;

Temperature

Temperature

 = 40 °C;

 = 40 °C

 = 80 °C; Extraction

Solvent/feed

 ratio = 10;

 power = 200 W; solvent

2.

 Sweet grass leaves

Temperature

 = 35 °C; Extraction

Temperature

 = ambient;

 power = 650 W;

Solvent/feed

**Bioactive compounds**

Artemisinin

 (92.1% db)

 **Remarks** High yields and selectivity compared to other

extraction methods.

**Reference**

[43]


## *Microwave-Assisted Extraction of Bioactive Compounds (Review) DOI: http://dx.doi.org/10.5772/intechopen.96092*

generally improve the extraction yield and result in a shorter extraction time [13, 29, 35]. On the other hand, if microwave power is too high, it can result in poor extraction yield leading to the degradation of thermally sensitive compounds in the plant matrix [29]. It is then important to select the appropriate microwave power to reduce the extraction time required to reach the set temperature and avoid a

*Microwave Heating - Electromagnetic Fields Causing Thermal and Non-Thermal Effects*

The characteristic of the plant sample and its water content can influence MAE. The extraction efficiency improves as the contact surface area of the plant sample increases. Moreover, finer samples give room for deeper penetration of microwave irradiation [36]. Nevertheless, too much finest of the plant sample may generate some technical difficulties; hence, filtration or centrifugation is employed in the preparation of the plant samples [27, 37]. During the sample preparation, the grinded sample is homogenized to improve contact between the solvent and the plant matrix. The plant particle sizes mostly fall within 2 and 100 mm [31]. Sometimes, the plant matrix is soaked before extraction to improve the yield; this is

Mostly, the recovery of bioactive compounds from the plant matrix tends to increase through its moisture that acts as a solvent. This moisture is heated up, evaporated, causes pressure within the cell, and dispenses the solutes through rupturing of the cell wall; thus, increase the yield of bioactive compounds [38]. An increase in the polarity of solvent causes the addition of water to have a positive influence on microwave-absorbing capability; thus, encourages the heating procedure [26]. Extra water generates hydrolyzation and reduces the oxidation of

There are three heating operational modes employed in the performance evalu-

ation of microwave-assisted extraction [28]. These include the constant-power heating mode, intermittent heating mode, and the constant temperature heating mode. Terigar et al. reported that the constant power heating mode presents the standard practice in the extraction of thermally sensitive active constituents of the plant matrix [35]. It is worthy to note that the microwave power alone does not provide an adequate explanation as to how energy is being absorbed in the extraction of the biological medium. Li et al. therefore studied the interrelationship between the microwave energy density and the extraction yield, it was concluded that for a unit of extracting solvent, microwave energy density is the most important factor affecting the extraction efficiency in a microwave-assisted

Gao et al. reported an accelerated effect on the ionic conduction and dipole rotation which in turn leads to an increase in the extraction yield [40]. This is due to the release of more microwave energy to the biological medium as the microwave power increases. Polar solvents rates of absorption improve with increasing power and ultimately resulting in higher heating and extraction rate [41]. Li et al. in [39] described the energy density of microwave heating as the power per unit quantity

*Energy density W*ð Þ¼ *<sup>=</sup>mL Microwave power W*ð Þ

*Volume of extracting solvent mL* ð Þ (1)

**3.5 Characteristic of plant sample and its water content**

"bumping" phenomenon [13].

known as pre-leaching [37].

bioactive compounds.

extraction [39].

**8**

**3.6 Microwave energy density**

of sample under extraction as shown in Eq. (1).


**Number**

**11**

 **Plant sample**

**Results obtained**

UAE:

Solvent = feed ratio = 25; Extraction time = 30 min;

Frequency = 33 kHz

SFE:

Pressure = 25 MPa; Solvent = CO2 + ethanol; Extraction time = 3 h

Shaking:

Solvent =

Extraction time = 3 h

HRE:

Solvent =

feed ratio = 25;

Extraction time = 1 h

MAE:

Global yield (11.62%)

High yields compared to other extraction

[48]

*Microwave-Assisted Extraction of Bioactive Compounds (Review)*

*DOI: http://dx.doi.org/10.5772/intechopen.96092*

methods.

Microwave

water (40:60 v/v);

Temperature

time = 7 min 3 cycles

UAE:

Global yield (6.78% db)

Microwave

water (40:60 v/v);

Temperature

time = 60 min 3 cycles

HRE:

Global yield (10.82% db)

Microwave

water (40: 60 v/v);

Temperature

time = 90 min 3 cycles

MAE:

Curcumin (90.47% db)

 High yields compared to other extraction

[49]

methods.

Microwave

Solvent/feed

Extraction time = 5 min

 = 3;

Temperature

 = 50 °C;

 power = 60 W; Solvent = acetone;

8.

 Turmeric plant

 = 50 °C; Extraction

Solvent/feed

 ratio = 30;

 power = 800 W; Solvent = ethanol/

 = 50 °C; Extraction

Solvent/feed

 ratio = 30;

 power = 250 W; Solvent = ethanol/

 = 50 °C; Extraction

Solvent/feed

 = 30;

 power = 900 W; Solvent = ethanol/

7.

 Yellow horn

ethanol/water

 (9.5:0.5 v/v); Solvent/

Temperature

 = 95 °C;

ethanol/water

 (9.5:0.5 v/v);

Temperature

 = 55 °C;

Global yield (2.58% db)

Global yield (2.22% db)

Global yield (1.52% db)

ethanol/water

 (9.5:0.5 v/v); Solvent/

**Bioactive compounds** Global yield (1.72% db)

 **Remarks**


## *Microwave-Assisted Extraction of Bioactive Compounds (Review) DOI: http://dx.doi.org/10.5772/intechopen.96092*

**Number**

**10**

4.

 Green tea leaves

 **Plant sample**

**Results obtained** Solvent = ethanol;

Extraction time = 10 h

MAE:

Tea polyphenols

Tea caffeine (4%)

 (30%),

High yields and selectivity compared to other

[18]

extraction methods.

Microwave

water (1:1 v/v);

Temperature

UAE:

Solvent =

feed = 20; time = 90 min

Heat reflux extraction:

Solvent =

feed = 20; time = 45 min

MAE:

Pectin (27.81%)

High yields compared to other extraction

[46]

*Microwave Heating - Electromagnetic Fields Causing Thermal and Non-Thermal Effects*

methods.

Microwave

Solvent/feed

time = 6 min

UAE:

Solvent = water; T = 70 °C; Extraction time = 25 min

UAE + MAE:

Microwave

feed = 30; Extraction time = 30 min for UAE

and 10 min for MAE

Heat batch: Solvent = water; Extraction time = 90 min

MAE:

Solvent = feed ratio = 25; Extraction time = 5 min

ethanol/water

 (9.5:0.5 v/v); Solvent/

Global yield (5.11% db)

 High yields compared to other extraction

[47]

methods.

Temperature

 = 90 °C;

6.

*Ganoderma*

 *atrum*

Solvent/feed

 = 30; T = 90 °C;

Pectin (19.16%)

 power = 0.45 kW; Solvent/

Solvent/feed

 ratio = 30;

Pectin (17.92%) Pectin (31.88%)

 ratio = 30; T = 20 °C; Extraction

 power = 0.9 kW; Solvent = water;

5.

 Grape fruit

Temperature

 = 85 °C; Extraction

ethanol/water

 (1:1 v/v); Solvent/

Tea polyphenols Tea caffeine (3.6%)

 (28%),

Temperature

 = 20–40 °C; Extraction

ethanol/water

 (1:1 v/v); Solvent/

Tea polyphenols

Tea caffeine (3.6%)

 (28%),

 = 20 °C; Extraction time = 4 min

Solvent/feed

 ratio = 20;

 power = 700 W; Solvent = ethanol/

Solvent/feed

 ratio = 10;

**Bioactive compounds**

 **Remarks**


**Number**

**13**

11.

*Cinnamomum*

*zeylanicum*

 **Plant sample**

**Results obtained**

MAE:

Microwave

water (50:50 v/v);

Temperature

UAE:

Solvent =

feed ratio = 10; Extraction time = 30 min

MAE:

Microwave

 power = 200 W;

Temperature

(50:50 v/v); time = 18 min

UAE:

Solvent =

feed ratio = 10; Extraction time = 30 min

MAE:

Microwave

 power = 200 W;

Temperature

(50:50 v/v); time = 18 min

UAE:

Solvent =

feed ratio = 10; Extraction time = 30 min

MHG:

Microwave

time = 15 min; Humidity = 57%

Agitated:

Solvent =

methanol/water

 (80:20 v/v);

 power = 400 W; Extraction

14.

 Sea buckthorn

ethanol:water

 (50:50 v/v), Solvent/

Phenolics content (0.500%

db)

Isorhamnetin

(0.123% db) Isorhamnetin

(0.097% db)

Quercetin (0.025% db) Isorhamnetin

Isorhamnetin

(0.187% db)

3-*O-*rutinoside

 (0.00084%

 db)

3-*O-*Glucoside

 3-

*O*-glucoside

3-*O-*rutinoside

Recovery of higher yields of bioactive

[52]

compound compared to other extraction

techniques.

 = 50 °C, Solvent =

Solvent/feed

 ratio = 20; Extraction

ethanol/water

13.

*Crocus sativus*

ethanol/water

 (50:50 v/v), Solvent/

Phenolics content (0.290%

db)

Phenolics content (2.939%

The recovery of phenolic compounds higher in MAE compare to other techniques.

 was

[51]

db)

 = 50 °C, Solvent =

Solvent/feed

 ratio = 20; Extraction

ethanol/water

12.

*Cuminum cyminum*

ethanol/water

 (50:50 v/v), Solvent/

 = 50 °C, Extraction time = 18 min

Solvent/feed

 ratio = 20; Phenolics content (0.506%

db)

Phenolics content (1.159%

The recovery of phenolic compounds higher in MAE compare to other techniques.

 was

[51]

*DOI: http://dx.doi.org/10.5772/intechopen.96092*

*Microwave-Assisted Extraction of Bioactive Compounds (Review)*

db)

 power = 200 W; Solvent = ethanol/

**Bioactive compounds** Phenolics content (1.679%

db)

 **Remarks** The recovery of phenolic compounds higher in MAE compare to other techniques.

 was

[51]


#### *Microwave-Assisted Extraction of Bioactive Compounds (Review) DOI: http://dx.doi.org/10.5772/intechopen.96092*

**Number**

**12**

 **Plant sample**

**Results obtained**

UAE:

Microwave

Solvent/feed

Extraction time = 5 min

Soxhlet:

Solvent = acetone; Solvent = 5; Extraction

time = 8 h

SFE:

Pressure = 30 MPa; Solvent = CO2 + ethanol

(10%); Extraction time = 240 min; flowrate = 5 mL/

min

MAE:

Silybinin (1.37 db)

High yields compared to other extraction

[50]

*Microwave Heating - Electromagnetic Fields Causing Thermal and Non-Thermal Effects*

methods.

Microwave

water (80:20 v/v); Extraction time = 2 min 6 cycles

Soxhlet:

Solvent = feed = 100; Extraction time = 12 h

Stirring:

Solvent = feed ratio = 100; Extraction time = 24 h

Maceration:

Solvent = feed ratio = 100; Extraction time = 24 h

MAE:

Phenolics content (0.082%

The recovery of phenolic compounds higher in MAE compare to other techniques.

 was

[51]

db)

Microwave

water (50:50 v/v);

Temperature

UAE:

Solvent = feed ratio = 10; Extraction time = 30 min

ethanol/water

 (50:50 v/v), Solvent/

 = 50 °C, Extraction time = 18 min

Solvent/feed

 = 20; Phenolics content (0.041%

db)

 power = 200 W; Solvent = ethanol/

10.

*Coriandrum*

 *sativum*

ethanol/water

 (80:20 v/v); Solvent/

ethanol/water

 (80:20 v/v); Solvent/

ethanol/water

 (80:20 v/v); Solvent/

Silybinin (1.09 db) Silybinin (0.48% db)

Silybinin (0.36 db)

Solvent/feed

 = 25;

 power = 600 W; Solvent = ethanol/

9.

*Silybum marianum* (L.) (milk

thistle)

Temperature

 = 50 °C;

 = 3;

Temperature

 = 21 °C; Curcumin (2.10% db) Curcumin (69.36% db)

 power = 150 W; Solvent = acetone;

**Bioactive compounds**

Curcumin (71.42% db)

 **Remarks**


**Number**

**15**

 **Plant sample**

**Results obtained**

Temperature

Soxhlet:

Solvent = hexane; Extraction time = 4 h

MASD:

Monoterpenes

Oxygenated

(78.29% db) Sesquiterpenes

Global yield (8.86% db)

Monoterpenes

Oxygenated

(75.14% db) Sesquiterpenes

Global yield (2.59% db)

Global yield (2.59% db)

High yields compared to other extraction

[57]

methods.

Carvone (67.59% db) Limonene (30.10% db) Global yield (2.54% db)

Carvone (66.89% db)

Limonene (30.30% db) Total phenolic contents

The recovery of phenolic compounds higher in MAE compare to other technique.

 was

[58]

(0.646% db)

 (2.87% db)

monoterpenes

 (4.92% db)

*Microwave-Assisted Extraction of Bioactive Compounds (Review)*

 (2.77% db)

monoterpenes

 (3.45% db)

Recovery of higher yields of a bioactive

[56]

*DOI: http://dx.doi.org/10.5772/intechopen.96092*

compound in lesser time compared to other

extraction techniques.

Microwave

Solvent/feed

time = 10 min

SD:

s = water; S/F = 4; t = 90 min

19.

 Caraway (*Carum carvi* L.)

 MDG: Microwave

time = 45 min Hydrodistillation:

Solvent/feed

time = 300 min

MAE:

Microwave

Solvent = methanol; Extraction time = 45 min

Shaker:

Solvent =

feed ratio = 50; Revolution = 400 rpm; Extraction time = 15 h

MWHD:

Global yield (1.14% db)

 High yields compared to other extraction

[59]

methods.

Microwave

Solvent/feed

Extraction time = 200 s

 ratio = 2;

Temperature

 = 100 °C;

 power = 300 W; Solvent = water;

21.

*Foeniculum*

Miller (seeds)

 *vulgare*

ethanol/water

 (60:40 v/v); Solvent/

Temperature

 = 45 °C;

Solvent/feed

 ratio = 50; Total phenolic contents

(0.603% db)

 power = 100 W;

20.

 Tomato

 ratio = 5; Extraction

 power = 100 W; Extraction

 ratio = 4; Extraction

 power = 500 W; Solvent = water;

18.

*Lavandula angustifolia*

Mill., Lamiaceae

(lavender flowers)

Solvent/feed

 ratio = 6.67;

 = 45 °C; Extraction time = 1 h

**Bioactive compounds** Global yield (8.65% wb)

 **Remarks**


### *Microwave-Assisted Extraction of Bioactive Compounds (Review) DOI: http://dx.doi.org/10.5772/intechopen.96092*

**Number**

**14**

15.

 Cranberry press cake

MAE:

Solvent = ethanol;

Temperature

time = 10 min

Stirring:

Solvent = ethanol; Extraction time = 2 h

 MAE: Microwave

water (80:20 v/v);

Temperature

UAE:

Solvent = ethanol;

Temperature

time = 60 min

Maceration:

Solvent = ethanol; Extraction time = 3 days

Soxhlet:

Solvent = ethanol;

Temperature

MAE:

Solvent/feed

C; Extraction time = 0.5 h

MAE + UAE:

Microwave

for MAE;

Solvent/feed

 ratio = 5;

 power = 60 W for UAE and 100 W

 ratio = 17.5;

Temperature

 = 120 °

Global yield (14.1% wb)

Global yield (16.5% wb)

High yields compared to other extraction

[55]

methods.

17.

 Soybean germ

 = 100 °C; Extraction time = 4 h

Solvent/feed

 ratio = 100;

Global yield (97.74% db)

Solvent/feed

 ratio = 100;

Global yield (63.33% db)

 = 60 °C; Extraction

Solvent/feed

 ratio = 100;

Global yield (62.23% db)

 = 60 °C; Extraction time = 15 min

Solvent/feed

 ratio = 100;

 power = 720 W; Solvent = ethanol/

16.

*Morinda citriflora* (roots)

Solvent/feed

 ratio = 5; Global yield (95.91% db)

High yields compared to other extraction

[54]

*Microwave Heating - Electromagnetic Fields Causing Thermal and Non-Thermal Effects*

methods.

Quercetin (0.1272% db)

 = 125 °C; Extraction

Solvent/feed

 ratio = 5.7;

 **Plant sample**

**Results obtained**

Solvent/feed

time = 8 min

 ratio = 10; Extraction

**Bioactive compounds**

Isorhamnetin

(0.162% db) Quercetin 3(0.016% db) Isorhamnetin

Quercetin (0.1537% db)

 (0.00064%

 db)

Recovery of higher yields of bioactive

[53]

compound in lesser time compared to other

extraction techniques.

*O*


 3-

*O*


 **Remarks**


**Number**

**17**

25.

*Mentha crispa* L.

(gardenmint)

 SFME: Microwave

 power = 500 W;

Temperature

time = 30 min

HD:

Solvent = water;

Temperature

SFME:

Microwave

 power = 500 W;

Temperature

HD: g -Terpinene

s = water; S/F = 12; T = 100 C; t = 4.5 h

> 27.

*Elletaria* 

L.

(cardamom)

*cardamomum*

SFME:

Microwave

 power = 390 W;

Temperature

Extraction time = 75 min

HD:

Solvent = water;

Temperature

MAE:

Microwave

Solvent =

feed ratio = 25; Extraction time = 6 min

Reflux:

Gymnemagenin

 (3.3% db)

methanol:water

 (85:15 v/v); Solvent/

 power = 280 W;

28.

*Gymnema sylvestre*

R. Br.

 = 100 °C; Extraction time = 6 h

Solvent/feed

 ratio = 10;

 = 100 °C; Humidity = 67%;

 = 100 C; Extraction = 30 min

 (22.8% wb a)

26.

*Thymus vulgaris* L.

(thyme)

 = 100 °C; Extraction time = 4.5 h

Solvent/feed

 ratio = 12;

 = 100 °C; Extraction

 **Plant sample**

**Results obtained** HD: Eugenol (11.0% wb a)

s = water; S/F = 12; T = 100 C; t = 4.5 h

**Bioactive compounds**

Eugenol (11.0% wb) Linalool (39.1%% wb) Global yield (0.028% wb)

Limonene (9.7% wb)

Recovery of higher yields of bioactive

[61]

compound compared to other extraction

techniques.

Carvone (64.9% wb) Global yield (0.095% wb)

Limonene (20.2% wb)

Carvone (52.3% wb) Global yield (0.095% wb)

γ-Terpinene

Eugenol (51.0% wb) Global yield 0.160% wb)

γ-Terpinene

Eugenol (40.5%% wb)

Global yield 0.161% wb)

Global yield (2.70% db)

1,8-Cineole

Linalool (5.29% db)

Terpin-4-ol

α-terpineol

Linalyl acetate (3.63% db)

α-terpinyl acetate (45.45%

db)

1,8-Cineole

 (26.23% db)

Gymnemagenin

 (4.3% db)

Recovery of higher yields of bioactive

[63]

compound compared to other extraction

techniques.

 (3.88% db)

 (2.60% db)

 (26.23% db)

Recovery of higher yields of bioactive

[62]

compound compared to other extraction

techniques.

 (22.8%% wb)

 (17.1% wb)

Recovery of higher yields of bioactive

[61]

*Microwave-Assisted Extraction of Bioactive Compounds (Review)*

*DOI: http://dx.doi.org/10.5772/intechopen.96092*

compound compared to other extraction

techniques.

 **Remarks**

