**4. Preparation of monoglycerides as antifungal agents**

Almost all monoglycerides are conventionally made from vegetable oils or animal fat through a lysis reaction approach using alcohol from glycerol. The reaction to break down triglycerides in vegetable oils or animal fats to monoglycerides using glycerol is called glycerolysis reaction. The glycerolysis reaction is a transesterification reaction that needs base catalysts, such as inorganic bases NaOH, KOH, and Ca (OH)2, and sodium alkoxide [20, 21]. The glycerolysis reaction of vegetable oils to produce monoglycerides always takes place at a high temperature around 220–260°C and under inert N2 gas conditions [17]. However, there are some weaknesses from the production of monoglyceride through the glycerolysis reaction of vegetable oils, i.e.:


antifungal activity against *C. albicans* fungus. The ability of monolaurin to inhibit the growth of *C. albicans* was also reported by Chinatangkul et al. [26]. Monolaurin was also able to be used against common foodborne pathogens, including *C. albicans* with a minimum inhibitory concentration (MIC) value of 0.64 mg/mL and

Various literature presented the synthesis routes of 1-monolaurin through three reaction pathways that are summarized below. The reaction routes are esterification reaction of lauric acid and glycerol using either homogeneous or heterogeneous acid catalysts or a lipase enzyme catalyst and transesterification reaction of methyl

a minimum bactericidal concentration (MBC) value of 5.0 mg/mL [27].

*4.1.1 Esterification reaction of lauric acid and glycerol catalyzed by acid catalysts*

can be easily separated from the reaction mixture and is reusable.

Monolaurin can be synthesized via esterification of lauric acid and glycerol in the presence of acid catalysts such as sulfuric acid (H2SO4) and *p*-toluenesulfonic acid (*p*TSA). The disadvantage of homogeneous catalyst is that it cannot be reused and needs to be neutralized. Utilization of heterogeneous acid catalysts in the esterification reaction of lauric acid and glycerol is expected to fulfill the drawbacks of homogeneous catalyst. The advantage of heterogeneous acid catalysts is that it

**Table 2** summarizes the conditions of the esterification reaction of lauric acid and glycerol in the presence of homogeneous and heterogeneous acid catalysts from several publications. From these data, it can be concluded that the *p*TSA (homogeneous acid catalyst) shows excellent catalytic activity in the synthesis of monolaurin with a moderate yield (43.54%) and high purity (100%). Among the heterogeneous acid catalysts, sulfated zirconia-loaded SBA-15 displays an excellent catalytic ability in the esterification reaction to produce monolaurin with high yield (79.1%) and

*4.1.2 Esterification reaction of lauric acid and glycerol catalyzed by lipase enzymes*

Various types of enzyme catalysts, especially lipase enzymes, have been applied to synthesize monolaurin via the esterification reaction of lauric acid and glycerol.

laurate with glycerol.

*The structure of monolaurin.*

*Monoglycerides as an Antifungal Agent DOI: http://dx.doi.org/10.5772/intechopen.91743*

**Figure 2.**

selectivity (83.42%).

**53**

The development of alternative reaction pathways for the synthesis of monoglyceride is essential, considering the high demand for monoglycerides as safe emulsifiers, antimicrobial agents (antibacterial, antifungal, antiviral), and other important applications. In this chapter, some reaction routes of monoglycerides are summarized, and their antifungal activities are also discussed.

#### **4.1 Monolaurin**

Monolaurin is a saturated monoglyceride from lauric acid (C12: 0) with 12 carbon atoms in the acyl group (**Table 1**). Lauric acid is a saturated fatty acid that can be found in coconut oil. Nitbani et al. [12] have reported that the percentage composition of lauric acid in coconut oil was 54% as methyl laurate by GC–MS analysis. Generally, derivatization of lauric acid and fatty acids are needed because their boiling points are too high to be detected by gas chromatography unless converted into their esters such as methyl laurate. From this brief explanation, it can be concluded that monolaurin can be developed or derived from the raw ingredients of coconut oil, lauric acid, or methyl laurate. Monolaurin can be classified into 1-monolaurin and 2-monolaurin based on the position of the acyl group, as can be seen in **Figure 2**.

Monolaurin is a well-known monoglyceride for its killing activities of various species of fungi, especially *Candida albicans* [22]. Monolaurin has also been reported to be very active against *Penicillium* spp., *Aspergillus* spp. [23], and *Fusarium* spp. [24], the dominant food spoilage organisms. Those fungi species contribute to the decrease of the economic value of some foods such as meat, fruits, and cereals. Burhannuddin et al. [25] have reported that monoglyceride from virgin coconut oil (VCO), with monolaurin as the dominant compound, showed good

*Monoglycerides as an Antifungal Agent DOI: http://dx.doi.org/10.5772/intechopen.91743*

**Figure 2.** *The structure of monolaurin.*

the solubility, almost all of the saturated monoglycerides with the acyl carbon chain length of C10–C18 are soluble in ethanol but not soluble in water. Only monocaprylin (C8) is slightly soluble in water but completely soluble in ethanol. That means the hydrophilic properties of monoglycerides are inversely proportional to the carbon

Almost all monoglycerides are conventionally made from vegetable oils or animal fat through a lysis reaction approach using alcohol from glycerol. The reaction to break down triglycerides in vegetable oils or animal fats to monoglycerides using glycerol is called glycerolysis reaction. The glycerolysis reaction is a transesterification reaction that needs base catalysts, such as inorganic bases NaOH, KOH, and Ca (OH)2, and sodium alkoxide [20, 21]. The glycerolysis reaction of vegetable oils to produce monoglycerides always takes place at a high temperature around 220–260°C and under inert N2 gas conditions [17]. However, there are some weaknesses from the production of monoglyceride through the glycerolysis reaction of vegetable oils, i.e.:

**4. Preparation of monoglycerides as antifungal agents**

a. Monoglycerides are obtained in a dark color and burnt smell.

summarized, and their antifungal activities are also discussed.

based on the position of the acyl group, as can be seen in **Figure 2**.

c. High reaction temperatures are not suitable for the production of heatsensitive monoglycerides such as monoglycerides from EPA and DHA.

d. It requires purification of monoglyceride products with molecular distillation.

The development of alternative reaction pathways for the synthesis of monoglyceride is essential, considering the high demand for monoglycerides as safe emulsifiers, antimicrobial agents (antibacterial, antifungal, antiviral), and other important applications. In this chapter, some reaction routes of monoglycerides are

Monolaurin is a saturated monoglyceride from lauric acid (C12: 0) with 12 carbon atoms in the acyl group (**Table 1**). Lauric acid is a saturated fatty acid that can be found in coconut oil. Nitbani et al. [12] have reported that the percentage composition of lauric acid in coconut oil was 54% as methyl laurate by GC–MS analysis. Generally, derivatization of lauric acid and fatty acids are needed because their boiling points are too high to be detected by gas chromatography unless converted into their esters such as methyl laurate. From this brief explanation, it can be concluded that monolaurin can be developed or derived from the raw ingredients of coconut oil, lauric acid, or methyl laurate. Monolaurin can be classified into 1-monolaurin and 2-monolaurin

Monolaurin is a well-known monoglyceride for its killing activities of various

species of fungi, especially *Candida albicans* [22]. Monolaurin has also been reported to be very active against *Penicillium* spp., *Aspergillus* spp. [23], and *Fusarium* spp. [24], the dominant food spoilage organisms. Those fungi species contribute to the decrease of the economic value of some foods such as meat, fruits, and cereals. Burhannuddin et al. [25] have reported that monoglyceride from virgin coconut oil (VCO), with monolaurin as the dominant compound, showed good

b. It requires high energy consumption.

**4.1 Monolaurin**

**52**

chain length of the acyl groups [3].

*Apolipoproteins,Triglycerides and Cholesterol*

antifungal activity against *C. albicans* fungus. The ability of monolaurin to inhibit the growth of *C. albicans* was also reported by Chinatangkul et al. [26]. Monolaurin was also able to be used against common foodborne pathogens, including *C. albicans* with a minimum inhibitory concentration (MIC) value of 0.64 mg/mL and a minimum bactericidal concentration (MBC) value of 5.0 mg/mL [27].

Various literature presented the synthesis routes of 1-monolaurin through three reaction pathways that are summarized below. The reaction routes are esterification reaction of lauric acid and glycerol using either homogeneous or heterogeneous acid catalysts or a lipase enzyme catalyst and transesterification reaction of methyl laurate with glycerol.

### *4.1.1 Esterification reaction of lauric acid and glycerol catalyzed by acid catalysts*

Monolaurin can be synthesized via esterification of lauric acid and glycerol in the presence of acid catalysts such as sulfuric acid (H2SO4) and *p*-toluenesulfonic acid (*p*TSA). The disadvantage of homogeneous catalyst is that it cannot be reused and needs to be neutralized. Utilization of heterogeneous acid catalysts in the esterification reaction of lauric acid and glycerol is expected to fulfill the drawbacks of homogeneous catalyst. The advantage of heterogeneous acid catalysts is that it can be easily separated from the reaction mixture and is reusable.

**Table 2** summarizes the conditions of the esterification reaction of lauric acid and glycerol in the presence of homogeneous and heterogeneous acid catalysts from several publications. From these data, it can be concluded that the *p*TSA (homogeneous acid catalyst) shows excellent catalytic activity in the synthesis of monolaurin with a moderate yield (43.54%) and high purity (100%). Among the heterogeneous acid catalysts, sulfated zirconia-loaded SBA-15 displays an excellent catalytic ability in the esterification reaction to produce monolaurin with high yield (79.1%) and selectivity (83.42%).

#### *4.1.2 Esterification reaction of lauric acid and glycerol catalyzed by lipase enzymes*

Various types of enzyme catalysts, especially lipase enzymes, have been applied to synthesize monolaurin via the esterification reaction of lauric acid and glycerol.


#### **Table 2.**

*Reaction conditions in the synthesis of monolaurin from lauric acid and glycerol catalyzed by an acid catalyst.*

**Table 3** presents some publications related to the synthesis condition of monolaurin. The Novozym 435 lipase enzyme produced by Novozym Inc. has the highest catalytic activity to catalyze the esterification reaction of glycerol and lauric acid to produce monolaurin with high yield and selectivity (up to 100%).

#### *4.1.3 Transesterification reaction of methyl laurate and glycerol*

Monolaurin can be produced from methyl laurate and glycerol via transesterification reaction. The methyl laurate can be obtained from the transesterification reaction of coconut oil [12]. Glycerol itself is a by-product of the biodiesel production process. A mass yield of glycerol produced from the biodiesel production from vegetable oils is around 10% [37–39].

The reaction conditions and the results from the reaction of glycerol and methyl laurate to produce monolaurin can be seen in **Table 4**. Based on the data, 1 monolaurin compounds can be produced in high yield (almost reached 83%) in a binary solvent of *tert*-butanol/*iso*propanol (20:80; wt/wt). The solvent plays an important role in creating effective collisions between methyl laurate molecule and glycerol so that the activation energy is reached and the product of monolaurin is obtained. The presence of the lipase enzyme also determines the success of the formation of monolaurin products via a transesterification reaction of methyl laurate and glycerol.

Compound 2-monolaurin can be synthesized through the ethanolysis reaction of coconut oil using the Lipozyme TL IM catalyst [42]. Coconut oil is rich in lauric acid so that it can be used as a raw material for synthesis 2-monolaurin. In this case, ethanol can break down the triglycerides from coconut oil into monoglycerides, catalyzed by the sn-1,3-specific lipase enzyme. Because it uses an sn-1,3-specific enzyme, the acyl groups released are in positions 1 and 3 of triglycerides. This reaction is referred to as the alcoholysis reaction of coconut oils. Nitbani et al. [18] have successfully synthesized 2-monolaurin with high purity through the

alcoholysis reaction of coconut oil using the Lipozyme TL IM enzyme. The 2 monolaurin compound was obtained in a yield of 30.1% and purity of 100% after purification using TLC preparation with a mixture of chloroform/acetone/methanol (9.5:0.45:0.05) as the eluent solvent. The Lipozyme TL IM enzyme is an sn-1,3-

*Reaction conditions in the synthesis of monolaurin from methyl laurate catalyzed by lipase enzymes.*

**Type of catalyst Reaction condition Yield References**

45.5% yield of monolaurin, 26.8% of dilaurin

17.52% yield of monolaurin

36% yield of monolaurin

59.45% yield of monoglycerides, 62.91% selectivity

50% yield of monolaurin, 34.6% yield of dilaurin

100% selectivity and 100% yield of monolaurin

> 47.6% monolaurin

82.5 2.5 (wt. %) yield of monolaurin

[32]

[33]

[34]

[17]

[35]

[36]

[40]

[41]

of 1:1 (glycerol/lauric acid), 3% (w/w) Lipozyme IM-20, solvent-

Temperature 50°C, 72 h, stirring at 200 rpm, the molar ratio of 1:1 (glycerol/lauric acid), 100% (w/w) molecular sieve, 2 mg of partially purified lipase from *Rhizopus* sp., solvent-free

Temperature 45–60°C, 6 h, stirring at 200 rpm, molar ratio of 3:1 (glycerol/lauric acid), 0.5 g CALB L immobilized on POS-PVA (from the total weight of reactant), solvent-free

Temperature 60°C, 6 h, stirring at 200 rpm, molar ratio of 8:1 (glycerol/lauric acid), 5% (w/w) lipase G immobilized on SiO2-PVA

Temperature 60°C, 3 h, molar ratio of 4:1 (glycerol/lauric acid), 4% (w/w) Lipozyme RM IM,

200 rpm, molar ratio of 4:1 (glycerol/lauric acid), Novozym 435 (60mg per mmol of carboxylic acid), nonaqueous reaction media: ionic liquid [C12mim][BF4]

*Reaction conditions in the synthesis of monolaurin from lauric acid and glycerol catalyzed by lipase enzymes.*

**Type of catalyst Reaction condition Yield References**

250rpm, molar ratio of 1:1 (glycerol/ methyl laurate), 5% (w/w) Novozym-

Temperature 50°C, 1.5 h, molar ratio of 1:6 (glycerol/ methyl laurate), 5% (w/w) Novozym 435, solvent: 15% (wt.) a binary solvent system (*tert*butanol/*iso*propanol, 20:80, wt./wt.), a continuous flow system at a flow

loading, solvent-free

solvent-free

Novozym 435 Temperature 60°C, 8 h, stirring at

Novozym 435 Temperature 50°C, 24 h, stirring at

435, solvent-free

rate of 0.1 mL/min

Lipozyme IM-20 Temperature 55°C, 6 h, molar ratio

free

The partially purified lipase from *Rhizopus* sp.

*Monoglycerides as an Antifungal Agent DOI: http://dx.doi.org/10.5772/intechopen.91743*

CALB lipase (C*andida antarctica B*) immobilized on polysiloxane-polyvinyl alcohol particles (POS-PVA)

Lipase G (*Penicillium camembertii lipase*) immobilized on epoxy SiO2-

Lipozyme RM IM (*Rhizomucor*

Lipozyme 435 (immobilized-*Candida Antarctic lipase* on a macroporous acrylic polymer

PVA composite

*mayhem lipase*)

**Table 3.**

resin)

**Table 4.**

**55**

*Monoglycerides as an Antifungal Agent DOI: http://dx.doi.org/10.5772/intechopen.91743*


#### **Table 3.**

**Table 3** presents some publications related to the synthesis condition of

acid to produce monolaurin with high yield and selectivity (up to 100%).

*4.1.3 Transesterification reaction of methyl laurate and glycerol*

vegetable oils is around 10% [37–39].

laurate and glycerol.

**54**

**Type of catalyst**

Silica gelcoated with propyl sulfonic acids

Sulfated zirconia-loaded SBA-15

Zeolite Y CBV

712

**Table 2.**

H2SO4 Temperature 130°C, 6 h, molar ratio of

*Apolipoproteins,Triglycerides and Cholesterol*

pTSA Temperature 60°C, 6 h, molar ratio of

solvent-free

free

1:1 (glycerol/lauric acid), 5% H2SO4 (w/w from lauric acid), solvent-free

8:1 (glycerol/lauric acid), 2.5% pTSA (w/w from lauric acid), solvent-free

Temperature 112°C, 8 h, molar ratio of 1:1 (glycerol/lauric acid), 5 wt% catalyst (relative to glycerol), solvent-free

Temperature 160°C, 6 h, molar ratio of 4:1 (glycerol/lauric acid), sulfated zirconia-loaded SBA-15 catalyst with 16 wt.% zirconium oxychloride loading,

Temperature 120–140°C, 7 h, molar ratio of 8:1 (glycerol/lauric acid), 15 wt% zeolite Y with dealumination, solvent-

monolaurin. The Novozym 435 lipase enzyme produced by Novozym Inc. has the highest catalytic activity to catalyze the esterification reaction of glycerol and lauric

*Reaction conditions in the synthesis of monolaurin from lauric acid and glycerol catalyzed by an acid catalyst.*

**Reaction condition Yield References**

91% purity

100% purity

31.05% yield of monolaurin,

43.54% yield of monolaurin,

79.1% yield and 83.42% selectivity of monolaurin, lauric acid conversion 94.9%

Reaction conversion: 97.8%, selectivity of 65%, and 59.5% yield of monolaurin

51% yield of monoglyceride [29]

[28]

[7]

[30]

[31]

Monolaurin can be produced from methyl laurate and glycerol via transesterification reaction. The methyl laurate can be obtained from the transesterification reaction of coconut oil [12]. Glycerol itself is a by-product of the biodiesel production process. A mass yield of glycerol produced from the biodiesel production from

The reaction conditions and the results from the reaction of glycerol and methyl

Compound 2-monolaurin can be synthesized through the ethanolysis reaction of coconut oil using the Lipozyme TL IM catalyst [42]. Coconut oil is rich in lauric acid so that it can be used as a raw material for synthesis 2-monolaurin. In this case, ethanol can break down the triglycerides from coconut oil into monoglycerides, catalyzed by the sn-1,3-specific lipase enzyme. Because it uses an sn-1,3-specific enzyme, the acyl groups released are in positions 1 and 3 of triglycerides. This reaction is referred to as the alcoholysis reaction of coconut oils. Nitbani et al. [18]

laurate to produce monolaurin can be seen in **Table 4**. Based on the data, 1 monolaurin compounds can be produced in high yield (almost reached 83%) in a binary solvent of *tert*-butanol/*iso*propanol (20:80; wt/wt). The solvent plays an important role in creating effective collisions between methyl laurate molecule and glycerol so that the activation energy is reached and the product of monolaurin is obtained. The presence of the lipase enzyme also determines the success of the formation of monolaurin products via a transesterification reaction of methyl

have successfully synthesized 2-monolaurin with high purity through the

*Reaction conditions in the synthesis of monolaurin from lauric acid and glycerol catalyzed by lipase enzymes.*


#### **Table 4.**

*Reaction conditions in the synthesis of monolaurin from methyl laurate catalyzed by lipase enzymes.*

alcoholysis reaction of coconut oil using the Lipozyme TL IM enzyme. The 2 monolaurin compound was obtained in a yield of 30.1% and purity of 100% after purification using TLC preparation with a mixture of chloroform/acetone/methanol (9.5:0.45:0.05) as the eluent solvent. The Lipozyme TL IM enzyme is an sn-1,3specific lipase enzyme that has excellent catalytic activity for lipid substrate-related reactions such as hydrolysis, alcoholysis (transesterification), esterification, and acidolysis [42].

#### **4.2 Monomyristin**

Monomyristin compound is a medium-chain saturated monoglyceride with a number of carbon atoms in the acyl chain as 14 (C14). Altieri et al. [24] reported that both myristic acid and monomyristin compounds could inhibit the growth of fungi *F. oxysporum* DSMZ 2018 and *F. avenaceum* DSMZ 62161, although they were still weaker than lauric acid and monolaurin. Jumina et al. [9] also reported that 1 monomyristin has high activity against *C. albicans* compared with 2-monomyristin (not active). Therefore, the synthesis route of 1-monomyristin is important to be discussed. The chemical structure of 1-monomyristin is shown in **Figure 3**.

The 1-monomyristin compound can be obtained from the reaction of myristic acid and glycerol in the presence of lipase enzyme catalyst [17]. Another reaction pathway is through the transesterification of ethyl myristate with protected glycerol (1,2-O-isopropylidene glycerol) followed by a deprotection reaction using Amberlyst-15 to produce 1-monomyristin. Some works related to the synthesis of 1-monomyristin are presented in **Table 5**.

From **Table 5**, it can be noticed that the Novozym 435 enzyme has displayed extraordinary catalytic activity in the esterification reaction of myristic acid and glycerol to produce 1-monomyristin with 100% selectivity and yield. It should be noted that this reaction takes place in an ionic liquid [C12mim][BF4]. The [C12mim][BF4] is an example of a temperature switchable ionic liquid/solid phase used for the selective synthesis of monoglycerides [36]. Monomyristin can also be produced through two stages of reaction of ethyl myristate with 1,2-Oisopropylidene glycerol (mol ratio 1:8) using K2CO3 as a catalyst, which produces an intermediate isopropylidene glycerol myristate as a yellowish liquid with a yield of 32.12% and purity of 95.55%. In the second step, the isopropylidene glycerol myristate compound is deprotected with Amberlyst-15 (mol ratio 1:10) for 30 hours at room temperature to produce 1-monomyristin in the form of white solid in 100% of yield.

#### **4.3 Monocaprin**

Monocaprin is a monoglyceride from capric acid comprising 10 carbon atoms (C10) (**Figure 4**).

Monocaprin is produced from vegetable oils that are relatively safe or nontoxic to the body. Monocaprin is known as a safe food additive, so it is widely used as an emulsifier in the food industry. Solutions containing monocaprin can also act as

microbicidal agents against *Candida albicans* [43]. Lipid compounds, including monoglycerides, are also known as antifungal agents [44]. Monocaprin has been reported to have antifungal activity against three food spoilage fungi *Saccharomyces cerevisiae*, *Aspergillus niger*, and *Penicillium citrinum* with minimum inhibitory concentration values of 0.31, 0.63, and 0.63 mg/mL, respectively. The minimum fungicidal concentrations were also reported to be 1.25, 2.50, and 2.50 mg/mL,

**Type of catalyst Reaction condition Yield References**

47.92% MAG, 79.92% selectivity

100% selectivity and 100% yield of monomyristin

100% yield of 1-monomyristin [17]

[36]

[9]

Temperature 60°C, 6 h, stirring at 200 rpm, molar ratio 8:1 (glycerol/ myristic acid), 5% Lipase G immobilized on SiO2-PVA loading

200 rpm, molar ratio 4:1 (glycerol/ myristic acid); Novozym 435 (60mg per mmol of carboxylic acid), nonaqueous reaction media: ionic

and 1,2-acetonide glycerol: temperature 140°C, 30 h, molar ratio 1:8 (ethyl caprate/1,2 acetonide glycerol), 5% K2CO3 (w/w), isolation product of isopropylidene glycerol myristate

b. Step 2: reaction of isopropylidene glycerol myristate and Amberlyst-

room temperature, 30 h, ethanol as solvent, weight ratio 1:10 (Amberlyst-15/ isopropylidene glycerol myristate), isolation of 1-monomyristin by filtration and

(w/w), solvent-free

liquid [C12mim][BF4]

using diethyl ether

Novozym 435 Temperature 60°C, 8 h, stir at

Potassium carbonate (K2CO3) a. Step 1: reaction of ethyl myristate

15:

*Reaction conditions in the synthesis of 1-monomyristin.*

evaporation

The production of monocaprin also has similarities with monomiristine and monolaurin, which involves esterification reactions of capric acid and glycerol. Another reaction pathway for the synthesis of monocaprin is by utilizing ethyl caprate and 1,2-acetonide glycerol (a protected glycerol compound). A summary of

respectively [45].

*The structure of 1-monocaprin.*

**Table 5.**

**Figure 4.**

**57**

Lipase G (*Penicillium camembertii* lipase) immobilized on epoxy SiO2-

*Monoglycerides as an Antifungal Agent DOI: http://dx.doi.org/10.5772/intechopen.91743*

PVA composite

**Figure 3.** *The structure of 1-monomyristin.*

*Monoglycerides as an Antifungal Agent DOI: http://dx.doi.org/10.5772/intechopen.91743*


#### **Table 5.**

specific lipase enzyme that has excellent catalytic activity for lipid substrate-related reactions such as hydrolysis, alcoholysis (transesterification), esterification, and

Monomyristin compound is a medium-chain saturated monoglyceride with a number of carbon atoms in the acyl chain as 14 (C14). Altieri et al. [24] reported that both myristic acid and monomyristin compounds could inhibit the growth of fungi *F. oxysporum* DSMZ 2018 and *F. avenaceum* DSMZ 62161, although they were still weaker than lauric acid and monolaurin. Jumina et al. [9] also reported that 1 monomyristin has high activity against *C. albicans* compared with 2-monomyristin (not active). Therefore, the synthesis route of 1-monomyristin is important to be discussed. The chemical structure of 1-monomyristin is shown in **Figure 3**.

The 1-monomyristin compound can be obtained from the reaction of myristic acid and glycerol in the presence of lipase enzyme catalyst [17]. Another reaction pathway is through the transesterification of ethyl myristate with protected glycerol

Amberlyst-15 to produce 1-monomyristin. Some works related to the synthesis of

From **Table 5**, it can be noticed that the Novozym 435 enzyme has displayed extraordinary catalytic activity in the esterification reaction of myristic acid and glycerol to produce 1-monomyristin with 100% selectivity and yield. It should be noted that this reaction takes place in an ionic liquid [C12mim][BF4]. The

[C12mim][BF4] is an example of a temperature switchable ionic liquid/solid phase used for the selective synthesis of monoglycerides [36]. Monomyristin can also be

isopropylidene glycerol (mol ratio 1:8) using K2CO3 as a catalyst, which produces an intermediate isopropylidene glycerol myristate as a yellowish liquid with a yield of 32.12% and purity of 95.55%. In the second step, the isopropylidene glycerol myristate compound is deprotected with Amberlyst-15 (mol ratio 1:10) for 30 hours at room temperature to produce 1-monomyristin in the form of white solid in 100%

Monocaprin is a monoglyceride from capric acid comprising 10 carbon atoms

Monocaprin is produced from vegetable oils that are relatively safe or nontoxic to the body. Monocaprin is known as a safe food additive, so it is widely used as an emulsifier in the food industry. Solutions containing monocaprin can also act as

(1,2-O-isopropylidene glycerol) followed by a deprotection reaction using

produced through two stages of reaction of ethyl myristate with 1,2-O-

1-monomyristin are presented in **Table 5**.

*Apolipoproteins,Triglycerides and Cholesterol*

acidolysis [42].

of yield.

**Figure 3.**

**56**

*The structure of 1-monomyristin.*

**4.3 Monocaprin**

(C10) (**Figure 4**).

**4.2 Monomyristin**

*Reaction conditions in the synthesis of 1-monomyristin.*

**Figure 4.** *The structure of 1-monocaprin.*

microbicidal agents against *Candida albicans* [43]. Lipid compounds, including monoglycerides, are also known as antifungal agents [44]. Monocaprin has been reported to have antifungal activity against three food spoilage fungi *Saccharomyces cerevisiae*, *Aspergillus niger*, and *Penicillium citrinum* with minimum inhibitory concentration values of 0.31, 0.63, and 0.63 mg/mL, respectively. The minimum fungicidal concentrations were also reported to be 1.25, 2.50, and 2.50 mg/mL, respectively [45].

The production of monocaprin also has similarities with monomiristine and monolaurin, which involves esterification reactions of capric acid and glycerol. Another reaction pathway for the synthesis of monocaprin is by utilizing ethyl caprate and 1,2-acetonide glycerol (a protected glycerol compound). A summary of


hypothesis that the saturated medium-chain monoglycerides such as monolaurin, monomiristine, and monocaprin have good antifungal activity. Based on their structure, each monoglyceride has an acyl group derived from lauric acid (C12: 0),

It is noted that the chemical structure of monoglyceride plays an important role in its antifungal activity by affecting the interaction with fungal organisms. Monoglycerides with lipophilic acyl groups and two hydrophilic hydroxyls (-OH) groups (**Figure 1**) are beneficial to interact with various chemical components that build

Prasad et al. [4] have reported that the current development of antifungal agents

One of the antifungal drugs that have been developed and are quite useful in invading fungal infections is polyene. There are three main types of fungal drugs from polyene compounds, i.e., Amphotericin B, Nystatin, and Natamycin [48]. These three fungal drugs are known as macrolides, which structurally are cyclic amphiphilic organic molecules. The amphiphilic aspects of macrolides are contributed by the unsaturated alkyl chain (around 14 C) as the lipophilic part that attached to the macrolactone ring and some hydroxyl (-OH) groups as the hydro-

The amphiphilic properties of some macrolide compounds (Amphotericin B, Nystatin, and Natamycin) from the polyene group are the main factors in their mechanism of action as the antifungal agents. Their amphiphilic structure allows these compounds to bind chemically to the components of lipid membrane, especially ergosterol, through van der Waals interactions. Interactions between these molecules will trigger the formation of pores on the cell membrane. Moreover, in the end, the pores will destabilize the cell membrane, damaging the balance of ions

Other interaction models can be predicted based on the chemical structure of macrolides as well as the chemical components of the fungal cell wall, such as mannans, glucans, and chitins. The hydrophilic part (hydroxyl groups) in

macrolide compounds is can possibly interact with polar groups found in mannans, glucans, and chitins through hydrogen bonding. This interaction is also predicted to contribute to the fungal cell wall damage, so the cell lysis can occur resulting in

Comparing the number of hydroxyl groups in monoglycerides, macrolides compounds have more hydroxyl groups. Therefore, the hydrogen bonding interactions of monoglycerides with polar components in the fungal cell wall is expected to be

in the cell membrane and further resulting in the cell death [4, 48, 50].

Monoglyceride compounds such as monolaurin, monomiristine, and monocaprin that have been proven to be antifungal agents are assumed to follow the inhibitory mechanism of macrolides (polyene) compounds. This assumption is very rational, considering that monoglycerides are having excellent amphiphilic properties (**Figures 1** and **2**). The acyl group of the lipophilic part of monoglycerides is expected to interact via van der Waals interaction with ergosterol in fungal cell walls and causes lysis and cell death. Meanwhile, the two hydroxyl groups in monoglycerides are responsible for the antifungal activity by forming hydrogen bonding with other polar components in the fungal cell wall (glucans, chitins) and

is aimed at interactions with the fungal cell wall. There are two main targets of antifungal agents, firstly, by targeting the interactions with chemical components of fungal cell walls such as mannans, glucans, and chitins. The second target is aiming at the interactions with several enzymes that responsible for bioactivity and the biosynthesis pathway of ergosterol. Ergosterol is one of the main sterol components that build fungal cell membranes and regulate the fluidity, permeability, and struc-

myristic acid (C14: 0), and capric acid (C10: 0).

*Monoglycerides as an Antifungal Agent DOI: http://dx.doi.org/10.5772/intechopen.91743*

fungal organisms.

philic part.

cell death.

**59**

assisting the cell membrane lysis process.

ture of the membranes [48, 49].

#### **Table 6.**

*Reaction conditions in the synthesis of 1-monocaprin.*

the reaction conditions on the synthesis of monocaprin can be seen in **Table 6**. It is noticed that monocaprin can be produced with high yield and purity via two reaction steps. The first stage involves the transesterification reaction of ethyl caprate with 1,2-acetonide glycerol to produce intermediate 1,2-acetonide-3-capryl glycerol with a yield of 88.12%. The second step is deprotection reaction of 1,2 acetonide-3-capryl glycerol using a heterogeneous catalyst (Amberlyst-15) to produce 1-monocaprin with 100% purity and a yield of 78.37% after purification. A lipase enzyme *Candida antarctica* (CAL) is also reported to be used as the catalyst in the esterification of capric acid and glycerol, with conversion rate reaching 96.9%. Production of monocaprin in a reverse micelle system using isooctane (reaction medium) and bis(2-ethylhexyl) sodium sulfosuccinate (AOT, anionic surfactant) has marked the conversion rate of esterification reaction of capric acid and glycerol at equilibrium condition at 62.7%, which is achieved using *Porcine liver carboxylesterase* (PLE) as a catalyst.

### **5. Mechanism of monoglycerides as antifungal agents**

Several publications related to the antifungal activity of monoglycerides such as monolaurin, monomiristine, and monocaprin have been explained in the previous section. The studies showed that monoglycerides with good amphiphilic properties were not only able to inhibit the fungal growth but also kill it, especially *C. albicans* (22) (9) and some food spoilage fungi species such as *Saccharomyces cerevisiae*, *Aspergillus niger*, and *Penicillium citrinum* [45]. Publication data supported a

#### *Monoglycerides as an Antifungal Agent DOI: http://dx.doi.org/10.5772/intechopen.91743*

hypothesis that the saturated medium-chain monoglycerides such as monolaurin, monomiristine, and monocaprin have good antifungal activity. Based on their structure, each monoglyceride has an acyl group derived from lauric acid (C12: 0), myristic acid (C14: 0), and capric acid (C10: 0).

It is noted that the chemical structure of monoglyceride plays an important role in its antifungal activity by affecting the interaction with fungal organisms. Monoglycerides with lipophilic acyl groups and two hydrophilic hydroxyls (-OH) groups (**Figure 1**) are beneficial to interact with various chemical components that build fungal organisms.

Prasad et al. [4] have reported that the current development of antifungal agents is aimed at interactions with the fungal cell wall. There are two main targets of antifungal agents, firstly, by targeting the interactions with chemical components of fungal cell walls such as mannans, glucans, and chitins. The second target is aiming at the interactions with several enzymes that responsible for bioactivity and the biosynthesis pathway of ergosterol. Ergosterol is one of the main sterol components that build fungal cell membranes and regulate the fluidity, permeability, and structure of the membranes [48, 49].

One of the antifungal drugs that have been developed and are quite useful in invading fungal infections is polyene. There are three main types of fungal drugs from polyene compounds, i.e., Amphotericin B, Nystatin, and Natamycin [48]. These three fungal drugs are known as macrolides, which structurally are cyclic amphiphilic organic molecules. The amphiphilic aspects of macrolides are contributed by the unsaturated alkyl chain (around 14 C) as the lipophilic part that attached to the macrolactone ring and some hydroxyl (-OH) groups as the hydrophilic part.

The amphiphilic properties of some macrolide compounds (Amphotericin B, Nystatin, and Natamycin) from the polyene group are the main factors in their mechanism of action as the antifungal agents. Their amphiphilic structure allows these compounds to bind chemically to the components of lipid membrane, especially ergosterol, through van der Waals interactions. Interactions between these molecules will trigger the formation of pores on the cell membrane. Moreover, in the end, the pores will destabilize the cell membrane, damaging the balance of ions in the cell membrane and further resulting in the cell death [4, 48, 50].

Other interaction models can be predicted based on the chemical structure of macrolides as well as the chemical components of the fungal cell wall, such as mannans, glucans, and chitins. The hydrophilic part (hydroxyl groups) in macrolide compounds is can possibly interact with polar groups found in mannans, glucans, and chitins through hydrogen bonding. This interaction is also predicted to contribute to the fungal cell wall damage, so the cell lysis can occur resulting in cell death.

Monoglyceride compounds such as monolaurin, monomiristine, and monocaprin that have been proven to be antifungal agents are assumed to follow the inhibitory mechanism of macrolides (polyene) compounds. This assumption is very rational, considering that monoglycerides are having excellent amphiphilic properties (**Figures 1** and **2**). The acyl group of the lipophilic part of monoglycerides is expected to interact via van der Waals interaction with ergosterol in fungal cell walls and causes lysis and cell death. Meanwhile, the two hydroxyl groups in monoglycerides are responsible for the antifungal activity by forming hydrogen bonding with other polar components in the fungal cell wall (glucans, chitins) and assisting the cell membrane lysis process.

Comparing the number of hydroxyl groups in monoglycerides, macrolides compounds have more hydroxyl groups. Therefore, the hydrogen bonding interactions of monoglycerides with polar components in the fungal cell wall is expected to be

the reaction conditions on the synthesis of monocaprin can be seen in **Table 6**. It is noticed that monocaprin can be produced with high yield and purity via two reaction steps. The first stage involves the transesterification reaction of ethyl caprate with 1,2-acetonide glycerol to produce intermediate 1,2-acetonide-3-capryl glycerol with a yield of 88.12%. The second step is deprotection reaction of 1,2 acetonide-3-capryl glycerol using a heterogeneous catalyst (Amberlyst-15) to produce 1-monocaprin with 100% purity and a yield of 78.37% after purification. A lipase enzyme *Candida antarctica* (CAL) is also reported to be used as the catalyst in the esterification of capric acid and glycerol, with conversion rate reaching 96.9%. Production of monocaprin in a reverse micelle system using isooctane (reaction medium) and bis(2-ethylhexyl) sodium sulfosuccinate (AOT, anionic surfactant) has marked the conversion rate of esterification reaction of capric acid and glycerol

**Reaction condition Yield References**

Capric acid conversion as

[46]

[47]

[6]

high as 96.9%

The degree of esterification at equilibrium state 62.7%

a. Yield, 88.12%; purity, 87% (1,2 acetonide-3-capryl glycerol) b. Yield, 78.37%; purity, 100% (1-monocaprin)

Temperature 60°C, 6 h, water (12% in glycerol (w/w)), molar ratio of 1:1 (glycerol/capric acid), lipase dosage (100 U/g) of capric acid, solvent-free, batch

Temperature 60 °C; 4 h; pH = 7; reverse micelles: isooctane (reaction medium) and bis(2-ethylhexyl) sodium sulfosuccinate (AOT, anionicsurfactant); R-value ([water]/[surfactant]): 0.1; G/F-value ([glycerol]/[fatty acid]) 3.0

a. *Step 1: reaction of ethyl caprate and 1,2 acetonide glycerol* Temperature 110°C; 24 h; molar ratio of ethyl caprate/1,2 acetonide glycerol, 1:8; 5% Na2CO3 (w/w); isolation product (1,2-asetonide-3-capryl glycerol) using n-hexane b. *Step 2: reaction of 1,2-acetonide-3-capryl*

Room temperature, 24 h, ethanol as a solvent, ratio weight 1:7 (Amberlyst-15/ 1,2-acetonide-3-capryl glycerol); isolation

recrystallization in n-hexane, purification of 1-monocaprin using preparative thin-

*glycerol and Amberlyst-15*

of crude 1-monocaprin with

layer chromatography

*Reaction conditions in the synthesis of 1-monocaprin.*

reactor

*Apolipoproteins,Triglycerides and Cholesterol*

at equilibrium condition at 62.7%, which is achieved using *Porcine liver*

Several publications related to the antifungal activity of monoglycerides such as monolaurin, monomiristine, and monocaprin have been explained in the previous section. The studies showed that monoglycerides with good amphiphilic properties were not only able to inhibit the fungal growth but also kill it, especially *C. albicans* (22) (9) and some food spoilage fungi species such as *Saccharomyces cerevisiae*, *Aspergillus niger*, and *Penicillium citrinum* [45]. Publication data supported a

**5. Mechanism of monoglycerides as antifungal agents**

*carboxylesterase* (PLE) as a catalyst.

**Type of catalyst**

*Candida antarctica* (CAL)

*Porcine liver carboxylesterase* (PLE)

Sodium carbonate (Na2CO3)

**Table 6.**

**58**

less effective than in macrolides. Based on the prediction of the mechanism of action and in vitro data of monoglycerides as antifungal agents, it can be concluded that monoglycerides, especially monolaurin, monomiristine, and monocaprin, have the potential to be developed as antifungal drugs. Thus, there will be new candidates for antifungal drugs from monoglyceride-based lipid.

**References**

**97**:130-136

126-136

2016;**4**:1-17

Mada; 2017

**34**(2):863-867

2016;**39**(16):74-80

**61**

[1] Wang X, Jin Q, Wang T, Huang J, Wang X. An improved method for the synthesis of 1-monoolein. Journal of Molecular Catalysis B: Enzymatic. 2013;

*Monoglycerides as an Antifungal Agent DOI: http://dx.doi.org/10.5772/intechopen.91743*

> [9] Jumina, Nurmala A, Fitria A, Pranowo D, Sholikhah E, Kurniawan Y, et al. Monomyristin and Monopalmitin derivatives: Synthesis and evaluation as potential antibacterial and antifungal agents. Molecules. 2018;**23**(12):3141

[10] Yu CC, Lee Y-S, Cheon BS, Lee SH. Synthesis of glycerol monostearate with high purity. Bulletin of the Korean Chemical Society. 2003;**24**(8):1229-1231

[11] Jumina J, Lavendi W, Singgih T, Triono S, Kurniawan YS, Koketsu M. Preparation of Monoacylglycerol derivatives from Indonesian edible oil and their antimicrobial assay against *Staphylococcus aureus* and *Escherichia coli*. Scientific Reports. 2019;**9**(1):1-8

[12] Nitbani FO, Jumina, Siswanta D, Solikhah EN. Isolation and antibacterial activity test of Lauric acid from crude coconut oil (*Cocos nucifera L.*). Procedia

Chemistry. 2016;**18**:132-140

[13] Ola PD, Tambaru D. Sintesis Biodiesel dan Minyak Epoksi dari Minyak Jarak (*Ricinnus communis L.*). Cendana, Kupang, Indonesia: Laporan Penelitian, Universitas Nusa; 2009

[14] Orsavova J, Misurcova L,

Ambrozova JV, Vicha R, Mlcek J. Fatty acids composition of vegetable oils and its contribution to dietary energy intake and dependence of cardiovascular mortality on dietary intake of fatty acids. International Journal of Molecular Sciences. 2015;**16**(6):12871-12890

[15] Naik MK, Naik SN, Mohanty S. Enzymatic glycerolysis for conversion

emulsifiers. Catalysis Today. 2014;**237**:

[16] Mba OI, Dumont M-J, Ngadi M. Palm oil: Processing, characterization and utilization in the food industry – A review. Food Bioscience. 2015;**10**:

of sunflower oil to food based

145-149

26-41

[2] Nitbani FO, Jumina SD, Sholikhah E.

monoacylglycerol from fat and oils. International Journal of Pharmaceutical Sciences and Research. 2015;**35**(1):

[3] Miao S, Lin D. Monoglycerides: Categories, Structures, Properties, Preparations, and Applications in the Food Industry. Elsevier: Encyclopedia of

[4] Prasad R, Shah AH, Rawal MK. Antifungals: Mechanism of action and

Sychrová H, Kschischo M, editors. Yeast Membrane Transport. Cham: Springer

[5] Seleem D, Chen E, Benso B, Pardi V, Murata RM. *In vitro* evaluation of antifungal activity of monolaurin against *Candida albicans* biofilms. PeerJ.

drug resistance. In: Ramos J,

International Publishing; 2016

[6] Nitbani FO. Synthesis of monoacylglycerol as antibacterial and immunostimulant agents from coconut oil (*Cocos nucifera L.*) [Ph.D Thesis]. Universitas Gadjah

[8] Nitbani FO, Siswanta D, Sholikhah EN. Synthesis and antibacterial activity test of 1 monocaprin. International Journal of Pharmaceutical Sciences and Research.

[7] Nitbani FO, Jumina, Siswanta D, Sholikhah EN, Fitriastuti D. Synthesis and antibacterial activity 1-monolaurin. Oriental Journal of Chemistry. 2018;

Reaction path synthesis of

Food Chemistry; 2019
