**3. Physicochemical properties and applications of monoglycerides**

Monoglycerides consist of a lipophilic and hydrophilic part in the molecules (**Figure 1**). Acyl groups from the fatty acid contribute to the lipophilic properties, while the two hydroxyl groups are responsible for the hydrophilic properties of monoglyceride. Because of its unique structure, monoglycerides are also known as an amphiphilic compound, which are widely used as surfactants. Surfactants are an active compound with lipophilic tail and hydrophilic head in a molecule that has a function to decrease the surface tension of molecules. Hydrophilic properties of ▬OH groups enable monoglycerides to interact with a water molecule, while the lipophilic from acyl groups make it possible to interact with oil or lipid.

Monoglycerides are classified as nonionic surfactants because the acyl groups do not have any charges. Based on its properties, monoglycerides are suitable to be used as an emulsifier to mix oils and water. Monoglycerides from vegetable oils are expected to be nontoxic emulsifier. Therefore, monoglycerides have broad applications in human life. Some studies supported the claim that monoglycerides have crucial and excellent applications as a safe emulsifier. This fact makes monoglycerides to be widely used in the food industry, detergents, plasticizers, cosmetics, and pharmaceutical formulations [3]. Naik et al. [15] have reported that almost 75% of emulsifiers in the food industry are using monoglycerides, making them the main food emulsifier. About 85,000,000 kg monoglycerides are purchased in the United

States each year [17]. The long-chain monoglycerides (monopalmitin and

Monoglycerides from polyunsaturated fatty acids, such as EPA

determining their wide range of applications in human life.

viruses, paralyzing these microorganisms.

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

is very stable at room temperature [18].

**51**

monostearate) have an excellent emulsifier properties compared to medium-chain monoglycerides (monolaurin and monocaprin). Moreover, the saturated monoglycerides have better emulsifying ability than unsaturated monoglycerides [3]. Some studies have reported that monoglycerides are promising antibacterial, antifungal, and antiviral agents [2, 9, 11, 18]. Medium-chain monoglycerides are revealed to have better antimicrobial activity than long-chain monoglycerides. The high antimicrobial activity of monoglycerides is contributed by its unique chemical structures and excellent amphiphilic properties. The amphiphilic nature of monoglycerides enables the formation of effective interactions with various chemical compositions that construct the membrane cell of pathogenic bacteria, fungi, or

(eicosapentaenoic acid) and DHA (docosahexaenoic acid), play an important function for human health. Wang et al. [1] have reported that monoolein has antioxidant and anti-atherosclerotic activity. Naik et al. [15] have described the antibacterial properties of monoglycerides, allowing them to be used as drug coating agents. Various applications of monoglycerides that have been presented previously prove that the nature and chemical structure of monoglycerides have an important role in

The compound of 1-monoglycerides can exist in four different polymorphic forms at different temperatures [3]. In the polymorphic form α, 1-monoglyceride is unstable but has active chemical properties and excellent emulsion ability. The transition of 1-monoglycerides from the polymorphic form α to sub polymorphic α is observed in a lower temperature condition (35–50°C). If 1-monoglycerides are stored for a long time at room temperature, it will change to a more stable polymorphic form β. The 1 monoglyceride compound can also crystallize rapidly in certain solvents and form a stable β'-form. For example, 1-monocaprin, 1-monolaurin, and 1-monomiristine will crystallize quickly to form white solids from n-hexane solvent [6]. Unsaturated 1 monoglyceride compounds such as 1-monoolein also exist in the β-polymorphic form [19]. The symmetrical molecular structure of 2-monoglycerides causes this compound to always be in the form of polymorphic β [19]. This fact can be seen in 2 monolaurin that can crystallize rapidly in n-hexane solvents to form white solids and

The saturated monoglycerides can be found in three physical appearances, such

monomiristine, monopalmitin), and waxy solid (monostearate and monobehenate).

increase in the melting point. Monocaprylin has a melting point of 40–42°C. As the Carbon chain length increases from monocaprylin to monobehenate, its melting point increases to 65–77°C. Unsaturated monoglycerides such as monoolein and monolinolein are present in liquid form with melting points below 35°C. Regarding

as thick liquid (monocaprylin), fatty solid (monocaprin, monolaurin,

The longer carbon chain length of the saturated monoglyceride leads to an

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

**Fatty acid structure Name**

Caprylic acid

Capric acid

Lauric acid

Myristic acid

Palmitic acid

Stearic acid

Behenic acid

Oleic acid

Ricinoleic acid

Linoleic acid

Docosahexaenoic acid

Eicosapentaenoic acid

*Saturated fatty acid*

*Apolipoproteins,Triglycerides and Cholesterol*

Un*saturated fatty acid*

*Polyunsaturated fatty acid* (PUFA)

**Table 1.**

**50**

*Fatty acids from vegetable oils.*

Monoglycerides are classified as nonionic surfactants because the acyl groups do not have any charges. Based on its properties, monoglycerides are suitable to be used as an emulsifier to mix oils and water. Monoglycerides from vegetable oils are expected to be nontoxic emulsifier. Therefore, monoglycerides have broad applications in human life. Some studies supported the claim that monoglycerides have crucial and excellent applications as a safe emulsifier. This fact makes monoglycerides to be widely used in the food industry, detergents, plasticizers, cosmetics, and pharmaceutical formulations [3]. Naik et al. [15] have reported that almost 75% of emulsifiers in the food industry are using monoglycerides, making them the main food emulsifier. About 85,000,000 kg monoglycerides are purchased in the United States each year [17]. The long-chain monoglycerides (monopalmitin and monostearate) have an excellent emulsifier properties compared to medium-chain monoglycerides (monolaurin and monocaprin). Moreover, the saturated monoglycerides have better emulsifying ability than unsaturated monoglycerides [3].

Some studies have reported that monoglycerides are promising antibacterial, antifungal, and antiviral agents [2, 9, 11, 18]. Medium-chain monoglycerides are revealed to have better antimicrobial activity than long-chain monoglycerides. The high antimicrobial activity of monoglycerides is contributed by its unique chemical structures and excellent amphiphilic properties. The amphiphilic nature of monoglycerides enables the formation of effective interactions with various chemical compositions that construct the membrane cell of pathogenic bacteria, fungi, or viruses, paralyzing these microorganisms.

Monoglycerides from polyunsaturated fatty acids, such as EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), play an important function for human health. Wang et al. [1] have reported that monoolein has antioxidant and anti-atherosclerotic activity. Naik et al. [15] have described the antibacterial properties of monoglycerides, allowing them to be used as drug coating agents. Various applications of monoglycerides that have been presented previously prove that the nature and chemical structure of monoglycerides have an important role in determining their wide range of applications in human life.

The compound of 1-monoglycerides can exist in four different polymorphic forms at different temperatures [3]. In the polymorphic form α, 1-monoglyceride is unstable but has active chemical properties and excellent emulsion ability. The transition of 1-monoglycerides from the polymorphic form α to sub polymorphic α is observed in a lower temperature condition (35–50°C). If 1-monoglycerides are stored for a long time at room temperature, it will change to a more stable polymorphic form β. The 1 monoglyceride compound can also crystallize rapidly in certain solvents and form a stable β'-form. For example, 1-monocaprin, 1-monolaurin, and 1-monomiristine will crystallize quickly to form white solids from n-hexane solvent [6]. Unsaturated 1 monoglyceride compounds such as 1-monoolein also exist in the β-polymorphic form [19]. The symmetrical molecular structure of 2-monoglycerides causes this compound to always be in the form of polymorphic β [19]. This fact can be seen in 2 monolaurin that can crystallize rapidly in n-hexane solvents to form white solids and is very stable at room temperature [18].

The saturated monoglycerides can be found in three physical appearances, such as thick liquid (monocaprylin), fatty solid (monocaprin, monolaurin, monomiristine, monopalmitin), and waxy solid (monostearate and monobehenate). The longer carbon chain length of the saturated monoglyceride leads to an increase in the melting point. Monocaprylin has a melting point of 40–42°C. As the Carbon chain length increases from monocaprylin to monobehenate, its melting point increases to 65–77°C. Unsaturated monoglycerides such as monoolein and monolinolein are present in liquid form with melting points below 35°C. Regarding

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 chain length of the acyl groups [3].
