**3. Lipids**

#### **3.1 Definition**

Unlike the various families of basic molecules in the living world characterized by chemical structures, lipids are defined by their solubility not on the basis of their chemical structure [6].

Lipids are among the primary metabolites, they consist of a heterogeneous group of compounds characterized by their insolubility in water, on the other hand they are soluble in non-polar organic solvents such as: chloroform and alcohols.

Lipids play mainly important roles in plants, as signaling and energy storage compounds [7].

#### **3.2 Classification**

Lipids mainly include fatty acids, simple lipids and complex lipids.

#### *3.2.1 Fatty acids*

The fatty acids are carboxylic acids R-COOH; radical R is an aliphatic chain of hydrocarbon type of variable length which gives the molecule its hydrophobic character (fatty).

They are generally mono carboxylic, and characterized by a linear chain with an even number of carbons [8].

#### *3.2.1.1 Saturated fatty acids*

A fatty acid consists of a hydrocarbon chain, more or less long, strongly apolar, and a polar carboxyl group. The general formula of fatty acids is CH3 - (CH2) n – COOH [8]. The most abundant fatty acids are: palmitic acid and stearic acid (**Figure 1**).

#### *3.2.1.2 Unsaturated fatty acids*

The structure of unsaturated fatty acids includes one or more double bonds; the presence of these double bonds gives them specific physicochemical properties (**Figure 2**) [8].

**35**

**Figure 3.**

*Glycerophospholipids.*

*Plants' Bioactive Metabolites and Extraction Methods DOI: http://dx.doi.org/10.5772/intechopen.96698*

present in animal fats or in microbial lipids [8].

Atypical fatty acids are characterized by an odd number of carbons; they are

Simple lipids or homolipids are ternary bodies (C, H, O), they are fatty acid

Complex lipids are hetero lipids which contain phosphate, sulfate or carbohydrate groups. They are classified according to the molecule that fixes fatty acids [8].

These are the most numerous and most represented lipids which are constructed

The alcohols of the C1 and C2 carbons of glycerol are esterified by fatty acids and the C3 carbon alcohol, unlike the glycerolipids, is not esterified, but it is linked

esters, depending on the alcohol we distinguish the following classes [8]:

• **Acylglycerols:** or glycerides are esters of glycerol,

• **Cerides:** long chain alcohol esters (fatty alcohol),

from the skeleton of a glycerol mono ester (**Figure 3**) [8].

to an ose by a glycosidic bond (**Figure 4**) [8].

• **Sterids:** sterol esters (polycyclic alcohol).

*3.2.1.3 Atypical fatty acids*

*3.2.2 Simple lipids*

**Figure 2.** *Oleic acid.*

*3.2.3 Complex lipids*

*3.2.3.1 Glycerophospholipids*

*3.2.3.2 Glyceroglycolipids*

**Figure 1.** *Palmitic acid.*

*Plants' Bioactive Metabolites and Extraction Methods DOI: http://dx.doi.org/10.5772/intechopen.96698*

#### **Figure 2.** *Oleic acid.*

*Bioactive Compounds - Biosynthesis, Characterization and Applications*

Unlike the various families of basic molecules in the living world characterized by chemical structures, lipids are defined by their solubility not on the basis of their

Lipids are among the primary metabolites, they consist of a heterogeneous group of compounds characterized by their insolubility in water, on the other hand they are soluble in non-polar organic solvents such as: chloroform and alcohols. Lipids play mainly important roles in plants, as signaling and energy storage

Lipids mainly include fatty acids, simple lipids and complex lipids.

The fatty acids are carboxylic acids R-COOH; radical R is an aliphatic chain of hydrocarbon type of variable length which gives the molecule its hydrophobic

They are generally mono carboxylic, and characterized by a linear chain with an

A fatty acid consists of a hydrocarbon chain, more or less long, strongly apolar,

The structure of unsaturated fatty acids includes one or more double bonds; the presence of these double bonds gives them specific physicochemical properties

and a polar carboxyl group. The general formula of fatty acids is CH3 - (CH2) n – COOH [8]. The most abundant fatty acids are: palmitic acid and stearic acid

• Antimicrobial;

• Antioxidant;

• Antiseptic

**3. Lipids**

**3.1 Definition**

compounds [7].

**3.2 Classification**

*3.2.1 Fatty acids*

character (fatty).

(**Figure 1**).

(**Figure 2**) [8].

even number of carbons [8].

*3.2.1.1 Saturated fatty acids*

*3.2.1.2 Unsaturated fatty acids*

chemical structure [6].

• Anti-inflammatory;

**34**

**Figure 1.** *Palmitic acid.*
