*3.2.2 Simple lipids*

Simple lipids or homolipids are ternary bodies (C, H, O), they are fatty acid esters, depending on the alcohol we distinguish the following classes [8]:


## *3.2.3 Complex lipids*

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

#### *3.2.3.1 Glycerophospholipids*

These are the most numerous and most represented lipids which are constructed from the skeleton of a glycerol mono ester (**Figure 3**) [8].

#### *3.2.3.2 Glyceroglycolipids*

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

**Figure 3.** *Glycerophospholipids.* *Bioactive Compounds - Biosynthesis, Characterization and Applications*

#### *3.2.3.3 Sphingolipids*

The skeleton from which these lipids are made is not glycerol but a long-chain carbon diol amine of the sphingoid type; the binding of a fatty acid to the amine group gives a ceramide which is the lipid precursor molecule of this group [8].

## **4. Alkaloids**

Alkaloids are natural compounds with low molecular weight [9] that are characterized by the presence of nitrogen atoms. They are mostly found in plants as secondary metabolites and some other animals and fungi [10].

They are derived from amino acids containing one or more heterocyclic nitrogen atoms [11]. Alkaloids have played a huge role in traditional medicine in various civilizations since antiquity due to their potential therapeutic properties. Toxic alkaloids were similarly used in poisonous arrows [12]. However, it was until 1804 that they were isolated and characterized by Friedrich Sertürner [13] and Derosne [9].

#### **4.1 Classification**

Due to their diverse structures, finding a common classification was complicated [14]. Some studies considered a classification based on the ring systems: indolizidine- and quinolizidine-based systems and quinoline-, quinazoline-, and acridone-based systems (**Figure 5**) [11]. Yet, this classification mode causes confusion as some alkaloids can be categorized in more than one class [15]. Henceforth, a new classification was adopted [9]:

True alkaloids: The nitrogen atom, originating from the precursor amino acid, is part of the alkaloid heterocyclic ring.

Protoalkaloids: The nitrogen atom, originating from the precursor amino acid, is not part of the alkaloid heterocyclic ring.

Pseudoalkaloids: They are not originated from amino acids, including steroidslike, purine-like and terpene-like alkaloids. Each class is divided to subclasses according to the precursor amino acid.

**37**

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

**4.2 Therapeutic usefulness**

*Alkaloids classes based on ring systems [11].*

anti-malarial [17].

**Figure 5.**

**4.3 Role for plants**

**4.4 Extraction methods**

to obtain alkaloids.

are followed [14].

boiling temperature [19].

reached.

others propose they are waste products [17].

Alkaloids have a wide range of potential therapeutic activities. Morphine has narcotic effect, cocaine is a potent central nervous system stimulant, taxol as an effective anticancer chemical, colchicine as an anti-inflammatory [11], tubocurarine is a poisonous alkaloid used to relax muscles prior to surgeries [16], vinblastine, one of the antitumor alkaloids, and quinine being an effective

Despite the various advantages they present for Man, their role in the plant is not well known. Some studies suggest that they help the process of seed formation [17] and protect the plant against herbivores and unwanted plants [18] whereas some

There exist as many extraction methods as the diversity of alkaloids structures [15]. They are extracted exploiting their solubility in organic solvents and water for their salts [19]. Base or acidic extractions followed by purification are widely used

Acidic extraction, on the other hand, processes the finely grounded raw plant material with weak acidic solutions mentioning acetic acid in water, methanol or ethanol... followed by the addition of basic solutions to convert alkaloids to basic forms to allow their extraction with organic solvents. The same purification steps

Different alkaloids are separated based either on the difference of solubility or

Base extraction consists of the use of alkaline solvents including 1,2 dichloroethane, chloroform, diethyl ether or benzene. Base Alkaloids are then converted to salts by the addition of weak acids and are washed with water to crystallize. The purification method is repeated until the desired purity is

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

#### **Figure 5.**

*Bioactive Compounds - Biosynthesis, Characterization and Applications*

The skeleton from which these lipids are made is not glycerol but a long-chain carbon diol amine of the sphingoid type; the binding of a fatty acid to the amine group gives a ceramide which is the lipid precursor molecule of this group [8].

Alkaloids are natural compounds with low molecular weight [9] that are characterized by the presence of nitrogen atoms. They are mostly found in plants as

They are derived from amino acids containing one or more heterocyclic nitrogen

atoms [11]. Alkaloids have played a huge role in traditional medicine in various civilizations since antiquity due to their potential therapeutic properties. Toxic alkaloids were similarly used in poisonous arrows [12]. However, it was until 1804 that they were isolated and characterized by Friedrich Sertürner [13] and Derosne [9].

Due to their diverse structures, finding a common classification was complicated [14]. Some studies considered a classification based on the ring systems: indolizidine- and quinolizidine-based systems and quinoline-, quinazoline-, and acridone-based systems (**Figure 5**) [11]. Yet, this classification mode causes confusion as some alkaloids can be categorized in more than one class [15]. Henceforth, a

True alkaloids: The nitrogen atom, originating from the precursor amino acid, is

Protoalkaloids: The nitrogen atom, originating from the precursor amino acid, is

Pseudoalkaloids: They are not originated from amino acids, including steroids-

like, purine-like and terpene-like alkaloids. Each class is divided to subclasses

secondary metabolites and some other animals and fungi [10].

**36**

*3.2.3.3 Sphingolipids*

**Figure 4.** *Glyceroglycolipids.*

**4. Alkaloids**

**4.1 Classification**

new classification was adopted [9]:

part of the alkaloid heterocyclic ring.

not part of the alkaloid heterocyclic ring.

according to the precursor amino acid.

*Alkaloids classes based on ring systems [11].*

#### **4.2 Therapeutic usefulness**

Alkaloids have a wide range of potential therapeutic activities. Morphine has narcotic effect, cocaine is a potent central nervous system stimulant, taxol as an effective anticancer chemical, colchicine as an anti-inflammatory [11], tubocurarine is a poisonous alkaloid used to relax muscles prior to surgeries [16], vinblastine, one of the antitumor alkaloids, and quinine being an effective anti-malarial [17].

#### **4.3 Role for plants**

Despite the various advantages they present for Man, their role in the plant is not well known. Some studies suggest that they help the process of seed formation [17] and protect the plant against herbivores and unwanted plants [18] whereas some others propose they are waste products [17].

#### **4.4 Extraction methods**

There exist as many extraction methods as the diversity of alkaloids structures [15]. They are extracted exploiting their solubility in organic solvents and water for their salts [19]. Base or acidic extractions followed by purification are widely used to obtain alkaloids.

Base extraction consists of the use of alkaline solvents including 1,2 dichloroethane, chloroform, diethyl ether or benzene. Base Alkaloids are then converted to salts by the addition of weak acids and are washed with water to crystallize. The purification method is repeated until the desired purity is reached.

Acidic extraction, on the other hand, processes the finely grounded raw plant material with weak acidic solutions mentioning acetic acid in water, methanol or ethanol... followed by the addition of basic solutions to convert alkaloids to basic forms to allow their extraction with organic solvents. The same purification steps are followed [14].

Different alkaloids are separated based either on the difference of solubility or boiling temperature [19].
