**1. Introduction**

Pectin considers one of the most plentiful natural compounds having different applications. It is heteropolysaccharides that compose the main components of the middle lamella and primary cell wall of higher plants and are responsible for the cohesion and the structural integrity of plant tissues [1, 2]. Generally, rhamnogalacturonans and galacturonans are two main chemical components in pectic materials, where C-6 carbon of galactate is oxidized along with arabinogalactans and arabinans. The produced components are colloidal polymeric in nature and structurally heterogeneous, containing a large backbone of anhydrogalacturonic acid units. The carboxyl groups of GalA are partially esterified by methyl residues and totally or moderately neutralized by different ions as potassium, sodium, and ammonium. α-1,4-d-galacturonate units are working as a master and connecting about 2-4% of L-rhamnose units that linked [β- (1 → 2) and β-(1 → 4) to galacturonate units. The side chains include simple carbohydrates (galactan, arabinan, arabinogalactan, fucose, or xylose) but vary in length and composition. They are associated with the central chain through their C1 and C2 atoms [3]. Hence, the main chain of the pectin polymer consists of galacturonic acid (GalA) linked by α-D-1,4- bonds and form three backbone regions [4], **Figure 1**:

	- This region is acylated and frequently substituted with arabinans, galactans, and arabinogalactans linked to rhamnose residue [10]. Also, xylose is found for substitutions [11].
	- RGII region, although the name, is not structurally related to RGI. It is a branched pectic domain-containing HG backbone substituted with heteropolymeric side chains involving different sugars [12]. Containing side chain of D-Apiose, 2-Omethyl-D-xylose, and 2-O-methyl-L-Fructose. The galacturonic residues are usually acetylated at the C-2 or C-3 position in rhamnogalacturonan 1 [13].

Most molecules are formed in the series by D-Galacturonic residue. Polymers do not make up a straight string in an aqueous medium, but it is curved and extended with high flexibility. The contrast was found in the configuration of pectin from different sources, and the pectin properties are strongly related to the

#### **Figure 1.**

*(a) pectin Structure (b) Pectin structure in traditional model displaying the homogalacturonan (HG) as the backbone, smooth region, and 60-sugar residue. Feruloyl pectic acids are engaged in organizing cell expansion, resistance to diseases, and lignification initiation. The properties of the pectin the hairy region consisting of Rhamnogalacturonan-I (RG-I) or Rhamnogalacturonan-II (RG-II) units [inspired by Noreen et al., [5].*
