**Abstract**

Pectin, a natural ionic polysaccharide found in the cell wall of terrestrial plants undergoes chain–chain association to form hydrogels upon addition of divalent cations. Based on its degree of esterification, pectin has been classified into two main types. The high methoxyl pectin with a degree of esterification greater than 50%, which is mainly used for its thickening and gelling properties and the low methoxyl pectin, which is widely used for its low sugar-content in jams, both applications being in the food industry. Pectin is mostly derived from citrus fruit peels, but can also be found in other plants such as waterleaf leaves, cocoa husk, and potato pulps. Pectin has been used as an excipient in pharmaceutical formulations for various functions. This chapter will focus on the various applications to which pectin has been used in the pharmaceutical industry.

**Keywords:** Pectin, Degree of Esterification, Drug Delivery, Polymer Matrix, Excipients

## **1. Introduction**

In the pharmaceutical industry, plants and plant products are continually used as sources of drugs and excipients. In particular, plant-derived polymers have contributed significant roles in drug delivery systems where they function as excipients [1]. Excipients refer to the non-pharmacological ingredients that are required to convert the Active Pharmaceutical Ingredient (API) into a dosage form. The International Pharmaceutical Excipients Council (IPEC, 1995) defines excipients as all substances contained in a dosage form other than the active substance or finished dosage form, which have been appropriately evaluated for safety and are included in a drug delivery system [2]. Excipients are included in drug delivery systems to assist in processing during manufacture, protect, support, enhance stability, bioavailability and patient acceptability, help in product identification, or enhance any other aspects of the drug delivery system's overall safety and effectiveness during use or storage [2–4]. Far from being just a random combination of ingredients, a pharmaceutical formulation is a well-rationalized formulation designed to satisfy quality and performance. Excipients are essential in the drug development process, as well as the formulation and administration of stable dosage forms [2]. Excipients are required in drug formulations to guarantee the potency, safety, predictability and reproducibility of the release of the API as well as its palatability and suitability for the patients [3].

The interest in excipients of plant origin over semi-synthetic or synthetic excipients is not far-fetched: low toxicity, relative abundance, cost-effectiveness and non-irritant nature make them preferable to others sources [5]. Plant-based polymeric excipients can be used in different pharmaceutical formulations where they act as diluents or bulking agents, thickeners, binders, disintegrants, suspending agents, emulsifiers, film formers, matrix formers, release modifiers, sweeteners and mucoadhesive polymers [6–9]. These natural polymers would have to fulfill the requirements of an ideal excipient to be successful candidates for use as excipients in various formulations for pharmaceutical use. The requirements for an ideal excipient includes being pharmacologically inert, non-toxic and non-irritant as well as being non-reactive with drug or with other substances present in the formulation and the packaging. In addition, they must be easy to handle, cost-effective and readily available for the sustainable manufacture of the pharmaceutical product. Numerous plant polymers fulfill many of these requirements and have found application in pharmaceutical formulations. These include Inulin; a polysaccharide obtained from plant sources like; onion, garlic, artichoke and chicory, starches which are polymeric carbohydrates with large glucose units joined by glycosidic bonds, gums, and mucilage such as: acacia gum, tragacanth gum, locust bean gum, okra mucilage, seaweed polysaccharides which include carrageenan, agar and alginates, microbial polysaccharides such as: xanthan gum and pullulan obtained by the fermentation of carbohydrate products by specific bacteria or fungus, and polysaccharides of the plant cell wall with cellulose, hemicelluloses, pectin being the main polymers of this group [10–16].

Pectin, a structural heteropolysaccharide, is considered the second most abundant component of the cell wall of all terrestrial plants [17, 18]. It is a hydrophilic polymer that is biodegradable, biocompatible and non-toxic, making it a good biomaterial for packaging, coating and various pharmaceutical applications. Pectin is normally produced during the initial stages of growth of the primary cell wall and constitutes about one-third of the dry substance of the cell wall of some monocotyledonous and dicotyledonous plants [19]. A white to light brown powder, pectin is found in numerous fruits and vegetables. The main raw materials for pectin production are dried citrus peels or apple pomace, both by-products of juice production that are often discarded as waste. Alternative sources of pectin extraction include sugar beet waste from sugar manufacturing, mango waste from mango canning factories and sunflower seeds used for extracting edible oil, waterleaf leaves, cocoa husk, and potato pulps [20–23].

Pectin is the methylated ester of polygalacturonic acid which contains 1, 4-linked α-D-galacturonic acid residues and a variety of neutral sugars like arabinose, galactose, rhamnose and lesser amounts of other sugars [24, 25]. It can be classified into different types based on the degree of esterification or the number of methoxy groups that substitutes the carboxylic acid moiety on the galacturonic acid residues [26]. The degree of esterification influences the gelation mechanism, processing conditions and properties of the pectin [18, 27]. High methoxyl pectin is primarily used for gelation and has a degree of esterification greater than 50%. It requires a large amount of sugar and is acid-sensitive. Because of hydrogen bonding and hydrophobic interactions between the pectin chains, high methoxyl pectin forms a gel at low pH and a high concentration of soluble particles [28]. Low methoxyl pectin has a degree of esterification of less than 50% and is widely used in the food industry to form low sugar jams since it does not require a large amount of sugar for gelation. It shows less sensitivity toward acidity and requires Ca2+ ions to form gel [29]. Low methoxyl pectin is generally formed by the de-esterification of high methoxy pectin using acids, alkali, pectin methylesterase and ammonia in alcohol or concentrated aqueous ammonia. Monovalent cation i.e. alkali metal salts of pectin is normally soluble in water while di- and trivalent cations are partially or completely insoluble in water. When dissolved, pectin decomposes rapidly by

*Pharmaceutical Applications of Pectin DOI: http://dx.doi.org/10.5772/intechopen.100152*

de-esterification or depolymerization. The rate of decomposition depends on the pH and temperature of the solution. The maximum stability of pectin is at pH 4 [30]. Low pH and high temperature increase the rate of degradation due to hydrolysis of the glycosidic linkage. At alkaline pH, pectin is rapidly de-esterified and degraded even at room temperature [31].

In this Chapter, the sections that follow would review in detail, some important pharmaceutical applications of pectin and possible modifications to enhance the future uses of pectin in pharmaceutical formulations.
