Polysaccharides consist of a number of monosaccharides (almost more than 10) linked by glycosidic bonds in branched or unbranched chains, usually referred to as one of the active compounds in medicinal plants (Ching, 2007). The hemiacetal group of one monosaccharide and the hydroxyl group of another monosaccharide join by a glycosidic bond to form building blocks (Clayden et al., 2001). There are many structural or storage-related biological functions of polysaccharides. For instance, storage polysaccharides are starch and structural polysaccharides are glycogen present in the plant's cell walls (Klemm et al., 2005). Polysaccharides are very complex polymers, generally referred to as “glycans”. Polysaccharides exhibit different fine structures as “polydisperse molecules’’ due to the wide range of molecular weights. About 90% of total natural polysaccharides can be found in vegetables (Werpy et al., 2004). Polysaccharides play a critical role in many physiological functions of life and these are universally found in numerous parts of plants (guar gum, cellulose, hemicelluloses, and pectin), seaweed (carrageenan, alginate, and agar-agar), animals (chondroitin, chitin, heparin, and hyaluronan), fungi, and bacteria (Zong et al., 2012). The increasing demand of plant-based products is generating millions of tons of waste increasing the intensity of agro-industrial activities acreage, and agricultural production. Some wastes like bio-agro wastes by horticulture and agricultural activities during cultivation, postharvest, and processing of plants. Such waste biomass is constituted by vegetable transformation residues like exhausted seeds, pulps, peels, and unemployed parts of plants, like roots, cobs, straw, and leaves (Sanchez-Vazquez et al., 2013).
Plant-based polysaccharides have many properties such as low-cost materials, abundant, and renewable. These are non-toxic, biocompatible, and biodegradable polyfunctional, owing chemical reactivity, chelating, and absorptive capacities (Crini, 2005). Plant-based polysaccharides also have some properties based on different functional groups present in their chemical structure. Some functional groups like primary hydroxyl (-CH2-OH) and amino (-NH2) groups, provide high chemical reactivity toward functionalization (Pillai et al., 2009). Some functional properties of polysaccharides are directly concerned by the primary sequence structure and the space-filling conformations adopted by the biopolymers. Some physicochemical properties of polysaccharides closely related to the biological activities are features of glycosidic linkages (configuration of glycosidic bonding, position of glycosidic bonding, arrangement of monosaccharides), ratios of constituent monosaccharides and molecular size (Ching, 2007). Polysaccharides consist of versatile renewable sources due to their diversity of structures and properties, which could be used as high-performance materials (Pillai et al., 2009).
Mangifera indica (MI), is also known as mango, aam (Shah et al., 2010). According to Ayurveda, different parts of the mango tree are attributed to many medicinal properties (Alaribe et al., 2012). Tannins and flavonoids are the rich components of the plant's organs. Leaves, fruit, seed kernel, gum, fruit pulp, roots, bark, and stem bark extracts are used widely for medicinal purposes in various countries (Nunez-Selles, 2005, Singh et al., 2005).
Natural gums obtained from plants are composed of monosaccharide units linked by glycosidic bonds. Gums are essentially cheap and easily available naturally occurring polysaccharides in plants. They are high molecular weights of hydrophilic carbohydrate polymers. Some gums are insoluble in organic solvents like hydrocarbons, ether, acetone, or alcohol (Goswami & Naik, 2014). Some of them give a viscous solution or jelly to swell up or disperse in cold water and some are soluble or absorb water (Wandrey et al., 2010). Polysaccharide gums are one of the most important industrial raw materials due to their sustainability, availability, biodegradability, and biosafety. ‘Gels’ are three-dimensional interconnected molecular networks. Mostly natural gums formed this network like gels. There are some factors such as ionic strength, pH, temperature, structure, and concentration that define the strength of the gel (Goyal et al., 2007).
In the present study, the increasing demand for polysaccharides for different industrial applications forces scientists to explore new sources of polysaccharides and improve their properties. So there is a need to modify polysaccharides in order to enhance their functionality and physicochemical properties and form new polymeric derivatives that are useful in a variety of applications. A lot of application of polysaccharides, it is carried out lead to the extraction, modification, and characterization of polysaccharides from the agro-waste Mangifera indica gum.