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Hello, I am looking for someone to write an essay on Pharmaceutics and Formulation. It needs to be at least 2000 words.Download file to see previous pages... Examples of these polysaccharides are Xant

Hello, I am looking for someone to write an essay on Pharmaceutics and Formulation. It needs to be at least 2000 words.

Download file to see previous pages...

Examples of these polysaccharides are Xanthan, xyloglucan, chitasan, pectin, alginate, guar gum, pullulan and also gellan gum. These substances are capable of forming hydrogels. Hydrogels have a 3 dimensional structure and hydrophilic networks which are capable of imbibing large amounts of water and are analogous to biological tissues. Pectins are naturally occurring polysaccharides and are important structural components of plant cell walls. They are methylated esters of polygalacturonic acids which are found in higher concentrations in the middle lamella of cells. Commercially, they are extracted from citrus peels, mango waste and sugar beet waste. This polysaccharide is made up of D- galacturonic acid units which are joined in chains by means of α (1-4) glycosidic linkages. These uronic acids have carboxyl groups and some of them occur naturally as methyl esters .Part of pectin backbone is made up of rhomnase, a natural sugar in which arabinose, galactose and xylose can be linked as side chains. Polygalacturonic acid chains are also partially esterified with methyl groups. The ratio of esterified Gal A groups to total Gal A groups is called De and is depended on tissue, species and maturity. Based on De, we can have high methoxyl pectins (Hm) and low methoxyl pectins (Lm). Hm pectins require a minimum amount of solution solids and PH within 3 so as to form gels. They often contain dispersion agent such as dextrose to prevent lumping. The LM pectins are not PH sensitive and forms gels independent of sugar and also requires the presence of controlled amount of calcium and divalent cations for gellation (Pornsak, n.d).They have been used in industries as thickening, gelling agents and in drug delivery systems. They show perfect biocompatibility, specific PH responses and can be used without any limitation as they are not toxic. They are also thought to lower blood cholesterol level, reduce or slow down glucose absorption and enhance excretion of toxic divalent metals (Tommasina et al., 2007).Pectin polysaccharides are anionic polyelectrolytes as they bind to oppositely charged surfaces thus associating with oppositely charged molecules and they can therefore be used as a polymeric coat in drug encapsulation. Pectin forms cross links through calcium bridges ((Muhiddonov et al., 2004).This cross linking can be physical chemical or effected through a combination of the two as acid insoluble gels show potential for enzymatic degradation in the colon by pectinases secreted by colonic bacterial. Alginates are naturally occurring polysaccharides, biodegradable, non toxic and can be obtained from marine brown algae as well as from certain bacterial and have both monomeric and polymeric structures. The monomeric units of alginate ?-L gluronate and ?-D manuronate are C5 epimers of each other. Alginate is organized as either homopolymeric G blocks, polygluronate poly (G) blocks and homopolymeric M blocks. All these blocks can be present in a single alginate molecule. The arrangement of the monomers in the block structure and size of alginate formed is very important as it affects both gel forming ability and viscosity of polymer. The poly (G) blocks forms ‘buckled’ chain conformation which binds calcium ions avidly thus producing firm but brittle gels.

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