Evaluation of Anacardium Occidentale(Cashew) Gum as a Pharmaceutical Excipent

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The current work deals with the study and development of Anacardium occidentale (Cashew) gum as a pharmaceutical excipient, namely: as a binding agent in tablet formulations, emulsifying agent in emulsions and as a suspending agent in suspensions. Crude and purified cashew gums were evaluated for their physicochemical properties and were found to be acidic in nature with satisfactory moisture content and insoluble matter. Atomic absorption spectrophotometric analysis of the gums showed that the crude gum had higher metallic ion content than the purified gum. This may be attributed to the purification process. The gums had relatively high levels of calcium, followed by magnesium, iron and zinc. Potassium and sodium were in trace amounts. Purified cashew gum was investigated as an emulsifying, suspending and binding agent. The emulsifying property of the gum was investigated by preparation of emulsions using different classes of oils and employing the wet and dry gum methods of preparation. The ratio of oil to water to gum for the preparation of stable primary emulsion was determined for the oils. The stability of the emulsions was assessed and an improvement in the stability was attempted using homogenization, a surface active agent, and the addition of a thickening agent. The results obtained demonstrated that stable emulsions could be prepared with the mineral oil and fixed oil with ease but not with the volatile oil. All the emulsions prepared creamed readily, but creaming was reduced by homogenization and the addition of very low concentrations of Tween 80. The addition of a thickening agent worsened the creaming of the emulsions. The suspending property of the gum was investigated by assessing parameters such as rate of sedimentation, apparent viscosity and ease of redispersibility of zinc oxide suspensions prepared with different concentrations of cashew gum, compared to those prepared with xanthan gum. Suspensions were successfully prepared using the gum, but the sediment showed a tighter packing as the concentration of the gum used was increased. Xanthan gum which was used as the standard for comparison showed a better suspending action than cashew gum. Investigation of the gum as a binding agent in metronidazole tablets included the formulation of tablets with different concentrations of cashew gum using the wet granulation technique. The binding property of cashew gum was compared to that of acacia, a standard binding agent. The flow properties of the granules were evaluated and the physical properties of the compressed tablets, namely uniformity of weight, hardness, friability, and disintegration time and dissolution rate determined. The granules had good flow properties as evidenced by their Hausner ratio and vii Carr’s index values. The gum was successfully employed as a binding agent in metronidazole tablet formulations with tablets of desired physical and release properties produced with different concentrations of cashew gum. Tablets produced from 30 % w/v cashew gum had similar characteristics to that produced from 20 % w/v acacia mucilage. The study shows that cashew gum can be successfully employed as a binder, emulsifying agent and a suspending agent in pharmaceutical formulations.
A thesis submitted to the School of Graduate Studies in partial fulfilment of the requirement for the Master of Philosophy(MPHIL)Pharceutical degree, May.