Abstract:
Centella asiatica dry extracts were white to pale yellow powder. They were very slightly soluble in water. They exhibited a poor flow property because they had various sizes and shapes. However, most of them were in rod shape. The extracts consisted of asiaticoside, madecassic acid and asiatic acid. They were degraded by acidic, basic agents and hydrogen peroxide at the stress condition. Compatibility test of these compounds at a accelerated condition, 45+-2 ํC, 75+5% RH, for 4 months found that the stability of Centella extract were improved by spray dried lactose, tulcum, silicon dioxide and magnesium stearate. On the other hand, with sodium starch glycolate or pregelatinized starch the active constituents were degraded slight lower the raw material. The core tablets were prepared by direct compression method and coated with various coating levels of chitosan, hydroxypropyl methylcellulose (HPMC) and polymethacrylate. The core and coated tablets exhibited good physical appearances the core tablets had white with smooth surface. The tablet coated with HPMC and polymethacrylate were white and glossy, while the tablet coated with chitosan were yellowish and glossy. The physicochemical properties of Centella tablets such as hardness, friability, weight variations, disintegration, content uniformity and drug content conformed to the specification of official USP 25. In addition, the drug dissolutions were more than 70% (Q). The stability study at ambient and accelerated conditions for 4 months found that the film coating and increasing of the coating level tended to increase the stability of the tablets. At the same coating level, the tablets coated with polymethacrylate showed the greatest stability. Moreover, under the accelerated condition the film former, particularly chitosan mainly affected the hardness, tablet disintegration, and the drug release characteristics of the film coated tablet. Either hardness or drug release of the chitosan coated tablets were decreased while the tablet disintegration time was increase. In addition, the higher intensity of the color of tablets coated with chitosan was related to the storage period. The drug releases of tablets coated with HPMC at high coating level were decreased; however, there was no change in physical appearance. Tablets coated with polymethacrylate were unchange in the physicochemical properties. Scaling-up of coating process found that the pan speed should be decreased in order to obtain good physical appearance of film coated tablets. There were no significant differences of hardness, friability, weight variation and disintegration between small scale and scale up batch.
