Protective coating of dried Vernonia amygdalina Extract by melt granulation and the implication for dissolution rates

Abstract

Dried Vernonia amygdalina (VA) extract has been wax coated with carnuba wax or goat fat by melt granulation technique with a view to protect against moisture uptake and to disguise bitter taste. The particles were wax-coated using different concentrations (0%, 1%, 2.5%, 5%, 7.5% and 10% w/w). The uncoated and coated particles were evaluated for packing, flow properties, moisture uptake potential and dissolution profiles. There was no statistically significant difference in the bulk and tap densities with increase in concentration of the different waxes used in coating. The angle of repose (index of flowability) for the uncoated dried particles was 460, while for coated particles at concentrations of 10% w/w, their mean values were 31±0.10 and 54±0.040 for carnuba wax and goat fat respectively. There was no measurable moisture uptake at relative humidity (RH) 1%. At RH 100%, moisture uptake decreased considerably by 50% as the wax content increased from 0 to 10% w/w. Generally, the drug release rate decreased as the wax content increased. The uncoated particles displayed an initial burst release of 37.2±1.2% of the drug within the first 10 min and up to a maximum release of 84±1.5% in 45 min. With the coated particles (wax content 10% w/w), the initial release within the first 10 min was 24.1±1.7% and 29±1.1% for goat fat and carnuba wax-coated particles respectively while their corresponding values in 45 min were 61±1.3% and 62.1±1.6%. The indication is that the dried VA extract can be protected from moisture uptake by wax coating without serious impairment to their dissolution profiles.