POST-GRADUATE STUDENTS

The intestinal absorption of many therapeutic compounds is very low due to their unfavourable physicochemical properties. Safe and effective delivery of these drugs via the oral route is still a major challenge. The use of absorption enhancing agents has been extensively investigated, but few are in clinical use due to toxicity. In a previous study Aloe vera gel and whole leaf extract increased the bioavailability of vitamins in humans and therefore their absorption enhancement potential was investigated in this study. The effect of Aloe vera gel and whole leaf extract on the transepithelial electrical resistance and transport of model compounds across Caco-2 cell monolayers have been evaluated. Both the Aloe vera components showed the ability to significantly reduce the electrical resistance of Caco-2 cell monolayers in a concentration dependent manner. Combining the Aloe vera products with a known absorption enhancing agent, N-trimethyl chitosan chloride, led to a synergistic effect in terms of transepithelial electrical resistance reduction. Furthermore, the transepithelial electrical resistance of the cell monolayers recovered to the original value after removal of the Aloe vera gel and whole leaf extract, which indicates a reversible effect that imply no damage to the cells or tight junctions. High performance liquid chromatography methods were developed and validated for three different model compounds (viz. insulin, luteolin and rutin) used in transport studies across Caco-2 cell monolayers. The drug absorption enhancing potential of Aloe vera gel and whole leaf extract was shown by means of significant increases in the permeation of three model compounds across Caco-2 cell monolayers, which was concentration- and pH-dependent. It can be concluded that Aloe vera gel and whole leaf extract are able to open the tight junctions between adjacent epithelial cells to allow for enhanced drug transport across the intestinal epithelium.