Author Beneke C., Viljoen A., Hamman J.
Aloe vera , Drug absorption enhancement , Transepithelial electrical resistance, In vitro transport, aloe materials on the transepithelial electrical resistance (TEER) as well as transport of a model compound (atenolol) in the apical-to-basolateral direction across rat intestinal tissue, Aloe vera gel polysaccharides have potential as drug absorption enhancing agents in novel pharmaceutical drug delivery systems, function of epithelial cells is to maintain distinct compartments within the body and also to act as barriers to separate the body from the external environment, molecules can cross the intestinal epithelium by three main pathways, namely transcellular passive diffusion, paracellular passive diffusion and carrier-mediated transport, drugs exhibit poor absorption after oral administration, Poor drug absorption across the intestinal epithelium is in many cases attributed to unfavorable physico-chemical properties of the drug molecule such as hydrophilicity and a large molecular weight, intestinal absorption of these drugs can be increased by different techniques such as co-administration of absorption enhancing agents, absorption enhancing agents may facilitate the absorption of poorly absorbable drugs by different mechanisms such as opening of tight junctions or changing the membrane structure or targeting transporter proteins, damage to the mucosal epithelium is a major problem with drug absorption enhancing agents, drug absorption enhancing agents can increase intestinal drug absorption in a reversible way without causing damage or toxic effects have ignited renewed interest in finding safe and effective drug absorption enhancers to increase drug bioavailability, Tight junctions between epithelial cells are dynamic structures that can be modulated by certain chemicals in such a way to enlarge the pores or fenestrae and thereby allow paracellular passage of hydrophilic macromolecules, drug absorption enhancement has the additional advantage of avoiding enzymatic degradation of susceptible molecules. Compounds that selectively open the intestinal epithelial tight junctions, referred to as paracellular permeability enhancers, have shown potential as novel excipients in advanced drug delivery systems, polysaccharides in Aloe Vera Gel gel consist mainly of linear chains of glucose and mannose molecules with considerably more mannose present than glucose. Acemannan (or aloverose) is a ?-(1,4)-linked galactomannan with acetylated mannose residues, activities of acemannan include antiviral effects, wound healing acceleration, anti-cancer, activation of macrophages and stimulation of T cells, high molecular weight polysaccharide isolated from aloe gel is aloeride. A smaller form of highly acetylated polysaccharide known as modified aloe polysaccharide was isolated from cellulose-treated aloe gel, Aloe Vera Gel gel and whole leaf materials were able to significantly reduce transepithelial electrical resistance (TEER) of Caco-2 cell monolayers and also significantly enhanced the transport of insulin across this cell culture model, transport enhancement effect of Aloe Vera Gel leaf materials is probably due to the opening of tight junctions to allow paracellular transport, TEER is a measure of tight junction integrity between adjacent intestinal epithelial cells, the size of the openings of the tight junctions increases in the presence of a paracellular permeability enhancer, the TEER of the intestinal epithelium will be reduced because of the increasing flow of ions through the opened tight junctions and intercellular spaces , aloe materials investigated in this study lowered the TEER of the excised rat intestinal tissue statistically significantly (P < 0.05) compared to the control group (atenolol alone), polysaccharides in the aloe materials are responsible for or contribute to a large extent to the effect on the TEER, reduction in TEER of the excised rat intestinal tissue by the aloe materials indicates their ability to open the tight junctions between epithelial cells, which indicates the potential of these materials to enhance drug transport across intestinal tissues, high molecular weight polysaccharides such as chitosan and N-trimethyl chitosan chloride
