Intestinal drug transport enhancement by Aloe vera

The effect of Aloe vera (L.) Burm. f. (Aloe barbadensis Miller) gel and whole leaf extract on the permeability of Caco-2 cell monolayers was determined. Solutions of gel and the whole leaf extract were applied to the cell monolayers, and the transepithelial electrical resistance was monitored for 2 hours, which was then continued for another 2 hours after removal of the test solutions to measure reversibility of the effect. The transport of insulin in the presence and absence of the A. vera gel and whole leaf extract solutions was also investigated. Both the A. vera gel and whole leaf extract were able to significantly reduce the transepithelial electrical resistance of the Caco-2 cell monolayers at concentrations above 0.5 % w/v and thereby showed the ability to open tight junctions between adjacent cells. This effect was fully reversible, as the electrical resistance of the cell monolayers returned to the original value upon removal of the test solutions. The A. vera gel and whole leaf extract solutions significantly enhanced the transport of insulin across the Caco-2 cell monolayers compared with the control. The results suggest that these plant products have a high potential to be used as absorption enhancers in novel dosage forms for drugs with poor bioavailabilities when administered orally. On the other hand, an uncontrolled increase in the bioavailability of drugs that are taken simultaneously with A. vera gel and whole leaf extract products may result in adverse effects, and the potential exists that toxic blood plasma levels may be reached.