Effect of Opuntia streptacantha Lem. on alpha-glucosidase activity

In Mexico, Opuntia streptacantha is used as part of a traditional medicine in the treatment of diabetes mellitus. Several studies have reported an anti-hyperglycemic effect from the plant, but none have focused on finding a mechanism of action to explain these results. This paper focuses on one of the most recurrent hypotheses for the effect of O. streptacantha: the mechanism of action is the hydrolysis of disaccharides, either by enzymatically inhibiting the alpha glucosidase inhibitors (AGIs) or mechanically acting as a barrier. To test our hypothesis, three different experiments were performed. A maltose tolerance test was carried out using the total extract (TE) and the juice of the plant. Six different extracts were tested in a free-enzyme assay, four of which were aqueous extracts varying according to the procedure of removing the insoluble particles in an attempt to reduce the loss of the water-soluble compounds. The main component of the total extract, a derivative of (4-hydroxy)-phenyl acetic acid, was also tested. For both the maltose tolerance test and the free-enzyme assay, acarbose was used as a control drug. Finally, an everted small intestine assay was also performed. The maltose tolerance test confirmed that an anti-hyperglycemic effect occurs at doses of 100mg/kg TE and 4mL/kg juice. No inhibition on AGIs was observed in the free-enzyme assay, and neither a mechanic nor enzymatic effect on disaccharide hydrolysis was observed in the everted intestine assay. The anti-hyperglycemic effect of O. streptacantha was confirmed, and the results presented here contribute to the understanding that this effect is not due to the action on alpha-glucosidases or related to the intestinal hydrolysis of disaccharides.