Hypoglycemic and antioxidant effects of five commercial turmeric (Curcuma longa) supplements

We evaluate the hypoglycemic and antioxidant effects of five commercial turmeric (Curcuma longa) supplements: (1) bulk samples, (2) turmeric root from India, (3) curcuma turmeric Pronat®, (4) turmeric & black pepper Swanson®, and (5) C3 complex® turmeric curcumin. Glucose diffusion and enzymatic starch digestion assays, using α‐amylase and α‐glucosidase, were performed. The antioxidant activity of turmeric supplements was measured through lipid peroxidation inhibition and the scavenging radical assay. A starch dose of 102 mg/Kg of body weight (equivalent to 1 g/day in humans) was used to perform the oral starch tolerance test (OSTT) in Wistar male rats. All turmeric supplements decreased glucose diffusion and α‐glucosidase enzyme activity, and inhibited lipid peroxidation. The rats that received bulk samples and CT showed significantly lower glucose levels than rats receiving acarbose and those of negative control group. Our results show that biological activities of turmeric supplements vary according to the commercial presentation. Practical applications The study results suggest that the hypoglycemic and antioxidant effects of five commercial turmeric supplements vary among them. The information provided would be useful to physicians and individuals using these supplements. Due to differences in their quality control and formulation, the bioactivity of turmeric supplements could vary among the commercial presentation available. The supplements that we evaluated exhibited hypoglycemic and antioxidant activities. The hypoglycemic effect was related to a decrease in glucose diffusion and also to the inhibition of α‐glucosidase. The differences in their biological activity could be related to other bioactive compounds present in these supplements.