Antioxidant Activity and Inhibition of Carbohydrate Digestive Enzymes Activities of L.

Background: Carbohydrate digestive enzymes play a major role in the management of the postprandial hyperglycemia. A chronic hyperglycemia can lead to serious health problems due to excessive production of several reactive oxygen species. Therefore, the inhibition of carbohydrate digestive enzyme and the use of antioxidant natural product can be an important strategy to control the glycaemia level and prevent against the complication of diabetes.

Aim: The study aims to perform a phytochemical analysis, antioxidant activity, inhibitory effect on α -amylase, α -glucosidase ( and ) and the intestinal glucose absorption in Wistar rats of aqueous extract (AcAE) and hydro-ethanolic extract (AcEE).

Results: The test of total phenolic content, show that the AcAE has the highest quantity of polyphenol (44.65 ± 0.54 μ g GAE/mg extract) compared to the AcEE (31.7 ± 0.53 μ g GAE/mg extract) significantly. The amount of flavonoid and condensed tannins content in AcAE is 24.41 ± 3.57 μ g QrE/mg extract, 14.31 ± 5.26 μ g CE/mg respectively. The AcAE has also exhibit a great antioxidant activity in DPPH-scavenging and Ferric reducing antioxidant power assay (FRAP) compared to AcEE with an IC 50 = 0.355 ± 0.057 mg/mL and IC 50 = 0.269 ± 0.025 mg/mL. However, in a β -carotene bleaching assay the AcEE has the highest effect with an IC 50 = 0.319 ± 0.097 mg/mL. The both extract of L. (250 mg/kg) decreased postprandial hyperglycemia in the normal and alloxane diabetic rats in a very significant manner after starch or sucrose administration as an α -amylase and α -glucosidase substrate respectively. This result is confirmed by a remarkable inhibitory effect on α -amylase digestive enzymes by an IC 50 = 1.259 ± 0.128 mg/mL and IC 50 = 0.602 ± 0.072 mg/mL receptively for AcAE and AcEE. For the α -glucosidase enzyme, the both extracts significantly inhibit α -glucosidase activity compared to the control and they are almost similar to each other. Using a jejunum perfusion technique (), L. decrease the intestinal D-glucose absorption activity significantly compared to the control and comparable to the Phlorizin used as a positive control by an amount of glucose absorbed equal a 6.53 ± 0.57, 5.34 ± 0.64 and 4.71 ± 0.24 mg/10 cm/h, for AcAE, AcEE and Phlorizin respectively.

Conclusions: These results showed that the L. has highest phenolic content, antioxidant activity and demonstrated a postprandial anti-hyperglycemic effect the inhibiting of the carbohydrate digestive enzyme ( α -amylase and α -glucosidase) and the intestinal glucose absorption.