Development of a Thin-Layer Chromatography-Enzymatic Test Combination Method for the Isolation of α-Glucosidase Inhibitors From Thymelaea hirsuta.

A rapid, easy and simple method for the isolation and purification of α-glucosidase inhibitors of the ethyl acetate extract of Thymelaea hirsuta (EaTh) by a combination of thin layer chromatography (TLC) and enzymatic test has been developed. EaTh was demonstrated previously a potent α-glucosidase inhibitory effect. In this study, we developed a simple TLC-enzymatic test (TLC/EZ) combination to isolate α-glucosidase inhibitors present in EaTh.EaTh was extracted by Soxhlet from Thymelaea hirsuta (T. hirsuta). The EaTh was separated on a silica gel column and then on a TLC plate. After TLC separation, the TLC/EZ combination method was applied. α-glucosidase inhibitors were detected directly in the TLC plate using the glucose oxidase peroxidase method (GOD-POD). A good detection of active compounds was obtained in the TLC favoring the TLC/EZ method. Active compounds were then characterized using high performance liquid chromatography-mass spectrometry (HPLC-MS) analysis. The main α-glucosidase inhibitors present in EaTh have a molecular ion [M + H]+ at m/z = 543. This proposed method is suitable for a reliable isolation and purification of α-glucosidase inhibitors present in EaTh. It could be proposed as an interesting alternative of the classical method for the isolation and purification of α-glucosidase inhibitors in plant extracts.

Inhibition of α-glucosidase and glucose intestinal absorption by Thymelaea hirsuta fractions.

BACKGROUND: Thymelaea hirsuta (L.) Endl. (Thymelaeaceae) is a medicinal plant used in Morocco to treat diabetes. In previous studies T. hirsuta has shown a potent antihyperglycemic effect. Our aim was to study the effect of the plant on α-glucosidase inhibition and intestinal glucose absorption. METHODS: Five fractions of T. hirsuta were tested, in vitro, in vivo and, in situ, to elucidate the inhibition of α-glucosidase and intestinal glucose uptake. RESULTS: The fractions induced, in vitro, a significant inhibition of α-glucosidase. The ethyl acetate fraction (EATh) had high activity and its inhibition mode was non-competitive. The EATh at 50 and 100 mg/kg doses, decreased significantly, in vivo, the postprandial hyperglycemia after sucrose loading in normal and diabetic mice. Moreover, 50 mg/kg of EATh significantly decreased intestinal glucose uptake, in situ, in rats. CONCLUSION: The antihyperglycemic effect of T. hirsuta can be explained, in part, by the inhibition of intestinal α-glucosidase and intestinal glucose absorption.