Phytochemical studies and hypoglycemic activity of extracts from Gleichenia squamulosa (Pteridophyta)

Abstract

Ferns have been used for ornamental purposes as well as for medicinal purposes. Accordingly, the production of secondary metabolites with various biological activities could be useful in the treatment of various diseases. In addition, pharmacological and ethnopharmacological studies have revealed that some ferns have compounds with hypoglycemic effects. The objectives of this study were to evaluate the inhibitory effect of different extracts of the fern Gleichenia squamulosa colleted en Chiloe on the enzyme α-glucosidase and to determine the presence of secondary metabolites. Metabolites phytochemical screening was performed by colorimetric and precipitation reactions. To evaluate the inhibitory capacity on a-glucosidase, extracts were prepared by Soxhlet (ethyl acetate, and methanol) and by maceration in water:methanol (70:30), and concentrated on a rotary evaporator. We studied the inhibitory capacity on α-glucosidase using p-nitrophenyl-1,4-α-glucopyranoside as substrate. Aqueous solutions were prepared at different concentrations of each extract (among 10 - 2000 μg mL-1). Extracts at different concentrations were tested as enzymatic inhibitors using acarbose as a positive control. The percent inhibition was determined by colorimetry on a UV-VIS spectrophotometer at 400 nm. Phytochemical studies showed the presence of flavonoids, sesquiterpene lactones, coumarins, tannins and phenols. The results of enzymatic inhibition present values of IC50 (50% of inhibition capacity) of 270, 645 and 733 μg mL-1 for methanol, ethyl acetate and hydro-alcohol respectively. In the case of acarbose, it showed an IC50 = 1016 μg mL-1. It has been documented that some phenolic compounds as myricetin, baicalein and epigallocatechingallate are responsible for inhibiting α-glucosidase. In conclusion, this study suggests that the presence of different secondary metabolites from Gleichenia squamulosa could have pharmacological activities as α- glucosidase inhibitor.