Purified Extract of Costus pictus D. Don containing 25 kDa protein induces antidiabetic activity by down-regulating gsk3β gene expression in pancreatic cell lines in vitro

Abstract

Costus pictus is found to have antidiabetic activity, but the real mechanism of action and the potent bioactive molecule responsible is still unknown. This work aims to identify the potential mechanism of action of the partially purified antidiabetic extract of C. pictus extract. The purified methanol extract of C. pictus was prepared and the presence and isolation of protein were done by ammonium sulfate precipitation. The carbohydrate enzyme, -amylase, and -glucosidase inhibition activity of the crude, protein, and nonprotein part of the extract were investigated in vitro. Glucose-induced insulin secretion assay and calcium levels in the cytoplasm were also evaluated using pancreatic cell lines. The effect of GSK3β gene expression was studied in RIN5MF cells treated with crude extract of C. pictus. The crude methanol extract showed the presence of several classes of compounds, with significant levels of polyphenols and flavonoids. A protein of 25 kDa molecular weight was found in the crude extract. Protein and crude extract showed enzyme inhibitory activity, glucose uptake, and increased calcium uptake, and increased insulin secretion. The effect was more in crude extract than protein and nonprotein parts. Moreover, the crude extract reduced the gene expression of GSK3β, which may be one of the possible mechanisms by which the antidiabetic property of C. pictus relies upon. The results showed that the antidiabetic and insulin secretagogue property of C. pictus involves multiple mechanisms and requires the involvement of both phytochemicals as well as the protein present in it.