Inhibitory Activities of Brimstone (Morinda lucida) Roots Extract on α-Amylase and α-Glucosidase – In vitro

Brimstone (Morinda lucida) root is one of the widely used herbs in folkore medicine for the management of diabetes while acarbose is a well-known antidiabetic drug. This study sought to characterize the phenolic constituents of brimstone (Morinda lucida) root, assess its interaction with key enzymes (α-amylase and α-glucosidase) relevant to type-II diabetes and evaluate its effect on acarbose in vitro. One milligram per millilitre of aqueous extract of brimstone root and acarbose were separately prepared. In addition, both the brimstone and acarbose solution (50:50 v/v) were thoroughly mixed until homogeneity was attained. The phenolic phytoconstituents of brimstone root were subsequently determined. Finally, the effects of brimstone root extract, acarbose solution and a mixture of acarbose and brimstone extract on a-amylase and α -glucosidase activities were assessed in vitro. Brimstone root extract was found to be rich in phenolic acids (p-coumaric acid, gallic acid, caffeic acid and chlorogenic acid) and flavonoid (apigenin). Acarbose had significantly (p < 0.05) higher α -amylase (IC50= 0.02 mg/ml) and α-glucosidase (IC50= 0.01 mg/ml) activities when compared to brimstone root extract [α–amylase (IC50=0.62 mg/ml); α-glucosidase (IC50= 0.33 mg/ml)]. Furthermore, the combination of acarbose and brimstone root extract showed synergistic effects on α-amylase and α –glucosidase inhibition (in vitro). This study may thus suggest that brimstone root represent a source of phenolic phytochemicals for the management of non-insulin dependent diabetes mellitus