Evaluation of In vitro Antidiabetic Potential of Thymus schimperi R. and Thymus vulgaris L.

Abstract

Diabetes has become the most common metabolic disease worldwide. In particular, type 2 diabetes is the most commonly encountered type of diabetes, which is characterized by impaired insulin secretion and/or action. One of the effective methods to control diabetes is to inhibit the activity of α-amylase and α-glucosidase enzymes which are responsible for the breakdown of starch to more simple sugars, using plant products. This study evaluated the total phenolic (TPC), total flavonoid (TFC), and antidiabetic potential of Thymus schimperi and Thymus vulgaris via in vitro inhibition of α-amylase and α-glucosidase, using the hot water and aqueous: methanol (20:80, v/v) extracts. The α-amylase inhibitory potentials of the extracts were investigated through reducing sugars analysis using 3,5-dinitrosalicylic acid color reagent (DNSA) using starch solution as substrate. The α-glucosidase inhibition was determined by pre-incubating α-glucosidase with different concentrations of the extracts followed by the addition of p-nitrophenylglucopyranoside (pNPG). Aqueous: methanol (20:80, v/v) extract of T. schimperi contained highest TPC (46.01 ± 4.54 mg GAE/g dw) and TFC (14.72 ± 1.14 mg QE/g dw) also showed stronger α-amylase inhibition activity (IC₅₀ = 0.33 ± 0.05 mg/mL) and the hot water extract exhibited stronger α-glucosidase inhibition (IC₅₀ = 0.05 ± 0.01 mg/mL) capacity than that of T. vulgaris. The TPC and TFC were positively related (p < 0.05) with α-amylase inhibition activity but negatively correlated (p > 0.05) with α-glucosidase inhibitory activity. These results indicated that the inhibition of these enzymes can lead to lower postprandial blood glucose.

Keywords: α-Amylase, Antidiabetic, Diabetes mellitus, α-Glucosidase, Thymus, Total phenolics

DOI: 10.7176/JHMN/69-02

Publication date: December 31^st 2019