Flavonoid constituents of<i>Amomum tsao-ko</i>Crevost et Lemarie and their antioxidant and antidiabetic effects in diabetic rats –<i>in vitro</i>and<i>in vivo</i>studies

Abstract

<i>Amomum tsao-ko</i> Crevost et Lemarie (<i>A. tsao-ko</i>) is a well-known dietary spice and traditional Chinese medicine. This study aimed to identify the flavonoids in <i>A. tsao-ko</i> and evaluate their antioxidant and antidiabetic activities in <i>in vitro</i> and <i>in vivo</i> studies. <i>A. tsao-ko</i> methanol extracts possessed a high flavonoid content (1.21 mg QE per g DW) and a total of 29 flavonoids were identified by employing UPLC-MS/MS. <i>In vitro</i>, <i>A. tsao-ko</i> demonstrated antioxidant activity (ORAC value of 34276.57 μM TE/100 g DW, IC₅₀ of ABTS of 3.49 mg mL^-1 and FRAP value of 207.42 μM Fe²⁺ per g DW) and α-amylase and α-glucosidase inhibitory ability with IC₅₀ values of 14.23 and 1.76 mg mL^-1, respectively. <i>In vivo</i>, type 2 diabetes mellitus (T2DM) models were induced by a combined high-fat diet (HFD) and streptozotocin (STZ) injection in rats. Treatment with the <i>A. tsao-ko</i> extract (100 mg freeze-dried powder per kg bw) for 6 weeks could significantly improve impaired glucose tolerance, decrease the levels of fasting blood glucose (FBG), insulin, and malondialdehyde (MDA), and increase the superoxide dismutase (SOD) level. Histopathology revealed that the <i>A. tsao-ko</i> extract preserved the architecture and function of the pancreas. In conclusion, the flavonoid composition of <i>A. tsao-ko</i> exhibits excellent antioxidant and antidiabetic activity <i>in vitro</i> and <i>in vivo</i>. <i>A. tsao-ko</i> could be a novel natural material and developed as a related functional food and medicine in T2DM management.