Tris hcl buffer solution

The pyrogallol autoxidation method was used for superoxide anion removal experiment (14 ). In a 10 mL corkscrew tube, 1 mL MDLE aqueous solution (0.2, 0.6, and 1.0 mg/mL) was mixed with 4.5 mL 0.1 mol/L TRIS-HCl buffer solution (pH = 8.2, Solarbio Life Science), and reacted at 37°C in a water bath for 20 min, then allowed to cool to 25°C. Then 0.4 mL of 50 mmol/L pyrolenol solution (Solarbio Life Science) was placed in a water bath at 37°C for 5 min, and then 0.1 mL of 8.0 mol/L concentrated HCl was added immediately to stop the reaction. All samples were prepared in duplicate.

DPP-4 (human recombinant, No. D3446) and Gly-Pro-7-amido-4-methylcoumarin hydrobromide (Gly-Pro-AMC, CAS 115035-46-6) were purchased from Sigma Aldrich (St. Louis, MO, U.S.A.). Flavonoid standards were obtained from Shanghai Yuanye Bio-Technology Co., Ltd. (Shanghai, China). Sitagliptin phosphate monohydrate, dimeththyl sulfoxide (DMSO), and Tris-HCl buffer solution (1.0 M, pH 8.0) were supplied by Beijing Solarbio Science & Technology Co., Ltd. (Beijing, China).