Simulated gastric fluid (SGF) was prepared according to Lian et al. [23] with slight modifications. Briefly, pepsin (3 g/L) was suspended in sterile NaCl solution(0.5%w/v).The pH of the solution was adjusted to pH 2.0 with 12 M HCl, and filtered through a 0.22-μm filter membrane (Pall Corporation, USA). SIF was prepared according to US Pharmacopeia [24]. Briefly, 6.8 g of monobasic potassium phosphate (Sigma, St. Louis, MO, USA) was dissolved in 250 mL of distilled water, followed by addition of 77 mL of 0.2MNaOH,and 500mL of distilled water.The solution was vortexed for 30 min and 10 g of pancreatin was added and mixed. pH of the solution was adjusted to 6.8 with 0.2 M NaOH or 0.2 M HCl. The total volume of the solution was made up to 1000mL,followed by filtration througha 0.45μm filter membrane to remove particulate material, and then filter sterilized through a 0.22-μm filter membrane.