Indexed on: 21 Aug '07Published on: 21 Aug '07Published in: Journal of Pharmaceutical and Biomedical Analysis
The degradation kinetics of -gingerol and -shogaol were investigated in simulated gastric (pH 1) and intestinal (pH 7.4) fluids at 37 degrees C. Degradation products were quantitatively determined by HPLC (Lichrospher 60 RP select B column, 5 microm, 125 mm x 4 mm; mobile phase: methanol-water-acetic acid (60:39:1 v/v); flow rate: 0.6 ml/min; detection UV: 280 nm). In simulated gastric fluid (SGF) -gingerol and -shogaol underwent first-order reversible dehydration and hydration reactions to form -shogaol and -gingerol, respectively. The degradation was catalyzed by hydrogen ions and reached equilibrium at approximately 200 h. In simulated intestinal fluid (SIF) both -gingerol and -shogaol showed insignificant interconversion between one another. Addition of amino acids glycine, 3-amino propionic acid (beta-alanine) and gamma-amino butyric acid (GABA), and ammonium acetate at a range of concentrations of 0.05-0.5mM had no effect on the rate of degradation of -shogaol in SGF and 0.1M HCl solution. However, at exceedingly high concentration (0.5M) of ammonium acetate and glycine, significant amounts of -shogaol ammonia and glycine adducts were detected. The degradation profile of -gingerol and -shogaol under simulated physiological conditions reported in this study will provide insight into the stability of these compounds when administered orally.