Assessment of plasma concentrations of (-)-epigallocatechin gallate in mice following administration of a dose reflecting consumption of a standard green tea beverage

The plasma exposure of (-)-epigallocatechin gallate (EGCg) is typically assessed following administration of EGCg at doses equivalent to the consumption of at least 10 cups of green tea in one sitting. This study determines the plasma concentrations of EGCg in mice following administration of a dose reflecting typical consumption of one standard green tea beverage. Swiss Outbred mice were orally administered 0.76mg/kg EGCg, and using a validated HPLC method, the Cmax of un-conjugated and total EGCg was determined to be 31.5±3.3 and 34.3±2.0nM, respectively (mean±s.d., n=3-5). The area under the plasma concentration versus time curve for un-conjugated and total EGCg was 114.3±4.1 and 116.4±4.1nM·h, respectively (mean±s.d., n=3-5). To minimise potential ex vivo plasma degradation, a novel stabilizing solution of 20mM ascorbic acid (AA) and 13mM tris[2-carboxyethyl]phosphine hydrochloride (TCEP) was employed. Comparative evaluation of the efficacy of the 20mM AA and 13mM TCEP stabilizing solution to the commonly used stabilizing solution of 114mM AA and 0.13mM Na2EDTA, indicated that the AA/TCEP solution provided significantly greater (p<0.05) protection to EGCg than the AA/Na2EDTA stabilizing solution. Overall, this study demonstrates that plasma concentrations of EGCg are in the low nM range following oral administration to mice at a dose reflecting the consumption of a standard green tea beverage. In addition, a novel stabilizing solution has been identified which may be useful in stabilizing plasma samples obtained from pharmacokinetic studies.