Development of a UPLC-MS/MS bioanalytical method for the pharmacokinetic study of (-)-epiafzelechin, a flavan-3-ol with osteoprotective activity, in C57BL/6J mice.

(-)-Epiafzelechin is a flavan-3-ol commonly found in plant source. Biological studies suggested that (-)-epiafzelechin may have anti-inflammatory, anti-oxidant and bone-protective effect. However, it's in vivo efficacy remains to be demonstrated. A specific detection method for (-)-epiafzelechin was successfully developed by using UPLC-MS/MS to quantify the amount of (-)-epiafzelechin present in mice plasma after a liquid-liquid extraction by ethyl acetate. The separation was achieved by using a reversed-phase C18 column with a 16 min gradient elution protocol consisting of water (0.1%, v/v, formic acid) and 0-70% ACN (0.1%, v/v, formic acid). The lower limit of quantitation for (-)-epiafzelechin was found to be 12.5 ng/mL. This method exhibited a good linearity (r(2)=0.992). The intra-day and inter-day precision were within 12%, while the accuracy was between 97.6 and 113. 4%. A quantity of 10mg/kg synthetic (-)-epiafzelechin was administered to C57BL/6J mice by intravenous (i.v.) and intraperitoneal (i.p.) injections and the blood was collected at different time points. The plasma was then analyzed by the UPLC-MS/MS method, and the plasma drug concentration-time curves for i.v. and i.p. (-)-epiafzelechin injection were constructed. The maximum concentrations (Cmax) of (-)-epiafzelechin in blood by i.v. and i.p. injection were found to be 10.6 and 6.0 μg/mL, respectively, while the time for reaching Cmax in i.p. injection was found to be 15 min. The distribution half-lives of (-)-epiafzelechin after i.v. and i.p. injection were found to be 7.0 and 12.6 min, respectively. Some of the PK parameters were found to be similar in both i.v. and i.p. injections of (-)-epiafzelechin owing to its high solubility in water.