[In vitro microdialysis recoveries of nine active ingredients in Mahuang decoction]

To detect the in vitro probe microdialysis recoveries based on an HPLC-DAD method for simultaneous quantification of nine active ingredients (ephedrine, pseudoephedrine, methylephedrine, amygdalin, liquiritin, cinnamyl alcohol, cinnamic acid, cinnamaldehyde and glycyrrhizic acid) in Mahuang decoction, which provides reference for in vivo pharmacokinetic study. The concentrations of nine active ingredients in dialysate were detected by HPLC-DAD, to investigate the effect of flow rates (incremental method and subtraction method) and intraday stability of the probe recoveries and medium concentrations on the recoveries. Nine active ingredients could be well separated in 52 min. At the perfusion rate of 1.0 μL x min(-1), the relative recoveries of ephedrine, pseudoephedrine, methylephedrine, amygdalin, liquiritin, cinnamyl alcohol, cinnamic acid, cinnamaldehyde and glycyrrhizic acid were (50.95 ± 0.82)%, (52.74 ± 1.13)%, (51.29 ± 0.51)%, (32.56 ± 0.84)%, (45.36 ± 0.83)%, (70.94 ± 0.99)%, (69.98 ± 2.30)%, (71.68 ± 0.63)%, and (22.14 ± 0.48)%, respectively. And the probe kept steady in 7 hours. At the same medium concentration, the probe recoveries decreased exponentially with the increase in flow rates. The recoveries of seven ingredients detected by these two methods were similar at certain flow rates, except for amygdalin and cinnamaldehyde. At the same flow rate, the relative recoveries of cinnamyl alcohol, cinnamic acid and cinnamaldehyde changed greatly (9.55%-16.2%) and the others six ingredients had less change (3.27%-5.71%) with the changes in medium concentrations. Microdialysis method could be used to detect the in vitro recoveries of nine ingredients in Mahuang decoction. Reverse dialysis method could be used for the in vivo probe recovery calibration of ephedrine, pseudoephedrine, methylephedrine, liquiritin, cinnamyl alcohol and cinnamic acid at the flow rate of 2.0 μL x min(-1).