It was recently revealed that Rhynchophylline （Rhy）, an important constituent of Uncaria rhynchophylla, possessed antihypertensive and neuroprotective effects. However, no information about the pharmacoldnetics of Rhy in a herbivorous species such as rabbit is available. Allometric scaling is valuable in designing human pharmacokinetic parameters from preclinical species. To investigate the characteristics of Rhy in vivo, a rapid and sensitive ultra performance liquid chromatography-tandem mass spectrometry （UPLC-MS/MS） method was developed and validated for the measurement of Rhy concentrations in rabbit plasma. The method was linear over the concentration range of 0.01-10.24 μg/mL. Intra-day and inter-day precision and accuracy were less than 8.0%. The recoveries were in the range of 94.17%-103.32%. Matrix effects （ME） were minor. After oral administration of Rhy at 20, 40 and 80 mg/kg, the mean elimination half-life （h/E） for these doses were 1.19, 1.49 and 1.37 h in rabbits, respectively. There was a proportionate increase in the maximum concentration （Cmax） and the area under the blood concentration-time curve （AUC∞） for three doses. The developed method was suitable for the study on pharmacokinetics of Rhy after oral administration and it may provide a valuable basis for clinical application of such a bioactive compound of herbal medicines.
