| Aim:Kumu injection(KMI)is made from the branches and stems of Picrasma quassiodes(D.Don)Benn.,and has been used clinically for the treatment of upper respiratory tract infection,acute tonsillitis,enteritis and bacillary dysentery.3-methylcanthin-2,6-dione,5-hydroxy-4-methoxycanthin-6-one and 4,5-dimethoxycanthin-6-one are the active ingredients of KMI because of its therapeutic effects.In recent years,many researches have focused on the pharmacological effects of the three canthinone alkaloids in vitro,but few reported the pharmacokinetics of them in vivo.The aim of this paper was to develop an efficient and sensitive liquid chromatography-tandem mass spectrometry(LC-MS/MS)method for simultaneous determination of 3-methylcanthin-2,6-dione,5-hydroxy-4-methoxycanthin-6-one and 4,5-dimethoxycanthin-6-one in rat plasma,and apply the method to investigate the pharmacokinetic profiles and the bioavailability of KMI in rats.Methods:Rats were divided into 5 groups,3 groups were administered intramuscularly with a single dose of KMI at 0.30,0.45 and 0.90 mL/kg,respectively;and the other 2 groups were administered intragastically or intravenously with a single dose of KMI at 0.90 mL/kg,respectively.The blood samples were collected by post-orbital venous sinus puncture at different time points,and the pharmacokinetic parameters were calculated in non-compartment model.Chromatographic conditions:The separation was carried out on a Shim-pack ODS column(4.6μm,150 mm X 2.0 mm i.d.Shimadzu)fitted with a guard column(4.6 μm,5 mm×2.0 mm i.d.Shimadzu)at a column temperature of 35 ℃.A mixture of solvent A(0.05%formic acid in water)and solvent B(acetonitrile)was used as the mobile phase at a flow rate of 0.2 mL/min,and the gradient elution program was as follows:0-5 min,15%B to 20%B;5-13 min,20%B to 85%B;13-15 min,85%B;15-16 min,85%B to 15%B;16-20 min,15%B.MS conditions:It was set in positive multiple reaction monitoring(MRM)mode.The MS transitions were m/z 251.0→195.1 for 3-methyl-canthin-2,6-dione,m/z 267.0→168.1for 5-hydroxy-4-methoxycanthin-6-one,m/z 281.0→167.1for 4,5-dimethoxycanthin-6-one and m/z 195.0→138.1for caffeine(IS).Results:The concentrations of 3-methylcanthin-2,6-dione,5-hydroxy-4-methoxycanthin-6-one and 4,5-dimethoxycanthin-6-one in KMI were 6.64,31.3 and 4.27 μg/mL,respectively.After the rats were administered intramuscularly by different doses,the pharmacokinetic parameters of 3-methylcanthin-2,6-dione were 0.0923、0.120、0.238 mg·min/L for AUC0-∞,0.980、1.70、3.30 μg/L for Cmax,14.2、13.8、12.3 min for ti/2,and 22.0、25.0、26.0 mL/min/kg for CL;the parameters of 5-hydroxy-4-methoxycanthin-6-one were 1.48、2.23、4.49 mg·min/L for AUC0-∞,42.1、66.8、80.9 μg/L for Cmax,41.0、51.3、49.7 min for t1/2,and 7.00、7.00、6.00 mL/min/kg for CL;the parameters of 4,5-dimethoxycanthin-6-one were 0.132、0.152、0.358mg·min/L for AUC0-∞,2.29、3.94、7.62 μg/L for Cmax,82.6、77.1、83.8 min for t1/2,and 10.0、13.0、11.0 L/min/kg for CL.The data illustrated that the AUC and Cmax of the three active canthinone alkaloids increased in a dose-dependent manner,while the t1/2 and CL remained unchanged,so the pharmacokinetic profiles of KMI were characterized by the first order kinetics.The results of the bioavailability of KMI after oral and intramuscular administration were 41.6%and 90.1%for 3-methylcanthin-2,6-dione,27.8%and 96.4%for 5-hydroxy-4-methoxycanthin-6-one,37.1%and 99.2%for 4,5-dimethoxycanthin-6-one.Conclusion:The established method was suitable for the quantitation of 3-methylcanthin-2,6-dione,5-hydroxy-4-methoxycanthin-6-one and 4,5-dimethoxycanthin-6-one in rat plasma.Furthermore the pharmacokinetic results indicated that all the three alkaloids were absorbed rapidly,and the pharmacokinetic profiles were characterized by the first order kinetics.The bioavailability of different drug-delivery ways suggested that intramuscular injection of KMI was suitable in clinical usage. |
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