Purpose: Usnic acid (UA) has been proposed as a potential topical treatment for microbial skin lesions, burn wounds as well as a sunscreen through the transdermal administration route. Skin penetration and permeation of the UA-loaded hydroxyethyl cellulose gel in vitro has been determined by HPLC. However, little information is available about the analytical method and pharmacokinetic profile of UA through the transdermal administration route. This is partially due to the lack of a sensitive analytical method to determine the low concentration of UA in rat plasma after transdermal administration. The aim of this study is to develop a rapid and sensitive method for UA determination in plasma and investigate pharmacokinetic profile of UA after transdermal administration.
Methods: A simple and sensitive liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS) method for the determination of UA in rat plasma was developed and validated. Pharmacokinetic experiment was performed in 12 rats through intravenous and transdermal administration.
Results: The present study developed and validated a simple and sensitive LC-MS/MS method for the determination of UA in rat plasma. The plasma samples were pretreated by an optimized protein precipitation procedure with methanol:acetonitrile(1:1,v/v). Chromatographic separation was accomplished on a Xtimate C18 column (50×2.1 mm i.d., 3 μm) with the mobile phase composed of methanol-water in gradient elution at a flow rate of 0.2 mL/min. The detection was performed by the multiple reaction monitoring (MRM) mode using electrospray ionization in negative ion mode. The monitoring transitions were set at m/z 343.1→328.1 for UA and m/z 269.1→225.1 for emodin (IS). Good linearity was observed in a concentration range of 1.6-80 and 40-2000 ng/mL for plasma samples, with a lower limit of quantification of 1.17 ng/mL. The within- and between-run precision results were less than 7% and their accuracies ranged from -17.7% to 9.0%. The recoveries of UA in rat plasma were more than 80% in quality control (QC) samples at three levels of concentrations. UA was stable during the analysis and storage period. The validated method was successfully applied to investigate the pharmacokinetics of UA after transdermal and intravenous administration in rats. The MRT0-∞h of UA after transdermal administration was twice as much as intravenous administration, indicating transdermal administration had a sustained release effect. The absolute bioavailability of UA after transdermal administration reached 16.39%, suggesting UA was suitable for transdermal drug delivery.
Conclusion: This study provided the effective LC-MS/MS following protein precipitation method that is highly selective, sensitive, accurate and precise for the determination of UA in rat plasma. The established method has been validated and successfully applied to the transdermal pharmacokinetics study of UA. The absolute bioavailability of UA after transdermal administration reached 16.39%.
Yanping Deng
– Fujian Medical University, FujianYanping Deng
– Fujian Medical University, Fujian
Yi Wang
– student, Fujian Medical University, Fuzhou
Guifeng Zhong
– T1430-06-046, Fujian Medical University, FujianXiangbin Yu
– School of pharmacy, Fujian Medical University, Fujian
Yi Wang
– student, Fujian Medical University, Fuzhou