An efficient approach to probe the bioactive transdermal components of traditional Chinese herbal patches by UHPLC-MS: Gutong patch as a case

Traditional Chinese herbal patches (TCHPs) characterized by good patient adherence and few side effects have been widely used in the clinic. However, their bioactive transdermal components, which are key to the quality and efficacy, have rarely been investigated.Establishing an approach to probe the bioactive transdermal components of TCHPs, using Gutong patch (GTP) as a case study.GTP constituents were identified using ultrahigh-pressure liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS). The identified GTP constituents were transferred to an ultrahigh-pressure liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC-QqQ-MS/MS) method in a dynamic multiple reaction monitoring (dMRM) mode for sensitively targeted analysis of transdermal components present at low concentrations. The ex vivo transdermal components were rapidly probed using a percutaneous permeation model and the release kinetics of marker components was assessed to evaluate the release behavior of GTP. The in vivo transdermal components were then studied in a rat model of arthritis and the changes in concentration of 15 representative bioactive transdermal components with time were well revealed.A total of 120 phytochemical constituents have been identified in GTP extracts and 61 ex vivo transdermal components were targetedly detected. The release kinetics of GTP were evaluated by eight marker components and fitted to a zero-order kinetic model. In vivo, 62 and 40 transdermal components were observed in the skin and subcutaneous tissues of arthritic rats, respectively. The concentration-time changes of 15 representative transdermal components with documented bioactivities have been successfully exhibited after GTP administration.We established a feasible approach to probe the bioactive transdermal components of TCHPs efficiently. The integration of mass spectrometry profiling and targeted detection in dMRM mode enabled a comprehensive investigation of phytochemical constituents and their transdermal delivery, thus addressing the challenge of direct probing of diverse transdermal components present at low concentrations. This approach could be used to rapidly probe the bioactive components and understand the mechanism of TCHPs.