The holistic approach of herbal medicines is becoming acceptable in many parts of the world. In order to determine, not only chemical but also biological activity profiles of traditional medicines, on-line liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) coupled to antioxidant assay was introduced. Here, we demonstrate the performance of this on-line monitor for quantitatively and qualitatively analyses of antioxidants in Sahasthara, a Thai traditional medicine. HPLC real-time coupling to ESI-MS and DPPH assay was applied to separate and identify the constituent compounds responsible for antioxidant activity. The antioxidant fingerprint was obtained together with the LC-MS chromatogram. The full scan MS and the multiple reaction monitoring (MRM) were used for structural confirmation and quantitation. Peak identification was performed by comparing retention times and mass spectra with reference compounds and published data. Based on their mass spectra, 13 antioxidant compounds were identified as gallic acid, chebulic acid, digalloyl glucoside, caffeoylferuloylquinic lactone, galloylshikimic acid, trigalloyl glucoside, corilagin, chebulanin, chebulagic acid, dicaffeoylquinic lactone, dicaffeoyl quinic acid, ellagic acid rhamnoside and ellagic acid. Gallic acid and ellagic acid were further quantitated and comprised 126.8±6.0 mg/g and 253.7±17.6 mg/g of Sahasthara, respectively. This on-line monitor is shown to be an effective tool for fast and simultaneous analyses of antioxidant compounds in complex formulations characteristic of many traditional medicines.
