HPLC-Triple detector (Coulometric array, diode array and mass spectrometer) for the analysis of antioxidants in officinal plants

This work demonstrates the use of a triple detector for the screening of antioxidants in officinal plants. The triple detector consisted of a coulometric array (CAD), a diode array (DAD) and a mass spectrometer (MS) detector, which were connected to a HPLC system. DAD gave an overall profile of bioactive compounds. CAD allowed to select the most promising redox species and quantify their concentration based on the Faraday's law. Finally, MS was used for identification. The approach was applied to screen the main antioxidants in 19 officinal plants. Furthermore, the electron transfer properties obtained by CAD were highly correlated with the results of classical DPPH (r = 0.80), FRAP (r = 0.87) and ORAC (r = 0.90) assays and, thus, could be used to predict the antioxidant capacity of plant extracts by stepwise linear regression models (R2 = 0.99). Overall, the triple detector system allows a comprehensive approach to screen and characterize the antioxidant compounds in natural plant extracts.