LIQUID-CHROMATOGRAPHIC UV DETECTION AND LIQUID-CHROMATOGRAPHIC THERMOSPRAY MASS-SPECTROMETRIC ANALYSIS OF CHIRONIA (GENTIANACEAE) SPECIES -A RAPID METHOD FOR THE SCREENING OF POLYPHENOLS IN CRUDE PLANT-EXTRACTS

The use of liquid chromatography-thermospray mass spectrometry (LC-TSP -MS) and liquid chromatography coupled with UV photodiode-array detect ion (LC-UV) in the analysis of crude plant extracts provides important structural information on metabolites directly in their biological ma trices. In the LC analysis of polyphenols (such as xanthones), shift r eagents can be added postcolumn and UV spectra recorded on-line. Infor mation on the position of free hydroxyl groups can be obtained by addi ng reagents such as AlCl3, weak and strong bases and boric acid. Thus, for certain polyphenols, the combination of LC-UV with postcolumn add ition of shift reagents and LC-MS permits a full on-line structural de termination involving no time-consuming isolation process. To illustra te this qualitative analytical approach, crude extracts of different G entianaceae (Chironia species) were submitted to LC-TSP-MS and LC-UV m easurements with postcolumn addition of shift reagents. This method pe rmitted the identification of a large number of xanthones which are of pharmaceutical interest as potential inhibitors of monoaminooxidases.