Electrospray tandem mass spectrometry analysis of methylenedioxy chalcones, flavanones and flavones

RATIONALE Several methylenedioxy chalcones, flavanones and flavones substituted with mono-, di- and trimethoxy groups have been used in the treatment of proliferative conditions like cancer and inflammatory diseases. The application of these flavonoids in biology requires an analytical method to ensure a detailed knowledge of their structures after drug metabolism. METHODS Electrospray ionization mass (ESI-MS) and tandem mass (ESI-MS/MS) spectra were acquired using a Q-TOF 2 instrument. Fragmentation patterns and their pathways were analyzed by CID-MS2–3 spectra acquired in a LXQ linear ion trap mass spectrometer using standard isolation and excitation procedures (activation q value of 0.25, activation time of 30 ms). ESI-MS and ESI-MSn conditions: spray voltage 5 kV, nitrogen 8.00 sheath gas flow rate (arb), heated capillary temperature 275°C, capillary voltage 10.99 V; tube lens voltage 75.01 V. RESULTS The ESI-MS/MS spectra of chalcones were nearly identical to their corresponding isomeric flavanones with 0,αA+/1,3A+ and 0,1'B+/1,4B+ cleavages. Other common losses are of •CH3, H2O, HCHO and C2H2O. The characteristic loss of C2H2O and absence of a 0,αB+/1,3B+ product ion allows to distinguish between the 2- or 4-methoxy-substituted chalcones and flavanones. Common losses of •CH3, •CH3 and •H, and C2H2O2 characteristic for the presence of methylenedioxy groups were observed in flavones. CONCLUSIONS The substitution pattern on the B-ring leads to distinct base peak formation in the flavones. In addition, differentiation of isomers with methoxy substituents in ortho and para positions of the B-ring was achieved using MS/MS in chalcones and flavanones. This method will be helpful for identification of these compounds in biological mixtures. Copyright © 2013 John Wiley & Sons, Ltd.