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.