ESI-MSⁿ and MSD-TOF as a Tool to Identifythe Microbial Transformed Metabolites of4ʹ-Hydroxyflavanone

Microorganisms have been utilized as a model for drug metabolism to predict the fate of xenobiotics in mammalian systems. Since this method gives sufficient quantities of metabolites, complete chemical structure and pharmacological activities could be determined [1]. Also, they can be used as analytical standards to detect and characterize particular flavonoid metabolites which are present in very small quantities in biological fluids [1]. 4ʹ-Hydroxyflavanone and its microbial transformed metabolites were studied using both positive and negative ion modes by ion-trap mass spectrometer (ESI-MSⁿ) and electrospray ionization MSD-TOF, respectively. The fragmentation patterns of three key intermediates of 4ʹ-hydroxyflavanone, 6,4ʹ-dihydroxyflavanone, 3ʹ,4ʹ-dihydroxyflavanone and 6,3ʹ,4ʹ-tryhydroxyflavanone, were analyzed. Their fragmentation behaviors were directly affected by the substitution of hydroxyl groups. According to the diagnostic fragmentation of these compounds, eight metabolites of 4ʹ-hydroxyflavanone have been further identified. In the positive ion mode, metabolites conjugating with glycoside presented [M+Na]⁺ ions. However, metabolites without glycoside conjugation showed [M-H] ⁻ fragments in the negative ion mode more easily. The present study can contribute to the determination of trace metabolites in crude extracts of microbial transformations, and offer background information for the structural characterization of similar experiments. Acknowledgements: This research is funded in part by “Science Based Authentication of Dietary Supplements” funded by the Food and Drug Administration grant number 2 U01 FD 002071-07 and the United States Department of Agriculture, Agricultural Research Service Specific Cooperative Agreement Number 58-6408-06-067 References: [1] Clark AM, et al. (1985) Med. Res. Rev. 5: 231–253.