Identification and assay of 3'-O-methyltaxifolin by UPLC-MS in rat plasma

A new metabolite of taxifolin: 3'-O-methyltaxifolin (3'-O-MTAX) in Caco-2 cells and in rat plasma was identified. The chemical structure of 3'-O-MTAX was determined by MS and (1)H NMR. A rapid, sensitive and specific UPLC-MS method to determine 3'-O-MTAX in rat plasma was also developed. Following ethyl acetate extraction, 3'-O-MTAX in plasma was separated on a Sunfire™ (2.1mm×50mm, 3.5μm) column and analyzed in the selected ion recording with a negative electrospray ionization mode using puerarin as the internal standard. The lower limit of quantification (LLOQ) was 2.75ng/mL. Intra- and inter-day precisions (% RSD) were all within 7.2% and accuracy (% deviation) ranged from -5.0 to 4.7%. The overall recoveries at four concentrations were all >72.0%. This validated method was successfully applied to measure 3'-O-MTAX in rat plasma after oral administration of taxifolin.