Background: Quercetin (Q) is one of the most abundant flavonoids in human dietary sources and has been related to the capacity to ameliorate obesity-related pathologies. Quercetin-3-O- β - d -glucuronide (Q3GA) is supposed to be the main metabolite in blood circulation, but the intracellular final effectors for its activity are still unknown. Hypothesis/purpose: To identify and quantitate the intracellular metabolites in hypertrophied adipocytes incubated with Q or Q3GA and to correlate them with the intracellular generation of oxygen radical species (ROS). Methods: Cytoplasmic fractions were obtained and quercetin metabolites were determined by liquid chro- matography coupled to a time-of-flight mass detector with electrospray ionization (HPLC-DAD-ESI-TOF). Intracellular ROS generation was measured by a ROS-sensitive fluorescent probe. Results: Both Q and Q3GA were absorbed by hypertrophied adipocytes and metabolized to some extent to Q3GA and Q, respectively, but Q absorption was more efficient (1.92 ± 0.03 μg/μg protein) and faster than that of Q3GA (0.12 ± 0.0015 μg/μg protein), leading to a higher intracellular concentration of the aglycone. Intracellular decrease of ROS correlated with the presence of the most abundant quercetin metabolite. Conclusion: Q and Q3GA are efficiently absorbed by hypertrophied adipocytes and metabolized to some extent to Q3GA and Q, respectively. The intracellular decrease of ROS in a hypertrophied adipocyte model treated with Q or Q3GA is correlated with the most abundant intracellular metabolite for the first time. Both compounds might be able to reach other intracellular targets, thus contributing to their bioactivity.
