LC-ESI-MS/MS analysis of quercetin in rat plasma after oral administration of biodegradable nanoparticles.

A simple, rapid and sensitive LC-MS/MS method was developed and validated for the determination of free quercetin in rat plasma, using fisetin as internal standard. The detection was performed by negative ion electrospray ionization under selected reaction monitoring. Chromatographic separation (isocratic elution) was carried out using acetonitrile-10 m m ammonium formate (80:20, v/v) with 0.1% v/v formic acid. The lower limit of quantification (4.928 ng/mL) provided high sensitivity for the detection of quercetin in rat plasma. The linearity range was from 5 to 2000 ng/mL. Intra- and inter-day variability (RSD) of quercetin extraction from rat plasma was <4.19 and 1.37% with accuracies of 98.77 and 99.67%. The method developed was successfully applied for estimating free quercetin in rat plasma, after oral administration of quercetin-loaded biodegradable nanoparticles (QLN) and quercetin suspension. QLN (C(max), 1277.34 ± 216.67 ng/mL; AUC, 17,458.25 ± 3152.95 ng hr/mL) showed a 5.38-fold increase in relative bioavailability as compared with quercetin suspension (C(max), 369.2 ± 108.07 ng/mL; AUC, 3276.92 ± 396.67 ng hr/mL).