UPLC-MS/MS quantification of total hesperetin and hesperetin enantiomers in biological matrices

Hesperidin (hesperetin-7-O-rutinoside), a flavonoid affecting vascular function, is abundant in citrus fruits and derived products such as juices. After oral administration, hesperidin is hydrolyzed by the colonic microbiota producing hesperetin-7-O-glucoside, the glucoside group is further cleaved and the resulting hesperetin is absorbed and metabolized. Flavanones have a chiral carbon generating (R)- and (S)-enantiomers, with potentially different biological activities. A rapid UPLC-MS/MS method for the analysis of (R)- and (S)-hesperetin enantiomers in human plasma and urine was developed and validated. Biological matrices were incubated with β-glucuronidase/sulfatase, and hesperetin was isolated by solid-phase extraction using 96-well plate mixed-mode cartridges having reversed-phase and anion-exchange functionalities. Racemic hesperetin was analyzed with a UPLC HSS T3 reversed phase column and hesperetin enantiomers with a HPLC Chiralpak IA-3 column using H(2)O with 0.1% CHOOH as solvent A and acetonitrile with 0.1% CHOOH as solvent B. The method was linear between 50 and 5000nM for racemic hesperetin in plasma and between 25 and 2500nM for (S)- and (R)-hesperetin in plasma. Linearity was achieved between 100 and 10,000nM for racemic hesperetin in urine and between 50 and 5000nM for (S)- and (R)-hesperetin in urine. Values of repeatability and intermediate reproducibility for racemic hesperetin and enantiomers in plasma and urine were below 15% of deviation in general, and maximum 20% for the lowest concentrations. In addition, the method was applied for the quantification of total hesperetin and of hesperetin enantiomers in human plasma and urine samples, obtained after oral ingestion of purified hesperetin-7-O-glucoside. In conclusion, the developed and validated method was sensitive, accurate and precise for the quantification of enantiomers of hesperetin in biological fluids.