Determination of Carnosic Acid by a Novel HPLC-UV Method in Human Plasma and Application to a Prototype Pharmacokinetic Study

An HPLC method with UV detection was developed for the determination of carnosic acid in human plasma and applied to a pharmacokinetic study after oral administration of Rosemary extract to a healthy volunteer. Sample preparation depends on liquid-liquid extraction with hexane. Chromatographic separation was achieved with C18 column (150 mm × 4.6 mm × 5 μm), at 25°C with isocratic elution, mobile phase composed of solution A (methanol), and solution B (2% o-phosphoric acid in water) (90:10, v/v) at flow rate of 1.0 mL/min. The analyte was detected at 230 nm. The retention time is 4.20 ± 0.03 min. The method was validated in terms of accuracy, precision, specificity, robustness and detection and quantification limits, in accordance with European Medicines Agency guidelines. LOD and LOQ were found to be 0.075 and 0.25 ng/mL, respectively. The method was applied to the analysis of carnosic acid in human plasma with good recovery as 91.7%. The plasma concentration-time profile and pharmacokinetic parameters: AUC0-t, AUC0-∞, Cmax, tmax, t1/2 were calculated according to the assays. The method can certainly be used for routine analysis of carnosic acid in human plasma after oral administration of Rosemary extract, and for phase I clinical studies and bioavailability-bioequivalance studies as well.