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

The article focuses on the development and validation of a high-performance liquid chromatography (HPLC) method with ultraviolet (UV) detection for quantifying carnosic acid (CA), a phenolic diterpene from Rosemary (Rosmarinus officinalis L.), in human plasma. The method employs liquid–liquid extraction with hexane and chromatographic separation on a C18 column using an isocratic mobile phase of methanol and 2% o-phosphoric acid in water, detecting CA at 230 nm with a retention time of approximately 4.20 minutes. Validated according to European Medicines Agency guidelines, the method demonstrated high accuracy, precision, sensitivity (limit of detection 0.075 ng/mL), and robustness, with a recovery rate of 91.7%. Applied to a pharmacokinetic study in a healthy volunteer after oral administration of Rosemary extract, the method enabled calculation of key pharmacokinetic parameters, supporting its suitability for routine analysis in clinical and bioavailability studies.