Liquid chromatographic analysis and examination of bioavailability of agnuside compound found in Vitex agnus-castus L. plant in plasma

In this study, a new high-performance liquid chromatography (HPLC) method was developed for plasma and pharmaceutical preparation assays that enables the determination of the compound called agnuside, which is found in Vitex agnus-castus L. plant and has various pharmacological effects, especially estrogenic effect. For this purpose, the analyte extracted from plasma samples by liquid-liquid extraction technique, then separated with C18 (150 mm × 4,6 mm × 5 μm) column and methanol:water (0.1 % formic acid) (35:65, v/v) mixture as mobile phase with isocratic flow and at a flow rate of 0.6 mL/min. The analyte has been detected by UV detection at 258 nm and with 9.7 ± 0.01 minutes retention time. The developed method has been validated according to ICH criteria in terms of selectivity, linearity, accuracy, repeatability, limit of detection (LOD), limit of quantitation (LOQ), robustness and stability. The linearity limits of the method are 5-125 µg/mL, and the correlation coefficient of the linearity equation obtained as a result of the calibration is 0.9915. The maximum RSD % value indicating the intra-day and inter-day precision of the method is 6.35. In order to check the clinical applicability of the developed method, a single dose of Castonex® capsule containing chasteberry extract was administered orally to a healthy volunteer, and then the method was used to calculate the pharmacokinetic parameters (Cmax, tmax, t1/2 and AUC0-t, AUC0-∞) of the compound. In addition to plasma assays, the amount of agnuside in pharmaceutical preparation was calculated with the regression equation of the aqueous standard solutions and the results were compared with those obtained by the validated comparison method at 95 % confidence level.