Permeability determination and pharmacokinetic study of nobiletin in rat plasma and brain by validated high-performance liquid chromatography method.

In the present study, we are reporting permeability and pharmacokinetics of nobiletin in rat plasma and brain, using a validated reverse phase high performance liquid chromatographic method. Protein precipitation method was used for the extraction of nobiletin and coumarin (IS) from rat plasma and brain tissue. The system was run in isocratic mode with mobile phase consisting of potassium dihydrogen ortho-phosphate (pH 4.5; 0.04 mM) and acetonitrile in ratio of 50:50, v/v. The total chromatographic run time was 9.0 min. The method was proved to be accurate and precise at linearity range of 0.05-10 μg/mL with a correlation coefficient (r) of ≥ 0.994 in rat plasma and ≥ 0.995 in rat brain. The intra- and inter-day precision and accuracy values are found to be within the assay variability limits as per the FDA guidelines. Nobiletin was found stable in the battery of stability studies viz., bench-top, auto-sampler, freeze/thaw cycles and long term storage in a freezer at -70±10°C. Maximum concentrations of nobiletin in both plasma and brain were observed at 1h after single oral dosing (50 mg/kg). The maximum concentration in plasma and brain were 1.78 and 4.20 μg/mL, respectively. The AUC(0-t) in plasma and brain were 7.49 and 20.66 μg·h/mL, respectively. The mean elimination half life (t(½) in plasma and brain were 1.80 and 11.42 h, respectively. The Parallel Artificial Membrane Permeability Assay (PAMPA) permeability of nobiletin was found to be high at both pH 4.0 and 7.0.