RP-HPLC method development, validation and pharmacokinetic applicability in preclinical evaluation of rhein treated with novel diacerein eutectics

The current study represents a bioanalytical method for the estimation of rhein (Rh, an active metabolite of diacerein, DIA) in rats treated with novel DIA eutectics to investigate the pharmacokinetics of DIA. A simple protein precipitation technique was used to extract Rh and the internal standard (IS), p-aminobenzoic acid, injected into a Phenomenex Gemini C₁₈ column. The separation was achieved by a gradient elution comprising ammonium acetate (10 mm; pH 3.0) and acetonitrile in an 18 min run time at a flow rate of 0.8 ml/min with retention times of 11.8 min (Rh) and 5.9 min (IS). The results revealed that the proposed method is linear over a range of 200-20,000 ng/ml (r² > 0.9988) of Rh and is precise and accurate. The method was fully validated as per the US Food and Drug Administration guidelines and a pharmacokinetic study in rats was performed for Rh following oral administration of the pure DIA and newly developed eutectics. Therefore, the present method could be used to estimate DIA to illustrate a comparative pharmacokinetic analysis. This can also be applied to its related multicomponent formulations for future studies.