Second derivative spectrophotometric and synchronous spectrofluorometric determination of lesinurad in the presence of its oxidative degradation product

Lesinurad is a novel selective uric acid reabsorption inhibitor which has been recently approved for the treatment of chronic gout. The present study is considered to report the first analytical methods for the quantitative and selective determination of lesinurad in the presence of its oxidative degradation product. Complete oxidative degradation of lesinurad has been done after extensive trials under different conditions. Identification of the lesinurad oxidative degradation product has been checked via mass spectrometry. Derivative mathematical manipulation has been introduced to resolve the overlap that existed between the recorded UV absorption spectra or the synchronous fluorescence spectra of lesinurad and its degradation product. The second derivative of the UV spectra has enabled the estimation of lesinurad by measuring the peak amplitudes at 279 nm without any interference from its degradation product. Alternatively, the second derivative of the synchronous fluorescence spectra has enabled the selective determination of lesinurad by measuring the peak amplitudes at 370 nm (Delta lambda = 60) nm without any interference from the degradation product. The developed methods have been optimized, validated and applied for quantitative determination of the studied drug in its pharmaceutical dosage form.