Analytical methods for assay of ellagic acid and its solubility studies

Ultra-violet (UV) spectrophotometric and high performance liquid chromatographic methods for quantitative determination of ellagic acid (EA), an antioxidant were developed. The analytical methods were validated for linearity, accuracy, intra- and inter-day variability, and precision. EA was eluted using a polyethylene glycol (PEG) column with mobile phase composed of acetonitrile and 5 mM potassium dihydrogen orthophosphate buffer pH 2.5 (80:20, v/v). The UV and high performance liquid chromatography (HPLC) methods have lower detection limits of 0.2 and 0.1 μg/ml, respectively. Because of the increasing pharmaceutical interest in phytochemicals and their solubility problems, solubility studies for EA were also carried out. Various organic solvents and surfactants were screened for assessing solubility of EA and the compound was found to be soluble in some pharmaceutically acceptable solvents like triethanolamine, polyethylene glycol 400 and N-methyl pyrrollidone (NMP). Aqueous and pH dependent solubility of EA were determined using UV and HPLC methods, respectively.