Dissolution and spectrophotometric determination of astaxanthin in aqueous solutions.

The poor solubility of astaxanthin in water can cause problems during dissolution tests of dosage forms because they are usually performed in water-based media. The aim of this study was the development of a convenient dissolution medium and a method for a spectrophotometric determination of astaxanthin in an aqueous solution. Three surfactants in different concentrations were tested as solubility-improving substances: sodium lauryl sulfate (SLS), polysorbate 80 (PS 80) and macrogolglycerol hydroxystearate (Cremophor RH 40, CR 40). Optimal conditions were determined. The dissolution of astaxanthin from solid dosage form is performed into 1000 g of a solution of sodium lauryl sulfate with the concentration 1.0% (w/w) at 37 degrees C by paddle method, 100 rotations per minute, dissolution time 30 minutes. The procedure is convenient for solid dosage forms with a content of 4 to 12 mg of astaxanthin. The spectrophotometric determination of astaxanthin in aqueous solution from the dissolution test is measured at 486 nm. The specific absorbance A(1%) 1cm for astaxanthin in water is 2000, a sodium lauryl sulfate solution (1%) was used as a blank.