Role of curcumin on the determination of the critical micellar concentration by absorbance, fluorescence and fluorescence anisotropy techniques

Curcumin (C21H20O6) is a natural antioxidant which has a wide range of physiological and pharmacological actions. Here, first time this is employed for the determination of the critical micellar concentration (cmc) of both ionic and nonionic surfactants using the measurements of UV absorption, fluorescence spectroscopy and fluorescence polarization anisotropy. Results on a number of surfactants have agreed with those evaluated from conductometric, tensiometric and calorimetric methods. The absorbance and fluorescence intensities of curcumin are enhanced by different micellar solutions. The profiles of the absorbance and fluorescence intensities as a function of concentration of surfactant can be described by sigmoidal function to evaluate the cmc of the studied amphiphiles. However, we have found that some of the anisotropy profiles are sigmoidal in nature.