Enhancement of Curcumin Fluorescence by Ascorbic Acid in Bicontinuous Microemulsion.

Abstract

Steady-state fluorescence spectro-photometric technique is used in this work to determine the chemical parameters of the complex formed between curcumin and ascorbic acid in bicontinuous microemuslion (Bμen). The Bμen liquid used is made up of a four-components system (water-oil-surfactant and co-surfactant (1-pentanol)) in the ratio of 42.11:13.7:21.34:22.85 % w/w. The oil and surfactant used are tetradecane and cetyltrimethylammonium bromide. Curcumin is known to have low solubility in water, but liberally soluble in Bμen, hence the use of Bμen in this study. The observed fluorescence intensity of curcumin was enhanced by introduction of ascorbic acid to the curcumin solution. The increase in the fluorescence intensity showed a very good linearity with a regression coefficient of 0.9974. The association constant, Ka, that resulted between curcumin and ascorbic acid was calculated as 2.15 × 10(4) with the free energy of association, ∆Ga, of -24.71 kJ/mol. The ratio of the complex that was formed by these two molecules was determined as 1:1.