Cyclodextrins are consisted of glucopyranose units and can be represented as a truncated cone structure with a hydrophobic cavity. It has been well established that the ability of cyclodextrins to enhance the stability and solubility of drugs. The present work was designated to study the complexation of quercetin utilizing cyclodextrin to improve the solubility and to determine the effect of the complexation process on its antioxidant capacity. An equimolar mixture of quercetin and cyclodextrin in water: ethanol (1:1) was stirred in room temperature for 10 h. The undissolved quercetin were removed by filtration and the inclusion complex was dried and stored as test compound. The reaction mixtures consisted of 20 μl BSA (1.5 μM) in phosphate buffer (pH 7.4) were preincubated with 2 μl the complex or quercetin(0.1-10μM) for 10 min at room temperature. The assay was monitored in fluorimeter after the addition of 50μl AAPH (40 mM), as radical source, every 5 min for 120 min. The obtained quenching curves of BSA fluorescence illustrate the AAPH radical scavenging ability of inclusion complex compared to that of quercetin. The reaction kinetics exhibited a concentration-dependent inhibition of BSA-fluorescence decay with inclusion complex concentration. Our results suggested that the inclusion complexation would have a potential application in food industry and pharmaceutical as enhanced antioxidant.
