Binding of Curcumin with Bovine Serum Albumin in the Presence of ι-Carrageenan and Implications on the Stability and Antioxidant Activity of Curcumin

This work studied the influences of formation of BSA/iota-carrageenan complexes on the binding, stability, and antioxidant activity of curcumin. In the presence of BSA and iota-carrageenan, curcumin gives higher intensities of absorption and fluorescence than free curcumin and curcumin only combined with BSA. The added iota-carrageenan is observed to promote curcumin for quenching the instrinsic fluorescence of BSA. These results are explained in terms of the formation of BSA/iota-carrageenan complexes, which help to stabilize the folded structure of BSA for providing curcumin with a more hydrophobic microenvironment. The small difference in anisotropy values of curcumin with BSA alone and of BSA/iota-carrageenan complexes suggests that iota-carrageenan acts as outer stretch conformation in BSA/iota-carrageenan complexes but does not directly disturb the hydrophobic pockets inside BSA, where curcumin is hydrophobically located. The determined values of the binding constant are higher for curcumin with BSA/iota-carrageenan complexes than with BSA alone. Moreover, BSA/iota-carrageenan complexes are found to be superior to single BSA for enhancing the stability and DPPH radical-scavenging ability of curcumin.