Spectrofluorimetric Investigation of Interaction of Coumarin-1 with Bovine Serum Albumin

Serum albumin is the most abundant protein in blood plasma. Many drugs, including anticoagulants, tranquilizers and general anesthetics are transported in the blood while bound to albumin. Coumarins constitute an imported group of natural products that show high binding affinity towards serum albumins. Binding of coumarin-1 (7-N,N-diethylamino-4- methylcoumarin) to bovine serum albumin (BSA) results in seven fold enhancement in its fluorescence intensity, 20 nm blue shift in emission maximum and ten fold increase in fluorescence anisotropy and around four fold increase in the fluorescence lifetime as compared to that in water indicating strong binding efficiency. It shows two binding sites in BSA determined by Job’s plot, and one high affinity site with a larger binding constant (ca. 105 M−1) and other low affinity site with a smaller binding constant (ca. 104 M−1) evaluated from Scatchard plot. The Edsall plot and Bjerrum plot reveal the highly interactive nature of the two binding sites and the site specific ligand displacement experiments suggests the binding of Cou 1 to the warfarin binding site i.e. site I in subdomain II