Interaction of noscapine with human serum albumin (HSA): A spectroscopic and molecular modelling approach

Noscapine hydrochloride (Nos), an opium derived anticancer agent manifests therapeutic applications and is compliant to beneficial modifications. In this paper, we study its interaction with human serum albumin (HSA) by different spectroscopic methods including UV-vis, fluorescence, circular dichroism and thermal denaturation and molecular docking. Using corrected fluorescence data, the binding constant and Stern-Volmer constant were found out to be 3.14 x 10(4) M-1 and 1.04 x 10(5) M-1 respectively. Further, type of interactions between Nos and HSA were also elucidated. The energy transfer and distance between donor and acceptor were computed in accordance with Forster mechanism as 0.654 nm and 2.17 nm respectively. The average lifetime of HSA decreased from 6.11 ns to 3.87 ns in presence of two equivalents of Nos. Through Job's plot, a 1:1 binding stoichiometry was also elucidated for interaction between Nos and HSA. It was finally demonstrated both experimentally using site markers and computationally that Nos binds HSA at Sudlow's Site II.