Competition of cytarabine and aspirin in binding to serum albumin in multidrug therapy

The aim of this study was to describe a competition between cytarabine (araC) and aspirin (ASA) in binding with bovine serum albumin (BSA). High‐affinity binding sites for both drugs were determined using a spectrofluorimetric method. Cytarabine as well as aspirin binds in the IIA hydrophobic subdomain of the transporting protein. Binding constants for araC–BSA and ASA–BSA were calculated by the Scatchard method. Analysis of ultraviolet (UV) difference spectra showed that araC, which has a higher affinity to BSA in comparison to ASA [ K a(araC) > K a(ASA) ] displaces ASA in high‐affinity binding sites. The competition between drugs in low‐affinity binding sites was investigated using 1 H nuclear magnetic resonance (NMR) and 13 C‐NMR spectra. We concluded that in the low‐affinity binding sites cytarabine decreases the affinity of albumin toward aspirin. However, the interaction between araC and BSA becomes more difficult in the presence of aspirin. © 2006 Wiley Periodicals, Inc. Biopolymers 81: 464–472, 2006 This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com