Tamoxifen and curcumin binding to serum albumin. Spectroscopic study

• Published in: Journal of molecular structure 2013-07, Vol.1044, p.194-200
• Main Authors: Maciążek-Jurczyk, M., Maliszewska, M., Pożycka, J., Równicka-Zubik, J., Góra, A., Sułkowska, A.
• Format: Article
• Language: English
• Subjects: Binding; binding capacity; binding sites; Biological effects; Breast; breast neoplasms; Cancer; chemoprevention; Curcumin; dietary supplements; Drugs; Fluorescence; fluorescence emission spectroscopy; human serum albumin; hydrophobicity; Serum albumin; Tamoxifen; Toxicity
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2012.11.024

Tamoxifen (TMX) is widely used for the breast cancer treatment and is known as chemopreventive agent. Curcumin (CUR) is natural phenolic compound with broad spectrum of biological activity e.g. anti-inflammatory, antimicrobial, antiviral, antifungal and chemopreventive. Combination of tamoxifen and curcumin could be more effective with lower toxicity than each agent alone in use for the treatment or chemoprevention of breast cancer. Binding of drugs to serum albumin is an important factor, which determines toxicity and therapeutic dosage of the drugs. When two drugs are administered together the competition between them for the binding site on albumin can result in a decrease in bound fraction and an increase in the concentration of free biologically active fraction of drug. To determine the binding site of TMX and CUR in the tertiary structure of human serum albumin (HSA) and to estimate their possible competition to the binding site fluorescence spectroscopy was used. One binding site in Sudlow’s site I for CUR and one binding site different than Sudlow’s site I for TMX were found. TMX binds to HSA with a binding constant of 2.58×105M−1 (both Scatchard and Isotherm method). The association constant for the binding of CUR to HSA is 11.26×105M−1 (Scatchard method), 11.72×105M−1 (Isotherm) and 1.16×105M−1 (Benesi–Hildebrand method). A blue shift by 45.5nm of fluorescence emission maximum of CUR in the presence of HSA shows that the binding of CUR to HSA was accompanied by an alteration of the hydrophobicity of the microenvironment. In the presence of CUR binding affinity of TMX to human serum albumin (HSA) decreases. A precaution is required in breast cancer treatment when dietary compounds and/or food supplements are used together with TMX because CUR affects the binding of TMX to HSA.