INTERACTIONS OF HUMAN SERUM ALBUMIN WITH BIOACTIVE 3H-IMIDAZO[4,5-a]ACRIDINES: INSIGHTS FROM FLUORESCENCE SPECTROSCOPIC STUDIES

© 2016 Maryam Rahbari*, Mehdi Pordel*^{, #}, and Jamshidkhan Chamani**

^#Phone: +98 0511 8414182; fax: +98 0511 8424020; e-mail: [email protected]

*Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran;
**Department of Biochemistry and Biophysics, Faculty of Sciences, Mashhad Branch, Islamic Azad University, Mashhad, Iran

Received July 20, 2015; in final form, September 1, 2015

Several 3H-imidazo[4,5-a]acridine derivatives were conveniently synthesized by the reaction of imidazo[4,5-a]acridones in boiling POCl3. The imidazoacridones were obtained by rearrangement of 3H-imidazo[4',5':3,4]benzo[c]isoxazoles in concentrated sulfuric acid containing nitrous acid at room temperature. The structures of all newly synthesized compounds were confirmed by IR, ¹H NMR, and mass spectral data. The interactions of 3H-imidazo[4,5-a]acridines with human serum albumin (HSA) were studied by fluorescence spectroscopy. The binding of 3H-imidazo[4,5-a]acridines quenches the HSA fluorescence, revealing a 1 : 1 interaction with a binding constant of about 2.34 x 10⁵ – 3.16 x 10⁶ M^–1. A decrease in fluorescence intensity at 339 nm, when excited at 280 nm, is attributed to changes in the environment of the protein fluorophores caused by the presence of the ligand. The differences in interactions of 3H-imidazo[4,5-a]acridines with HSA were observed using spectrofluorimetry technique.

Keywords: 3H-imidazo[4',5':3,4]benzo[c]isoxazole, imidazo[4,5-a]acridines, human serum albumin, interaction, fluorescence spectroscopy.

Биоорг. химия 2016, 42 (1): 44-49