Synthesis, Characterization, Biological Activity and Interaction with Bovine Serum Albumin of 8-or 6-(3-Chlorobenzoyl)coumarin Derivatives

Two new compounds, 4-methyl-7-hydroxy-8-(3-chlorobenzoyl) coumarin (1) and 4-methyl-7-hydroxy-6-(3-chlorobenzoyl) coumarin (2), were synthesized and characterized by elemental analysis, infrared spectra, H-1 NMR and single crystal X-ray diffraction methods. The crystals of compounds 1 and 2 belong to monoclinic system with space group P2(1)/c, compound 1: alpha=1.21527 (14) nm, b=1.01550 (12) nm, c= 1.5045(2) nm, beta=112.377 (2)degrees, V=1.7169 (4) nm(3), D-c = 1.396 g/cm(3), Z = 4, F (000)= 752, R-1 = 0.0415, wR(2) = 0.0981 [I>2 sigma (I)], S=1.063; compound 2: alpha = 2.0168(2) nm, b =0.76229(12) nm, c= 2.25497 (17) nm, beta=123. 987 (6)degrees, V=0.8745 (6) nm(3), D-c=1.454 g/cm(3), Z = 8, F(000) = 1296, R-1= 0.0604, wR2 = 0.1384 [I>2 sigma (I)], S = 0.948. The results of antibacterial experiment showed that the title compounds had the activity for inhibiting growth of E. coli, B. subtilis and S. aureus. The antioxidation activity of the title compounds were investigated by the O-2(-)center dot, DPPH center dot and center dot OH methods. The results showed that the title compounds had strong antioxidation activity. The interactions of title compounds and bovine serum albumin(BSA) were investigated by fluorescence spectroscopy at different temperatures. The results indicated that the title compounds caused the fluorescence quenching of BSA through a static quenching procedure. The corresponding thermodynamic parameters enthalpy change (Delta H), entropy change (Delta S), Gibbs free energy change(Delta G), between the title compounds and BSA were calculated. The interaction between the compound 1 (Delta H>0, Delta S>0, Delta G<0) and BSA was driven mainly by hydrophobic force, whereas the interaction between compound 2(Delta H<0, Delta S<0, Delta G<0) and BSA was driven mainly by hydrogen bond force or van der Waals force. The binding average distance r between the donor(BSA) and acceptors(compounds 1 and 2) were obtained to be 2.59 and 2.38 urn, respectively, based on the Foster's theory, which indicate the energy transfer can occur from BSA to title compounds with high probability.