Synthesis And Biological Evaluation Of Azole Compounds As Antimicrobial Agents And Their Interaction With Serum Albumins

Human serum albumin (HSA) and bovine serum albumin (BSA) are the most abundant serum proteins in the systemic circulation. They are capable of binding reversibly with a large variety of endogenous and exogenous drugs or bioactive small molecules, thus altering their pharmacokinetic properties such as drug distribution, free concentration, metabolism and elimination, and consequently affect the levels of the drug’s activity and toxicity. Many promising new drugs have been rendered ineffective because of their unusually high or too low affinity to these proteins. Therefore, interactive investigations between serum albumins and drugs or bioactive small molecules not only provide a proper understanding of the vital pharmacokinetic processes such as drugs absorption, transportation, distribution, metabolism and excretion, but also are significant to design, modify and screen drug molecules.Based on the recent development in the interaction of bioactive small molecules with serum albumins, a series of azole compounds were synthesized and evaluated their antimicrobial activities. Further studies about the binding behaviors between the most bioactive compounds and serum albumin were investigated to preliminarily evaluate their transportation and pharmacokinetic properties. This thesis consists of the following contents:(1) The target thiophene-derived benzimidazole derivatives were synthesized via multistep reactions from commercially available chloroacetonitrile; All the newly synthesized compounds were characterized by1H NMR,13C NMR, IR and MS spectra; Bioactive assay manifested that alkyl substituted benzimidazoles lla-f and halobenzyl substituted ones12a-f exhibited moderate to excellent efficacy. Particularly, compound11d with decyl pendant displayed the best antibacterial activity, especially for MRSA, E. coli and P. aeruginosa, which was more potent than Norfloxacin and Chloromycin, respectively. Benzimidazole derivatives12a-f bearing a variety of halobenzyl groups gave comparable inhibitory potency to Chloromycin, but were relatively weaker than the alkyl ones; The Lipophilicity/hydrophilicity (logp) of the target compounds was calculated experimentally by traditional saturation shake flask approach, the results suggested that suitable lipophilicity/hydrophilicity is necessary for good antimicrobial activities; The quenching mechanism, binding constants, binding sites and thermodynamic parameters of the interaction between the most bioactive compound lid with BSA were obtained by Fluorescence and UV-vis absorption spectroscopic method. The results indicated that the hydrogen bond and van der Waals forces played major roles in the strong association of benzimidazole lid and BSA; Molecular docking method suggested that hydrogen bond between compound lid and Lys-524of HSA is involved in the binding process.(2) The desired target berberine-derived triazoles19a-h were synthesized from commercially available chlorobenzyl halides, diethanolamine and1,2,4-triazole; All the newly synthesized compounds were characterized by1H NMR、13C NMR、IR and MS spectra; Bioactive assay indicated that berberine triazoles showed good antimicrobial activities, especially for P. Vulgaris, compound19a exhibited low inhibitory concentration of2μg/mL, which was better than the reference drug Fluconazole; The effect of the metal ions on the binding constant of compound19a-HSA complex suggested that the participation of Mg2+and Fe3+ions increased the binding constants of compound19a-HSA complex, suggesting the presence of Mg2+and Fe3+ions could increase the concentration of free compound19a, shorten the storage time and half-life of compound19a in the blood, and thus improving its antimicrobial efficacy.(3) The desired target berberine-derived imidazole compound22, benzimidazoles24a-c and benzotriazole derivative26were synthesized from commercially available chlorobenzyl halides, diethanolamine, azoles (benzotriazole, imidazole, benzimidazole,2-mercaptobenzimidazole and5,6-dimethyl-benzimidazole) and berberine; All the newly synthesized compounds were characterized by1H NMR、13C NMR、IR and MS spectra; Berberine-derived imidazole22and benzimidazoles24a-b gave moderate antimicrobial activities, but berberine mercaptobenzimidazole24c and benzotriazole derivative26exhibited poor activities; The quenching mechanism, binding constants, binding sites and thermodynamic parameters of interaction between compound19a with HSA were obtained by Fluorescence and UV-vis absorption spectroscopic method on the molecular level. The obtained results indicated that the hydrogen bonds and hydrophobic interaction played major roles in the strong association of berberine triazole19a and HSA. According to the Forster’s theory, the binding distance was calculated and gave r=2.97nm which suggesting the existence of energy transfer between compound19a and HSA; The docking mode with the lowest binding free energy (-11.32KJ mol-1) was obtained by the docking software (eHiST). The results indicated that compound19a is surrounded by Arg-218,257, Lys-195,199, Leu-198,238,260, Ala-291,455, Ile-264,290, Asp-451, Phe-211, Trp-214. Hydrophobic interactions exist between aromatic ring of compound19a and Ile-264,290, Leu-198,238,260, Ala-291, Lys-199in HSA, and hydrogen bond between compound19a and Arg-257in HSA is also involved in the binding process.