The Bacteriostatic Effects Of A Novel Series Of Rare Earth-phen-indoleacetic (Indolebutyric) Acid Complexes

Objective: The rare earth (RE) elements are composed by the lanthanide elements including lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu), and yttrium (Y) and scandium (Sc). The RE has excellent physical and chemical properties with unique electron shell structure. It has been revealed that the RE complexes own antibacterial, anti-inflammatory, antitumor, anticoagulants and hypoglycemic effects. In current thesis, the bacteriostatic effects of a novel series of RE complexes formed by lanthanide ions coordinated with the ligands of phenanthroline indoleacetic acid (IAA) and indolebutyric acid (IBA), on five strains of pathogenic bacteria including Golden staph, Escherichia coli, Candida albicans, Pseudomonas aeruginosa, Bacillus subtilis. Their potential acting mechanism through the cleavage of bacterial DNA was also representatively studied.Methods: The new series of ternary complexes formed by RE elements, phenanthroline and IAA or IBA. The bacterial strains used in current thesis are Golden staph,Escherichia coli,Candida albicans,Pseudomonas aenlgimosa and Bacillus subtilis. RE complexes were prepared in four kinds of concentrations using the doubling dilution method. And the quantities of the bacteria were determined. The bateriostasis effects of the corresponding RE-phen-IAA(IBA) compounds against the five bacterial strains were then measured using the plate method of inhibition zone. Agarose gel electrophoresis was performed to determine and quantify the products cleavaged from E. coli DNA by representative RE complexeResults: (1) Both the series of RE complexes of RE-phen-IAA and RE-phen-IBA show broad spectrum bacteriostasis effects against the bacteria strains tested in current thesis; (2) The bacteriostasis effects of these two series RE complexes are potentially dose-dependent; however, (3) their bacteriostasis effects are not specific except that they all show weak inhibiting effects on Golden staph; (4) Synergistic bacteriostatic effects are existing between the lanthanide elements of La, Ce, Pr, Nd, Sm, Eu, Tb and Dy and phenanthroline by promoting the corresponding bacteriostasis abilities; (5) Pr-phen-IBA compound cleaves E. coli DNA with dose-response relationship.Conclusions: (1) The new series of RE-phen-IAA and RE-phen-IBA compounds showed certain bateriostatic effects with dose-response relationships and (2) with broad spectrum antibacterial activities against the bacterial strains used in current work. (3)RE-phen-IAA and RE-phen-IBA complexes show antibacterial capacities against the five types of strains of bacterium utilized. In addition, positive cooperativities exist for La, Ce, Pr, Nd, Sm, Eu, Tb, Dy and phenanthroline ligand by promoting the antibacterial activity. As La, Ce, Pr, Nd, Sm and Eu belong to the family of light rare-earth elements (LREE), a preliminary conclusion might be made that the LREE related compounds have better antibacterial activity than the corresponding heavy rare-earth element ones. (4) Further experiment results indicated that RE-phen-IAA (IBA) might potentially inhibit the growth of bacteria by braking the DNA of bacteria.