Antibacterial Activities Of Natural Products Chalcones’ Derivatives And Their Complexes

Chalcones are a class of natural organic flavonoid compounds which widely present in licorice, safflower and psoralen and other medicinal plants. Due to their molecular structure could bind different receptors, they have a lot of biological activities, such as anti-tumor, anti-bacterial, anti-inflammatory and anti-parasitic, etc. Benzimidazole, as a nitrogen-containing electron-rich heterocyclic system, could be formed complexes with the metal ions containing empty orbitals. Chalcones and their derivatives containing benzimidazole group are excellent precursor compounds. Besides, on chalcone parent ring, there may have a dozen or substituted position, which has great potential for structural modification changes. So the study on chalcones’ compounds and complexes containing benzimidazole group is a very meaningful work.A series of chalcones’ compounds and their transition metal complexes containing benzimidazole group was prepared by author, the ligands and their complexes were characterized by MS, NMR, IR and MFS.The main work of this paper is as follows:1. Using o-phenylenediamine, lactic acid, pyridine aldehyde and salicylaldehyde as raw materials to synthesize five ligands [(E)-1-(1H- benzimidazol-2-yl)-3-(pyridin-2-yl)-2-propen-1-one)(L1),((E)-1-(1H-benzimidazol-2-yl)-3-(pyridin-3-yl)-2-propen-1-one)(L2),((E)-1-(1H- benzimidazol-2-yl)-3-(pyridin-4-yl)-2-propen-1-one)(L3),((E)-1-(1H-benzo[d]imidazol-2-yl)-3-(2-hydroxyphenyl)-2-propen-1-one)(L4) and the derivative of L2(2- [5-(pyridin-3-yl)-4,5-dihydro-1H- pyrazol-3-yl ]-1Hbenzimidazol)(L5)]. Using 2-acetyl benzimidazole and hydrazide as raw materials to synthesize three ligands [(N’~2,N’~6-bis((E)-1-(1H-benzo[d]imidazol-2-yl)ethylidene) pyridine-2,6-carboxylic acid hydrazide)(S1),(N’~1,N’~6-bis((Z)-1-(1H-benzo[d] imidazol-2-yl)ethylidene)adipo- hydrazide)(S2),(N’~1,N’~3-bis((Z)-1-(1H-benzo[d] imidazol-2-yl)ethylidene)malono- hydrazide)(S3)], and all of them were characterized by MS, NMR and IR.2. Using L1, L2, L3, L5 and S1 as ligands, a series of transition metal complexes were synthesized, and the fluorescence properties of the ligands and their complexes were discussed. The results showed that the fluorescent emission intensity of complexes generally increased owing to the addition of Zn(II) ions, but several other metals such as Cu(II), Ni(II), Mn(II) and Cd(II) complexes, the fluorescence emission intensity is to reduce as a whole, and even lead to some fluorescence quenching.3. The antibacterial activities of ligands such as L1, L2, L3, L4, L5, S1 and their metal complexes were studied, and the regularity of anti-bacterial effects were summarized. The results showed that the ligands and their 18 kinds of transition metal complexes have different degree inhibitory effects on Escherichia coli, Staphylococcus albus, Salmonella, Sarcina luteus, but relatively weak Inhibition on Bbacillus subtilis, Staphylococcus aureus, Bacillus cereus, and ligand L3 and L5 exhibited broad spectrum antimicrobial activity. The introduction of metal ions displayed significant differenences of antibacterial activities among the ligands and their complexes. These conclusions provide very important theoretical foundation for chalcones’ compounds and their complexes containing benzimidazole group in the medical field.