Studies On The Synthesis And Antimicrobial Activities Of Brominated Dihydroxy Nitro Diphenyl Ethers

Many kinds of nocuous bacteria were harmful to a lot of aspects such as human's health, industry, agriculture, animal breed aquatics. One of the available methods to solve these problems was making use of various chemical antimicrobials effectively. However, it would make the capability of antimicrobials decline since bacteria were able to endure certain medicine using for a long time. Thus, it was required that we explored new antimicrobials with good antimicrobial abilities constantly.It was always a goal that searching for antimicrobials with much better antimicrobial abilities, much wider area of application, better selectivity and lower toxicity for scientists applying themselves to chemical and medical researches pursuing. In the past a few decades, according to the study of brominated hydroxy diphenyl ethers and their ramifications, scientists found that these compounds showed good antimicrobial abilities against Gram positive bacteria and Gram negative bacteria. In order to expand the research on brominated dihydroxy diphenyl ethers and look for the brominated dihydroxy diphenyl ethers with better biological activity, we synthesized brominated dihydroxy nitro diphenyl ethers which were new target compounds and made a pilot study on antimicrobial abilities of these compounds based on the prior relevant studies. There were the following progresses in the research:(1) Designed and synthesized seven new brominated nitro 2, 2′, 2, 4′and 4, 4′- dihydroxy diphenyl ethers. The structures of these compounds were confirmed by the means of 1H NMR, IR, MS and element analysis.(2) It was found that 7c, 8a, 8c had remarkable antimicrobial abilities (restraint rate over 100%) at 5ppm concentration through the study of antimicrobial abilities against two kinds of bacteria. The growth of bacteria could be entirely controlled by these compounds, which was very important in practice. Moreover, compounds 7a, 7b, 8b, 9c were also able to control bacteria growth (restraint rate over 100%) at 50ppm concentration. Among these compounds, 7c and 8c performed much better than triclosan, which was an antimicrobial agent with great performance and lower toxin widely used in the field of medicine, agriculture, textile, chemical commodity, public sanitation etc. It was possible to find new kinds of antimicrobial with much better capability if a further research could be carried out.(3) Found some relationships between the structures and the characters of these target compounds: a) both biomimetic natural brominated nitro 2,2′-dihydroxy diphenyl ethers and the new designed brominated nitro 2,4′and 4,4′-dihydroxy diphenyl ethers performed well against bacteria; b) among these compounds, the new designed brominated nitro 4,4′-dihydroxy diphenyl ethers performed remarkably well; c) the rule for the amount of substituted bromine atom in the molecule to affect the antimicrobial abilities was unobvious.(4) Bromine atoms in all target molecules were not at the ortho-positions of ether linkages of diphenyl ethers, it was impossible to generate brominated dibenzo-p-dioxins with high toxicity.The study offered references to further design of new diphenyl ethers antimicrobial with good biological activity and lower toxicity. This kind of target compounds would have applicable value in fields of medical treatment and agrochemical.