The Antibacterial Activity In Vitro And Metabolite Profiling In Vivo Of Novel Structural Hybrids Between Sulfonamides And Pleuromutilin Derivatives

The extensive and abuse use of antibacterial agents in the clinical has resulted in the increasingly serious bacterial drug resistance phenomenon which has brought a serious threat to human and animal health. Thus, it is urgent to alleviate or even eliminate the occurrence of drug-resistant bacteria. Hybrid antimicrobial agents, i.e., hybrid molecules which combine two drugs or their derivatives by chemical bonds can expand its antibacterial spectrum, enhance the antimicrobial activity against drug resistance pathogens and reduce the odds of developing bacterial resistance due to the dual action. Recently it has become the hot spot of research and development novel antibacterial drugs. In this paper, the antimicrobial activity of novel structural hybrids between sulfonamides and pleuromutilin derivatives B1 ~ B6 aganist common pathogen of standard strains and clinical strains were assessed, and the antimicrobial activity of novel structural hybrids between sulfonamides and pleuromutilin derivatives A1, A3, A6 aganist clinical strains were further studied. Besides, the metabolic characteristics in rats of representative hybrid A1 which performed good activity aganist bacteria in vitro was investigated, in order to provide the theoretical basis for study on the mechanism of action and pharmacokinetic, residual research of this kind hybrids. 1 Study on the antibacterial activity of hybrids between sulfonamides and pleuromutilin derivativesThe antimicrobial activity of hybrids B1~B6 against Staphylococcus aureus ATCC 6538 p, Streptococcus suis CVCC 3307, Streptococcus agalactiae CVCC 1886, Mycoplasma gallisepticum S6 and Escherichia coli ATCC 25922 were measured using micro-broth dilution method. The results showed that hybrids B1, B2, B3 performed excellent activities against above-mentioned bacterial strains(except Escherichia coli ATCC 25922), the minimum inhibitory concentration(MIC) of which were 0.008, 0.5, 0.25, 0.008, >128 ?g/m L; 0.03, 2, 0.5, 0.008, >128 ?g/m L; 0.004, 0.25, 0.5, 0.004, 128 ?g/m L; respectively.The antimicrobial activity of hybrids A1?A3?A6 and B1~B6 against 212 clinical isolations of staphylococcus aureus were tested by the agar dilution method. The results showed that hybrids A1, A3, A6 and B1, B2, B3 performed the most potent inhibitory activities, the MIC50 and MIC90 of which were 0.008, 0.008 ?g/m L; 0.03, 0.03 ?g/m L; 0.12, 0.25 ?g/m L; 0.03, 0.03 ?g/m L; 0.12, 0.12 ?g/m L; 0.016, 0.016 ?g/m L, respectively. The results of antimicrobial activity in vitro indicated that hybrids A1, A3, A6 and B1, B3, B6 showed great antimicrobial activity against gram-positive bacterium especiallly Staphylococcus aureus, which were far better than sulfonamides contrast drugs and intermediate pleuromutilin derivatives III, equal to or better than valnemulin contrast drug. 2 Study on the metabolism in rats of hybrid A1 between sulfanilamide and pleuromutilin derivativeA sensitive and specific method for separation and identification of metabolites of A1 in rats was established by UPLC/Q-TOF MS. Plasma, urine, liver, kidney and faeces samples were collected after A1 was administered to rats by caudal vein administration at a dose of 100 mg/kg, which were isolated and identified using UPLC/Q-TOF MS in negative ion mode after pretreatment. The metabolite structures were identified according to the exact mass and fragments information from UPLC/Q-TOF MS, combining with the metabolic reaction rule. Besides A1, 30 metabolites were identified, among which 2 species were found in the plasma, 23 species in urine, 27 species in liver, 26 species in kidney, 28 species in faeces, respectively. The possible metabolic pathways of A1 in rats were mainly found to be hydroxylation in the mutilin part( the nuclear parent of A1) and oxidization on the sulfur of the side chain. Meanwhile, metabolites formed by hydrolysis of the amido bond were not found, which suggested that A1 exerted its pharmacologic action in the form of hybrid molecule that laid theoretical foundation for the subsequent pharmacokinetic and residual study of this kind of hybrids.