Anti-methicillin-resistant Staphylococcus aureus assay of azalomycin F_5a and its derivatives

AIM:To discover anti-methicillin-resistant Staphylococcus aureus(anti-MRSA) microbial natural products or their derivatives.METHOD:Azalomycin F5a(1) was prepared through fermentation of Streptomyces hygroscopicus var.azalomyceticus,and its derivatives were synthesized through hydrocarbylation in hydrocarbyl alcoholic-AcOH(4:1) and subsequent demalonylation with 2 molL-1 KOH in MeOH-H2O(7:3).Their activities against MRSA ATCC 33592 and three clinical MRSA isolates were evaluated by the agar diffusion and broth microdilution methods.RESULTS:Four demalonylazalomycin F5a derivatives 2 to 5 were synthesized.The anti-MRSA activity assay indicated that compounds 1 to 5 showed remarkable activity against MRSA,and their minimum inhibitory concentrations(MICs) were respectively 3.0-4.0,0.5-1.0,0.67-1.0,0.67-0.83,and 0.5-0.83 gmL-1.CONCLUSION:Azalomycin F5a and the demalonylazalomycin F5a derivatives 2-5 showed remarkable anti-MRSA activity,and the anti-MRSA activities of 2 to 5 were higher than that of 1,while the anti-MRSA activities of 2 to 5 showed no obvious differences.It was also shown that the malonyl monoester group of azalomycin F5a was less important for its anti-MRSA activity.