ABSTRACT
Amphiphilic lysine-ligated neomycin B building blocks were prepared by reductive amination of a protected C5â³-modified neomycin B-based aldehyde and side chain-unprotected lysine or lysine-containing peptides. It was demonstrated that a suitably protected lysine-ligated neomycin B conjugate (NeoK) serves as a building block for peptide synthesis, enabling incorporation of aminoglycoside binding sites into peptides. Antibacterial testing of three amphiphilic lysine-ligated neomycin B conjugates against a representative panel of Gram-positive and Gram-negative strains demonstrates that C5â³-modified neomycin-lysine conjugate retains antibacterial activity. However, in most cases the lysine-ligated neomycin B analogs display reduced potency against Gram-positive strains when compared to unmodified neomycin B or unligated peptide. An exception is MRSA where an eightfold enhancement was observed. When compared to unmodified neomycin B, the prepared lysine-neomycin conjugates exhibited a 4-8-fold enhanced Gram-negative activity against Pseudomonas aeruginosa and up to 12-fold enhanced activity was observed when compared to unligated reference peptides.
Subject(s)
Aminoglycosides/chemistry , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/pharmacology , Framycetin/blood , Lysine/chemistry , Peptides/chemical synthesis , Anti-Bacterial Agents/chemistry , Framycetin/analogs & derivatives , Magnetic Resonance Spectroscopy , Microbial Sensitivity Tests , Molecular Structure , Peptides/chemistry , Peptides/pharmacology , Pseudomonas aeruginosa/drug effectsABSTRACT
An improved liquid chromatographic (LC) method was developed for the determination of neomycin B in bovine kidney tissue. The tissue is homogenized twice in phosphate buffer; homogenate is centrifuged, and the supernatant is deproteinated by heat. The extract is acidified and mixed with ion-pair concentrate, and neomycin B is determined by an LC system consisting of an ion-pairing mobile phase, a reversed-phase ODS column, postcolumn derivatization with o-phthalaldehyde reagent, and fluorometric detection. Average recoveries of neomycin B from kidney tissues spiked at 3, 6, and 12 ppm were 103, 99, and 104%, with 9.7, 7.9, and 3.7% intralaboratory coefficients of variation, respectively, using a standard curve prepared in buffer. The method was used to determine neomycin B in kidney tissue obtained from a calf killed 14 days after intramuscular dosing with neomycin (5 mg/lb). The tissue was found to contain about 3 ppm neomycin B. The LC conditions were also used to assay control samples of muscle, liver, milk, plasma, and urine. No interfering peaks were noted at the elution position of neomycin B.
