Cephalexin

These three compounds only show reversible inhibition and do not permanently inactivate the enzyme. This implies that the enzyme can be reused for next batches when exposed to either of these three compounds. This is an important observation as the enzyme accounts for a substantial part of the total cost of enzymatically prepared cephalosporins. It should be noted that compounds 1 and 3 are also effective in the complexation with Cephalexin and accordingly also suitable for the clathration mediated enzymatic synthesis of this antibiotic. In Table 3 the residual activity of Assemblase when exposed to either of the three complexing agents as a percentage of the enzyme activity in the absence of complexing agent is listed. These residual activities are similar to those measured after exposure toβ-naphthol, a naphthalene derivative that has a significant beneficial effect on the yield of the enzymatic synthesis of Cephalexin.12 Although a lower enzyme activity on itself is not desirable, it has the advantageous effect that it diminishes the diffusion limitations of Assemblase. This effect was observed for the enzymatic synthesis of Cephalexin using in situ clathration with β-naphthol and has been described in a quantitative manner using models developed for Assemblase and free Penicillin G acylase.

This approach combines in an iterative fashion of ligand docking techniques with those for modeling receptor conformational changes. Results of IFD are illustrated in Table 1 (best 5 compounds), which clearly show that all the screened compounds have more affinity for SrtA. Most commonly, the amino acid residues of SER1, LEU2, GLU4, GLY5, CYS136, LYS141 and ARG145 are involved in interaction with hit compounds. The best five compounds namely amoxicillin, cefixime, esomeprazole, cephalexin, and losartan show better scoring and interactions. Of all these compounds, Losartan shows comparatively low energetics towards SrtA. Esomeprazole and losartan show three hydrogen bond interactions and other three compounds show very good interactions with the SrtA binding site amino acids. The distance between the protein ligand interactions was found to be satisfactory with a standard level distance of 1.6–2.4 Å (Table 2). Amoxicillin, cefixime and cephalexin compounds have more than five hydrogen bonds for interaction and the IFD score was found to be -331.10, -330.94 and -328.72, respectively. The esomeprazole and losartan ligands showed only three H-bonds that interact with the receptor and the IFD score was -330.05 and -327.54, respectively.

In a second approach, the same group purified the PVD produced by P. aeruginosa ATCC 15692, for the preparation of conjugates with cephalexin, another beta-lactam antibiotic. For this purpose, the arginine side chain of the chromopeptide was crosslinked with N-4,6-dioxoheptanoyl-cephalexin under buffered conditions. The resulting pyrimidine linker was described as stable in biological medium. The PVD–cephalexin conjugate 12 (PDPyrCeph) (Fig. 6) was tested against bacteria and was found to have no activity against P. aeruginosa ATCC 15692.

Cephalexin is a lactam antibiotic which is widely used to treat infections of the urinary tract, the upper respiratory tract, the skin, the middle ear and other common bacterial infections. Despite its efficiency, excessive use of cephalexin is extremely harmful to the human body, for example, it is well known that excessive use of cephalexin will cause acute renal failure in humans and experimental animals. Therefore, developing effective analytical methods for the sensitive and selective detection of trace amounts of cephalexin is especially important. Compared with many other methods, like high-performance liquid chromatography (HPLC), liquid chromatography (LC), flow injection analysis, electrochemical methods, fluorescence assays have several advantages, such as high sensitivity and fast analysis. However, to the best of our knowledge, the use of fluorescence probe for analysis of cephalexin is very rare. Lately, Li et al. proposed a fluorescence probe based on the fluorescence quenching of L-Cysteine capped core–shell CdTe/ZnS nanoparticles to detect cephalexin. The above photoluminescence material suffer from complex synthesis route and expensive regents. Accordingly, the development of a simple, economical, and green preparative strategy toward photoluminescence materials is meaningful.