7-aminocephalosporanic Acid Derivatives Research Articles

Synthesis and Biological Activity Evaluation of Two Derivatives of 7-Aminocephalosporanic Acid

Synthesis and Biological Activity Evaluation of Two Derivatives of 7-Aminocephalosporanic Acid

Toxic Effects of Cephalosporins with Specific Functional Groups as Indicated by Zebrafish Embryo Toxicity Testing

Cephalosporins, derivatives of 7-aminocephalosporanic acid (7-ACA), are potent antibacterial agents. The toxicity prediction of these compounds is of considerable importance in new drug development. Zebrafish embryo toxicity testing was thought to be suitable for evaluation of the toxic properties of cephalosporins. Here, five kinds of cephalosporins and their isomers were used for investigation of the toxic functional groups of cephalosporins and for further evaluation of the efficacy of zebrafish embryo toxicity testing. Computational chemistry methods were also used to study the conformations of the stereoisomers of cephalosporins in aqueous solution to explore the relationship between the stereoisomers and the experimental results of toxicity tests on zebrafish embryos. Our results suggest that both the C-7 and C-3 substituents of cephalosporins are toxic functional groups. The toxic functional groups increase the toxic reaction of 7-ACA and can induce variable abnormal phenotypes in zebrafish embryo toxicity testing. The embryonic toxicities of cephalosporins were involved in organogenesis, mainly in the development of the cranial nerve, cardiovascular system, notochord and abdomen, and pigment formation; those tissues and organs are derived from ectoderm, mesoderm, and endoderm. The theoretical calculations showed a strong negative correlation between topological polar surface area (TPSA) values and the toxic effect, which indicated that molecular polarity may be crucial to the toxic effects of the isomers of cephalosporins. The concept of toxic functional groups may help us understand the safety differences of cephalosporins.

Synthesis and preliminary antimicrobial activities of new arylideneamino-1,3,4-thiadiazole-(thio/dithio)-acetamido cephalosporanic acids.

New derivatives of 7-aminocephalosporanic acid 1–8 were synthesized by acylation of the 7-amino group of the cephem nucleus with various arylidinimino-1,3,4-thiadiazole-thio(or dithio)-acetic acid intermediates 3a–d and 5a–d, respectively, so the acyl side chains of these new cephalosporins contained a sulfide or disulfide bond. This unique combination of a Schiff base with the sulfide or disulfide bonds in the acyl side chain afforded new cephalosporins of reasonable potencies, some of which were found to possess moderate activities against the tested microorganisms. Their chemical structures were characterized by ¹H-NMR, IR spectroscopy and elemental microanalysis. Preliminary in vitro antimicrobial activities of the prepared cephalosporins were investigated using a panel of selected microorganisms. Results indicated that the newly synthesized cephalosporins containing disulfide bonds (compounds 5–8) exhibited better activities against Staphylococcus aureus and Escherichia coli. The cephalosporins cross-linked by a sulfide bond (compounds 1–4) showed a slight change in antimicrobial activities when compared with that of the reference cephalosporin (cephalexin).

Synthesis and antibacterial activity of novel aminothiazolyl beta-lactam derivatives.

The synthesis and in vitro antibacterial profile of a series of (Z)-(2-amino-4-thiazolyl)-[(2,3-dialkoxypropoxy)imino]acetyl derivatives of 7-aminocephalosporanic acid and 3-aminomonobactamic acid are reported.

3-Acylthiomethyl cephalosporins.

A series of new derivatives of 7-aminocephalosporanic acid in which the acetoxymethylfunction at C3 has been replaced with a heteroaromatic carbonylthiomethylmoiety and the 7-amino group has been acylated with D-phenylglycine has beenprepared. Many of these derivatives were well absorbed following oral administrationto mice.

Properties of β-lactamases produced by three species of mycobacteria

1. Mycobacterium smegmatis (N.C.T.C. 8158), M. fortuitum and M. phlei (MPI) produce a constitutive beta-lactamase that has penicillinase and cephalosporinase activity. 2. The beta-lactamases of these three species of acid-fast bacteria were mainly cell-bound, only small amounts of activity being liberated into the extracellular fluid. The total beta-lactamase activity of these mycobacteria was much lower than that of certain Gram-positive organisms, but comparable with that reported for species of Gram-negative bacteria. 3. The beta-lactamases of intact cells of the mycobacteria were not freely accessible to any of the substrates tested, but the apparent crypticity factor to benzylpenicillin was greater than that to cephaloridine and cephalosporin C. 4. Attempts to induce beta-lactamase activity in M. smegmatis and M. phlei failed even with high concentrations of inducer. 5. The beta-lactamases obtained from the three species of mycobacteria showed different substrate specificities, including different relative activities as cephalosporinases and penicillinases respectively. 6. Certain derivatives of 6-aminopenicillanic acid and 7-aminocephalosporanic acid were found to be resistant to hydrolysis by beta-lactamases of M. smegmatis and M. fortuitum. 7. The beta-lactamase of M. smegmatis was competitively inhibited by a number of beta-lactamase-resistant derivatives of 6-aminopenicillanic acid, but not by similar derivatives of 7-aminocephalosporanic acid.

An iodometric assay of some derivatives of 7-aminocephalosporanic acid.

An iodometric assay of some derivatives of 7-aminocephalosporanic acid.

Cephalosporinase and penicillinase activities of a beta-lactamase from Pseudomonas pyocyanea.

1. Pseudomonas pyocyanea N.C.T.C. 8203 produces a beta-lactamase that is inducible by high concentrations of benzylpenicillin or cephalosporin C. Methicillin appeared to be a relatively poor inducer, but this could be attributed in part to its ability to mask the enzyme produced. Much of the enzyme is normally cell-bound. 2. No evidence was obtained that the crude enzyme preparation consisted of more than one beta-lactamase and the preparation appeared to contain no significant amount of benzylpenicillin amidase or of an acetyl esterase. 3. The maximum rate of hydrolysis of cephalosporin C and several other derivatives of 7-aminocephalosporanic acid by the crude enzyme was more than five times that of benzylpenicillin. Methicillin, cloxacillin, 6-aminopenicillanic acid and 7-aminocephalosporanic acid were resistant to hydrolysis, and methicillin and cloxacillin were powerful competitive inhibitors of the action of the enzyme on easily hydrolysable substrates. 4. Cephalosporin C, cephalothin and cephaloridine yielded 2 equiv. of acid/mole on enzymic hydrolysis, and deacetylcephalorsporin C yielded 1 equiv./mole. Evidence was obtained that the opening of the beta-lactam ring of cephalosporin C and cephalothin is accompanied by the spontaneous expulsion of an acetoxy group and that of cephaloridine by the expulsion of pyridine. 5. A marked decrease in the minimum inhibitory concentration of benzylpenicillin and several hydrolysable derivatives of 7-aminocephalosporanic acid was observed when the size of the inoculum was decreased. This suggested that the production of a beta-lactamase contributed to the factors responsible for the very high resistance of Ps. pyocyanea to these substances. It was therefore concluded that the latter might show synergism with the enzyme inhibitors, methicillin and cloxacillin, against this organism.

The interaction of penicillinase with penicillins IV. Structural aspects of catalytic and non-catalytic interactions

The interaction of penicillinase (penicillin amidohydrolase, EC 3.5.2.6) with substrates and with their analogs produces a conformational change in the active site of the enzyme, which is manifested in changed reactivity towards iodine and p-chloromercuribenzoate (p-hydroxymercuribenzoate) and in modified stability to heat, photo-oxidation, -and proteolysis. The analogs studied were (a) derivatives of 6-aminopenicillanic acid, which differ from the substrates in the structure of the side-chain, and (b) derivatives of 7-aminocephalosporanic acid, which differ in the structure of the nucleus.

ANTIBACTERIAL ACTIVITY OF SOME DERIVATIVES OF 7-AMINOCEPHALOSPORANIC ACID AGAINST STAPHYLOCOCCUS AUREUS AND SYNERGISM BETWEEN THESE AND OTHER ANTIBIOTICS.

The N-phenylacetyl derivative of 7-aminocephalosporanic acid (cephaloram) had roughly the same activity as benzylpenicillin against a number of Gram-positive organisms and about one-eighth of the activity of benzylpenicillin against penicillinsensitive strains of Staphylococcus aureus. This derivative and the N-alpha-phenoxypropionyl derivative of 7-aminocephalosporanic acid were 4 to 8 and 4 to 16 times as active as methicillin against penicillinase- and nonpenicillinase-producing staphylococcal strains, respectively. Neither the presence of horse serum nor changes in inoculum size appreciably affected the activities of any of the derivatives of 7-aminocephalosporanic acid which were tested. After forty-eight subcultures in the presence of antibiotic the increase in minimum inhibitory concentration against the staphylococcus was about four-times as great for cephaloram as for cephalosporin C. The resistant penicillinase-producing strains remained stable after six subcultures in antibiotic-free medium, and all the strains retained coagulase activity. Some degree of cross-resistance was found between the derivatives of 7-aminocephalosporanic acid and those of 6-aminopenicillanic acid. Synergism was observed in vitro between certain derivatives of 7-aminocephalosporanic acid and 6-aminopenicillanic acid when they were tested together or with fusidic acid or cephalosporin P(1) against a weak penicillinase-producing strain of Staphylococcus aureus. Cephalosporin C and cephalosporin C (pyridine), each in combination with benzylpenicillin, showed a significant degree of synergism in protection experiments in mice infected with a strong penicillinase-producing strain of Staphylococcus aureus.

PRODUCTION OF A CEPHALOSPORINASE BY PSEUDOMONAS PYOCYANEA.

CRUDE preparations of penicillinase from Bacillus cereus N.R.R.L. 569, unlike the purified penicillinase from this organism or crude penicillinase from Staphylococcus aureus R1, have been shown to catalyse the hydrolysis of the β-lactam ring of cephalosporin C and other derivatives of 7-aminocephalosporanic acid at a significant rate. The enzyme responsible for this hydrolysis was termed a cephalosporinase1,2. The maximum rate of hydrolysis (Vmax) of cephalosporin C obtained with a crude enzyme from B. cereus was only 5 per cent of that of benzyl-penicillin, but this value increased to 33 per cent after selective inactivation of penicillinase in aqueous solution at 60° C. Subsequent studies were made with a crude enzyme from Bacillus subtilis N.C.T.C. 6346, induced with cephalosporin C and freed from the cells by the action of lysozyme3. With this enzyme preparation Vmax for cephalosporin C was about 10 per cent that for benzyl-penicillin, but attempts to separate a cephalosporinase from a penicillinase, or selectively inactivate a penicillinase, were unsuccessful.

Distribution and Substrate Specificity of Benzylpenicillin Acylase1

Benzylpenicillin acylase, which hydrolyzes benzylpenicillin to 6-aminopenicillanic acid, was found to be widely distributed among members of the Schizomycetes, particularly in gram-negative bacteria, and in the genus Nocardia. The hydrolysis of a series of biosynthetic and semisynthetic penicillins by freeze-dried cells of a strain of Nocardia and of Proteus was studied. Benzylpenicillin was the preferred substrate; all departures from the benzylpenicillin side-chain structure led to reduction of substrate activity (the greater the departure, the greater the reduction in activity). Penicillin amides and methyl esters were also hydrolyzed, as were suitable N-acyl derivatives of 7-aminocephalosporanic acid. Occurrence of an enzyme activity which hydrolyzes benzylpenicillinamide to benzylpenicillin was detected in certain strains of yeasts.

Distribution and Substrate Specificity of Benzylpenicillin Acylase

Benzylpenicillin acylase, which hydrolyzes benzylpenicillin to 6-aminopenicillanic acid, was found to be widely distributed among members of the Schizomycetes , particularly in gram-negative bacteria, and in the genus Nocardia . The hydrolysis of a series of biosynthetic and semisynthetic penicillins by freeze-dried cells of a strain of Nocardia and of Proteus was studied. Benzylpenicillin was the preferred substrate; all departures from the benzylpenicillin side-chain structure led to reduction of substrate activity (the greater the departure, the greater the reduction in activity). Penicillin amides and methyl esters were also hydrolyzed, as were suitable N -acyl derivatives of 7-aminocephalosporanic acid. Occurrence of an enzyme activity which hydrolyzes benzylpenicillinamide to benzylpenicillin was detected in certain strains of yeasts.

Behaviour of some derivatives of 7-aminocephalosporanic acid and 6-aminopenicillanic acidas substrates, inhibitors and inducers of penicillinases.

Behaviour of some derivatives of 7-aminocephalosporanic acid and 6-aminopenicillanic acidas substrates, inhibitors and inducers of penicillinases.