Some biological properties of cephalosporin P1

The Diverse Search for Synthetic, Semisynthetic and Natural Product Antibiotics From the 1940s and Up to 1960 Exemplified by a Small Pharmaceutical Player

The 1940s and 1950s witnessed a diverse search for not just natural product antibiotics but also for synthetic and semisynthetic compounds. This review revisits this epoch, using the research by a Danish pharmaceutical company, LEO Pharma, as an example. LEO adopted a strategy searching for synthetic antibiotics toward specific bacterial pathogens, in particular Mycobacterium tuberculosis, leading to the discovery of a new derivative of a known drug. Work on penicillin during and after WWII lead to the development of associated salts/esters and a search for new natural product antibiotics. This led initially to no new, marketable compounds, but concluded with the serendipitous discovery of fusidic acid, an antibiotic used to treat infections by Staphylococcus aureus, in 1960. The discovery process included contemporary approaches such as open innovation; targeting specific pathogens and/or specific organs in the patient; examining the effects of antimicrobial compounds on bacterial virulence as well as on antibiotic-resistant variants, and searching for antibiotic producers among microorganisms not previously well explored. These activities were promoted by the collaboration with a renowned Danish clinical microbiologist, K. A. Jensen, as well as company expertise in fermentation technologies, chemical synthesis and purification of bioactive compounds from organic materials.

Three new fusidic acid derivatives and their antibacterial activity

Two steroid acids, cephalosporin P1 and isocephalosporin P1, were isolated from Hapsidospora irregularis FERM BP-2511. These compounds are structurally related to fusidic acid. Their NMR data were completely assigned on the basis of the 2D NMR spectra. Incubation of these two compounds with Microbacterium oxydans CGMCC 1788 in Luria-Bertani broth yielded the same set of three new 3-dehydrogenated products, 3-keto-isocephalosporin P1, 3-keto-cephalosporin P1 and 6-deacetyl-3-keto-cephalosporin P1. The final pH of the bacterial culture was 9.0. Incubation of 3-keto-isocephalosporin P1 or 3-keto-cephalosporin P1 in Tris-HCl buffer (pH 9.0) revealed that these two compounds can convert to each other by shifting the acetyl group between C-6 and C-7. The acetyl group at C-6 or C-7 can also be removed by hydrolysis to yield the minor product 6-deacetyl-3-keto-cephalosporin P1. These fusidic acid derivatives were tested for the antibacterial activity against the Gram-positive pathogen Staphylococcus aureus. 3-Keto-cephalosporin P1 showed the highest activity among the five compounds, with a minimal inhibition concentration (MIC) of 4 μg/mL, which is more potent than the substrate cephalosporin P1. Both cephalosporin P1 and 3-keto-cephalosporin P1 were active against methicillin-resistant S. aureus, with the same MIC of 8 μg/mL.

Protostane and fusidane triterpenes: a mini-review

Protostane triterpenes belong to a group of tetracyclic triterpene that exhibit unique structural characteristics. Their natural distribution is primarily limited to the genus Alisma of the Alismataceae family, but they have also been occasionally found in other plant genera such as Lobelia, Garcinia, and Leucas. To date, there are 59 known protostane structures. Many of them have been reported to possess biological properties such as improving lipotropism, hepatoprotection, anti-viral activity against hepatitis B and HIV-I virus, anti-cancer activity, as well as reversal of multidrug resistance in cancer cells. On the other hand, fusidanes are fungal products characterized by 29-nor protostane structures. They possess antibiotic properties against staphylococci, including the methicillin-resistant Staphylococcus aureus (MRSA). Fusidic acid is a representative member which has found clinical applications. This review covers plant sources of the protostanes, their structure elucidation, characteristic structural and spectral properties, as well as biological activities. The fungal sources, structural features, biological activities of fusidanes are also covered in this review. Additionally, the biogenesis of these two types of triterpenes is discussed and a refined pathway is proposed.

Cephalosporins 1945-1986

In 1945, after penicillin had been introduced into medicine, an antibiotic-producing species of Cephalosporium was isolated from a sewage outfall in Sardinia. Four years later in Oxford, this organism was found to produce several antibiotics, one of which was a penicillin with a new side-chain, penicillin N. During a chemical study in 1953, this penicillin was shown to be contaminated with a second substance, cephalosporin C, which contained a beta-lactam ring but was resistant to hydrolysis by a penicillinase (beta-lactamase). At that time, penicillinase-producing Staphylococci were causing a serious problem in hospitals. The isolation of the nucleus of cephalosporin C (7-ACA) enabled pharmaceutical manufacturers to produce many thousands of cephalosporins, some of which have been effective in the treatment of serious infections by a number of Gram-positive and Gram-negative bacteria. The cephalosporins, like the newer penicillins, have a very low toxicity and have greatly extended the range of chemotherapy. New, sensitive screening methods have revealed further families of clinically useful substances that contain a reactive beta-lactam ring. Genetic engineering has now begun to throw light on the nature of the enzymes that are involved in the biosynthesis of penicillins and cephalosporins, and x-ray crystallography may soon provide detailed 3-dimensional pictures of some of the bacterial enzymes with which the active beta-lactam ring reacts. Rational approaches to the production and design of new and potentially useful compounds may then be within sight.

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.

The effect of some antibiotics on coccal infection in mice

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