The structures of the antibiotics, active against a few Gram-negative bacteria and Clostridium difficile, were determined on the basis of physicochemical analyses on the intact molecules and on the acid hydrolysate of A21459 A. FAB-MS and 1H and 13C NMR investigations identified the amino acid units and determined their sequence. Antibiotics A21459 A and B are homodetic cyclic peptides constituted by eight amino acid units. They are glycine, methoxytryptophan, tryptophan, cysteine, alanine, sarcosine, dehydroalanine, and alpha-aminobutyric acid for A21459 A (alanine for A21459 B). Cysteine and alanine condensed to form a thiazole moiety, according to the biosynthesis of thiazole containing antibiotics.

Components of GE2270 Complex, an antibiotic active against Gram-positive bacteria and anaerobes, were identified by continuous-flow fast-atom bombardment mass spectrometry and by combined liquid chematography and mass spectrometry under electrospray and thermospray ionization conditions. Electrospray ionization seems to be the most suitable technique for the routine analysis of crude extracts of antibiotics from fermentation broths.

A new teicoplanin-like antibiotic was discovered when using Actinoplanes teichomyceticus strain 3/W, the fermentation medium containing Alburex, and the fermentation time 275 hours. The new product was separated from teicoplanin complex by polyamide resin chromatography and purified by Amberlite XAD-7 and affinity resin chromatographies. The structure was established on the basis of the physico-chemical characteristics of the complex and of its aglycone. The new structure is that of teicoplanin with a carbonyl group substituting for the CHNH2 group of amino acid 1. We hypothesize that the novel complex is a transformation product of teicoplanin due to a simple transamination reaction, as supported by its structure and by the concomitant decrease in teicoplanin concentration during its production.

GE37468 A is a novel antibiotic produced by Streptomyces sp. ATCC 55365. It has molecular mass 1309.48 and formula C59H52O12N14S5 and belongs to the thiazolyl peptide group of antibiotics. The structure was elucidated by 1H and 13C NMR and MS studies on intact molecule and its hydrolysis products. The antibiotic is a highly modified peptide containing a macrocycle and a side chain composed of a thiazole ring and two dehydroalanine units.

The two enantiomers of cispentacin, an antifungal antibiotic, are determined by reversed phase HPLC, after derivatization with Marfey's reagent, in 24 h urine samples collected from rats treated sc and iv with 20 mg/kg cispentacin racemate obtained by synthesis. The application range of the method is 25-250 mg/L for each enantiomer with a precision of 4.0-9.0%. Comparison with an authentic sample of natural origin (-)-cispentacin indicated that (-) enantiomer is excreted unchanged in smaller percentage than (+) enantiomer, which is almost completely eliminated as such.

Elfamycin antibiotics have been studied by mass spectrometry, using direct-liquid-introduction chemical ionization and fast-atom bombardment (FAB), but these techniques are not suitable for the identification of the interaction product between antibiotic and elongation factor-Tu (EF-Tu). A new mass spectrometric technique, matrix-assisted laser desorption (MALD), has been employed to clearly identify the complex formed between EF-Tu and kirromycin. Using MALD operated in the positive-ion mode, molecular weight values of 43 330 and 44 234 Da were obtained for EF-Tu and the adduct EF-Tu/kirromycin, respectively; both are close to the theoretically calculated values of 43 225 and 44 060. These measurements suggest that MALD techniques can be used to obtain useful information on EF-Tu/elfamicyn antibiotic interaction. Other techniques, such as desorption chemical ionization, FAB and thermospray have been used to obtain information on the fragmentation patterns of some elfamycins (kirromycin, aurodox, efrotomycin). In particular, the positive-ion FAB spectrum of efrotomycin obtained by using a matrix of glycerol and water containing K+ ions, contained the quasimolecular ion [M + K]+ at m/z 1184. Thermospray appeared to be the best technique for structural elucidation studies. In fact, positive-ion spectra of kirromycin, aurodix and efrotomycin are characterized by significant fragmentation ions, while molecular ions are of very low intensity.

Teicoplanin, a lipoglycopeptide antibiotic, consists of five major components (A2-1 through A2-5), one hydrolysis component (A3-1), and four minor components (RS-1 through RS-4). All the major components contain an N-acyl-beta-D-glucosamine, but they differ in the lengths and branchings of their acyl-aliphatic chains. Previous studies with radiolabeled teicoplanin in rats and humans have shown that the drug is eliminated by the renal route and that metabolic transformation is very minor, about 5%. A possible metabolic transformation of teicoplanin into A3-1 was also suggested. In the present study in humans, two metabolites (metabolites 1 and 2; 2 to 3% of total teicoplanin) were isolated after intravenous administration of radiolabeled teicoplanin. After purification, their structures were determined by fast atom bombardment mass spectroscopy and 1H nuclear magnetic resonance spectroscopy on the basis of the well-known correlations established in this field, and they were found to be new teicoplaninlike molecules, bearing 8-hydroxydecanoic and 9-hydroxydecanoic acyl moieties. This metabolic transformation is likely due to hydroxylation in the omega-2 and omega-1 positions for metabolites 1 and 2, respectively, of the C-10 linear side chain of component A2-3. This might explain the low extent of metabolism of teicoplanin if we consider that only component A2-3 has a linear chain that is susceptible to such oxidation.

The direct coupling systems operating under vacuum and the systems in which the thermobalance works under atmospheric pressure are described in detail. In addition, the characteristics of the most widely used mass spectrometers and computer facilities are also discussed.To illustrate the potential and limitations of this coupling, some typical cases of qualitative and quantitative applications are considered. These examples demonstrate that the coupling is used extensively for the identification of thermal degradation products, to determine their sequence of release and to resolve thermogravimetric curves. The technique is used only to a limited extent for quantitative analysis and kinetic studies.

Structures of the fatty acid residues characterizing the various components of A40926 were determined by gas chromatography/mass spectrometry on the methyl esters obtained by methanolysis of the complex. The results confirm the residues previously assigned to Factor A (n-undecanoic acid) and B (10-methyl-undecanoic acid) and establish the residues of Factor A1 (9-methyl-decanoic acid), B1 (n-dodecanoic acid), RS1 (8-methyl-nonanoic acid), RS2 (n-decanoic acid), and RS3 (n-tridecanoic acid). As the Actinomadura species contain in their mycelia large quantities of C15-C17 fatty acid residues as membrane phospholipids, these mycelia were saponified and the fatty acids obtained were analyzed as above. There is a close correlation between the fatty acid content of A40926 complex and that of the longer homologues in the producer mycelia.

Direct liquid introduction negative ion mass spectra have been studied for some kirromycin class antibiotics. A scheme for the interpretation of the mass spectral fragmentation patterns is presented and shown to be useful for structure elucidation and novelty determination. Since these spectra are obtained by liquid chromatography/mass spectrometry, antibiotic isolates need not be highly purified. However, where pure preparations are available confirmation of molecular weight assignments may be obtained with fast atom bombardment ionization.

GE2270A is a novel antibiotic active against Gram-positive bacteria and anaerobes. Its structure originates from a peptidic backbone, the amino acids of which have been modified to produce a macrocycle and a side-chain. It contains a heterocyclic chromophoric system, a number of thiazoleamino acids and three unmodified natural amino acids. The structure [relative molecular mass (RMM) 1289] was determined using various spectroscopic techniques, of which fast atom bombardment mass spectrometry, gas chromatography/mass spectrometry, desorption chemical ionization mass spectrometry and fast atom bombardment tandem mass spectrometry played an important role. The mass spectrometric approach was applied to the intact molecule and to the various hydrolysis products, including the chromophoric part (RMM 634).

A specific and sensitive assay is described. Zetidoline is extracted with ethyl ether from 1 ml of plasma or saliva added with the internal standard. The extract is carefully purified and injected into a gas chromatography-mass spectrometry system equipped with a crosslinked capillary column and operated in single ion monitoring mode by electron impact. Quantitative response is linear in the range 2-50 ng/ml. The detection limit is 1 ng/ml.

Teicoplanin, a glycopeptide antibiotic produced by Actinoplanes teichomyceticus, comprises five main components, denoted T-A2-1 to T-A2-5, differing in the structure of their acyl side chain, which is linear in T-A2-1 and T-A2-3 and branched in the other components. Production of T-A2-1, characterized by a linear C10:1 acyl moiety, is entirely dependent on the presence of linoleate in the fermentation medium. Addition to the medium of oleic acid esters at 2 g l-1 increases the yields of T-A2-3, characterized by a linear C10:0 acyl chain, about threefold. The antibiotic linear side chains thus appear to originate from C18 unsaturated acid by beta-oxidation degradation. The percentage of T-A2-2, T-A2-4 and T-A2-5, bearing the iso-C10:0, anteiso-C11:0 and iso-C11:0 acyl moieties, respectively, is strongly influenced by the presence in the medium of the amino acids known to be precursors of branched-chain fatty acids. Thus, valine increases the production of T-A2-2 whereas isoleucine or leucine increase the relative yields of T-A2-4 or T-A2-5, respectively. Analysis of the total cell lipids upon addition of the same amino acid shows corresponding increases in the proportion of the iso-C16:0, iso-C15:0 or anteiso-C17:0. A mutant A. teichomyceticus strain, which produces a novel teicoplanin with a linear C9:0 chain, differs from the wild strain in the presence of the linear C17:1 acid in its lipids.(ABSTRACT TRUNCATED AT 250 WORDS)

Addition of a hydroxy-containing matrix to an aldehyde was observed in fast-atom bombardment (FAB). This FAB-induced interference reaction, observed in the case of a microbial alkaline protease inhibitor, shows a characteristic time behaviour. This can be explained by a fast-order reaction kinetics scheme which leads to equilibrium, for which rate and equilibrium constants were also determined. These data suggest that in situ reaction kinetics can be studied by FAB mass spectrometry.

Examples of various chemical reactions occurring in the matrix or in the selvedge region in fast atom bombardment (FAB) mass spectrometry are discussed. These are categorized as oxidations and reductions; substitutions; clusterings and additions; and sample decomposition or transformation. Some reactions observed showed significant time behaviour and in one case it was possible to determine rate constants. These data suggest that chemical reactions can be accelerated significantly by fast atom bombardment.

The single components of the teicoplanin complex, glycopeptide antibiotics active against Gram-positive bacteria, can be converted in the corresponding de-mannosyl derivatives by cultures of Nocardia orientalis NRRL 2450 or Streptomyces candidus NRRL 3218. Conversely, teicoplanin aglycone and other teicoplanin de-mannosyl derivatives can be converted in the corresponding teicoplanin mannosyl derivatives by cultures of Actinoplanes teichomyceticus ATCC 31121. The biological transformation yields are approximately 40% for de-mannosylation and 90% for mannosylation. The processes allow for the preparation of gram quantities of the de-mannosyl derivatives of teicoplanin and of teicoplanin mannosyl derivatives. De-mannosyl teicoplanin and teicoplanin mannosyl-pseudoaglycone were not amenable to preparation by either acidic or basic chemical hydrolysis.

AbstractResults of 16 different mass spectrometric ionization and sample‐introduction methods are compared for the case of a thermally very labile antibiotic, rifapentine. These suggest that extensive thermal decomposition occurs during evaporation when the sample can come into contact with hot metal parts, usually the source housing. The intensity of the molecular ion and the extent of fragmentation depend on various parameters, such as the ionization process, positive or negative‐ion detection and the type of sample introduction. The most informative methods for rifapentine seem to be ‘in‐beam’ electron impact, negative ionization with particle beam and direct liquid introduction interfaces and positive‐ and negative‐ion fast atom bombardment.

A42867 is a new glycopeptide antibiotic of the ristocetin-vancomycin class active against aerobic and anaerobic Gram-positive bacteria. A42867 is produced by a strain of Nocardia nov. sp. ATCC 53492. A42867 was isolated during a screening program aimed at the discovery of new members of this glycopeptide class of antibiotics, by affinity chromatography based on an acyl-D-alanyl-D-alanine probe. The structure of A42867 was elucidated by fast atom bombardment MS, high field 2D 1H NMR spectroscopy, and HPLC analysis of the hydrolyzed carbohydrates. A42867 differs from vancomycin in the sugar portion and in the presence of only one chlorine atom in the peptide core. Its biological activity on Gram-positive aerobic and anaerobic bacteria is similar to that of other antibiotics of this group.