Biomedical subjects
Publications and source records attributed to L Heinisch.
A series of 2,3-dihydroindole-2-thiones was evaluated for in vitro antimycobacterial activity against Mycobacterium tuberculosis, M. kansasii, M. fortuitum, two strains of M. intracellulare and three strains of M. avium. 2,3-Dihydro-1-methyl-2-thioxoindole-3-one and 2,3-dihydro-1-butyl-2-thioxoindole-3-one were the most active substances against potentially pathogenic strains, being more active than isoniazide.
In connection with a systematic study of antimycobacterial agents against potentially pathogenic strains the series of 12 S-alkylisothiosemicarbazones was evaluated for in vitro antimycobacterial activity against Mycobacterium tuberculosis, M. kansasii, M. fortuitum, two strains of M. intracellulare and three strains of M. avium. Quinoline-4-carbaldehyde-S-hexyl-isothiohydrazone was found to be more active against potentially pathogenic strains than isoniazide.
Linking of siderophores to antibiotics improves the penetration and therefore increases the antibacterial activity of the antibiotics. We synthesized the acylated catecholates and hydroxamates as siderophore components for antibiotic conjugates to reduce side effects of unprotected catecholate and hydroxamate moieties. In this paper, we report on bis- and tris-catecholates and mixed catecholate hydroxamates based on diamino acids or dipeptides. These compounds were active as siderophores in a growth promotion assay under iron limitation. Most of the conjugates with beta-lactams showed high in vitro activity against Gram-negative bacteria especially Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Serratia marcescens and Stenotrophomonas maltophilia. The compounds with enhanced antibacterial activity use active iron uptake routes to penetrate the bacterial outer membrane barrier, demonstrated by assays with mutants deficient in components of the iron transport system. Correlation between chemical structure and biological activity was studied.
The synthesis of two saccharide-based enterobactin analogues, methyl 2,3,4-tris-O[-N[2,3-di(hydroxy)benzoyl-glycyl]-aminopropyl]-alpha-D-glucopyranoside (H(6)L(A)) and methyl 2,3,4-tris-O-[N-[2,3-di(hydroxy)benzoyl]-aminopropyl]-alpha-D-glucopyranoside (H(6)L(B)), are reported along with their pK(a) values, Fe(III) binding constants, and aqueous solution speciation as determined by spectrophotometric and potentiometric titration techniques. Use of a saccharide platform to synthesize a hexadentate triscatechol chelator provides some advantages over other approaches to enterobactin models, including significant water solubility, resistance to hydrolysis, and backbone chirality which may provide favorable recognition and availability to cells. The protonation constants for the catechol ligand hydroxyl moieties were determined for both ligands and found to be significantly different, which is attributed to the differences in the spacer chain of the two triscatechols. Proton dependent Fe(III)-ligand equilibrium constants were determined using a model involving the sequential protonation of the Fe(III)-ligand complex. These results were used to calculate the formation constants, log beta(110) = 41.38 for Fe(III)-H(6)L(A) and log beta(110) = 46.38 for Fe(III)-H(6)L(B). The calculated pM values of 28.6 for H(6)L(A) and 28.3 for H(6)L(B) indicate that these ligands possess Fe(III) affinities comparable to or greater than other enterobactin models and are thermodynamically capable of removing Fe(III) from transferrin.
New artificial catecholate siderophores with methyl alpha-D-glucopyranoside as scaffold were synthesized. The dihydroxy- or di(acetoxy)benzoyl moieties were attached either directly or via aminopropyl spacer groups, to the carbohydrate scaffold. The siderophore activity of the prepared siderophore analogs was examined by a growth promotion assay using various Gram-negative bacteria and mycobacteria and by the CAS-assay.
New analogs of bacterial siderophores with one, two or three catecholate moieties were synthesized using various mono- and diamino acid and dipetide scaffolds, respectively. In addition to 2,3-dihydroxybenzoyl siderophore analogs and their acylated derivatives, 3,4-dihydroxybenzoyl derivatives were prepared. Furthermore, the synthesis of a new triscatecholate serving as an intimate model for enterobactin is reported. Most of the new compounds gave a positive CAS-test and were active as siderophores tested by growth promotion assays with a set of siderophore indicator mutants under iron limitation. Structure-activity-correlations have also been studied.
8-Acyloxy-1,3-benzoxazine-2,4-diones as masked catechol derivatives represent a novel type of siderophore components, whose growth promoting activity is low or not existing if tested alone. But after conjugation with beta-lactam antibiotics the resulting conjugates show a significantly increased antibacterial activity against Gram-negative bacteria compared with their parent antibiotics. Investigations using a set of penetration and iron transport mutants demonstrated that the conjugates use iron transport systems to penetrate the bacterial outer membrane. Title compounds were synthesized from (2,3-dimethoxycarbonyloxy)-benzoic acid and different amino compounds. Conjugates with penicillins and cephalosporins were prepared.
Madurahydroxylactone is a secondary metabolite from Nonomuria rubra (former Actinomadura rubra) with in vitro activity against gram-positive bacteria and belongs to the family of benzo[a]naphthacenequinones. A series of derivatives of madurahydroxylactone were synthesized to investigate the effect on the antibacterial activity. Reaction with alcohols and amines gave cyclic acetals or aminals derived from the lactone form, whereas other amino reagents like hydroxylamines and acyl or sulfonyl hydrazides led to the corresponding imine derivatives of the aldehyde. Hydrazine, alkyl and aryl hydrazines react with madurahydroxylactone under cyclization to give compounds of the new heterocyclic basic structure naphthaceno[1,2-g]phthalazine. Some new compounds strongly inhibit gram-positive bacteria, in part stronger than the parent compound.
A novel 1,3,5-triamino-myo-inositol derivative is presented as a readily available scaffold for the design of tripodal siderophore mimetics. Based on this scaffold, various hexadentate catecholate-type siderophore analogs were synthesized by attaching the catechols to the inositol scaffold via spacer units of different structure and length. The potential to tune the polarity of the inositol containing siderophore analogs has also been demonstrated by varying the protection group strategy. The siderophore activity of the prepared siderophore analogs was examined by cross-feeding tests with various Gram-negative bacteria and mycobacteria.
New ureido, oxamoyl, fumaramoyl and terephthalamoyl derivatives of ampicillin or amoxicillin were synthesized by reaction of acylpenicillines with o-dihydroxy- or o-diacyloxy substituents containing aromatic amines bound over CO- or dicarboxylic groups. Corresponding compounds derived from 3,4-diacetoxyaniline showed significant increase of activity against pseudomonas and salmonella in contrast to derivatives without catechol substituents. No increase of activity was observed by corresponding derivatives of bi- and tricyclic amines. Derivatives with oxamoyl, fumaramoyl or terephthalamoyl groups were found to be more active than the corresponding ureido derivatives. Studies with mutants possessing higher membrane permeability have shown that the high activities of catechol containing derivatives are connected with the improved penetration through the outer membrane. Some new penicillin derivatives are more stable against beta-lactamases compared with azlocillin.
New ampicillin derivatives were synthesized from glyoxylic acid benzhydrazones by reaction with chloroformates via mixed anhydrides and ampicillin. These compounds were tested in an agar diffusion test against six different bacterial strains and also for their stability against beta-lactamases. Studies about structure-activity relationships have shown, that the activity against different bacterial strains is influenced in different manner by hydrophilic or hydrophobic and electronic properties of substituents.
The toxicity and the bioavailability of new ampicillin derivatives with glyoxylic acid benzhydrazones as site chain depend on the hydrophobic properties of the site chain. Substituents with lower hydrophobicity (expressed by the hydrophobic substituent constant pi according to Hansch) show a lower toxicity (maximal tolerated doses) and also a lower bioavailability.
Synthesis and Antibacterial Activity of Benzoylaminoacyl Penicillins and Related Compounds with and without Acylated Catechol Substituents. Syntheses of benzoyl, cinnamoyl, and benzoylhydrazido glyoxyloyl aminoacyl penicillins with and without acylated catechol substituents by condensation of corresponding acids or acylchlorides with ampicillin or amoxycillin and also of a 6-a-methoxy-derivative and corresponding esters are reported. Acylated catechol substituents improve the antibacterial activity against Gram-negative bacteria, especially against Pseudomonas strains and Salmonella. MIC tests of bacterial mutants with higher outer membrane penetrability and of the corresponding wild typs show that the increase of antibacterial activity by catechol substituents is caused by improvement of the penetration through the bacterial outer membran. The affinity to penicillin binding proteins is not influenced by catechol substituents. Stability against beta-lactamases is partly higher than that of azlocillin.
The complexation of some thiosemicarbazones and isothiosemicarbazones of isatin and quinolin-2-aldehydes with Cu2+, Zn2+ and Mn2+ ions was spectrometrically investigated. Semiquantitative data, obtained from extinction values, about the relative complexing tendencies within some groups of homologous substances were brought in relation to their antiviral effects and binding to bovine serum albumin. The complexing tendencies were greatest in compounds with methyl substituents and decreased for higher alkyl substituents. whereas the binding to protein increased in the same order. The well-known maxima of the antiviral observed with medium alkyl groups may be explained by a superposition of these effects.
The synthesis of copper(III)-complexes from quinoline-2- or quinoxaline-2-aldehyde-isothiosemicarbazones in pyridine and the elucidation of their structure are described. Some of the new substances exhibit an inhibitory action on growth of gram-positive bacteria, especially Bacillus subtilis (ATCC 6633), furthermore in vitro the beta-lactamase I action is inhibited. Using penicillin-resistant Staphylococci as test strains a strong penicillin-synergistic action was discovered.
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