Quantitative structure-antimicrobial activity relationship in 5 beta-cholanyl-24-benzylamine derivatives

Comparative Physicochemical and Biochemical Characterization of Small-Molecule Glucosides

Glycosylation of small molecules can significantly improve their physicochemical and biological properties. Only recently, decisive improvements in the biotechnological production of small-molecule glucosides (SMGs) have resulted in a large number of these compounds now being commercially available. In this study, we have analyzed a number of physical, chemical, and biological parameters of 31 SMGs, including solubility, stability, melting and pyrolysis points, partition coefficient log P, minimum inhibitory concentration against Escherichia coli (MIC), and enzymatic degradability. The properties such as water solubility, pH stability, and MICs of the glycosides were strongly dependent on the structures of the respective aglycones, which is why the SMG clustered according to their aglycones in most cases. Phenolic and furanone glucosides were readily hydrolyzed by saliva and skin microflora, whereas monoterpenol glycosides were poorer substrates for the enzymes involved. The results of this comparative analysis of SMGs provide valuable information for elucidating the biological functions of SMGs and the future technological applications of these useful natural products.

Chemical modifications of bile acids under high-intensity ultrasound or microwave irradiation

High-intensity ultrasound (HIU) and microwave (MW) irradiation, having emerged as effective promoters of organic reactions, were exploited for the synthesis of bile acids derivatives. Esterification, amidation, hydrolysis, oxidation, and reduction were investigated. Compared to conventional methods, both techniques proved much more efficient, increasing product yields and dramatically cutting down reaction times. Scaled-up studies are now under way.

Antimicrobial activities of squalamine mimics

We investigated the antimicrobial properties of compounds with structural features that were designed to mimic those of squalamine, an antibiotic isolated from the stomach of the dogfish shark. The mimics, like squalamine, are sterol-polyamine conjugates. Unlike squalamine, the mimics were simple to prepare, at high yield, from readily available starting materials. Several squalamine mimics showed activity against gram-negative rods, gram-positive cocci including methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecium, and fungi. Some had little or no hemolytic activity. The hydrophobicity of the sterol backbone and the length and the cationic charge of the side chains appeared to be critical determinants of activity. One of the squalamine mimics, SM-7, was bactericidal against Escherichia coli, Pseudomonas aeruginosa, and S. aureus; its activity was decreased by divalent or monovalent cations and by bovine serum albumin. Subinhibitory concentrations of SM-7 markedly enhanced the antimicrobial activity of rifampin against gram-negative rods. These results suggest that the compounds may disrupt an outer membrane of gram-negative rods. Squalamine mimics are a new class of broad-spectrum antimicrobial agents. The antagonism of their activity by serum and albumin and their hemolytic properties may limit their use as systemic agents. The squalamine mimics, because of their potencies, broad spectra of antimicrobial activity, and potential for systemic toxicity, appear to be good candidates for development as topical antimicrobial agents.

Relationship between the hydrophobic and hydrophilic molecular parameters of some monoamine oxidase inhibitory drugs, determined by means of adsorptive and reversed-phase thin-layer chromatography

The absorption capacity, the specific hydrophilic surface area, the lipophilicity and the specific hydrophobic surface area of 17 monoamine oxidase inhibitory drugs were determined by means of adsorptive and reversed-phase thin-layer chromatography for future application of these molecular parameters in quantitative structure-activity relationship studies. Principal component analysis suggests that most of the physicochemical parameters have a different information content, and their application in the elucidation of their mode of action is therefore justified.

Effect of basic cholane derivatives on intestinal cholic acid metabolism: in vitro and in vivo activity

A representative series of hydroxy-5 beta-cholanyl-24-amines were tested both in vitro and in vivo with respect to their activity against the intestinal bacteria responsible for bile acid metabolism. For the in vitro studies, radiolabeled [14C]cholic acid was incubated with human stools both in aerobic and anaerobic conditions in the presence of the title compounds at a dose of 10 micrograms/mL, and the biotransformation of cholic acid into radiolabeled deoxycholic acid and other metabolites was followed by TLC-radiochromatography. Of the compounds studied, 3 alpha, 12 alpha-dihydroxy-5 beta-cholan-24-N-methylamine showed the highest activity. This compound was used for the in vivo studies and was shown to inhibit the formation of endogenous secondary bile acids when chronically administered to rats at a dose of 60 micrograms/day for 15 days. The treated rats showed an increased ratio of taurocholic acid (primary bile acid) to taurodeoxycholic acid (secondary bile acid) in bile, a fact further suggesting a potent antibacterial activity of the compound toward bacteria responsible for bile acid metabolism.

Inhibitors of immune complex-induced inflammation: 5-substituted 3-[1-(2-benzoxazolyl)hydrazino]propanenitrile derivatives

A number of 5-substituted 3-[1-(2-benzoxazolyl)hydrazino]propanenitrile analogues have been studied as inhibitors of the rat pleural reverse passive Arthus reaction, and quantitative structure-activity relationships (QSAR) of these analogues have been examined. The QSAR equations indicate that hydrophilic substituents at the 5-position produce more potent compounds, while electron-releasing groups decrease activity. The results supplement QSAR data we previously obtained from the dermal reverse passive Arthus reaction.