The Mechanisms of Alpha-Amylase Inhibition by Flavan-3-Ols and the Possible Impacts of Drinking Green Tea on Starch Digestion.

Many studies have shown that flavan-3-ols inhibit mammalian alpha-amylases but the published IC and K values vary up to a thousand times. We therefore tested the effects of 6 pure flavan-3-ols-abundant in green tea-on the activity of pure porcine pancreatic alpha-amylase (PPA) under steady-state kinetic conditions. We used both amylose and maltopentaose as substrates, along with spectrophotometry and chromatography as analytical tools, respectively.

The rutin catabolic pathway with special emphasis on quercetinase.

The aim of this review is to give a general account on the oxidative microbial degradation of flavonols. Since now 50 years, various research groups have deciphered the way microorganisms aerobically deal with this important class of flavonoids. Flavonols such as rutin and quercetin are abundantly found in vegetal tissues and exudates, and it was thus patent that various microorganisms will bear the enzymatic machinery necessary to cope with these vegetal secondary metabolites.

Alkylaminoquinolines inhibit the bacterial antibiotic efflux pump in multidrug-resistant clinical isolates.

Over the last decade, MDR (multidrug resistance) has increased worldwide in microbial pathogens by efflux mechanisms, leading to treatment failures in human infections. Several Gram-negative bacteria efflux pumps have been described. These proteinaceous channels are capable of expelling structurally different drugs across the envelope and conferring antibiotic resistance in various bacterial pathogens.

Benzo[b]-1,8-naphthyridine derivatives: synthesis and reversal activity on multidrug resistance.

A series of benzo[b]-1,8-naphthyridine derivatives branched with various side-chains and substituents were prepared with the aim of being investigated as multidrug resistance (MDR) modulators. The syntheses were achieved from 2-halonicotinic acid and suitable aryl-amines according to a three-step procedure. All the derivatives were tested in vitro on mouse T-Lymphoma cell line L5178 transfected by MDR1 gene and the chemosensitizing properties of the compounds were compared to those of verapamil and propranolol, as well as to several other tricyclic derivatives like phenothiazines and acridines.

Computer simulation of spermine-porin channel interactions.

Porin channels play a prominent role during fluoroquinolone uptake and spermine strongly alters the diffusion rate of norfloxacine. Consequently the interactions between spermine and bacterial porin were studied by computer simulation. The results indicate that various residues (E62, D 113, E 117,.

Membrane permeation by multidrug-resistance-modulators and non-modulators: effects of hydrophobicity and electric charge.

This study was designed to test the hypothesis that lipophilic cationic drugs with only roughly similar structures mediate the reversal of multidrug-resistance (MDR) by interacting with membrane phospholipids. The permeation properties of MDR-modulators and non-modulators were studied by quantifying their ability to induce the leakage of Sulphan blue through the membrane of negatively charged unilamellar liposomes. Of the 22 compounds under investigation, only those bearing a net positive electric charge per molecule (z) > or = 0.

Inhibition of cryptosporidium parvum in vitro by 9-(alkylthio)acridine derivatives.

The synthesis of several acridinic thioethers is described. Compounds prepared were tested in vitro as potential drugs against the opportunistic infection known as cryptosporidiosis. With a view to predict activity, the quantitative structure-activity relationships were investigated.

Effect of new thioacridine derivatives on P-gp function and on mdr1 gene expression.

We studied the effect of thioacridine derivatives on the function of P-glycoprotein in MDR mouse T-lymphoma cell line L5178 and in MDR human leukemia cell line K562/ADR by rhodamine 123 uptake assay. The effect of some selected thioacridines was also investigated on the expression of the mdr1 gene. Expression was analysed by RT-PCR.

Antimicrobial activity of 9-oxo and 9-thio acridines: correlation with interacalation into DNA and effects on macromolecular biosynthesis.

The antimicrobial activity of several new 9-acridinones and 9-thioalkylacridines towards Escherichia coli, Staphylococcus aureus, Mycobacterium smegmatis and Candida albicans was investigated. Minimal inhibitory, bactericidal and fungicidal concentrations were determined using a microplate assay which enabled inhibitory, bactericidal and fungicidal indices to be calculated. These indices facilitated structure/activity relationship studies.