Susceptibility of Staphylococcus aureus strains toward combinations of oxacillin-2,4-dihydroxychalcone.

In order to determine the existence of synergism of the bacteriostatic action of flavonoids against G(+) bacteria between a clinically interesting conventional antibiotic and a flavonoid, combinations of oxacillin (OXC) and 2,4-dihydroxychalcone (DCH) as enhancer were assayed against methicillin-sensitive Staphylococcus aureus ATCC 29 213 and methicillin-resistant S. aureus ATCC 43 300. Using a kinetic-turbidimetric method, growth kinetics was monitored in a broth containing variable amounts of OXC alone and combinations of variable OXC-constant DCH. The minimum inhibitory concentrations (MIC) of OXC alone and in combination with DCH were evaluated. For the 29 213 strain, OXC MIC was 25 microg/mL, while combinations of 2-8 microg/mL OXC with 10 microg/mL of DCH totally inhibited growth and showed synergism. The resistance of the 43 300 strain in the presence of OXC was verified; OXC-DCH combinations decreased bacterial growth by 35 %. DCH augments the action of OXC against methicillin-susceptible S. aureus and therefore constitutes a good bacteriostatic agent for methicillin-resistant S. aureus.

Antimicrobial activity and synergism of some substituted flavonoids.

Natural and synthetic substituted chalcones, flavones and flavanones were tested for antibacterial activity. In order to determine synergism, new combinations of substituted flavonoids against Staphylococcus aureus, Escherichia coli and Enterobacter aerogenes were assayed. The results allow us to establish relationships between antimicrobial effect of the compounds and membrane structures of these microorganisms. When flavonoid combinations were employed a stronger effect was found against E. coli than against S. aureus. This fact is due to the existence of porins in the outer membrane of G(-)-bacteria. The compound that acts as enhancer acts by blocking the charges of amino acids in the porins and thus facilitates the passage of the other compound by diffusion into the bacterial cell.

Salicylic acid permeation: a comparative study with different vehicles and membranes

Considering the skin's function, different dermal pharmaceutical forms can be developed according to the type of therapeutic activity, active principle and excipients involved in the formulation, such as [quot ]transdermal preparations[quot ]. In the present study, the permeation parameters of the non-steroidal anti-inflammatory drug, salicylic acid (SA) through synthetic membrane, polyvinyliden difluoride, and a biological membrane, egg shell membrane, with different vehicles, propylene glycol, isopropyl alcohol and carbopol gel, were determined. The reported physicochemical parameters of SA from CG were significantly higher than those obtained using PG and IP. This is attributed to the lipophilic nature of the vehicle that facilitates the release and penetration of the active principle, thus acting sinergicall y. The permeation profiles of SA allow us to state that permeation kinetics is of first order, so that the flux values obtained are in direct proportion to the specific rates of drug release.

Salicylic acid permeation: a comparative study with different vehicles and membranes

Considering the skins function, different dermal pharmaceutical forms can be developed according to the type of therapeutic activity, active principle and excipients involved in the formulation, such as [quot ]transdermal preparations[quot ]. In the present study, the permeation parameters of the non-steroidal anti-inflammatory drug, salicylic acid (SA) through synthetic membrane, polyvinyliden difluoride, and a biological membrane, egg shell membrane, with different vehicles, propylene glycol, isopropyl alcohol and carbopol gel, were determined. The reported physicochemical parameters of SA from CG were significantly higher than those obtained using PG and IP. This is attributed to the lipophilic nature of the vehicle that facilitates the release and penetration of the active principle, thus acting sinergicall y. The permeation profiles of SA allow us to state that permeation kinetics is of first order, so that the flux values obtained are in direct proportion to the specific rates of drug release.(AU)

Bacteriostatic action of synthetic polyhydroxylated chalcones against Escherichia coli

In previous work the bacteriostatic action of trihydroxylated chalcones against Staphylococcus aureus ATCC 25 923 was investigated. In this work the action of 2',4',2-(OH)3-chalcone, 2',4',3-(OH)3-chalcone and 2',4',4-(OH)3-chalcone against Escherichia coli ATCC 25 922 was evaluated. Growth kinetic curves of E. coli were made in nutritive broth added with increasing drug concentrations. The specific growth rates of the microorganisms were calculated by a kinetic turbidimetric method, which was previously probed and the minimal inhibitory concentrations (MIC's) were evaluated by a mechanism of action proposed. The MICs of 2',4',3-(OH)3-chalcone and 2',4',2-(OH)3-chalcone were 46 microg/ml and 122 microg/ml, respectively. The 2',4',4-(OH)3-chalcone was inactive. The MIC value of 2',4',3-(OH)3-chalcone (46 microg/ml), more active than 2',3-(OH)2-chalcone (72.2 microg/ml) may be due to the introduction of an electron donating group (-OH) at position 4' in the aromatic A-ring, which activates the region that includes the 2'-hydroxyl neighbor group and the alpha,beta-unsaturated carbonyl group.

Bacteriostatic action of synthetic polyhydroxylated chalcones against Escherichia coli

In previous work the bacteriostatic action of trihydroxylated chalcones against Staphylococcus aureus ATCC 25 923 was investigated. In this work the action of 2,4,2-(OH)3-chalcone, 2,4,3-(OH)3-chalcone and 2,4,4-(OH)3-chalcone against Escherichia coli ATCC 25 922 was evaluated. Growth kinetic curves of E. coli were made in nutritive broth added with increasing drug concentrations. The specific growth rates of the microorganisms were calculated by a kinetic turbidimetric method, which was previously probed and the minimal inhibitory concentrations (MICs) were evaluated by a mechanism of action proposed. The MICs of 2,4,3-(OH)3-chalcone and 2,4,2-(OH)3-chalcone were 46 microg/ml and 122 microg/ml, respectively. The 2,4,4-(OH)3-chalcone was inactive. The MIC value of 2,4,3-(OH)3-chalcone (46 microg/ml), more active than 2,3-(OH)2-chalcone (72.2 microg/ml) may be due to the introduction of an electron donating group (-OH) at position 4 in the aromatic A-ring, which activates the region that includes the 2-hydroxyl neighbor group and the alpha,beta-unsaturated carbonyl group. (AU)

First and second order derivative spectrophotometric determination of benzyl alcohol and diclofenac in pharmaceutical forms.

Diclofenac sodium is a drug with analgesic, antipyretic and anti-inflammatory properties. It is present in numerous pharmaceutical preparations. In injectable forms, it is usually accompanied by benzyl alcohol as an excipient, which is used as a blocking anesthetic (4%) and an antiseptic (4-10%). In this work spectrophotometric methodology was used in order to determine diclofenac and benzyl alcohol in injectable formulations by applying, on the one hand, the first-derivative method of crossing zero for diclofenac sodium and on the other, second derivative for benzyl alcohol. The results obtained show that this method has a significant advantage over other techniques and it is appropriate for routine pharmaceutical analysis.

News analytical reagents for europium(III).

The complexant reactions of 2'-hydroxychalcones with europium(III) are studied by the spectrophotometric method. The apparent formation constants are evaluated using a simple graphical linear method. The sequence of these constant values is explained and compared with aluminium(III) complexant reactions.

Rapid and accurate determination of chlorpheniramine maleate, noscapine hydrochloride and guaiphenesin in binary mixtures by derivative spectrophotometry.

Rapid and accurate binary mixture resolution of chlorpheniramine maleate-noscapine hydrochloride and chlorpheniramine maleate-guaiphenesin, was performed. Derivative spectrophotometry, by the zero-crossing measurements, was used due to the drugs closely overlapping absorption spectra. Neither sample pretreatment nor separation were required. Linear calibration graphs of first derivative values at 268.0 and 261.0 nm for chlorpheniramine-maleate-noscapine hydrochloride and at 273.2 and 261.0 nm for chlorpheniramine-guaiphenesin were obtained vs. concentration with negligible intercept on the y-axis. Thus, the derivative spectrophotometry method was applied to the determination of these drugs in binary mixtures obtaining selectivity, accuracy and precision.

Complexant efficiency of 2'-hydroxy-4-R-chalcones for Aluminium (III) and substituent's effect.

The complexant efficiency with aluminium of 2'-hydroxy-4-R-chalcones, which depends on the nature and positions of the substituent was studied by a spectrophotometric method. The apparent formation constant was determined. The quantitative analysis of the substituent's influence on the complexation reaction equilibrium was made using the Hammett relation. The constant sigma magnitudes of groups OH, OCH(3), Cl and F in the 4-position agree with values reported in the literature.

[Kinetics of the bacteriostatic activity of natural and synthetic chalcones on a strain of Staphylococcus aureus]. / Cinética de la acción bacteriostática de chalconas naturales y de síntesis sobre una cepa de Staphylococcus aureus.

The bacteriostatic action exerted by natural chalcones (2',4'-dihydroxychalcone and 2'-hydroxy-4'-methoxychalcone) and by synthetic chalcones (chalcone, 2'-hydroxychalcone, 2'4-dihydroxychalcone and 2'-hydroxy-4-methoxychalcone) on Staphylococcus aureus (ATCC 25 923 Strain) was investigated. In addition, the influence of the concentration, nature and position of the substituents of the mentioned drugs on the specific growth rate of the germ was determined. Qualitative tests made on nutritive agar plates showed the inhibitory action of chalcone and its dihydroxyl derivatives. Quantitative experiments were made in nutritive broth at 33 degrees C, with permanent stirring (200 rpm), measuring the microbial growth by turbidimetry at 720 nm. The results distinguish the strong bacteriostatic effect of 2',4'-dihydroxychalcone and 2',4-dihydroxychalcone, which at low concentrations caused complete inhibition of microorganism growth, from the other chalcones studies which only reduced the up to a limiting value. The presence of an hydroxyl group in the A or B ring of 2'-hydroxychalcone increases its bacteriostatic activity, being this effect stronger at position 4' (ring A) than at position 4 (ring B). The introduction of a methoxy group into the 2'-hydroxychalcone structure causes a decrease of its inhibitory power.

Cinética de la acción bacteriostática de chalconas naturales y de síntesis sobre una cepa de Staphylococcus aureus. / [Kinetics of the bacteriostatic activity of natural and synthetic chalcones on a strain of Staphylococcus aureus]

The bacteriostatic action exerted by natural chalcones (2,4-dihydroxychalcone and 2-hydroxy-4-methoxychalcone) and by synthetic chalcones (chalcone, 2-hydroxychalcone, 24-dihydroxychalcone and 2-hydroxy-4-methoxychalcone) on Staphylococcus aureus (ATCC 25 923 Strain) was investigated. In addition, the influence of the concentration, nature and position of the substituents of the mentioned drugs on the specific growth rate of the germ was determined. Qualitative tests made on nutritive agar plates showed the inhibitory action of chalcone and its dihydroxyl derivatives. Quantitative experiments were made in nutritive broth at 33 degrees C, with permanent stirring (200 rpm), measuring the microbial growth by turbidimetry at 720 nm. The results distinguish the strong bacteriostatic effect of 2,4-dihydroxychalcone and 2,4-dihydroxychalcone, which at low concentrations caused complete inhibition of microorganism growth, from the other chalcones studies which only reduced the up to a limiting value. The presence of an hydroxyl group in the A or B ring of 2-hydroxychalcone increases its bacteriostatic activity, being this effect stronger at position 4 (ring A) than at position 4 (ring B). The introduction of a methoxy group into the 2-hydroxychalcone structure causes a decrease of its inhibitory power.

Cinética de la acción bacteriostática de chalconas naturales y de síntesis sobre una cepa de Staphylococcus aureus / Kinetics of the bacteriostatic action of synthetic and natural chalcones on a Staphylococcus aureus strain

Se estudió la acción bacteriostática ejercida por chalconas naturales (2,4-dihidroxichalcona y 2-hidroxi-4-metoxichalcona) y de síntesis (chalcona, 2-hidroxicalcona, 24-dihidroxichalcona y 2-hidroxi-4-metoxichalcona) sobre Staphylococcus aureus (cepa ATCC 25 923). Se determinó la influencia de la concentración de la natureza y posición de los sustituyentes de las drogas empleadas sobre la tasa de crecimiento específica del germen. Los ensayos cualitativos se hicieron en placas de agar nutritivo y mostraron la acción inhibitoria de chalcona y sus derivados dihidroxilados. Los resultados obtenidos distiguen el potente efecto bacteriostático de 2,4-dihidroxichalcona y 2,4-dihidrochalcona que en bajas concentraciones provocaron inhibición total en el crecimiento del microorganismo, de las otras chalconas estudiadas que solamente disminuyeron la tasa de crecimiento específica del germe hasta un valor límite. Se observa que la presencia de un grupo oxihidrilo en el anillo A o B de la 2-hidroxichalcona potencia su actividad bacteriostática siendo este efecto más pronunciado en la posición 4(anillo A) respecto de la posición 4 (anillo B). La introducción de un grupo metoxilo en la estructura de la 2-hidroxichalcona produce un decrecimiento de su potencia inhibitoria (AU)

Cinética de la acción bacteriostática de chalconas naturales y de síntesis sobre una cepa de Staphylococcus aureus / Kinetics of the bacteriostatic action of synthetic and natural chalcones on a Staphylococcus aureus strain

Se estudió la acción bacteriostática ejercida por chalconas naturales (2',4'-dihidroxichalcona y 2'-hidroxi-4'-metoxichalcona) y de síntesis (chalcona, 2'-hidroxicalcona, 2'4-dihidroxichalcona y 2'-hidroxi-4-metoxichalcona) sobre Staphylococcus aureus (cepa ATCC 25 923). Se determinó la influencia de la concentración de la natureza y posición de los sustituyentes de las drogas empleadas sobre la tasa de crecimiento específica del germen. Los ensayos cualitativos se hicieron en placas de agar nutritivo y mostraron la acción inhibitoria de chalcona y sus derivados dihidroxilados. Los resultados obtenidos distiguen el potente efecto bacteriostático de 2',4'-dihidroxichalcona y 2',4'-dihidrochalcona que en bajas concentraciones provocaron inhibición total en el crecimiento del microorganismo, de las otras chalconas estudiadas que solamente disminuyeron la tasa de crecimiento específica del germe hasta un valor límite. Se observa que la presencia de un grupo oxihidrilo en el anillo A o B de la 2'-hidroxichalcona potencia su actividad bacteriostática siendo este efecto más pronunciado en la posición 4'(anillo A) respecto de la posición 4 (anillo B). La introducción de un grupo metoxilo en la estructura de la 2'-hidroxichalcona produce un decrecimiento de su potencia inhibitoria