Stereo- and regioselective hydroxylation of grindelic acid derivatives by Aspergillus niger.

Stereo- and regioselective hydroxylation of grindelane derivatives on position 3beta was catalyzed by cultures of Aspergillus niger. Grindelic acid (1), methyl grindelate (2), 15-hydroxy-7(8)-en-9alpha,13(S)-oxide-ent-labdane (3) and 7alpha,8alpha-epoxymethylgrindelate (4) were bioconverted into the corresponding 3beta-hydroxy derivatives as the only biotransformation products. 13(S),15-dihydroxy-8(9)-en-ent-labdane (5) remained unreacted under the same conditions. The conformational and electronic studies of the substrates are discussed.

Inhibition of Taq DNA polymerase by catalpol.

DNA polymerases have recently emerged as important cellular targets for chemical intervention in the development of anti-cancer agents. This report describes a PCR assay as a method to investigate the action mechanism of the inhibition of Taq DNA polymerase by catalpol. This inhibition was not primer or template specific, nor was it due to chelation of Mg2+ ions. In assays of hyperchromicity of double-stranded DNA, catalpol did not affect melting profile. The inhibitory effect of catalpol does not appear to depend on DNA concentration. In contrast, increasing dNTP concentration rescue the Taq DNA polymerase activity, suggestingthat catalpol acts in a competitive way with dNTPs at the binding site of the enzyme. Theoretical calculations reinforce the experimental data and the proposed mode of action of catalpol.

[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 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

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)