Membrane stabilizing effect

Abstract: The free radical scavenger and antihepatotoxic activity from Rosmarinus tomentosus ethanolic extract and its fractions were studied, and also its membrane stabilizing activity in rat erythrocytes. Pretreatment with an ethanolic extract of R. tomentosus caused an important decrease in the CCl4-induced toxicity in rats liver, made evident by its effect on the levels of GPT and bilirubin in the serum and the malondialdehyde (MDA) concentration in the liver. These effects are similar to those produced by silymarin. The chloroformic fraction showed the greatest antihepatotoxic activity and the ethyl acetate fraction the greatest free radical scavenger activity.

Abstract: The hypothesis concerning the active form and the site of action of tertiary amine local anesthetics (Narahashi et al. , 1970) predicts that there should be certain quaternary compounds capable of blocking action potentials only from inside the nerve membrane. A quaternary compound, hemicholinium-3, and two quaternary derivatives of lidocaine, QX-314 and QX-572, have been found to block the action potential of squid giant axons much more effectively from the inside of the nerve membrane than from the outside. The blocking potency of the internally applied quaternary compounds was independent of pH changes in either internal or external solutions. Neither choline nor acetylcholine, when applied inside, had any effect on the action potential or any protective action against the blockage caused by hemicholinium-3. Therefore, the blockage by hemicholinium-3 is not due to the lack of choline. The results strongly support the hypothesis that local anesthetics block the action potential from inside the nerve membrane in charged forms.

Abstract: In this present study, a comparative evaluation of the antioxidant capacities, phenol and polyphenol composition, membrane stabilization, and cytotoxicity to brine shrimps (Arthemia salina) of the leaf and stem extracts of Cissus multistriata were carried out. 2,2- Diphenyl-1-picryl hydrazyl (DPPH) radical scavenging effect of the extracts was determined spectrophotometrically. The highest radical scavenging effect was observed in the stem extract with IC50 of 29.25 ig/ml. The potency of radical scavenging effect of the stem extract was close to the synthetic antioxidant quercetin with IC50 of 21.05 ig/ml. The antioxidant activities of each extract increased with increasing concentration of extracts. The phenol and polyphenol content of the stem varied between 0.564 ± 0.000 to 6.200 ± 0.557% and that of the leaf content is lower (0.523 ± 0.000 to 3.400 ± 0.355%). The higher amount of phenolic compound in the stem could be contributory to the greater radical scavenging effects observed. The methanolic extracts exhibited minimum and maximum percentage membrane stability of 51.364 ± 11.241 and 56.098 ± 14.654% on human erythrocyte. The highest membrane stabilizing activity was observed in the stem extract with percentage stability of 56.098 ± 14.654%. The activity of the extracts was comparable to the standard anti-inflammatory drug (Indomethacin) used. The extracts are less toxic to the cell (Arthenia salina) with their LC/EC50 higher than that of standard potassium dichromate used. The results obtained in this present study indicate that C. multistriata can be a potential source of natural antioxidant and is relatively safe.

Abstract: 1. 4-Hydroxypropranolol, a metabolite produced after oral administration of propranolol, has been shown to be a β-adrenoceptor blocking drug. It is of similar potency to propranolol in antagonizing the effects of isoprenaline on heart rate and blood pressure in cats and against isoprenaline protection of guinea-pigs from bronchospasm. It is not cardioselective. 2. In rats depleted of catecholamine 4-hydroxypropranolol produced an increase in heart rate, suggesting that it has intrinsic sympathomimetic activity. 3. In anaesthetized dogs 4-hydroxypropranolol produced a decrease in heart rate and dP/dt and an increase in A-V conduction time at doses within the range 0·09-1·25 mg/kg. These effects are a result of β-adrenoceptor blockade. In dogs depleted of catecholamines these same doses produced an increase in heart rate and dP/dt and a decrease in A-V conduction time. These responses were antagonized by propranolol, and were due to the intrinsic sympathomimetic activity of the compound. At higher doses (5·25 and 13·25 mg/kg) a further dose dependent decrease in heart rate and dP/dt and an increase in A-V conduction time occurred. This trend was also seen in animals depleted of catecholamines. These changes represent membrane stabilizing activity of 4-hydroxypropranolol. 4. 4-Hydroxypropranolol is a potent β-adrenoceptor blocking drug with both intrinsic sympathomimetic activity and membrane stabilizing activity.