Level Of Free Radical Scavenging Activity Research Articles

A study of the antioxidant and membranotropic activities of luteolin using different model systems

Luteolin, a water-insoluble 3′,4′,5,7-tetrahydroxyflavon, is one of the best-studied representatives of bioflavonoids. Luteolin is an essential food component for humans and other mammals that possesses a wide spectrum of biological activities by affecting the activities of various metabolic enzymes, target receptors, and signal transduction pathways. In this study, we conducted a comparative study of the antioxidant (free-radical scavenging) properties of luteolin in 2,2′-azobis(2-methylpropionamidine) dihydrochloride–luminol and hemoglobin–hydrogen peroxide–luminol systems and assessed its effect on the permeability of planar lipid bilayer membranes. Trolox was used as a reference antioxidant, while ascorbic acid and dihydroquercetin were taken as standards. Luteolin shows moderate antioxidant activity, exhibiting a higher antioxidant capacity than trolox and ascorbic acid, but it was less effective than dihydroquercetin in tests for antioxidant activity in the studied systems. The studied compounds can be ranked according to the effectiveness of their antioxidant action: dihydroquercetin > luteolin > trolox > ascorbic acid. It should be noted that the antioxidant activity of a water-soluble form of luteolin, luteolin disulfate, is comparable with that of luteolin. Luteolin does not cause significant changes in the permeability of planar bilayer membranes in the dose range from 1.5 to 30 μM. Our findings indicate the presence of a high level of free-radical scavenging activity and the absence of a primary membranotropic effect for luteolin. It can be assumed that the multiple pleiotropic nature of luteolin activity towards a variety of biological systems is associated not only with a neutralizing effect in regard to reactive oxygen species, but also with the ability of luteolin to block and modulate different cell-signaling processes and biochemical pathways. The presumed mechanisms of the biological activity of luteolin and luteolin disulfate are discussed.

Bioassay-guided Isolation and Identification of Antioxidative Compounds from the Bark of Eugenia polyantha

Eugenia polyantha bark extracts were found to have potential antioxidative activities. This study is an effort to investigate the antioxidative compounds in E. polyantha. In vitro antioxidatve assay were used as guided tools for the isolation of antioxidative compounds. The methanol-water extracts showed the highest level of free radical-scavenging activity (ED50) = 180 microg mL(-1) and protection from beta-carotene bleaching (8.7 microg mL(-1)). The methanol-water (1:1) extracts exhibited strong DPPH scavenging activity and protection against beta carotene bleaching and was subjected to repeated silica gel column chromatography. The n-butanol, acetone and ethyl acetate solubles exhibited the highest antioxidative activities, derivatization was conducted to the isolated antioxidative compounds prior to identification. Catechin, gallic acid and rutin were isolated from those solubles as active compounds present in the Eugenia polyantha bark.

Bioactivity of Centaurea persica boiss. (Asteraceae)

The free-radical-scavenging property, antibacterial activity and brine shrimp toxicity of petroleum ether (PE), dichloromethane (DCM) and methanol (MeOH) extracts of Centaurea persica, a Turkish medicinal plant, were assessed using the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) assay, the resazurin microtiter plate based assay, and the brine shrimp lethality assay, respectively. Additionally, the disc diffusion assay was also used to assess antibacterial activity. Only the MeOH extract of C. persica exhibited a significant free-radical-scavenging property in the DPPH assay, with an RC50 value of 0.025 mg/mL. However, in the TLC-based qualitative assay, petroleum ether and DCM extracts showed an extremely low level of free-radical-scavenging property. Among the solid-phase extraction fractions of the MeOH extract, the fractions eluted with 60% and 80% MeOH in water exhibited the highest level of free-radicalscavenging activity (RC50 = 0.010 and 0.015 mg/mL, respectively). While DCM extract showed reasonable antibacterial activity against five out of the nine test strains both in the disc diffusion assay and in the resazurin assay, the MeOH extract was highly active against both Escherichia coli and ampicillin-resistant E. coli strains. Among the solid-phase extraction fractions of the MeOH extract, fractions eluted with 80% MeOH in water and 100% MeOH displayed significant antibacterial potencies against both E. coli species. None of the extracts showed any significant toxicity towards brine shrimps (LD50 = >1.00 mg/mL).

Assessment of free-radical-scavenging and antibacterial activities, and brine shrimp toxicity of Scutellaria pinnatifida (Lamiaceae)

SUMMARY Scutellaria pinnatifida A. Hamilt. (Lamiaceae) is an endemic Turkish herb. This plant is also endemic to Iran, and grows abundantly in other central and western Asian countries. Several species of the Scutellaria are known for their traditional uses in the treatment of hypertension, arteriosclerosis, inflammatory diseases, hepatitis, allergy, cancer and diarrhoea. Free-radical-scavenging property, antibacterial activity and brine shrimp toxicity of the n-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of S. pinnatifida were assessed using the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) assay, the resazurin microtitre plate based assay, and the brine shrimp lethality assay, respectively. The DCM and MeOH extracts exhibited free-radical-scavenging property, with the RC values of 0.362 and 0.127 mg/ml, respectively. Among the solid-phase extraction fractions of the MeOH extract, the 50% aqueous-MeOH fraction showed the highest level of free-radicalscavenging activity (RC = 0.039 mg/ml). While the DCM extract showed low level of antibacterial activity against Bacillus subtilis and ampicillin-resistant Escherichia coli, the MeOH extract was active against B. cereus, B. subtilis, E. coli and ampicillin-resistant E. coli. However, the minimum inhibitory concentrations (MIC) of the MeOH extract against these bacterial strains were >10 mg/ml. None of the extracts showed any significant toxicity towards brine shrimps (LD = > 1.00 mg/ml).

In vitro Antioxidative Activities and Polyphenol Content of Eugenia polyantha Wight Grown in Indonesia

Antioxidative activities of three bark extracts (methanol, methanol-water and water) from Eugenia polyantha Wight grown in Indonesia were evaluated using various in vitro assays; 2, 2-diphenyl-1-picrylhydrazyl radical-scavenging, hydrogen peroxide-scavenging and beta-carotene bleaching assays. From the assays, Eugenia polyantha bark extracts were found to be potential antioxidative activities. The methanol-water extract showed the highest level of free radical-scavenging activity (Effective dose (ED50) = 0.18 mg mL-1) and protection from beta-carotene bleaching (85.7% at 100 microg mL-1). The methanol-water extracts showed the highest total phenolic content (856 mg gallic acid equivalent (GAE)/g and 161 mg catechin equivalent (CE)/g) and total antioxidative capacity (449 mg ascorbic acid equivalent (AAE)/g). Furthermore, it exhibited dose-dependent antioxidative activities. A relationship between total antioxidative capacity and total phenolic content was recognized in the three extracts from Eugenia polyantha bark.

Bioactivity of extracts of Centaurea polyclada dc. (Asteraceae)

The free radical-scavenging property, antibacterial activity, and brine shrimp toxicity of n-hexane, dichloromethane (DCM), and methanol (MeOH) extracts of Centaurea polyclada, an endemic Turkish species, were assessed using the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) assay, the resazurin microtiter plate-based assay, and the brine shrimp lethality assay, respectively. The DCM and MeOH extracts of C. polyclada exhibited free radical-scavenging ability with RC50 values 1.17 and 0.015 mg/mL, respectively. Among solid-phase extraction fractions of the MeOH extract, the fraction eluted with 60% MeOH in water demonstrated the highest level of free radical-scavenging activity (RC50 = 0.016 mg/mL). Only the DCM extract showed considerable antibacterial activity against all nine test strains except Escherichia coli, with MIC ranging from 1.25 to 2.50 mg/mL. This antibacterial activity pattern was also observed with solid-phase extraction fractions of the DCM extract with varied potencies. None of the extracts showed any significant toxicity towards brine shrimps (LD50 = >1.00 mg/mL).