BackgroundMany diseases are associated with oxidative stress caused by free radicals. Current research is directed towards finding naturally-occurring antioxidants of plant origin. The aim of the present study was to evaluate the in vitro antioxidant activities of Spondias pinnata stem bark extract.MethodsA 70% methanol extract of Spondias pinnata stem bark was studied in vitro for total antioxidant activity, for scavenging of hydroxyl radicals, superoxide anions, nitric oxide, hydrogen peroxide, peroxynitrite, singlet oxygen and hypochlorous acid, and for iron chelating capacity, reducing power, and phenolic and flavonoid contents.ResultsThe extract showed total antioxidant activity with a trolox equivalent antioxidant concentration (TEAC) value of 0.78 ± 0.02. The IC50 values for scavenging of free radicals were 112.18 ± 3.27 μg/ml, 13.46 ± 0.66 μg/ml and 24.48 ± 2.31 μg/ml for hydroxyl, superoxide and nitric oxide, respectively. The IC50 for hydrogen peroxide scavenging was 44.74 ± 25.61 mg/ml. For the peroxynitrite, singlet oxygen and hypochlorous acid scavenging activities the IC50 values were 716.32 ± 32.25 μg/ml, 58.07 ± 5.36 μg/ml and 127.99 ± 6.26 μg/ml, respectively. The extract was found to be a potent iron chelator with IC50 = 66.54 ± 0.84 μg/ml. The reducing power was increased with increasing amounts of extract. The plant extract (100 mg) yielded 91.47 ± 0.004 mg/ml gallic acid-equivalent phenolic content and 350.5 ± 0.004 mg/ml quercetin-equivalent flavonoid content.ConclusionThe present study provides evidence that a 70% methanol extract of Spondias pinnata stem bark is a potential source of natural antioxidants.

BackgroundCellular damage caused by reactive oxygen species (ROS) has been implicated in several diseases, and hence natural antioxidants have significant importance in human health. The present study was carried out to evaluate the in vitro antioxidant and reactive oxygen species scavenging activities of Terminalia chebula, Terminalia belerica and Emblica officinalis fruit extracts.MethodsThe 70% methanol extracts were studied for in vitro total antioxidant activity along with phenolic and flavonoid contents and reducing power. Scavenging ability of the extracts for radicals like DPPH, hydroxyl, superoxide, nitric oxide, hydrogen peroxide, peroxynitrite, singlet oxygen, hypochlorous acid were also performed to determine the potential of the extracts.ResultsThe ability of the extracts of the fruits in exhibiting their antioxative properties follow the order T. chebula >E. officinalis >T. belerica. The same order is followed in their flavonoid content, whereas in case of phenolic content it becomes E. officinalis >T. belerica >T. chebula. In the studies of free radicals' scavenging, where the activities of the plant extracts were inversely proportional to their IC50 values, T. chebula and E. officinalis were found to be taking leading role with the orders of T. chebula >E. officinalis >T. belerica for superoxide and nitric oxide, and E. officinalis >T. belerica >T. chebula for DPPH and peroxynitrite radicals. Miscellaneous results were observed in the scavenging of other radicals by the plant extracts, viz., T. chebula >T. belerica >E. officinalis for hydroxyl, T. belerica >T. chebula >E. officinalis for singlet oxygen and T. belerica >E. officinalis >T. chebula for hypochlorous acid. In a whole, the studied fruit extracts showed quite good efficacy in their antioxidant and radical scavenging abilities, compared to the standards.ConclusionsThe evidences as can be concluded from the study of the 70% methanol extract of the fruits of Terminalia chebula, Terminalia belerica and Emblica officinalis, imposes the fact that they might be useful as potent sources of natural antioxidant.

The first examples of Ru(ii) and Ir(iii) metalla-rectangles [1](4+)-[4](4+) containing a BODIPY-based linker are reported; some of these compounds exhibited highly selective anticancer activity and interact strongly with DNA as well as protein. The characteristic green fluorescence of a BODIPY ligand and associated aggregation-induced emission (AIE) permitted visualization of compounds inside the cells using confocal microscopy.

Communication between distant DNA sites is a central feature of many DNA transactions. Negative regulation of the galactose (ga/) operon of Escherichia coli requires repressor binding to two operator sites located on opposite sides of the promoter. The proposed mechanism for regulation involves binding of the repressor to both operator sites, followed by a protein-protein association that loops the intervening promoter DNA (double occupancy plus association). To assess these requirements in vivo, we have previously converted ga/operator sites to lac and shown that both operator sites must be occupied by the homologous repressor protein (Lac or Gal) for negative regulation of the ga/operon. We have now addressed more directly the need for proteinprotein association by the use of the converted operator sites and a mutant Lac repressor defective in association of the DNA-binding dimers. We have compared the biological and biochemical activity of two Lac repressors: the wild-type (tetramer) I + form, in which the DNA-binding dimer units are tightly associated; and the mutant I "~ repressor, in which the dimer units do not associate effectively. The I ÷ repressor is an efficient negative regulator of the ga/operon in vivo, but the I "~ mutant is an ineffective repressor. Purified I + repressor efficiently forms DNA loops between operator sites that we have visualized by electron microscopy; the I °~ repressor fails to form DNA loops, although the protein binds effectively to both operator sites. From the clear correlation between looping in vitro and repression in vivo, we conclude that regulation of the ga/operon depends on the association of repressor proteins bound to the two operator sites. Repression is likely to involve a DNA-wound nucleoprotein complex in which RNA polymerase is present but unable to carry out a productive interaction with the promoter sequence.

Repressors encoded by mycobacteriophages differ significantly from the repressor proteins of lambda and related phages at functional level but at structural level they are nearly similar.