Comparative study of the antioxidant and reactive oxygen species scavenging properties in the extracts of the fruits of Terminalia chebula, Terminalia belerica and Emblica officinalis

<p>Abstract</p> <p>Background</p> <p>Cellular 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 <it>in vitro </it>antioxidant and reactive oxygen species scavenging activities of <it>Terminalia chebula</it>, <it>Terminalia belerica </it>and <it>Emblica officinalis </it>fruit extracts.</p> <p>Methods</p> <p>The 70% methanol extracts were studied for <it>in vitro </it>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.</p> <p>Results</p> <p>The ability of the extracts of the fruits in exhibiting their antioxative properties follow the order <it>T. chebula </it>><it>E. officinalis </it>><it>T. belerica</it>. The same order is followed in their flavonoid content, whereas in case of phenolic content it becomes <it>E. officinalis </it>><it>T. belerica </it>><it>T. chebula</it>. In the studies of free radicals' scavenging, where the activities of the plant extracts were inversely proportional to their IC₅₀values, <it>T. chebula </it>and <it>E. officinalis </it>were found to be taking leading role with the orders of <it>T. chebula </it>><it>E. officinalis </it>><it>T. belerica </it>for superoxide and nitric oxide, and <it>E. officinalis </it>><it>T. belerica </it>><it>T. chebula </it>for DPPH and peroxynitrite radicals. Miscellaneous results were observed in the scavenging of other radicals by the plant extracts, viz., <it>T. chebula </it>><it>T. belerica </it>><it>E. officinalis </it>for hydroxyl, <it>T. belerica </it>><it>T. chebula </it>><it>E. officinalis </it>for singlet oxygen and <it>T. belerica </it>><it>E. officinalis </it>><it>T. chebula </it>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.</p> <p>Conclusions</p> <p>The evidences as can be concluded from the study of the 70% methanol extract of the fruits of <it>Terminalia chebula</it>, <it>Terminalia belerica </it>and <it>Emblica officinalis</it>, imposes the fact that they might be useful as potent sources of natural antioxidant.</p

Cerium oxide nanoparticles accelerate the decay of peroxynitrite (ONOO−)

Cerium oxide nanoparticles (CeO(2) NPs) have been shown to possess a substantial oxygen storage capacity via the interchangeable surface reduction and oxidation of cerium atoms, cycling between the Ce(4+) and Ce(3+) redox states. It has been well established in many studies that depending on their reactivity and surface chemistry, CeO(2) NPs can effectively convert both reactive oxygen species (superoxide, O(2)(•−), and hydrogen peroxide) into more inert species and scavenge reactive nitrogen species (RNS)(nitric oxide, •NO), both in vitro and in vivo. Since much of damage attributed to •NO and O(2)(•−) is actually the result of oxidation or nitration by peroxynitrite or its breakdown products and due to the multiple species that these nanoparticles target in vivo, it was logical to test their interaction with the highly reactive molecule peroxynitrite (ONOO(−)). Here, we report that CeO(2) NPs significantly accelerated the decay of ONOO(−) by three independent methods. Additionally, our data suggest the ability of CeO(2) NPs to interact with ONOO(−) is independent of the Ce(3+)/Ce(4+) ratio on the surface of the CeO(2) NPs. The accelerated decay was not observed when reactions were carried out in an inert gas (argon), suggesting strongly that the decay of peroxynitrite is being accelerated due to a reaction of CeNPs with the carbonate radical anion. These results suggest that one of the protective effects of CeO(2) NPs during RNS is likely due to reduction in peroxynitrite or its reactive breakdown products

CD11b+Ly6G+ cells induced by dsRNA

PolyI:C, a synthetic double-stranded RNA analog, acts as an immune-enhancing adjuvant that regresses tumors via cytotoxic T lymphocyte (CTL)-dependent and CTL-independent fashions, the latter of which remains largely unknown. Tumors contain CD11b+Ly6G+ cells, granulocytic myeloid-derived suppressor cells (G-MDSCs), or tumor-associated neutrophils (TANs), which play a critical role in tumor progression and development. Here, we demonstrate that CD11b+Ly6G+ cells respond to polyI:C and exhibit tumoricidal activity in an EL4 tumor implant model. PolyI:C-induced inhibition of tumor growth was attributed to caspase-8/3 cascade activation in tumor cells, which occurred independently of CD8α+/CD103+ dendritic cells (DCs) and CTLs. CD11b+Ly6G+ cells acted as anti-tumor effectors because depletion of CD11b+Ly6G+ cells totally abrogated tumor regression and caspase activation after polyI:C treatment. CD11b+Ly6G+ cells that had been activated with polyI:C showed cytotoxicity and inhibition of tumor growth through the production of reactive oxygen species (ROS)/reactive nitrogen species (RNS). These responses were abolished in either toll/interleukin-1 receptor domain-containing adaptor molecule-1 (TICAM-1)-/- or interferon (IFN)-αβ receptor 1 (IFNAR1)-/- mice. Thus, our results suggest that polyI:C targets myeloid cells in tumors, where CD11b+Ly6G+ cells exhibit anti-tumor activity through TLR3/TICAM-1 and IFNAR pathways, independent of those in CD8α+/CD103+ DCs that prime CTLs