Inhibitory effects of some natural products on metal-induced lipid oxidation in cooked fish

Divalent metal ions (Fe²⁺, Cu²⁺, Zn²⁺, Ni²⁺, and Mn²⁺) induced lipid oxidation in cooked, but not in raw fish. The extent of lipid oxidation, measured by the production of thiobarbituric acid reactive substances (TBRS), was increased with higher concentrations of iron, zinc, and nickel, but was decreased with increasing concentrations of copper and manganese. The natural products: ellagic acid, tannic acid, myricetin, and quercetin, inhibited lipid oxidation in cooked fish. The enhanced lipid oxidation caused by cupric ions (10³ pmol/100 g fish) was also inhibited by the natural products. The degree of inhibition in copper-treated fish, however, was less than that in fish that had no added copper. The inhibition was concentration dependent. The antioxidative potency of the various natural products was independent of the type of metal ion-induced lipid oxidation. Ellagic acid was the most potent antioxidant (75.7–83.9%), followed by tannic acid (60.4–77.3%), myricetin (52.9–70.4%), and quercetin (32.6–44.2%).     

Inhibitory effect of α-mangostin on Acinetobacter baumannii biofilms – an in vitro study

The present study was designed to investigate the anti-biofilm potential of alpha-mangostin (α-MG) against Acinetobacter baumannii (AB). The biofilm inhibitory concentration (BIC) of α-MG against AB was found to be 2 μg ml^?1. α-MG (0.5, 1 and 2 μg ml^?1) exhibited non-bactericidal concentration-dependent anti-biofilm activities against AB. However, α-MG failed to disintegrate the mature biofilms of AB even at a 10-fold increased concentration from its BIC. Results from qRT-PCR and in vitro bioassays further demonstrated that α-MG downregulated the expression of bfmR, pgaA, pgaC, csuA/B, ompA, bap, katE, and sodB genes, which correspondingly affects biofilm formation and its associated virulence traits. The present study suggests that α-MG exerts its anti-biofilm property by interrupting initial biofilm formation and the cell-to-cell signaling mechanism of AB. Additional studies are required to understand the mode of action responsible for the anti-biofilm property.     

Computational genomic analysis of hemorrhagic fever viruses

A number of distinct viruses are known as hemorrhagic fever viruses based on a shared ability to induce hemorrhage by poorly understood mechanisms, typically involving the formation of blood clots (“disseminated intravascular coagulation”). It is well documented that selenium plays a significant role in the regulation of blood clotting via its effects on the thromboxane/prostacyclin ratio, and effects on the complement system. Selenium has an anticlotting effect, whereas selenium deficiency has a proclotting or thrombotic effect. It is also well documented that extreme dietary selenium deficiency, which is almost never seen in humans, has been associated with hemorrhagic effects in animals. Thus, the possibility that viral selenoprotein synthesis might contribute to hemorrhagic symptoms merits further consideration. Computational genomic analysis of certain hemorrhagic fever viruses reveals the presence of potential protein coding regions (PPCRs) containing large numbers of in-frame UGA codons, particularly in the −1 reading frame. In some cases, these clusterings of UGA codons are very unlikely to have arisen by chance, suggesting that these UGAs may have some function other than being a stop codon, such as encoding selenocysteine. For this to be possible, a downstream selenocysteine insertion element (SECIS) is required. Ebola Zaire, the most notorious hemorrhagic fever virus, has a PPCR with 17 UGA codons, and several potential SECIS elements can be identified in the viral genome. One potential viral selenoprotein may contain up to 16 selenium atoms per molecule. Biosynthesis of this protein could impose an unprecedented selenium demand on the host, potentially leading to severe lipid peroxidation and cell membrane destruction, and contributing to hemorrhagic symptoms. Alternatively, even in the absence of programmed selenoprotein synthesis, it is possible that random slippage errors would lead to increased encounters with UGA codons in overlapping reading frames, and thus potentially to nonspecific depletion of SeC in the host.     

In vitro and in vivo efficacy of rosmarinic acid on quorum sensing mediated biofilm formation and virulence factor production in Aeromonas hydrophila

Rosmarinic acid (RA) was assessed for its quorum sensing inhibitory (QSI) potential against Aeromonas hydrophila strains AH 1, AH 12 and MTCC 1739. The pathogenic strains of A. hydrophila were isolated from infected zebrafish and identified through biochemical analysis and amplification of a species-specific gene (rpsL). The biofilm inhibitory concentration (BIC) of RA against A. hydrophila strains was found to be 750 μg ml^?1. At this concentration, RA reduced the QS mediated hemolysin, lipase and elastase production in A. hydrophila. In FT-IR analysis, RA treated A. hydrophila cells showed a reduction in cellular components. Gene expression analysis confirmed the down-regulation of virulence genes such as ahh1, aerA, lip and ahyB. A. hydrophila infected zebrafish upon treatment with RA showed increased survival rates. Thus, the present study demonstrates the use of RA as a plausible phytotherapeutic compound to control QS mediated biofilm formation and virulence factor production in A. hydrophila.     

Low Band Gap Benzimidazole COF Supported Ni3N as Highly Active OER Catalyst

Covalent organic frameworks (COFs) have structures and morphologies closely resembling graphenes, whose modular construction permits atomic‐level manipulations. This, combined with their porous structure, makes them excellent catalyst supports. Here, the high electrocatalytic activity of a composite, formed by supporting Ni₃N nanoparticles on a benzimidazole COF, for oxygen evolution reaction is shown. The composite oxidizes alkaline water with a near‐record low overpotential of 230 mV @ 10 mA cm^?2 (η ₁₀). This high activity is attributed to the ability of the COF to confine the Ni₃N nanoparticles to size regimes otherwise difficult to obtain and to its low band gap character (1.49 eV) arising from the synergy between the conducting Ni₃N nanoparticles and the π‐conjugated COF. The COF itself, as a metal‐free self‐standing framework, has an oxygen evolution reaction activity with η ₁₀ of 400 mV. The periodic structure of the COF makes it serve as a matrix to disperse the catalytically active Ni₃N nanoparticles favoring their high accessibility and thereby good charge‐transport within the composite. This is evident from the amount of O₂ evolved (230 mmol h^?1 g^?1), which, to the best of our knowledge, is the highest reported. The work reveals the emergence of COF as supports for electrocatalysts.