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paniculata (C.B. Clarke) Munir Leaves on Various Gastric Aggressive Factors
Published in Parimelazhagan Thangaraj, Phytomedicine, 2020
P. S. Sreeja, K. Arunachalam, Parimelazhagan Thangaraj
In addition, another class of drugs that was introduced include the proton pump inhibitors (inhibits H+, K+-ATPase pathway in parietal cells) represented by omeprazole, lansoprazole, rabeprazole, pantoprazole, and omeprazole. These drugs were considered as effective in minimizing acid secretion and cellular restitution during the treatment of gastric ulcers (Palileo and Kaunitz 2011). The process for decreasing acid in the gastric environment by these drugs occurs through the acid secretory canaliculi of the parietal cell. By this action, the inactivation of the proton pump occurs via the formation of disulfide bonds between the structure of the drugs and the protein structure of said pump. Its active form, cyclic sulfenamide or sulfenic acid, reacts by covalently binding to the sulfhydryl group of the proton pump extracellular domain cysteine, which enables the inhibition of the hydrochloric acid secretion. However, this type of drug therapy causes side effects, such as lower vitamin B12 and iron absorption, hypergastrinemia, thrombocytopenia, risk of pneumonia, headaches, nausea, weakness, diarrhea, and gastric cancer, as well as a greater susceptibility to bone fractures (Dacha et al. 2015; Singh et al. 2018).
Antioxidants
Published in Leslie R. Rudnick, Lubricant Additives, 2017
Robert G. Rowland, Jun Dong, Cyril A. Migdal
Sulfoxides RS(O)R can decompose by a Cope elimination to form a sulfenic acid, RSOH. Most sulfenic acids are too reactive to be isolated for direct use as an additive. The O–H bond of a sulfenic acid is very weak and readily donates H• to peroxyl radicals. The resulting RSO• radical is stabilized by the sulfur atom [144].
Reactive oxygen species and neuroepithelial interactions during wound healing
Published in David M. Gardiner, Regenerative Engineering and Developmental Biology, 2017
The second messenger functions of H2O2 are largely achieved via oxidation of specific cysteine thiols in signaling proteins, which are often found in catalytic domains of signaling enzymes (Claiborne et al. 1999). Oxidation of cysteine thiols stimulates the formation of sulfenic acid (sulfenylation), a highly unstable metabolite that can rapidly convert to other metabolites, such as sulfinic acid and sulfonic acid, or nitrosothiol (Leonard et al. 2009). However, a more common metabolic process in which sulfenic acid participates is to promote disulfide bond formation. It was found that this can lead to a conformational change in signaling proteins, which modulates their enzymatic activity, either activating or inactivating the enzyme (Stone and Yang 2006; Leonard and Carroll 2011; Truong and Carroll 2012). This has been shown to lead to the modulation of phosphorylation cascades within cells, often by activating kinases and deactivating phosphatases (Claiborne et al. 1999; Gough and Cotter 2011). In zebrafish, oxidative activation of the kinase, Lyn, a member of the Src-family kinase (SFK), recruits neutrophils toward the wound site (Niethammer et al. 2009; Yoo et al. 2011). Hydrogen peroxide oxidizes a specific cysteine residue (C466) in the kinase domain, which promotes autophosphorylation and Lyn activation (Yoo et al. 2011). A homolog of Lyn in Drosophila is Src42A, which also harbors this oxidation-sensitive cysteine residue 466, indicating the conservation of this signaling mechanism in fruit flies. It was demonstrated that Src42A similarly stimulates immune cell migration through interactions with two downstream targets, Draper/CED1 and Shark, which have been implicated in the vertebrate adaptive immune response (Underhill and Goodridge 2007). Oxidative regulation of wound repair is also conserved in the nematode Caenorhabditis elegans. However, mitochondrial superoxide rather than H2O2 mediates this process. The skin in nematodes, the hypodermis, is an epithelium that consists of large syncytial cells. Puncture or laser wounding of the hypodermis leads to a calcium-dependent repair mechanism by which an actin purse string contracts around the wound to seal the injury (Xu and Chisholm 2014). Injuries rapidly trigger the formation of calcium flashes emanating from the wound site. The calcium enters the mitochondria via the mitochondrial calcium uniporter (MCU-1). Once in the mitochondria, calcium stimulates the production of superoxide (mtROS) and subsequent local inhibition of Rho-1 GTPase activity via a redox-sensitive motif and oxidation of Cys16, leading to actin reorganization and closure.
DFT studies on exposure of sulfur impregnated and sulfur functionalized activated carbon to Hg0 vapors
Published in Journal of Sulfur Chemistry, 2023
From Figure 15(a), the electronic energy AC with the sulfenic acid edge is the highest and sulfonic acid is the least. AC with the sulfenic acid edge will be the most reactive to interact with Hg0 vapors. Figure 15(b) shows that the binding energy of Hg0 vapors is the least for AC with the sulfenic acid edge due to its higher reactive nature. The trend in binding energy is sulfenic acid edge < sulfinic acid edge < sulfonic acid edge. This trend is due to the reverse trend in electronic energy sulfenic acid edge > sulfinic acid edge > sulfonic acid edge. The optimized structure of Hg0 adsorbed on AC with different sulfur-containing functional groups may be seen in Figure 16. It may be seen from Table 2 the atomic distances between the Hg and the sulfur atom at the AC edge are similar for the sulfinic acid and sulfenic acid edge. Hg atoms strongly bond with O atoms in the sulfonic acid edge AC. This shows that Hg0 vapors interact with oxygen atoms more strongly than sulfur atoms in all the cases considered. Oxygen atom being more electronegative, draws electrons towards itself in the functional groups [26]. This causes higher affinity of oxygen atoms towards Hg atoms; hence, instead of sulfur atoms, Hg atoms bind to oxygen.
The generation and reactions of sulfenate anions. An update
Published in Journal of Sulfur Chemistry, 2022
Adam B. Riddell, Matthew R. A. Smith, Adrian L. Schwan
In 2004, the Schwan group re-introduced the sulfenate anion and its reactivity by way of a comprehensive review article [21]. Since that time investigators have demonstrated new modes for sulfenate generation, and a breadth of reaction modes have revealed novel protocols for the formation of sulfoxides and other functionalities. Some of these discoveries have been the focus of more recent reviews. The Madec/Poli group summarized their and others’ contributions employing organometallic chemistry in a 2010 review [22]. A subsequent review provided sulfenate chemistry in conjunction with recent achievements in sulfenic acid chemistry [23]. Our own group provided a summary of past achievements in 2013 [24]. Although some of the reviewed findings are addressed herein, the reader is urged to view these past compilations where greater detail may be provided for some chemistries. A review appearing in late 2021 from Yang, Zeng and coworkers [25] provides a valuable summary of the synthetic value of sulfenates for the preparation of sulfoxides under catalytic and asymmetric conditions.
Virtual screening of sulfur compounds of Allium against coronavirus proteases: E-Ajoene is a potential dual protease targeting covalent inhibitor
Published in Journal of Sulfur Chemistry, 2023
Shamasoddin Shekh, Smriti Moi, Konkallu Hanumae Gowd
The compounds S3 and S14 can potentially undergo chemical reactions with cysteine-free thiols leading to the formation of covalent products. To gain more insights, S3 and S14 compounds were further subjected to the possible modes of reactions with cysteine-free thiol and calculated energetics of corresponding reactions. N-acetyl cysteine amide was used as a model compound of cysteine thiol of the proteases to aid the calculations using density functional theory (DFT). The distance between the Cys145 of Mpro and sulfur of S3 and S14 are 5.7 Å to 5.9 Å. Similarly, the distance between Cys111 of PLpro and sulfur of S3 and S14 are 12.2 Å to 10.1 Å (Table S5a and Table S5b). Scheme-S1 shows the ΔG values for the putative reactions between cysteine thiol and S3, S14, and their corresponding isomers. The possibility-I reaction of cysteine thiol with E-ajoene yields S-thioallylation with allyl sulfinyl propene thiol as by-product. The allyl sulfinyl propene thiol undergoes tautomerization to give the reactive allyl sulfinyl propane thial (Scheme-S1a). The ΔG of the net reaction is 3.5 kcal/mol. The ΔG for the similar reaction with Z-ajoene has 5.1 kcal/mol. The possibility-II reaction of cysteine thiol with E-ajoene yields S-thioallyl sulfinyl propenylation with allyl thiol as by product. The ΔG of the reaction is − 2.3 kcal/mol. The ΔG for the similar reaction with Z-ajoene has 1.8 kcal/mol (Scheme-S1a). These thermodynamic properties suggest that the reactivity of cysteine thiol with E-ajoene is preferred over Z-ajoene. The reaction of cysteine thiol with 1-propenyl allyl thiosulfinate results in formation of propenyl disulfide with ally sulfenic acid as the by product. The ΔG of the reaction is − 7.9 kcal/mol. The ΔG for the similar reaction with allicin as reported previously is −17.9 kcal/mol. Interestingly, the by-products of both the molecules cause S-thioallylation with allicin acting as dual S-thioallylating agent. Calculation of energetics of the putative reactions indicates that the S3 and S14 compounds can covalently modify the protease cysteine thiol and the resulting byproduct also reactive in nature which may further covalently modify the proteins. The report further calculates the energy profile diagram for the putative reactions of cysteine thiol with S3 and S14 compounds of Allium. Figure 5 shows the energy profile diagram of reactions of cysteine thiol with E-ajoene and 1-propenyl allyl thiosulfinate. The activation energy barrier for the S-thioallylation of cysteine thiol by the E-ajoene is +28.8 kcal/mol and that of the S-thioallyl sulfinyl propenylation is +95.6 kcal/mol. The activation energy barrier is lower for S-thioallylation by the E-ajoene. The activation energy barrier for the S-thiopropenylation of cysteine thiol by the 1-propenyl allyl thiosulfinate is +42.2 kcal/mol.