Purpurogallin, a scavenger of polymorphonuclear leukocyte-derived oxyradicals

Syntheses of 6,7-Benzotropolones by a Sequence of Acylation (or α-Hydroxyalkylation/Oxidation), Ring-Closing Metathesis, and Hydrolysis/β-Elimination

Starting from ortho-bromostyrenes, 12 6,7-benzotropolones were synthesized in 3 or 4 steps. Br/Li exchanges provided the respective ortho-lithiostyrenes. The latter were acylated by a Weinreb amide, if unhindered, or hydroxyalkylated by an aldehyde, if hindered (an oxidation ensuing thereafter). Acetonide-containing benzannulated nonatrienones resulted. Ring-closing olefin metatheses converted them into acetonide-containing benzocycloheptadienones. Treatment with aq. HCl caused hydrolyses followed by β-elimination reactions giving 6,7-benzotropolones.

Tandem isonitrile insertion/azacyclopropylidene-annulated cyclohexenone–tropone rearrangement of p-QMs and TosMIC: de novo synthesis of pyrrolotropones with anti-cancer activity

TosMIC causes ring expansion of p-QMs: highly substituted pyrrolotropones are rapidly assembled in a domino process mediated by DBU. The utility of the method was highlighted by follow-up transformation and biological activity identification.

Synthesis of Naturally Occurring Tropones and Tropolones

Tropones and tropolones are an important class of seven-membered non-benzenoid aromatic compounds. They can be prepared directly by oxidation of seven-membered rings. They can also be derived from cyclization or cycloaddition of appropriate precursors followed by elimination or rearrangement. This review discusses the types of naturally occurring tropones and tropolones and outlines important methods developed for the synthesis of tropone and tropolone natural products.

Benzotropolone inhibitors of estradiol methylation: kinetics and in silico modeling studies

Natural and synthetic benzotropolone compounds were assessed in vitro for their ability to inhibit hydroxyestradiol methylation by catechol-O-methyltransferase (COMT). The compounds were also modeled in silico with a homology model of human COMT. Purpurogallin (1), purpurogallin carboxylic acid (2), and theaflavin-3,3'-digallate (6) were the most potent inhibitors of 2-hydroxy and 4-hydroxyestradiol methylation (IC(50) 0.22-0.50microM). Compounds 1 and 6 decreased the V(max) and increased the K(m) of COMT, indicating a mixed-type inhibition. Compounds 1 and 2 bound to COMT by inserting the six-membered ring of the benzotropolone into the active site. Decreased acidity of the hydroxyl groups on this ring or increased bulkiness reduced potency. Compound 6 bound by inserting the galloyl ester into the active site, which allowed the compound to overcome increased bulkiness and resulted in restored potency. Further studies are needed to determine the impact in vivo of COMT inhibition by these compounds.

Platelet-activating factor induces lung inflammation and leak in rats: hydrogen peroxide production along neutrophil-lung endothelial cell interfaces

Interleukin-1 (IL-1) levels and neutrophils are increased in the lung-lavage fluid of patients with acute lung injury (ALI), and instilling IL-1 intratracheally into rats causes rapid lung-neutrophil influx and neutrophil-dependent lung leakage. IL-1 insufflation also increases platelet-activating factor (PAF) activity in rat lung, and PAF is increased in the lung-lavage fluid of ALI patients. To assess the direct effects of PAF on the lung, we administered PAF intratracheally in rats. We found that rats given PAF (5 microg) intratracheally had increased lung nuclear factor-kappaB activation, myeloperoxidase activity, numbers of lavage neutrophils, lavage neutrophil nitroblue tetrazolium reduction, and leakage compared with sham-treated rats administered saline solution intratracheally. Electron microscopic examination also indicated that lungs from rats given PAF intratracheally had increased neutrophil infiltration, cell damage, and neutrophil-endothelial cell interface cerium chloride staining - a marker of hydrogen peroxide production - compared with sham-treated rats. Simultaneous treatment with a PAF receptor-antagonist, WEB 2086, decreased the aforementioned changes observed after intratracheal administration of PAF.

Platelet-activating factor contributes to acute lung leak in rats given interleukin-1 intratracheally

Lung lavage fluid of patients with acute lung injury (ALI) has increased levels of interleukin-1 (IL-1) and neutrophils, but their relationship to the lung leak that characterizes these patients is unclear. To address this concern, we investigated the role of the neutrophil agonist platelet-activating factor [1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (PAF)] in the development of the acute neutrophil-dependent lung leak that is induced by giving IL-1 intratracheally to rats. We found that PAF acetyltransferase and PAF activities increased in lungs of rats given IL-1 intratracheally compared with lungs of sham-treated rats given saline intratracheally. The participation of PAF in the development of lung leak and lung neutrophil accumulation after IL-1 administration was suggested when treatment with WEB-2086, a commonly used PAF-receptor antagonist, decreased lung leak, lung myeloperoxidase activity, and lung lavage fluid neutrophil increases in rats given IL-1 intratracheally. Additionally, neutrophils recovered from the lung lavage fluid of rats given IL-1 intratracheally reduced more nitro blue tetrazolium (NBT) in vitro than neutrophils recovered from control rats or rats that had been given WEB-2086 and then IL-1. Histological examination indicated that the endothelial cell-neutrophil interfaces of cerium chloride-stained lung sections of rats given IL-1 contained increased cerium perhydroxide (the reaction product of cerium chloride with hydrogen peroxide) compared with lungs of control rats or rats treated with WEB-2086 and then given IL-1 intratracheally. These in vivo findings were supported by parallel findings showing that WEB-2086 treatment decreased neutrophil adhesion to IL-1-treated cultured endothelial cells in vitro. We concluded that PAF contributes to neutrophil recruitment and neutrophil activation in lungs of rats given IL-1 intratracheally.

Molecular structure and antioxidant specificity of purpurogallin in three types of human cardiovascular cells

Purpurogallin (PPG) in an active cytoprotector found in certain oak barks. We have shown that PPG prolongs the survival of cultured cardiocytes from rats and rabbits against different oxidants better than do antioxidants such as Trolox (a hydrophilic analogue of vitamin E) in a morphometric assay system. First, we verified by X-ray crystallography that PPG is a bicyclic molecule comprising a phenolic ring fused with a seven-membered ring in a highly planar conformation. In analogues of PPG wherein the two double bonds in the seven membered ring of the parent molecule are saturated or where the four OH groups of the parent compound are substituted by four OCH3 groups, the derivatives are less planar and less protective of the human cells than native PPG. Second, PPG in a concentration-dependent manner protected myocytes and endothelial cells of humans against oxyradicals generated with any one of the following oxyradical generators: (a) xanthine oxidase plus hypoxanthine, (b) menadione, or (c) paraquat. In each case, PPG was more cytoprotective than comparative antioxidants. Also, PPG protected erythrocytes against peroxyl radicals better than the two PPG derivatives mentioned. Third, the cytoprotective action of PPG detected in vitro was accompanied by declines of malondialdehyde. Finally, we observed that PPG chelated ferrous ions and, therefore, can suppress the formation of radicals in the Fenton reaction. Thus, PPG with its molecular architecture and presumably its affinity for ferrous ions protects multiple types of cardiovascular cells against oxyradicals.