The Experts below are selected from a list of 13446 Experts worldwide ranked by ideXlab platform
Jerry L Atwood - One of the best experts on this subject based on the ideXlab platform.
-
Pyrogallol[4]arenes in Self-Assembly
Comprehensive Supramolecular Chemistry II, 2017Co-Authors: Harshita Kumari, Jerry L AtwoodAbstract:A “macrocycle” is defined by IUPAC as “a cyclic macromolecule or a macromolecular cyclic portion of a macromolecule.” The resulting cyclic entity is a preorganized ensemble with a hydrophobic core and a hydrophilic upper/lower rim that allows for either hydrogen bonding or metal coordination. Such coordination assists in the formation of self-assembled supramolecular complexes, which are often either bilayer/cocrystals or discrete nanoassemblies, which mimic Platonic or Archimedean solids. The discrete nanoassemblies often possess cavities, which are capable of hosting a wide variety of guest species. In this article, we will focus on discussing cyclic oligomer of 1,2,3-trihydroxybenzene, commonly known as Pyrogallol[4]arene. C -alkylPyrogallol[4]arene (PgC n , where n = alkyl tail length) macrocycles are synthesized by an acid condensation reaction between Pyrogallol and aldehyde. The four alkyl groups radiate from the linker carbon atoms forming the lower rim of the macrocycle, while the 12 hydroxyl groups form the upper rim of the macrocycle. Pyrogallol[4]arene has been shown to complex with a variety of metals, solvents, and crown ethers to form a plethora of varied supramolecular complexes. Most commonly, Pyrogallol[4]arenes have been shown to form bilayers, nanocapsules, nanotubes, supramolecular organic frameworks (SOFs), and tethered MOF-like structures. Pyrogallol[4]arenes-based bilayers are primarily hydrogen-bonded, which self-assemble through macrocycle–solvent–guest interactions. Nanocapsules and nanotubes of Pyrogallol[4]arenes are either assembled through hydrogen bonding or through metal coordination. SOFs and tethered-MOF-like structures are another category of complexes that are constructed from divergent spacer ligands.
-
process development for separation of conformers from derivatives of resorcin 4 arenes and Pyrogallol 4 arenes
Chemistry: A European Journal, 2016Co-Authors: Rahul S Patil, Chen Zhang, Jerry L AtwoodAbstract:Macrocyclic compounds, such as resorcin[4]arenes and Pyrogallol[4]arenes, have proven to be useful building blocks in the construction of supramolecular organic frameworks (SOFs) because of their unique bowl-like shape and ability to interact through variety of intermolecular interactions. Herein, we report the synthesis and crystal structures of two functionalized resorcin[4]arenes and pyroagllol[4]arenes, 4-hydroxyphenylresorcin[4]arenes, and 4-hydroxyphenylPyrogallol[4]arenes. These phenyl-functionalized macrocycles usually have different conformers, such as cone, boat, chair, saddle, and diamond. The successful separation of predominant conformers from the crude product was carried out with solvent-extraction technique. The shape and molecular arrangement of these conformers in the individual crystal structure was verified with single-crystal X-ray diffraction studies.
-
Endo vs Exo Bowl: Complexation of Xanthone by Pyrogallol[4]arenes
Crystal Growth & Design, 2014Co-Authors: Constance R. Pfeiffer, Drew A. Fowler, Jerry L AtwoodAbstract:Cocrystal systems containing Pyrogallol[4]arene, xanthone, and solvent molecules are examined and discussed. Three types of Pyrogallol[4]arenes are cocrystallized with xanthone in isopropanol, acetonitrile, dimethyl sulfoxide, and a mixture of isopropanol and methanol. It is found that the solvent controls complexation of the xanthone molecule, whereas Pyrogallol[4]arene tail length affects cocrystal packing. With a single-solvent system, the xanthone molecule is outside (exo) of the bowl of the Pyrogallol[4]arene, but with a two-solvent system, the xanthone molecule is inside (endo) of the bowl of the Pyrogallol[4]arene.
-
Cocrystallization of C-butyl Pyrogallol[4]arene and C-propan-3-ol Pyrogallol[4]arene with gabapentin
CrystEngComm, 2011Co-Authors: Drew A. Fowler, Jian Tian, Charles L. Barnes, Simon J. Teat, Jerry L AtwoodAbstract:The single crystal X-ray diffraction structures for three cocrystals of C-butyl Pyrogallol[4]arene and C-propan-3-ol Pyrogallol[4]arene with the pharmaceutical gabapentin are described. The variation of solvent conditions and functionalities of the Pyrogallol[4]arene tails demonstrates how these calixarene-like molecules can be used in the design of cocrystals with target molecules.
-
On the synthesis and structure of the very large spherical capsules derived from hexamers of Pyrogallol[4]arenes
Journal of Supramolecular Chemistry, 2001Co-Authors: Jerry L Atwood, Leonard J. Barbour, Agoston JergaAbstract:Abstract The acid-catalyzed condensation of Pyrogallol and aldehydes yields Pyrogallol[4]arenes, which associate in the form of hexameric capsules of extraordinary stability due to the presence of 48 intermolecular hydrogen bonds seaming the individual Pyrogallol[4]arenes together.
Sung Zoo Kim - One of the best experts on this subject based on the ideXlab platform.
-
Pyrogallol as a glutathione depletor induces apoptosis in HeLa cells.
International Journal of Molecular Medicine, 2008Co-Authors: Yong Hwan Han, Sung Zoo Kim, Suhn Hee Kim, Woo Hyun ParkAbstract:Pyrogallol, a polyphenol, is known to be a superoxide anion (O2(.-)) generator. We investigated the involvement of glutathione (GSH) and reactive oxygen species (ROS) in Pyrogallol-induced HeLa cell death. We measured the changes of ROS levels, GSH levels, sub-G1 cells, annexin V/PI staining cells and mitochondria membrane potential (DeltaPsi m) in HeLa cells treated with Pyrogallol and/or ROS scavenger. The intracellular ROS levels were decreased or increased depending on the concentration of Pyrogallol. The level of O2(.-) was significantly increased and superoxide dismutase (SOD) activity was down-regulated by Pyrogallol. Pyrogallol reduced intracellular GSH content in HeLa cells. The ROS scavengers, Tempol, Tiron, Trimetazidine and N-acetylcysteine (NAC), did not down-regulate the production of O2(.-). However, treatment with NAC showed the recovery of GSH depletion and significantly rescued cells from Pyrogallol-induced apoptosis. In addition, the recovery of GSH depletion by SOD and catalase was accompanied by the decrease of apoptosis levels. Furthermore, NAC and SOD significantly inhibited CMF-negative (GSH-depleted) and PI-positive cells induced by Pyrogallol. Taken together, Pyrogallol potently increased intracellular O2(.-) levels and decreased GSH content in HeLa cells, and NAC, SOD and catalase significantly rescued HeLa cells from Pyrogallol-induced apoptosis accompanied by the recovery of GSH depletion.
-
apoptosis in Pyrogallol treated calu 6 cells is correlated with the changes of intracellular gsh levels rather than ros levels
Lung Cancer, 2008Co-Authors: Yong Hwan Han, Sung Zoo Kim, Suhn Hee Kim, Woo Hyun ParkAbstract:We investigated the involvement of glutathione (GSH) and reactive oxygen species (ROS) such as H2O2 and O2-* in the deaths of Pyrogallol-treated Calu-6 cells. Pyrogallol inhibited the growth of Calu-6 cells with an IC50 of approximately 50 microM. Levels of intracellular H2O2 were not altered or were decreased in Pyrogallol-treated Calu-6 cells at 72 h. However, levels of O2*- were increased. Treatment with Pyrogallol also reduced the intracellular GSH content. The activity of SOD was down-regulated, but the activity of catalase was up-regulated by Pyrogallol at 72 h. ROS scavengers, including Tempol, Tiron, Trimetazidine, and N-acetylcysteine (NAC), did not reduce the levels of the intracellular O2*-. Tempol showing the recovery of GSH depletion in Pyrogallol-treated cells significantly prevented apoptosis, while Tiron prevented the loss of mitochondrial transmembrane potential (DeltaPsi(m)). In contrast, treatment with NAC showing an increased effect on O2*- levels and depletion of GSH intensified Pyrogallol-induced apoptosis. In addition, treatment with SOD and catalase significantly prevented the loss of mitochondrial transmembrane potential (DeltaPsi(m)) in Pyrogallol-treated Calu-6 cells. However, only catalase showing a decreased effect on O2*- levels and depletion of GSH prevented Pyrogallol-induced apoptosis. Taken together, apoptosis in Pyrogallol-treated Calu-6 cells is correlated with the changes of intracellular GSH levels rather than ROS levels.
-
a superoxide anion generator Pyrogallol inhibits the growth of hela cells via cell cycle arrest and apoptosis
Molecular Carcinogenesis, 2008Co-Authors: Sang Wook Kim, Suhn Hee Kim, Yong Whan Han, Soo Teik Lee, Hey Jin Jeong, Seong Hun Kim, In Hee Kim, Seung Ok Lee, Dae Ghon Kim, Sung Zoo KimAbstract:We investigated the in vitro effects of Pyrogallol on cell growth, cell cycle regulation, and apoptosis in HeLa cells. Pyrogallol inhibited the growth of HeLa cells with an IC(50) of approximately 45 microM. Pyrogallol induced arrest during all phases of the cell cycle and also very efficiently resulted in apoptosis in HeLa cells, as evidenced by flow cytometric detection of sub-G1 DNA content, annexin V binding assay, and DAPI staining. This apoptotic process was accompanied by the loss of mitochondrial transmembrane potential (DeltaPsi(m)), Bcl-2 decrease, caspase-3 activation, and PARP cleavage. Pan-caspase inhibitor (Z-VAD) could rescue some HeLa cells from Pyrogallol-induced cell death, while caspase-8 and -9 inhibitors unexpectedly enhanced the apoptosis. When we examined the changes of the ROS, H(2)O(2) or O(2)(*-) in Pyrogallol-treated cells, H(2)O(2) was slightly increased and O(2)(*-) significantly was increased. In addition, we detected a decreased GSH content in Pyrogallol-treated cells. Only pan-caspase inhibitor showing recovery of GSH depletion and reduced intracellular O(2)(*-) level decreased PI staining in Pyrogallol-treated HeLa cells, which indicates dead cells. In summary, we have demonstrated that Pyrogallol as a generator of ROS, especially O(2) (*-), potently inhibited the growth of HeLa cells through arrests during all phases of the cell cycle and apoptosis.
-
Pyrogallol ros generator inhibits as4 1 juxtaglomerular cells via cell cycle arrest of g2 phase and apoptosis
Toxicology, 2007Co-Authors: Woo Hyun Park, Yong Hwan Han, Suhn Hee Kim, Sung Zoo KimAbstract:Abstract Pyrogallol as a catechin compound has been employed as an O2 − generator and often used to investigate the role of ROS in the biological system. Here, we investigated the in vitro effect of Pyrogallol on cell growth, cell cycle and apoptosis in As4.1 juxtaglomerular cells. Dose-dependent inhibition of cell growth was observed with IC50 of about 60 μM for 48 h using MTT assay. Pyrogallol (100 μM) did not alter intracellular H2O2 level and catalase activity, but increased the intracellular O2 − level and decreased SOD activity in As4.1 cells. DNA flow cytometric analysis indicated that 50 and 100 μM Pyrogallol significantly increased G2 phase cells as compared with those of Pyrogallol-untreated cells. Also, Pyrogallol induced apoptosis as evidenced by flow cytometric detection of sub-G1 DNA content, annexin V binding assay and DAPI staining. This apoptosis process was accompanied with the loss of mitochondrial transmembrane potential (ΔΨm), Bcl-2 decrease, caspase-3 activation and PARP cleavage. Pan caspase inhibitor (Z-VAD) could significantly rescue As4.1 cells from Pyrogallol-induced cell death. But, the inhibitors of caspase-3, caspase-8, and caspase-9 did not prevent apoptotic events in Pyrogallol-treated As4.1 cells. Taken together, we have demonstrated that an ROS inducer, Pyrogallol inhibits the growth of As4.1 JG cells via cell cycle arrest and apoptosis, and suggest that the compound exhibits an anti-proliferative efficacy on these cells.
-
A superoxide anion generator, Pyrogallol induces apoptosis in As4.1 cells through the depletion of intracellular GSH content.
Mutation Research, 2007Co-Authors: Woo Hyun Park, Suhn Hee Kim, Yong Whan Han, Sung Zoo KimAbstract:Abstract We investigated the involvement of ROS such as H2O2 and O2 −, and GSH in As4.1 cell death induced by Pyrogallol. The intracellular H2O2 levels were decreased or increased depending on the concentration and incubation time of Pyrogallol. The levels of O2 − were significantly increased. Pyrogallol reduced the intracellular GSH content. And ROS scavengers, Tempol, Tiron, Trimetazidine and NAC could not significantly down-regulate the production of H2O2 and O2 −. However, these ROS scavengers slightly inhibited apoptosis. Interestingly, Tempol showing the recovery of GSH depletion induced by Pyrogallol significantly decreased apoptosis without the significant reduction of intracellular O2 − levels. SOD and catalase did not change the level of H2O2 but decreased the level of O2 −. The inhibition of GSH depletion by these was accompanied with the decrease of apoptosis, as evidenced by sub-G1 DNA content, annexin V staining, mitochondria membrane potential (ΔΨm) and Western data. In addition, ROS scavengers and SOD did not alter a G2 phase accumulation of the cell cycle induced by Pyrogallol. However, catalase changed the cell cycle distributions of Pyrogallol-treated cells to those of Pyrogallol-untreated cells. In summary, we have demonstrated that Pyrogallol potently generates ROS, especially O2 −, in As4.1 JG cells, and Tempol, SOD and catalase could rescue to a lesser or greater extent cells from Pyrogallol-induced apoptosis through the up-regulation of intracellular GSH content.
Yong Yao - One of the best experts on this subject based on the ideXlab platform.
-
microwave irradiation assisted synthesis alkylation reaction and configuration analysis of aryl Pyrogallol 4 arenes
Tetrahedron, 2007Co-Authors: Chao-guo Yan, Weifeng Chen, Jiao Chen, Tiantian Jiang, Yong YaoAbstract:Abstract A series of aryl Pyrogallol[4]arenes were efficiently synthesized in excellent yields by cyclocondensation of Pyrogallol with aromatic aldehydes under microwave irradiation. The structures of aryl Pyrogallol[4]arenes were confirmed by characterization of their acylated derivatives. Under microwave irradiation, alkylation reactions of aryl Pyrogallol[4]arenes with some alkylating reagents such as n-butyl iodide, benzyl chloride, and ethyl α-chloroacetate were also finished quickly to yield fully O-alkylated products. The 1H NMR spectra and crystal structures showed that the acylated and alkylated aryl Pyrogallol[4]arenes existed mainly in rctt (cis–trans–trans) configuration.
Bernhard Schink - One of the best experts on this subject based on the ideXlab platform.
-
Towards the reaction mechanism of Pyrogallol-phloroglucinol transhydroxylase of Pelobacter acidigallici
Biochimica et Biophysica Acta, 1999Co-Authors: Wolfram Reichenbecher, Bernhard SchinkAbstract:Abstract Conversion of Pyrogallol to phloroglucinol was studied with the molybdenum enzyme transhydroxylase of the strictly anaerobic fermenting bacterium Pelobacter acidigallici. Transhydroxylation experiments in H2 18O revealed that none of the hydroxyl groups of phloroglucinol was derived from water, confirming the concept that this enzyme transfers a hydroxyl group from the cosubstrate 1,2,3,5-tetrahydroxybenzene (tetrahydroxybenzene) to the acceptor Pyrogallol, and simultaneously regenerates the cosubstrate. This concept requires a reaction which synthesizes the cofactor de novo to maintain a sufficiently high intracellular pool during growth. Some sulfoxides and aromatic N-oxides were found to act as hydroxyl donors to convert Pyrogallol to tetrahydroxybenzene. Again, water was not the source of the added hydroxyl groups; the oxides reacted as cosubstrates in a transhydroxylation reaction rather than as true oxidants in a net hydroxylation reaction. No oxidizing agent was found that supported a formation of tetrahydroxybenzene via a net hydroxylation of Pyrogallol. However, conversion of Pyrogallol to phloroglucinol in the absence of tetrahydroxybenzene was achieved if little Pyrogallol and a high amount of enzyme preparation was used which had been pre-exposed to air. Obviously, the enzyme was oxidized by air to form sufficient amounts of tetrahydroxybenzene from Pyrogallol to start the reaction. A reaction mechanism is proposed which combines an oxidative hydroxylation with a reductive dehydroxylation via the molybdenum cofactor, and allows the transfer of a hydroxyl group between tetrahydroxybenzene and Pyrogallol without involvement of water. With this, the transhydroxylase differs basically from all other hydroxylating molybdenum enzymes which all use water as hydroxyl source.
-
Towards the reaction mechanism of Pyrogallol–phloroglucinol transhydroxylase of Pelobacter acidigallici
Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1999Co-Authors: Wolfram Reichenbecher, Bernhard SchinkAbstract:Abstract Conversion of Pyrogallol to phloroglucinol was studied with the molybdenum enzyme transhydroxylase of the strictly anaerobic fermenting bacterium Pelobacter acidigallici. Transhydroxylation experiments in H2 18O revealed that none of the hydroxyl groups of phloroglucinol was derived from water, confirming the concept that this enzyme transfers a hydroxyl group from the cosubstrate 1,2,3,5-tetrahydroxybenzene (tetrahydroxybenzene) to the acceptor Pyrogallol, and simultaneously regenerates the cosubstrate. This concept requires a reaction which synthesizes the cofactor de novo to maintain a sufficiently high intracellular pool during growth. Some sulfoxides and aromatic N-oxides were found to act as hydroxyl donors to convert Pyrogallol to tetrahydroxybenzene. Again, water was not the source of the added hydroxyl groups; the oxides reacted as cosubstrates in a transhydroxylation reaction rather than as true oxidants in a net hydroxylation reaction. No oxidizing agent was found that supported a formation of tetrahydroxybenzene via a net hydroxylation of Pyrogallol. However, conversion of Pyrogallol to phloroglucinol in the absence of tetrahydroxybenzene was achieved if little Pyrogallol and a high amount of enzyme preparation was used which had been pre-exposed to air. Obviously, the enzyme was oxidized by air to form sufficient amounts of tetrahydroxybenzene from Pyrogallol to start the reaction. A reaction mechanism is proposed which combines an oxidative hydroxylation with a reductive dehydroxylation via the molybdenum cofactor, and allows the transfer of a hydroxyl group between tetrahydroxybenzene and Pyrogallol without involvement of water. With this, the transhydroxylase differs basically from all other hydroxylating molybdenum enzymes which all use water as hydroxyl source.
Chao-guo Yan - One of the best experts on this subject based on the ideXlab platform.
-
microwave irradiation assisted synthesis alkylation reaction and configuration analysis of aryl Pyrogallol 4 arenes
Tetrahedron, 2007Co-Authors: Chao-guo Yan, Weifeng Chen, Jiao Chen, Tiantian Jiang, Yong YaoAbstract:Abstract A series of aryl Pyrogallol[4]arenes were efficiently synthesized in excellent yields by cyclocondensation of Pyrogallol with aromatic aldehydes under microwave irradiation. The structures of aryl Pyrogallol[4]arenes were confirmed by characterization of their acylated derivatives. Under microwave irradiation, alkylation reactions of aryl Pyrogallol[4]arenes with some alkylating reagents such as n-butyl iodide, benzyl chloride, and ethyl α-chloroacetate were also finished quickly to yield fully O-alkylated products. The 1H NMR spectra and crystal structures showed that the acylated and alkylated aryl Pyrogallol[4]arenes existed mainly in rctt (cis–trans–trans) configuration.
-
Synthesis, crystal structure and configuration of acetylated aryl Pyrogallol[4]arenes
Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2007Co-Authors: Jun Han, Xiaokai Song, Li Liu, Chao-guo YanAbstract:A series of aryl and ferrocenyl Pyrogallol[4]arenes have been synthesized by the HCl-catalyzed condensation reactions of Pyrogallol with aromatic aldehydes and ferrocenecarbaldehyde. The fully acetyl and ethoxycarbonylmethoxy derivatives were also prepared and fully characterized. The crystal structures show that acylated phenyl Pyrogallol[4]arene exists in rctt (cis-trans-trans) configuration, while the corresponding ferrocenyl Pyrogallol[4]arene in rccc (all cis) configuration.
