Palmatine antioxidant and anti-acetylcholinesterase activities: A pre-clinical assessment.

There is evidence that palmatine (PA), an alkaloid isolated from the Guatteria friesiana plant, has some important biological activities, including anti-inflammatory and antidepressant effects. In this study, the antioxidant and anti-acetylcholinesterase (AChE) effects of PA were assessed. The antioxidant capacity was evaluated in vitro and in vivo through 7 distinct assays, and the anti-AChE activity was determined in vitro.

Vitex negundo Linn.: phytochemical composition, nutritional analysis, and antioxidant and antimicrobial activity.

Vitex negundo (VN) is a widely used plant in folk medicine, namely for the treatment of jaundice, wounds, body ache, toothache, asthma, eye pain, and migraine. These effects have been increasingly attributed to its chemical composition. Here, we assessed the VN chemical and nutritional composition and biological activity, with particular emphasis on antioxidant and antimicrobial effects.

A bipyridine-ligated zinc(II) complex with bridging flavonolate ligation: synthesis, characterization, and visible-light-induced CO release reactivity.

Metal-flavonolate compounds are of significant current interest as synthetic models for quercetinase enzymes and as bioactive compounds of importance to human health. Zinc-3-hydroxyflavonolate compounds, including those of quercetin, kampferol, and morin, generally exhibit bidentate coordination to a single Zn center. The bipyridine-ligated zinc-flavonolate compound reported herein, namely bis(μ-4-oxo-2-phenyl-4H-chromen-3-olato)-κO:O,O;κO,O:O-bis[(2,2'-bipyridine-κN,N')zinc(II)] bis(perchlorate), {[Zn(CHO)(CHN)](ClO)}, (1), provides an unusual example of bridging 3-hydroxyflavonolate ligation in a dinuclear metal complex.

Synergy between Experimental and Computational Chemistry Reveals the Mechanism of Decomposition of Nickel-Ketene Complexes.

A series of (dppf)Ni(ketene) complexes were synthesized and fully characterized. In the solid state, the complexes possess η-(C,O) coordination of the ketene in an overall planar configuration. They display similar structure in solution, except in some cases, the η-(C,C) coordination mode is also detected.

Anion Effects in Oxidative Aliphatic Carbon-Carbon Bond Cleavage Reactions of Cu(II) Chlorodiketonate Complexes.

Aliphatic oxidative carbon-carbon bond cleavage reactions involving Cu(II) catalysts and O2 as the terminal oxidant are of significant current interest. However, little is currently known regarding how the nature of the Cu(II) catalyst, including the anions present, influence the reaction with O2. In previous work, we found that exposure of the Cu(II) chlorodiketonate complex [(6-Ph2TPA)Cu(PhC(O)CClC(O)Ph)]ClO4 (1) to O2 results in oxidative aliphatic carbon-carbon bond cleavage within the diketonate unit, leading to the formation of benzoic acid, benzoic anhydride, benzil, and 1,3-diphenylpropanedione as organic products.

A Structurally-Tunable 3-Hydroxyflavone Motif for Visible Light-Induced Carbon Monoxide-Releasing Molecules (CORMs).

Molecules that can be used to deliver a controlled amount of carbon monoxide (CO) have the potential to facilitate investigations into the roles of this gaseous molecule in biology and advance therapeutic treatments. This has led to the development of light-induced CO-releasing molecules (photoCORMs). A goal in this field of research is the development of molecules that exhibit a combination of controlled CO release, favorable biological properties (e.

Structure and properties of nitrogen-rich 1,4-dicyanotetrazine, C4N6: a comparative study with related tetracyano electron acceptors.

The crystal structure, redox electrochemical stability, and reaction chemistry of 1,4-dicyanotetrazine (DCNT) has been experimentally characterized. These experimental results were rationalized by the results of theoretical calculations of the electronic structure, spin and charge distributions, electronic absorption spectra, and electron affinity and compared with the results for related the tetracyano electron acceptors tetracyanoethylene (TCNE), 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), and 2,3,5,6-tetracyanopyrazine (TCNP). DCNT is made from the dehydration of 1,2,4,5-tetrazine-3,6-dicarboxamide, and because of the unusual deep-magenta color of the dicarboxamide in the solid state, its hydrogen-bonded layered structure, electronic structure, and electronic absorption spectra were determined.

Halide-promoted dioxygenolysis of a carbon-carbon bond by a copper(II) diketonate complex.

A mononuclear Cu(II) chlorodiketonate complex was prepared, characterized, and found to undergo oxidative aliphatic carbon-carbon bond cleavage within the diketonate unit upon exposure to O2 at ambient temperature. Mechanistic studies provide evidence for a dioxygenase-type C-C bond cleavage reaction pathway involving trione and hypochlorite intermediates. Significantly, the presence of a catalytic amount of chloride ion accelerates the oxygen activation step via the formation of a Cu-Cl species, which facilitates monodentate diketonate formation and lowers the barrier for O2 activation.

(6S*)-6-[(1S*,2R*)-1,2-Di-hydroxy-pent-yl]-4-meth-oxy-5,6-di-hydro-2H-pyran-2-one.

The title compound, C11H18O5, was isolated from a liquid culture of Pestalotiopsis sp. In the mol-ecule, the pyran-2-one ring assumes a half-chair conformation. The two terminal C atoms of the pentyl group were refined as disordered over two sets of sites, with refined occupancies of 0.

Pb(II)-promoted amide cleavage: mechanistic comparison to a Zn(II) analogue.

Two new Pb(II) complexes of the amide-appended nitrogen/sulfur epppa (N-((2-ethylthio)ethyl)-N-((6-pivaloylamido-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine) chelate ligand, [(epppa)Pb(NO3)2] (4-NO3) and [(epppa)Pb(ClO4)2] (4-ClO4), were prepared and characterized. In the solid state, 4-NO3 exhibits κ(5)-epppa chelate ligand coordination as well as the coordination of two bidentate nitrate ions. In acetonitrile, 4-NO3 is a 1:1 electrolyte with a coordinated NO3(-), whereas 4-ClO4 is a 1:2 electrolyte.

First row transition metal(II) thiocyanate complexes, and formation of 1-, 2-, and 3-dimensional extended network structures of M(NCS)2(solvent)2 (M = Cr, Mn, Co) composition.

The reaction of first row transition M(II) ions with KSCN in various solvents form tetrahedral (NMe4)2[M(II)(NCS)4] (M = Fe, Co), octahedral trans-M(II)(NCS)2(Sol)4 (M = Fe, V, Ni; Sol = MeCN, THF), and K4[M(II)(NCS)6] (M = V, Ni). The reaction of M(NCS)2(OCMe2)2 (M = Cr, Mn) in MeCN and [Co(NCMe)6](BF4)2 and KSCN in acetone and after diffusion of diethyl ether form M(NCS)2(Sol)2 that structurally differ as they form one-dimensional (1-D) (M = Co; Sol = THF), two-dimensional (2-D) (M = Mn; Sol = MeCN), and three-dimensional (3-D) (M = Cr; Sol = MeCN) extended structures. 1-D Co(NCS)2(THF)2 has trans-THFs, while the acetonitriles have a cis geometry for 2- and 3-D M(NCS)2(NCMe)2 (M = Cr, Mn).

endo,endo-Tetra-cyclo-[6.2.1.1(3,6).0(2,7)]dodeca-9-en-anti-11-yl 4-bromo-benzoate.

The title compound 1-OPBB, C(19)H(19)BrO(2), contains a dechlorinated and hydrogenated isodrin backbone with an anti-4-bromo-benzoate substituent at one of the methano bridges. The dihedral angle between the CO(2) ester plane and the benzene ring plane is 8.5 (2)°.

Bicyclo-[2.2.1]hept-7-yl p-bromo-benzoate.

The title compound, C(14)H(15)BrO(2), contains a sterically unencumbered norbornyl group. The dihedral angle between the plane of the carboxyl-ate group and the mean plane of the adjacent benzene ring is 5.3 (2)°.

Regioselective aliphatic carbon-carbon bond cleavage by a model system of relevance to iron-containing acireductone dioxygenase.

Mononuclear Fe(II) complexes ([(6-Ph(2)TPA)Fe(PhC(O)C(R)C(O)Ph)]X (3-X: R = OH, X = ClO(4) or OTf; 4: R = H, X = ClO(4))) supported by the 6-Ph(2)TPA chelate ligand (6-Ph(2)TPA = N,N-bis((6-phenyl-2-pyridyl)methyl)-N-(2-pyridylmethyl)amine) and containing a β-diketonate ligand bound via a six-membered chelate ring have been synthesized. The complexes have all been characterized by (1)H NMR, UV-vis, and infrared spectroscopy and variably by elemental analysis, mass spectrometry, and X-ray crystallography. Treatment of dry CH(3)CN solutions of 3-OTf with O(2) leads to oxidative cleavage of the C(1)-C(2) and C(2)-C(3) bonds of the acireductone via a dioxygenase reaction, leading to formation of carbon monoxide and 2 equiv of benzoic acid as well as two other products not derived from dioxygenase reactivity: 2-oxo-2-phenylethylbenzoate and benzil.

Bicyclo-[2.2.1]hept-2-en-7-yl 4-bromo-benzoate.

The structure of the title compound, C(14)H(13)BrO(2), which contains a norbornenyl group and a 4-bromo-benzoate ester at the single C-atom bridge, has been redetermined [see McDonald & Trotter (1965 ▶). Acta Cryst.19, 456-463] to modern standards to establish high-precision geometrical data to compare with norbornyl and other tetra-cyclic 4-bromo-benzoates.

3-Carbamoylquinoxalin-1-ium chloride.

The title compound, C(9)H(8)N(3)O(+)·Cl(-), was isolated from a liquid culture of streptomyces sp. In the cation, the ring system makes a dihedral angle of 0.2 (2)° with the amide group.

Photochemically initiated oxidative carbon-carbon bond-cleavage reactivity in chlorodiketonate Ni(II) complexes.

Three mononuclear Ni(II) complexes containing a 2-chloro-1,3-diketonate ligand and supported by the 6-Ph(2)TPA chelate, as well as analogues that lack the 2-chloro substituent on the β-diketonate ligand, have been prepared and characterized. Upon irradiation at 350 nm under aerobic conditions, complexes containing the 2-chloro-substituted ligands undergo reactions to generate products resulting from oxidative cleavage, α-cleavage, and radical-derived reactions involving the 2-chloro-1,3-diketonate ligand. Mechanistic studies suggest that the oxidative cleavage reactivity, which leads to the production of carboxylic acids, is a result of the formation of superoxide, which occurs through reaction of reduced nickel complexes with O(2).

Imidazolidene carboxylate bound MBPh4 complexes (M = Li, Na) and their relevance in transcarboxylation reactions.

Combination of 1,3-bis(2,6-diisopropylphenyl)imidazolum-2-carboxylate (IPrCO(2)) with the Lewis acids MBPh(4), where M = Li or Na, provided two separate complexes. The crystal structures of these complexes revealed that coordination to NaBPh(4) yielded a dimeric species, yet coordination of IPrCO(2) with LiBPh(4) yielded a monomeric species. Combination of 1,3-bis(2,4,6-trimethylphenyl)imidazolum-2-carboxylate (IMesCO(2)) with LiBPh(4) also afforded a dimeric species that was similar in global structure to that of the IPrCO(2)+NaBPh(4) dimer.

Influence of water on the formation of O2-reactive divalent metal enolate complexes of relevance to acireductone dioxygenases.

Reaction conditions were evaluated for the preparation of [(6-PhTPA)Ni(PhC(O)C(OH)C(O)Ph)]ClO(4) (3) and [(6-Ph(2)TPA)Co(PhC(O)C(OH)C(O)Ph)]ClO(4) (7), two complexes of structural relevance to the enzyme/substrate (ES) adduct in Ni(II)- and Co(II)-containing forms of acireductone dioxygenase. The presence of water in reactions directed at the preparation of 3 and 7 was found to result in isomerization of the enolate precursor 2-hydroxy-1,3-diphenylpropane-1,3-dione to give the ester 2-oxo-2-phenylethylbenzoate. Performing synthetic procedures under dryer conditions reduced the amount of ester production and enabled the isolation of 3 in high yield.

Photochemically-induced dioxygenase-type CO-release reactivity of group 12 metal flavonolate complexes.

Exposure of 3-hydroxyflavonolate complexes of the group 12 metals to UV light under aerobic conditions results in oxidative carbon-carbon bond cleavage and CO release. This reactivity is novel in that it occurs under mild reaction conditions and suggests that light-induced CO-release reactivity involving metal flavonolate species may be possible in biological systems.

Hexanickel enediolate cluster generated in an acireductone dioxygenase model reaction.

A nickel(II) enediolate cluster (2) forms upon treatment of [(6-Ph(2)TPA)Ni(PhC(O)C(OH)C(O)Ph)]ClO(4) (1) with Me(4)NOH x 5 H(2)O in CH(3)CN. Crystallographic studies of 2 revealed a hexanuclear structure of S(6) symmetry with a formula of {[Ni(PhC(O)C(O)C(O)Ph)(CH(3)OH)] x 1.33 CH(3)OH}(6).

O2-dependent aliphatic carbon-carbon bond cleavage reactivity in a Ni(II) enolate complex having a hydrogen bond donor microenvironment; comparison with a hydrophobic analogue.

A mononuclear Ni(II) complex having an acireductone type ligand, and supported by the bnpapa (N,N-bis((6-neopentylamino-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine) ligand, [(bnpapa)Ni(PhC(O)C(OH)C(O)Ph)]ClO(4) (14), has been prepared and characterized by elemental analysis, (1)H NMR, FTIR, and UV-vis. To gain insight into the (1)H NMR features of 14, the air stable analogue complexes [(bnpapa)Ni(CH(3)C(O)CHC(O)CH(3))]ClO(4) (16) and [(bnpapa)Ni(ONHC(O)CH(3))]ClO(4) (17) were prepared and characterized by X-ray crystallography, (1)H NMR, FTIR, UV-vis, mass spectrometry, and solution conductivity measurements. Compounds 16 and 17 are 1:1 electrolyte species in CH(3)CN.

Thioester hydrolysis promoted by a mononuclear zinc complex.

The mononuclear zinc complex [(bpta)Zn](ClO(4))(2).0.5H(2)O promotes the hydrolysis of the thioester PhCH(OH)C(O)SCD(3) when dissolved in CH(3)CN:H(2)O (50:50 buffered at pH 9.

Synthesis, characterization, and ligand exchange reactivity of a series of first row divalent metal 3-hydroxyflavonolate complexes.

A series of divalent metal flavonolate complexes of the general formula [(6-Ph(2)TPA)M(3-Hfl)]X (1-5-X; X = OTf(-) or ClO(4)(-); 6-Ph(2)TPA = N,N-bis((6-phenyl-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine; M = Mn(II), Co(II), Ni(II), Cu(II), Zn(II); 3-Hfl = 3-hydroxyflavonolate) were prepared and characterized by X-ray crystallography, elemental analysis, FTIR, UV-vis, (1)H NMR or EPR, and cyclic voltammetry. All of the complexes have a bidentate coordinated flavonolate ligand. The difference in M-O distances (Delta(M-O)) involving this ligand varies through the series, with the asymmetry of flavonolate coordination increasing in the order Mn(II) approximately Ni(II) < Cu(II) < Zn(II) < Co(II).

Charge density analysis of the (C-C)-->Ti agostic interactions in a titanacyclobutane complex.

The experimental electron density study of Ti(C(5)H(4)Me)(2)[(CH(2))(2)CMe(2)] provides direct evidence for the presence of (C-C)-->Ti agostic interactions. In accord with the model of Scherer and McGrady, the C(alpha)-C(beta) bond densities no longer show cylindrical symmetry in the vicinity of the Ti atom and differ markedly from those of the other C-C bonds. At the points along the C(alpha)-C(beta) bond where the deviation is maximal the electron density is elongated toward the metal center.