Combinations of chiral and prochiral singlet radical-pairs in reaction cavities of polyethylene films. Control and analysis of radical tumbling and translation.

The regio- and stereo-chemistries of combination products from chiral 1-naphthoxy/(R)-2-phenylpropanoyl and prochiral 1-naphthoxy/1-phenylethyl singlet radical-pairs (radical-pairs A and B, respectively) have been studied at different temperatures in polyethylene (PE) films with different crystallinities. The radical-pairs have been generated as intermediates along the photo-Fries reaction course of 1-naphthyl (R)-2-phenylpropanoate ((R)-1) and the photo-Claisen reaction course of 1-naphthyl (R)-1-phenylethyl ether ((R)-2). Radical-pair was produced directly upon lysis of the first excited singlet state of (R)-2 and indirectly after irradiation of (R)-1 and subsequent decarbonylation of the 2-phenylpropanoyl radical of radical-pair A. Comparison of the fates of the directly and indirectly formed radical-pairs provides detailed information about the nature of the reaction cavities within the polyethylene hosts and how the combinations of the radical-pairs are influenced by their initial locations within a cavity. The results, especially when taken with those from irradiations in n-alkanes, indicate that the cavities are "templated" by the (R)-1 and (R)-2 guest molecules and that the templated shapes are retained in some form for periods that are at least as long as the time required for decarbonylation of a 2-phenylpropanoyl radical. In addition, the enantiomeric excesses of the decarbonylated photoproducts from (R)-1(2, 2-(1-phenylethyl)-1-naphthol (2BN), and 4-(1-phenylethyl)-1-naphthol (4BN)) or 2BN and 4 BN from (R)-2 indicate different influences of temperature on translational and tumbling motions of the radicals of radical-pairs B within their polyethylene cages.     

Rapid kinetics of tyrosyl radical formation and heme redox state changes in prostaglandin H synthase-1 and -2.

Hydroperoxide-induced tyrosyl radicals are putative intermediates in cyclooxygenase catalysis by prostaglandin H synthase (PGHS)-1 and -2. Rapid-freeze EPR and stopped-flow were used to characterize tyrosyl radical kinetics in PGHS-1 and -2 reacted with ethyl hydrogen peroxide. In PGHS-1, a wide doublet tyrosyl radical (34-35 G) was formed by 4 ms, followed by transition to a wide singlet (33-34 G); changes in total radical intensity paralleled those of Intermediate II absorbance during both formation and decay phases. In PGHS-2, some wide doublet (30 G) was present at early time points, but transition to wide singlet (29 G) was complete by 50 ms. In contrast to PGHS-1, only the formation kinetics of the PGHS-2 tyrosyl radical matched the Intermediate II absorbance kinetics. Indomethacin-treated PGHS-1 and nimesulide-treated PGHS-2 rapidly formed narrow singlet EPR (25-26 G in PGHS-1; 21 G in PGHS-2), and the same line shapes persisted throughout the reactions. Radical intensity paralleled Intermediate II absorbance throughout the indomethacin-treated PGHS-1 reaction. For nimesulide-treated PGHS-2, radical formed in concert with Intermediate II, but later persisted while Intermediate II relaxed. These results substantiate the kinetic competence of a tyrosyl radical as the catalytic intermediate for both PGHS isoforms and also indicate that the heme redox state becomes uncoupled from the tyrosyl radical in PGHS-2.     

Optical resolution of 1-(1-naphthyl)ethylamine by its dicarboxylic acid derivatives: Structural features of the oxalic acid derivative diastereomeric salt pair

Optical resolution methods were established for racemic 1-(1-naphthyl) ethylamine. The resolving agents were synthesized by N-derivatizing (R)-1-(1-naphthyl) ethylamine with dicarboxylic acids. Oxalic, malonic, and succinic acid derivatives were found to be suitable resolving agents. These resolutions are parallel to a series of optical resolutions of 1-phenylethylamine which had been previously performed by our research group using similar derivative resolving agents (Balint et al., Tetrahedron: Asymmetry 2001;12:1511-1518.) The comparison of the results of the enantiomer separations is performed. The diastereomeric salts formed with (R)-N-[1-(1-naphthyl)ethyl]oxalamic acid were investigated by single crystal X-ray diffraction. The crystal structures were compared with the previously published structures of the diastereomers of the phenyl-substituted analogue, namely (R)- and (S)-1-phenylethylammonium (R)-N-(1-phenylethyl)oxalamates (Balint et al., Tetrahedron: Asymmetry 2001;12:1511-1518).     

Free radical biology and medicine: it's a gas, man!

We review gases that can affect oxidative stress and that themselves may be radicals. We discuss O(2) toxicity, invoking superoxide, hydrogen peroxide, and the hydroxyl radical. We also discuss superoxide dismutase (SOD) and both ground-state, triplet oxygen ((3)O(2)), and the more energetic, reactive singlet oxygen ((1)O(2)). Nitric oxide ((*)NO) is a free radical with cell signaling functions. Besides its role as a vasorelaxant, (*)NO and related species have other functions. Other endogenously produced gases include carbon monoxide (CO), carbon dioxide (CO(2)), and hydrogen sulfide (H(2)S). Like (*)NO, these species impact free radical biochemistry. The coordinated regulation of these species suggests that they all are used in cell signaling. Nitric oxide, nitrogen dioxide, and the carbonate radical (CO(3)(*-)) react selectively at moderate rates with nonradicals, but react fast with a second radical. These reactions establish "cross talk" between reactive oxygen (ROS) and reactive nitrogen species (RNS). Some of these species can react to produce nitrated proteins and nitrolipids. It has been suggested that ozone is formed in vivo. However, the biomarkers that were used to probe for ozone reactions may be formed by non-ozone-dependent reactions. We discuss this fascinating problem in the section on ozone. Very low levels of ROS or RNS may be mitogenic, but very high levels cause an oxidative stress that can result in growth arrest (transient or permanent), apoptosis, or necrosis. Between these extremes, many of the gasses discussed in this review will induce transient adaptive responses in gene expression that enable cells and tissues to survive. Such adaptive mechanisms are thought to be of evolutionary importance.     

Reactions of reactive oxygen species (ROS) with curcumin analogues: Structure-activity relationship

Three curcumin analogues viz., bisdemethoxy curcumin, monodemethoxy curcumin, and dimethoxycurcumin that differ at the phenolic substitution were synthesized. These compounds have been subjected for free radical reactions with DPPH radicals, superoxide radicals (O(2)(?-)), singlet oxygen ((1)O(2)) and peroxyl radicals (CCl(3)O(2)(?)) and the bimolecular rate constants were determined. The DPPH radical reactions were followed by stopped-flow spectrometer, (1)O(2) reactions by transient luminescence spectrometer, and CCl(3)O(2)(?) reactions using pulse radiolysis technique. The rate constants indicate that the presence of o-methoxy phenolic OH increases its reactivity with DPPH and CCl(3)O(2)(?), while for molecules lacking phenolic OH, this reaction is very sluggish. Reaction of O(2)(?-) and (1)O(2) with curcumin analogues takes place preferably at β-diketone moiety. The studies thus suggested that both phenolic OH and the β-diketone moiety of curcumin are involved in neutralizing the free radicals and their relative scavenging ability depends on the nature of the free radicals.     

Reaction of beta-alkannin (shikonin) with reactive oxygen species: detection of beta-alkannin free radicals

beta-Alkannin (shikonin), a compound isolated from the root of Lithospermum erythrorhizon Siebold Zucc., has been used as a purple dye in ancient Japan and is known to exert an anti-inflammatory activity. This study aimed to understand the biological activity in terms of physico-chemical characteristics of beta-alkannin. Several physico-chemical properties including proton dissociation constants, half-wave potentials and molecular orbital energy of beta-alkannin were elucidated. This compound shows highly efficient antioxidative activities against several types of reactive oxygen species (ROS), such as singlet oxygen ((1)O2). superoxide anion radical (.O2), hydroxyl radical (.OH) and tert-butyl peroxyl radical (BuOO.) as well as iron-dependent microsomal lipid peroxidation. During the reactions of beta-alkannin with 1O2, .O2- and BuOO., intermediate organic radicals due to beta-alkannin were detectable by ESR spectrometry. Compared with the radicals due to naphthazarin, the structural skeleton of beta-alkannin, the beta-alkannin radical observed as an intermediate in the reactions with (1)O2, and .O2- was concluded to be a semiquinone radical. On the other hand, during the reactions of beta-alkannin and naphthazarin with BuOO., ESR spectra different from the semiquinone radical were observed, and proposed to result from the abstraction of hydrogen atoms from phenolic hydroxyl groups of beta-alkannin by BuOO.. Based on the ROS-scavenging abilities of beta-alkannin, the compound was concluded to react directly with ROS and exhibits antioxidative activity, which in turn exerts anti-inflammatory activity.     

ESR evidence of the photogeneration of free radicals (GDHB*-, O2*-) and singlet oxygen ((1)O2) by 15-deacetyl-13-glycine-substituted hypocrellin B

15-Deacetyl-13-glycine-substituted hypocrellin B (GDHB) is a new type of hypocrellin derivative with an enhanced red absorption longer than 600 nm and water solubility. Visible light (> 470 nm) irradiation of an anaerobic aqueous solution of GDHB, the formation of GDHB*- was detected by an ESR method in the absence or presence of electron donor. When exposed to oxygen, superoxide anion radical and singlet oxygen were formed. The superoxide anion radical was generated by GDHB*- via electron transfer to oxygen and this process was significantly enhanced by the presence of electron donors. Singlet oxygen ((1)O2) was also formed in the photosensitization of GDHB in aerobic solution and 1,4-diazabicyclo [2,2,2] octane (DABCO), sodium azide (NaN3) and histidine inhibited the generation of (1)O2. A 9,10-diphenyl antracene (DPA)-bleaching method was used to determine the quantum yield of (1)O2 generated from GDHB photosensitization. The (1)O2 quantum yield was estimated to be 0.65. With the depletion of oxygen, the accumulation of GDHB*- would replace that of (1)O2. Evidence accumulated that the photodynamic action of GDHB may proceed via both type I and type II mechanisms and that a type II mechanism will be transformed into a type I mechanism as oxygen gets depleted.     

Dual role of triplet localization on the accessory chlorophyll in the photosystem II reaction center: photoprotection and photodamage of the D1 protein

Infrared absorption and electron spin resonance studies have shown that the excited triplet state of chlorophyll formed by radical pair recombination in the PSII reaction center is mainly localized on the accessory chlorophyll, which is most probably located in the D1 protein (Chl(1)). This triplet localization plays two contrasting roles, depending on the redox state of Q(A), in the process of acceptor-side photoinhibition of PSII. In the early stage of photoinhibition, in which singly reduced Q(A) is reversibly stabilized, the triplet state of Chl(1) ((3)Chl(1)*) is rapidly quenched (t(1/2) = 2-20 micro s) by the interaction with Q(A)(-), preventing formation of harmful singlet oxygen. In the next inhibitory stage, in which Q(A) is doubly reduced and then irreversibly released from the Q(A) pocket, the lifetime of (3)Chl(1)* becomes longer by more than two orders of magnitude (t(1/2) = 1-3 ms). As a result, singlet oxygen is produced around Chl(1) in the D1 protein, causing damage preferably to the D1 protein, which induces subsequent proteolytic degradation. Thus, (3)Chl(1)* functions as a switch to change from the protective to the degradative phase of the PSII reaction center by sensing either reversible or irreversible inhibited state at the Q(A) site.     

Pulse radiolysis studies of beta-carotene in oxygenated DMSO solution. Formation of beta-carotene radical cation

The spectroscopic and kinetic characteristics of beta-carotene radical cation (beta-carotene(.+)) were studied by pulse radiolysis in aerated DMSO solution. The buildup of beta-carotene(.+) with k(1) = (4.8 +/- 0.2) x 10(8) dm(3) mol(-1) s(-1) [lambda(max) = 942 nm, epsilon = (1.6 +/- 0.1) x 10(4) dm(3) mol(-1) cm(-1)] results from an electron transfer from beta-carotene to DMSO(.+). The beta-carotene(.+) species decays exclusively by first-order reaction, k = (2.1 +/- 0.1) x 10(3) s(-1), probably by two processes: (1) at low substrate concentration by hydrolysis and (2) at high concentrations also by formation of dimer radical cation (beta-carotene)(2)(.+). Under the experimental conditions, a small additional beta-carotene triplet-state absorption ((3)beta-carotene) in the range of 525 to 660 nm was observed. This triplet absorption is quenched by oxygen (k = 7 x 10(4) s(-1)), resulting in singlet oxygen ((1)O(2)), whose reactions can also lead to additional formation of beta-carotene(.+).     

Kinetic resolution of a tryptophan-radical intermediate in the reaction cycle of Paracoccus denitrificans cytochrome c oxidase

The catalytic mechanism, electron transfer coupled to proton pumping, of heme-copper oxidases is not yet fully understood. Microsecond freeze-hyperquenching single turnover experiments were carried out with fully reduced cytochrome aa(3) reacting with O(2) between 83 micros and 6 ms. Trapped intermediates were analyzed by low temperature UV-visible, X-band, and Q-band EPR spectroscopy, enabling determination of the oxidation-reduction kinetics of Cu(A), heme a, heme a(3), and of a recently detected tryptophan radical (Wiertz, F. G. M., Richter, O. M. H., Cherepanov, A. V., MacMillan, F., Ludwig, B., and de Vries, S. (2004) FEBS Lett. 575, 127-130). Cu(B) and heme a(3) were EPR silent during all stages of the reaction. Cu(A) and heme a are in electronic equilibrium acting as a redox pair. The reduction potential of Cu(A) is 4.5 mV lower than that of heme a. Both redox groups are oxidized in two phases with apparent half-lives of 57 micros and 1.2 ms together donating a single electron to the binuclear center in each phase. The formation of the heme a(3) oxoferryl species P(R) (maxima at 430 nm and 606 nm) was completed in approximately 130 micros, similar to the first oxidation phase of Cu(A) and heme a. The intermediate F (absorbance maximum at 571 nm) is formed from P(R) and decays to a hitherto undetected intermediate named F(W)(*). F(W)(*) harbors a tryptophan radical, identified by Q-band EPR spectroscopy as the tryptophan neutral radical of the strictly conserved Trp-272 (Trp-272(*)). The Trp-272(*) populates to 4-5% due to its relatively low rate of formation (t((1/2)) = 1.2 ms) and rapid rate of breakdown (t((1/2)) = 60 micros), which represents electron transfer from Cu(A)/heme a to Trp-272(*). The formation of the Trp-272(*) constitutes the major rate-determining step of the catalytic cycle. Our findings show that Trp-272 is a redox-active residue and is in this respect on an equal par to the metallocenters of the cytochrome c oxidase. Trp-272 is the direct reductant either to the heme a(3) oxoferryl species or to Cu (2+)(B). The potential role of Trp-272 in proton pumping is discussed.     

Structural characterization of arachidonyl radicals formed by aspirin-treated prostaglandin H synthase-2

Peroxide-generated tyrosyl radicals in both prostaglandin H synthase (PGHS) isozymes have been demonstrated to couple the peroxidase and cyclooxygenase activities by serving as the immediate oxidant for arachidonic acid (AA) in cyclooxygenase catalysis. Acetylation of Ser-530 of PGHS-1 by aspirin abolishes all oxygenase activity and transforms the peroxide-induced tyrosyl radical from a functional 33-35-gauss (G) wide doublet/wide singlet to a 26-G narrow singlet unable to oxidize AA. In contrast, aspirin-treated PGHS-2 (ASA-PGHS-2) no longer forms prostaglandins but retains oxygenase activity forming 11(R)- and 15(R)-hydroperoxyeicosatetraenoic acid and also retains the EPR line-shape of the native peroxide-induced 29-30-G wide singlet radical. To evaluate the functional role of the wide singlet radical in ASA-PGHS-2, we have examined the ability of this radical to oxidize AA in single-turnover EPR studies. Anaerobic addition of AA to ASA-PGHS-2 immediately after formation of the wide singlet radical generated either a 7-line EPR signal similar to the pentadienyl AA radical obtained in native PGHS-2 or a 26-28-G singlet radical. These EPR signals could be accounted for by a pentadienyl radical and a strained allyl radical, respectively. Experiments using 11d-AA, 13(R)d-AA, 15d-AA, 13,15d(2)-AA, and octadeuterated AA (d(8)-AA) confirmed that the unpaired electron in the pentadienyl radical is delocalized over C11, C13, and C15. A 6-line EPR radical was observed when 16d(2)-AA was used, indicating only one strongly interacting C16 hydrogen. These results support a functional role for peroxide-generated tyrosyl radicals in lipoxygenase catalysis by ASA-PGHS-2 and also indicate that the AA radical in ASA-PGHS-2 is more constrained than the corresponding radical in native PGHS-2.     

New route to enantiopure MalphaNP acid, a powerful resolution and chiral 1H NMR anisotropy reagent

MalphaNP acid (+/-)-1, 2-methoxy-2-(1-naphthyl)propionic acid, was enantioresolved by the use of phenylalaninol (S)-(-)-4; a diastereomeric mixture of amides formed from acid (+/-)-1 and amine (S)-(-)-4 was easily separated by fractional recrystallization and/or HPLC on silica gel, yielding amides (R;S)-(-)-5a and (S;S)-(+)-5b. Their absolute configurations were determined by X-ray crystallography by reference to the S configuration of the phenylalaninol moiety. Amide (R;S)-(-)-5a was converted to oxazoline (R;S)-(+)-8a, from which enantiopure MalphaNP acid (R)-(-)-1 was recovered. In a similar way, enantiopure MalphaNP acid (S)-(+)-1 was obtained from amide (S;S)-(+)-5b. These reactions provide a new route for the large-scale preparation of enantiopure MalphaNP acid, a powerful chiral reagent for the enantioresolution of alcohols and simultaneous determination of their absolute configurations by (1)H NMR anisotropy.     

DNA alterations induced by the carbon-centered radical derived from the oxidation of 2-phenylethylhydrazine

The possible significance of carbon-centered radicals in hydrazine-induced carcinogenesis is explored by studies of the interaction between the 2-phenylethyl radical and DNA. The radical is efficiently generated during oxidation of phenelzine (2-phenylethylhydrazine) promoted by oxyhemoglobin or ferricyanide, as demonstrated by spin-trapping experiments and analysis of the reaction products. In the ferricyanide promoted oxidation, ethylbenzene formation accounts for about 40% of the initial drug concentration, from 5 to 100 mM phenelzine. By contrast, product formation in the presence of oxyhemoglobin depends on the enzyme concentration due to the fact that the prosthetic heme is destroyed during catalytic turnover. Covalent binding of the 2-phenylethyl radical to oxyhemoglobin is demonstrated by experiments with 2-[3H]phenelzine, where tritium incorporation to the protein is inhibited by the spin-trap, alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone. The 2-phenylethyl radical is also able to alkylate DNA as suggested by electrophoretic studies with plasmid DNA, and proved by experiments with 2-[3H]-phenelzine. The carbon-centered radical has a preference for attacking guanine residues as demonstrated by the use of sequencing techniques with 32P-DNA probes. The results indicate that the 2-phenylethyl radical is an important product of phenelzine oxidation and that this species can directly damage protein and DNA.     

Investigation of DNA binding mechanism, photoinduced cleavage activity, electrochemical properties and biological functions of mixed ligand copper(II) complexes with benzimidazole derivatives: synthesis and spectral characterization

The benzimidazole derivative Schiff bases and their copper(II) (Cu(II)) mixed-polypyridyl complexes (1-4) have been synthesized and characterized by the spectral and analytical techniques. DNA binding/cleavage studies indicate a stronger binding capability for the complex 4 which is confirmed by the absorbance, viscometric and gel-electrophoresis studies. The photocleavage of plasmid pBR322 DNA reveals that hydroxyl radical (OH(?)) and singlet oxygen ((1)O(2)) are likely to be the reactive species. Analysis of the growth activity shows that the antimicrobial effect of these Schiff bases on Gram-negative bacteria is higher than that on Gram-positive. Furthermore, the complexes having nitro group show an increased antimicrobial effect.     

Enantioselective detoxication of optical isomers of glycidyl ethers

The detoxication of the enantiomers of glycidyl 4-nitrophenyl ether (GNPE), (?)-(R)- and (+)-(S)-GNPE, and glycidyl 1-naphthyl ether (GNE), (?)-(R)- and (+)-(S)-GNE, by rat liver glutathione transferase and epoxide hydrolase was studied. Enantioselectivity was observed with both enzymes favoring the (R)-isomers as determined by the formation of conjugate, diol, and remaining substrate measured by HPLC. Enantiomers of GNE were detoxified by cytosolic epoxide hydrolase but those of GNPE were not. Substantial nonenzymatically formed conjugates of enantiomers of GNPE were detected showing (S)-GNPE the more reactive of the pair. © 1993 Wiley-Liss, Inc.     

Modelling the sulfoxygenation activity of vanadate-dependent peroxidases

Vanadate-dependent peroxidases contain, in their active center, vanadate covalently attached to histidine in an overall trigonal-bipyramidal array. We describe here the synthesis and characterization of optically active amino alcohols and their vanadium(V) complexes, and we show that the structural models of the active center thus obtained are also functional models for the sulfide-peroxidase activity of the enzyme in heterogeneous catalysis. The heterogeneous systems were obtained by immobilizing the complexes on silica gel and mesoporous silicas, and by aggregation. The following ligands, ligand precursors, and V compounds have been structurally characterized: (R)-(2-phenylethanol)-(R)-1-phenylethylamine (HL(A)), (R,R)-bis[2-phenyl(ethylmethylether)]ammonium chloride ([L(D)]+Cl(-)), the carbasilatranes (R,R)-methoxy{N,N',N'-2,2',3-[bis(1-phenylethanolato)propyl]amino}silane ((R,R)-Si(OMe)L(E)), (R,R)-methoxy-{N,N',N'-1,2',3-[(1-phenylethanolato)-(2-phenylethanolato)propyl]amino}silane ((R,R)-Si(OMe)L(E')), and [VO(L(F))(OSiMe2(t)Bu)], where H2L(F)=ethylbis(2-hydroxy-2-phenylethyl)amine.     

Mechanism of electron transfer processes photoinduced by lumazine

UV-A (320-400 nm) and UV-B (280-320 nm) radiation causes damage to DNA and other biomolecules through reactions induced by different endogenous or exogenous photosensitizers. Lumazines are heterocyclic compounds present in biological systems as biosynthetic precursors and/or products of metabolic degradation. The parent and unsubstituted compound called lumazine (pteridine-2,4(1,3H)-dione; Lum) is able to act as photosensitizer through electron transfer-initiated oxidations. To get further insight into the mechanisms involved, we have studied in detail the oxidation of 2'-deoxyadenosine 5'-monophosphate (dAMP) photosensitized by Lum in aqueous solution. After UV-A or UV-B excitation of Lum and formation of its triplet excited state ((3)Lum*), three reaction pathways compete for the deactivation of the latter: intersystem crossing to singlet ground state, energy transfer to O(2), and electron transfer between dAMP and (3)Lum* yielding the corresponding pair of radical ions (Lum˙(-) and dAMP˙(+)). In the following step, the electron transfer from Lum˙(-) to O(2) regenerates Lum and forms the superoxide anion (O(2)˙(-)), which undergoes disproportionation into H(2)O(2) and O(2). Finally dAMP˙(+) participates in subsequent reactions to yield products.     

Physicochemical characterization of deflazacort: thermal analysis, crystallographic and spectroscopic study

The solid state properties of deflazacort (1-(1beta,16alpha)-21-(acetyloxy)-11-hydroxy-2'-methyl-5'H-pregna-1,4-dieno[17,16-d]oxazole-3,20-dione, 1) were investigated using differential scanning calorimetry (DSC), thermogravimetry (TG), single-crystal X-ray diffraction, solid and liquid nuclear magnetic resonance spectroscopy ((13)C NMR), Fourier transform infrared and Raman spectroscopy (FTIR and FT Raman). From the trends observed in the crystal structure and spectral data some conclusions can be made about hydrogen bonding, molecular conformation and crystal packing. Compound 1 crystallizes in an orthorhombic cell, space group P2(1)2(1)2(1) and the following lattice parameters: a=11.2300(5), b=12.8161(8), c=16.171(1)A, V: 2327.4(2)A(3), D(c): 1.260g/cm(3), R1=0.0479, wR2=0.1012. The crystal structure is stabilized by intra and intermolecular interactions, which provides for a very closely packed form. The NMR data indicated that 1 shows a similar conformation in solid and liquid state; while, thermal data revealed that 1 follows a monophasic pattern with a DSC melting peak at 258.4 degrees C (DeltaH 99.7Jg(-1), n=3), indicating that 1 is thermally stable as solid; but, as liquid is unstable to undergo a thermal decomposition reaction. The reactivity of 1 toward light and moisture was examined via DSC and TLC. The data indicated that 1 do not interact with water to give hydrated forms or decomposition products; however, light degrades 1.     

Anti-oxidant and pro-oxidant behaviour of bucillamine.

Bucillamine (BUC) is used clinically for the treatment of rheumatoid arthritis. Some of the pharmacological action of BUC has been reported as being dependent on the production of reactive oxygen species (ROS). In this paper the reactivity of BUC with superoxide anion radical (O(2) (*-)) generated from potassium superoxide/18-crown-6 ether dissolved in DMSO, hydroxyl radical (HO(*)) produced in the Cu(2+)-H(2)O(2) reaction, peroxyl radical (ROO(*)) from 2,2'-azobis (2-amidino-propane) dichloride decomposition, and singlet oxygen ((1)O(2)) from a mixture of alkaline aqueous H(2)O(2) and acetonitrile, have been investigated. Chemiluminescence, fluorescence, electron paramagnetic resonance (EPR) spin-trapping techniques and the deoxyribose and oxygen radical absorbance capacity towards ROO(*) (ORAC(ROO)) assays were used to elucidate the anti- and pro-oxidative behaviours of BUC towards ROS. The results indicated that BUC efficiently inhibited chemiluminescence from the O(2) (*-)-generating system at relatively high concentrations (0.5-2 mmol/L); however, at lower concentrations (<0.5 mmol/L) the drug enhanced light emission. The behaviour of BUC was correlated with a capacity to decrease the chemiluminescence signal from the Cu(2+)-H(2)O(2) system; scavenging HO(*) was effective only at high concentrations (1-2 mmol/L) of the drug. Bucillamine also prevented deoxyribose degradation induced by HO(*) in a dose-dependent manner, reaching maximal inhibition (24.5%) at a relative high concentration (1.54 mmol/L). Moreover, BUC reacts with ROO(*); the relative ORAC(ROO) was found to be 0.34 micromol/L Trolox equivalents/micromol sample. The drug showed quenching of (1)O(2)-dependent 2,2,6,6-tetramethylpiperidine-N-oxide radical formation from 2,2,6,6-tetramethyl-piperidine (e.g. 90% inhibition was found at 1 mmol/L concentration). The results showed that BUC may directly scavenge ROS or inhibit reactions generating them. However, the drug may have pro-oxidant activity under some reaction conditions.     

In vitro scavenging activity for reactive oxygen species by N-substituted indole-2-carboxylic acid esters.

The hydroxyl radical (HO*)- and superoxide anion radical (O* (2))-scavenging activity, as well as the singlet oxygen ((1)O(2))-quenching property of N-substituted indole-2-carboxylic acid esters (INDs) were investigated by deoxyribose degradation assay, a chemiluminescence method and the electron spin resonance (ESR) spin-trapping technique. This novel group of compounds was developed as a search for cyclooxygenase-2 (COX-2)-selective enzyme inhibitors. The results obtained demonstrated that of the 16 compounds examined, five inhibited light emission from the superoxide anion radical (O* (2))-DMSO system by at least 60% at a concentration of 1 mmol/L, nine prevented the degradation of deoxyribose induced by the Fenton reaction system (range 3-78%) or scavenged hydroxyl radicals (HO*) directly (range 8-93%) and 14 showed the (1)O(2)-quenching effect (range 10-74%). These results indicate that majority of the indole esters tested possess the ability to scavenge O(-) (2) and HO radicals and to quench (1)O(2) directly, and consequently may be considered effective antioxidative agents.