New bis-catechols 5-lipoxygenase inhibitors.

Three polyhydroxy-2-phenylnaphthalenes (1-3) and the oxy analogue of tetrahydroxypavinan (4) were prepared and evaluated for their antioxidant properties (inhibition of diphenylpycrylhydrazyl radical (DPPH), reduction of iron (III) ion) and inhibition of 5-lipoxygenase (5-LO) activity. Their three-dimensional structures were established on the basis of spectroscopic data and semiempirical calculations. Compounds 1 and 2 were found as potent 5-LO inhibitors as nordihydroguaiaretic acid (NDGA), whereas 4 is 2.5 times less potent than NDGA. The reliability of the 3-D structures with the 5-LO inhibition properties is discussed. Their antioxidant properties show that tested compounds are expected to act as redox inhibitors.

Beneficial effects of different flavonoids, on functional recovery after ischemia and reperfusion in isolated rat heart.

Three newly synthesised lipid peroxidation inhibitors (7, 11, 14) were evaluated for their effects on myocardial functional recovery during reperfusion after 30 min global ischemia in isolated rat hearts. The flavonoid compounds (7, 11, 14, rutin) reduce ischemia/reperfusion-induced cardiac dysfunction.

Role of flavonoids in oxidative stress.

Flavonoids are a group of naturally occuring compounds which are widely distributed in nature. Epidemiological evidence suggests an inverse relationship between dietary intake of flavonoids and cardiovascular risk. The biological activities of flavonoids are related to their antioxidative effects. But a number of studies have found both anti and prooxidant effects for many of these compounds. This review article presents the synthetic pathways of flavonoids and discusses the structure-activity relationships between, xanthine oxidase inhibitive activities and their chemical structures, between the antioxidant and prooxidant activities and the chemical structure. Then we will show the antioxidant properties of new flavonoids in a few models. In these compounds one or two di-tert-butylhydroxyphenyl (DBHP) groups replace the catechol moiety at the position 2 of the benzopyrane heterocycle. New structures are compared with quercetin and BHT in an LDL-oxidation system, in protecting cultured bovine aortic endothelial cells against mO-LDL cytotoxicity and on myocardial functional recovery during reperfusion after 30 min global ischemia in isolated rat hearts.

Di-tert-butylhydroxylated flavonoids protect endothelial cells against oxidized LDL-induced cytotoxicity.

The protective effect of di-tert-butylhydroxylated flavonoids (chalcones and arylidenes) against minimally oxidized LDL (mO-LDL)-induced cytotoxicity was studied in cultured bovine aortic endothelial cells. Most of the tested compounds decreased aldehydes formation in medium containing mO-LDL, but their capacity to inhibit LDL oxidation in the cellular medium was not sufficient to totally reduce the cellular toxicity of mO-LDL. Most of the tested flavonoids improved the integrity of cells exposed to mO-LDL, whereas butylated hydroxytoluene was ineffective and quercetin worsened the toxicity of mO-LDL. Moreover these flavonoids induced an increase in GSH cellular levels and their protective effects might be because of their inability to reduce metal ion. Arylidene 6 substituted at position 7 by a hydroxyl group was the most potent compound.

Antioxidant properties of di-tert-butylhydroxylated flavonoids.

Epidemiological evidence suggests an inverse relationship between dietary intake of flavonoids and cardiovascular risk. The biological activities of flavonoids are related to their antioxidative effects, but they also can be mutagenic, due to the prooxidant activity of the catechol pattern. To prevent these problems, we synthesized new flavonoids where one or two di-tert-butylhydroxyphenyl (DBHP) groups replaced catechol moiety at position 2 of the benzopyrane heterocycle. Two DBHP moieties can also be arranged in an arylidene structure or one DBHP fixed on a chalcone structure. Position 7 on the flavone and arylidene or position 4 on the chalcone was substituted by H, OCH(3), or OH. New structures were compared with quercetin and BHT in an LDL oxidation system induced by Cu(II) ions. Arylidenes and chalcones had the best activities (ED(50) = 0.86 and 0.21) compared with vitamin E, BHT, and quercetin (ED(50) = 10.0, 7. 4, and 2.3 microM). Activity towards stable free radical 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) was measured by log Z and ECR(50) parameters. Synthesized flavones proved to be poor DPPH radical scavengers, the activity increasing with the number of DBHP units. In contrast, arylidenes and chalcones were stronger DPPH radical scavengers (log Z > 3, 0.3 < ECR(50) < 2.12) than BHT (log Z = 0.75, ECR(50) = 12.56) or quercetin (log Z = 2.76, ECR(50) = 0.43). Unlike quercetin, synthesized compounds neither chelated nor reduced copper, proving that these new flavonoids had no prooxidant activity in vitro.

Purification of human ceruloplasmin as a by-product of C1-inhibitor.

Human ceruloplasmin (Cp) has been purified from cryoprecipitate-poor plasma as a by-product of the C1-inhibitor production chain. Highly purified Cp was obtained by subsequent ion-exchange chromatography on sulfate-Fractogel EMD and TMAE-Fractogel EMD. Treatments for viral safety included application of the solvent-detergent method and two nanofiltration steps using 35- and 15-nm pore size filters at the end of the process. Overall antigen yield was 95 (+/-5) %. Purified human ceruloplasmin was studied by electron spin resonance (ESR) to characterize its different types of copper complexes and to check its antioxidant properties. We distinguished three types of complexes: one type-2 Cu(II) with g// = 2.25 and A// = 180 G and two type-I Cu(II) exhibiting different narrow hyperfine splitting (A// = 72 G and A// = 90 G) with close g// (2.20 and 2.21). Purified Cp has a specific activity of 24.5+/-0.2 mU/mg of proteins. This process provides a method for Cp purification that could be easily integrated into modern plasma fractionation.

Salen-anthraquinone conjugates. Synthesis, DNA-binding and cleaving properties, effects on topoisomerases and cytotoxicity.

A series of amidoethylamino-anthraquinone derivatives bearing either one or two salen (bis(salicylidene)ethylenediamine) moieties complexed with CuII or NiII have been synthesized, and their DNA-binding and cleaving properties examined. The effects of the mono- and di-substituted anthracenedione-salen conjugates on DNA cleavage mediated by topoisomerases I and II have also been determined, as well as their cytotoxicity toward human KB cells. The anthraquinone-salen. NiII conjugates bind to GC-rich sequences in DNA, but do not cleave the macromolecule. By contrast, the anthraquinone-salen. CuII hybrids do not recognize particular nucleotide sequences but efficiently induce single-strand breaks in DNA after activation. The 5,8-dihydroxy-anthraquinone conjugates are more cytotoxic and more potent toward topoisomerase II than the non-hydroxylated analogues, but they are less cytotoxic than the salen-free anthraquinones. The attachment of a salen. CuII complex to the anthraquinone chromophore can confer DNA cleaving properties in vitro, but this is at the expense of cytotoxic activity. Anthraquinone-salen. CuII complexes may find useful employ as footprinting probes for investigating ligand-DNA interactions.

Antioxidant properties of hydroxy-flavones.

The antioxidant properties of 24 hydroxy-flavones were evaluated. Results show that 2',3',4'-OH substitution on the B ring plays a crucial role in radical scavenger activity in the DPPH assay and in the inhibitory effect on pereoxydation of tissue lipids in the MDA test. The formation of stable radicals for this type of compounds has been studied by ESR. In addition, it has been found that 7-hydroxy-flavones are potent competitive inhibitors of xanthine oxidase. It is proposed that the C-7 OH of flavones may take the place of the C-2 or C-6 OH of xanthine in the active site of the enzyme. A C-4' OH or C-4' OMe substitution on the 7-hydroxy flavones is not favourable to a fit in the active site. The 2',3',4'-trihydroxy-flavones inhibited XO by another process, which remains to be determined. In summary, this study provides evidence that hydroxy-flavones exhibit interesting antioxidant properties expressed either by the capacity to scavenge free radicals (for 2',3',4'-trihydroxy-flavones) or to competitively inhibit xanthine oxidase (for 7-hydroxy-flavones). These compounds may be drug candidates for treating pathologies related to free radical oxidation.

Antioxidant activities of dihydroxylated salicylic acid derivatives.

The ability of hydroxylated metabolites of salicylic acid to scavenge reactive oxygen species and to inhibit arachidonic acid metabolism was investigated. The tested trihydroxybenzoic acids (THBAs) were potent scavengers of hydroxyl and superoxide anion radicals produced by Fenton reaction and xanthine/xanthine oxidase system or activated macrophages respectively. In the same tests, salicylic acid possessed moderate O2(-) and low OH'scavenging activities. Our results demonstrate that adding two hydroxyl groups to salicylic acid strongly increases the reactive oxygen species (ROS) scavenging activities. Adding two hydroxyl groups at position 4 and 5 (2,4,5-THBA) affords the most active ROS scavenging activity probably due to the ortho unsubstituted catechol moiety. In fact, we can consider that the ROS scavenging properties of salicylic acid are essentially due to its metabolic products such as 2,3- and 2,5-DHBAs, catechol and also to THBAs.

Scavenger and antioxidant properties of ten synthetic flavones.

To study the effect of the hydroxyl groups on biological activities of flavones, we synthesized 10 polyhydroxyflavones with varied substitution patterns. The abilities of the 10 compounds to act as radical scavengers were investigated using chemiluminescence in two biological models: the xanthine/xanthine oxidase system and the oxidative burst of rat alveolar macrophages. Stable radical formation was observed by electron spin resonance (ESR) spectroscopy. We found that the presence of the pyrogallol moiety in the B component of flavones gave rise to radical scavenger activity and that C-6 substituted hydroxyl group may also provide the basis for biological activity. Furthermore, compounds with a hydroxyl at C-7 position appeared to be xanthine oxidase inhibitors. One particular compound exhibited radical scavenger activity and xanthine oxidase inhibition. This type of compound should prove to be useful in the treatment of ischemia, for which both properties were required.

Redox chemistry of complexes of nickel(II) with some biologically important peptides in the presence of reduced oxygen species: an ESR study.

The reactions between some Ni(II) oligopeptides (Gly-His-Lys, (Gly)4, Asp-Ala-His-Lys, Gly-Gly-His, beta Ala-His, and serum albumin) and reduced oxygen species have been characterized by spin-trapping experiments using DMPO and Me2SO. Most of the peptides possessed superoxide dismutase- and catalase-like activities leading to the formation of either oxene [NiO]2+ or, in the case of beta Ala-His, hydroxyl radicals. Both these species may affect DNA integrity through distinct mechanisms.

Generation of free radicals by simple prenylated hydroquinone derivatives, natural antitumor agents from the marine urochordate Aplidium californicum.

The redox properties of simple prenylated hydroquinone derivatives with cytotoxic properties have been studied by absorption and ESR spectroscopies. Both methods evidenced an autoxidation process in which the hydroquinones give rise to a semiquinone radical. Molecular oxygen is the electron acceptor, as demonstrated by spin trapping. No secondary radicals were found in the ESR spectra, either in the presence of hydroxyl anion (alkaline medium) or in the presence of glutathione. Nevertheless, a redox cycle can be initiated by glutathione, giving rise to substantial free-radical production. Thus, although not fully elucidated, the antitumor properties of the three hydroquinones described here can be correlated with their redox properties and their reactivity with thiol-containing peptides such as glutathione.

Pharmacomodulation of 7-(2-methylene-butyryl)-2,3-dihydrobenzoxazin-[1,4]-3-one structure and normolipemic activity.

A series of compounds from 7-(2-methylene butyryl)-2,3-dihydro benzoxazin-[1,4]-3-one was synthesized and evaluated for its lipid lowering action in animal models. Substitutions in positions 2, 4 and 7 were performed. The results of the structure-activity relationships are very difficult to be interpreted. The different modifications tested did not show any improvement in the normolipemic activity.

Antioxidant properties of natural hydroquinones from the marine colonial tunicate Aplidium californicum.

Antioxidant prenylated hydroquinones and non active chromene or chroman extracted from the marine colonial tunicate Aplidium californicum have been studied in order to throw some light on their biological activity. It has been found that the active compounds inhibit superoxide anion production in rat alveolar macrophages and in the xanthine/xanthine oxidase system. The antioxidant activity may be ascribed rather to a direct reaction of the superoxide anion with the hydroquinones than to an enzymatic inhibition or a membrane signal transfer. A physiological activity close to that of alpha tocopherol can be considered.

Conformational study of the threonine-rich C-terminal pentapeptide of peptide T.

The conformation of the synthetic pentapeptide Thr-Thr-Asn-Tyr-Thr, the C-terminal part of peptide T has been studied using 2D NMR experiments. The nuclear Overhauser effects (NOESY) and the low temperature coefficients for two particular NH chemical shifts allow the proposal for two distinct beta-turn arrangements. This conformation is not in accordance with recent reports but is consistent with observed beta-bends in two sequences of ribonuclease A. The semi-rigid conformation found in the pentapeptide in which the hydroxyl groups are exposed at the periphery of the molecule could be a crucial feature to explain the ability of peptide T to bind to a specific receptor and to correlate with the observed biological activity against HIV.