Role of the catechol group in the antioxidant and neuroprotective effects of virgin olive oil components in rat brain.

The aim of the present study was to determine the role of the catechol group in the antioxidant and neuroprotective effects of minor components of virgin olive oil in rat brain tissue. Hydroxytyrosol ethyl ether (HT, 2 OH), tyrosol ethyl ether (Ty, 1 OH) and 3,4-di-ortho-methylidene-hydroxytyrosol ethyl ether (MET, no OH) were compared. Oxidative stress was induced with ferrous salts (lipid peroxidation induction), diethylmaleate (depletion of glutathione) and hypoxia-reoxygenation in brain slices. Lipid peroxidation was inhibited in direct proportion to the number of OH groups: HT>Ty>MET. Exposure to HT led to partial recovery of the glutathione system after chemical inhibition or hypoxia-reoxygenation. All three compounds inhibited cell death in hypoxia-reoxygenation experiments (HT≥Ty>MET). Peroxynitrite formation (3-nitrotyrosine) and inflammatory mediators (prostaglandin E2 and interleukin 1ß) were inhibited by all three compounds. In conclusion, the presence of OH groups in the molecule of these phenolic compounds from virgin olive oil is a determinant factor in their antioxidant effect in brain tissue, but this antioxidant effect is not the only explanation for their neuroprotective effect.

Antiplatelet effect of new lipophilic hydroxytyrosol alkyl ether derivatives in human blood.

PURPOSE: To investigate the in vitro antiplatelet and anti-inflammatory effects of five alkyl hydroxytyrosol (HT) ether derivatives in human whole blood and compare these effects with those of HT. METHODS: Blood samples from healthy volunteers were incubated with HT and HT alkyl ether derivatives (ethyl, butyl, hexyl, octyl and dodecyl). Maximum intensity of platelet aggregation was induced with collagen, arachidonic acid or ADP. Calcium-induced thromboxane B(2) and nitric oxide production, LPS-induced prostaglandin E(2) and nitric oxide production and LPS-induced interleukin 1ß production were measured. RESULTS: All compounds inhibited platelet aggregation, thromboxane B(2) and inflammatory mediators in a concentration-dependent manner. The concentrations of each compound that inhibited the corresponding variable by 50 % compared to control samples (IC(50)) were in the range of 10(-7)-10(-6) M for HT hexyl ether; for the other compounds, these values were in the range of 10(-5) M. The IC(50) for thromboxane B(2) production was in the range of 10(-4) M. The effects of HT alkyl ether derivatives were greater than those of HT. These compounds increased nitric oxide production. There was no direct relationship between the effects of these compounds and alkyl chain length. Maximum effects were observed in the C4-C6 range. CONCLUSIONS: Alkyl ether derivatives of HT exert antiplatelet and anti-inflammatory effects that are greater than those of HT.

Neuroprotective effect of alkyl hydroxytyrosyl ethers in rat brain slices subjected to a hypoxia-reoxygenation model.

The aim of the present study was to investigate the antioxidant and possible neuroprotective and antioxidant effects of five alkyl hydroxytyrosyl (HT) ethers (ethyl, butyl, hexyl, octyl and dodecyl) in rat brain slices. None of the compounds modified lipid peroxidation or glutathione concentrations (GSH) in oxygenated samples. The effects of oxidative stress were investigated with ferrous salts to induce lipid peroxidation and diethylmaleate (DEM) to reduce GSH. All compounds inhibited lipid peroxidation with an inhibitory concentration 50% (IC(50)) one tenth that of HT. These compounds, especially the butyl derivative, prevented GSH depletion after incubation with DEM. We also explored the neuroprotective effect of these compounds in an experimental model of hypoxia-reoxygenation in rat brain slices. All compounds showed neuroprotective and antioxidant effects. Our results established a relationship between these effects and the length of the carbon chain (maximum effect in the range of C4-C8).

Preparation and antioxidant activity of tyrosyl and homovanillyl ethers.

Preparation of tyrosyl and homovanillyl lipophilic derivatives was carried out as a response to the food industry's increasing demand for new synthetic lipophilic antioxidants. Tyrosyl and homovanillyl ethers were synthesized in high yields by a three-step procedure starting from tyrosol (Ty) and homovanillic alcohol (HMV). The antioxidant activity of these new series of alkyl tyrosyl and homovanillyl ethers was evaluated by the Rancimat test in a lipophilic food matrix and by the FRAP, ABTS and ORAC assays and compared to free Ty and HMV as well as two antioxidants widely used in the food industry, butylhydroxytoluene (BHT) and α-tocopherol. The results pointed out the higher activity of homovanillyl series in comparison with tyrosyl series with all the assayed methods. However, while both synthetic series were less antioxidant than BHT and α-tocopherol in a lipophilic matrix after their Rancimat test evaluation, homovanillyl alkyl ethers showed the best reducing power and radical scavenging activity of all evaluated compounds. This batch of synthetic lipophilic compounds, derived from biologically active compounds such as Ty and HMV, provide interesting and potentially bioactive compounds.

Determination of the chemical structure of the capsular polysaccharide of strain B33, a fast-growing soya bean-nodulating bacterium isolated from an arid region of China.

We have determined the structure of a polysaccharide from strain B33, a fast-growing bacterium that forms nitrogen-fixing nodules with Asiatic and American soya bean cultivars. On the basis of monosaccharide analysis, methylation analysis, one-dimensional 1H- and 13C-NMR and two-dimensional NMR experiments, the structure was shown to consist of a polymer having the repeating unit -->6)-4-O-methyl-alpha-D-Glcp-(1-->4)-3-O-methyl-beta-D-GlcpA-(1--> (where GlcpA is glucopyranuronic acid and Glcp is glucopyranose). Strain B33 produces a K-antigen polysaccharide repeating unit that does not have the structural motif sugar-Kdx [where Kdx is 3-deoxy-D-manno-2-octulosonic acid (Kdo) or a Kdo-related acid] proposed for different Sinorhizobium fredii strains, all of them being effective with Asiatic soya bean cultivars but unable to form nitrogen-fixing nodules with American soya bean cultivars. Instead, it resembles the K-antigen of S. fredii strain HH303 (rhamnose, galacturonic acid)n, which is also effective with both groups of soya bean cultivars. Only the capsular polysaccharide from strains B33 and HH303 have monosaccharide components that are also present in the surface polysaccharide of Bradyrhizobium elkanii strains, which consists of a 4-O-methyl-D-glucurono-L-rhamnan.

Determination of phenols, flavones, and lignans in virgin olive oils by solid-phase extraction and high-performance liquid chromatography with diode array ultraviolet detection.

A simple analytical method for the quantitative determination of phenols, flavones, and lignans in virgin olive oils was developed. The polar fraction was isolated from small amounts of oil sample (2.5 g) by solid-phase extraction (SPE) using diol-phase cartridges, and the extract was analyzed by reversed-phase HPLC coupled with diode array UV detection. Chromatographic separation of pinoresinol, cinnamic acid, and 1-acetoxypinoresinol was achieved. Repeatability (RSD < 6.5%), recovery (> 90%), and response factors for each identified component were determined. SPE on amino-phase cartridges was used for isolating acidic phenols and as an aid for phenol identification. For the first time, 2-(4-hydroxyphenyl)ethyl acetate was detected in olive oils. The aldehydic structure of the ligstroside aglycon was confirmed by NMR spectroscopy. The colorimetric determination of total o-diphenolic compounds by reaction with molybdate was consistent with their HPLC determination. Differences between results obtained by liquid-liquid extraction and SPE were not statistically significant.

Studies on the solution conformation and dynamics of a polysaccharide from Sinorhizobium fredii HH103 and its monosaccharide repeating unit.

The conformational behavior of the homopolysaccharide isolated from Sinorhizobium fredii HH103 and its monosaccharide repeating unit (5-acetamido-3,5,7,9-tetradeoxy-7-(3-hydroxybutyramido)-L-glycero- L- manno-nonulosonic acid) was analyzed by nuclear magnetic resonance (NMR) spectroscopy and extensive molecular dynamics simulations (MD). The results indicate that the glycosidic linkages and lateral chains may adopt a variety of conformations. MD simulations using the generalized Born solvent-accessible surface area (GB/SA) continuum solvent model for water and the MM3* force field provide a population distribution of conformers that satisfactorily agrees with the experimental NMR data for the torsional degrees of freedom of the molecule.

Retamatrioside, a new flavonol triglycoside from Retama sphaerocarpa.

A new flavonol triglycoside, retamatrioside (1), has been isolated from the aerial parts of Retama sphaerocarpa. The structure of 1 has been determined as rhamnazin 3-O-beta-D-glucopyranosyl-(1-->5)-[beta-D-apiofuranosyl(1-->2)]-al pha -L-arabinofuranoside, using spectroscopic methods.

Structural determination of a 5-acetamido-3,5,7, 9-tetradeoxy-7-(3-hydroxybutyramido)-L-glycero-L-manno-nonulos onic acid-containing homopolysaccharide isolated from Sinorhizobium fredii HH103.

The structure of a polysaccharide from Sinorhizobium fredii HH103 has been determined. This polysaccharide was isolated by following the protocol for lipopolysaccharide extraction. On the basis of monosaccharide analysis, methylation analysis, fast atom bombardment MS, matrix-assisted laser desorption ionization MS, electron-impact high-resolution MS, one-dimensional (1)H-NMR and (13)C-NMR and two-dimensional NMR experiments, the structure was shown to consist of a homopolymer of a 3:1 mixture of 5-acetamido-3,5,7, 9-tetradeoxy-7-[(R)- and (S)-3-hydroxybutyramido]-l-glycero-l-manno-nonulosonic acid. The sugar residues are attached via a glycosidic linkage to the OH group of the 3-hydroxybutyramido substituent and thus the monomers are linked via both glycosidic and amidic linkages. In contrast with the Sinorhizobium K-antigens previously reported, which are composed of a disaccharide repeating unit, the K-antigen polysacharide of S. fredii HH103 is a homopolysaccharide.

Structural determination of a 5-O-methyl-deaminated neuraminic acid (Kdn)-containing polysaccharide isolated from Sinorhizobium fredii.

The structure of a polysaccharide from Sinorhizobium fredii SVQ293, a thiamine auxotrophic mutant of S. fredii HH103, has been determined. This polysaccharide was isolated following the protocol for lipopolysaccharide extraction. On the basis of monosaccharide analysis, methylation analysis, fast atom bombardment MS, collision-induced dissociation tandem MS, one-dimensional 1H and 13C NMR and two-dimensional NMR experiments, the structure was shown to consist of the following trisaccharide repeating unit-->2)-alpha-d-Galp-(1-->2)-beta-d-Ribf-(1-->9)-alpha-5-O-Me-++ +Kdnp- (2-->, in which Kdn stands for deaminated neuraminic acid; 25% of the Kdn residues are not methylated. The structure of this polysaccharide is novel and this is the first report of the presence of Kdn in a rhizobial polysaccharide, as well as being the first structure described containing 5-O-Me-Kdn. This Kdn-containing polysaccharide is not present in the wild-type strain HH103, which produces a 3-deoxy-d-manno-2-octulosonic acid (Kdo)-rich polysaccharide. We conclude that it is likely that the appearance of this new Kdn-containing polysaccharide is a consequence of the mutation.

Structural analysis of the exopolysaccharides produced by Lactobacillus spp. G-77.

The exopolysaccharide produced by a ropy strain of Lactobacillus spp. G-77 in a semi-defined medium, was found to be a mixture of two homopolymers composed of D-Glc. The two poly-saccharides were separated and, on the basis of monosaccharide and methylation analyses, 1H, 13C, 1D and 2D NMR experiments, one of the polysaccharides was shown to be a 2-substituted-(1-3)-beta-D-glucan, identical to that described for the EPS from Pediococcus damnosus 2.6 (M.T. Dueñas-Chasco, M.A. Rodríguez-Carvajal, P. Tejero-Mateo, G. Franco-Rodríguez, J. L. Espartero, A. Irastorza-Iribar, and A.M. Gil-Serrano, Carbohydr. Res., 303 (1997) 453-458), and the other polysaccharide was shown to consist of repeating units with the following structure [formula: see text]

Structural analysis of the exopolysaccharide produced by Pediococcus damnosus 2.6.

The exopolysaccharide produced by a ropy strain of Pediococcus damnosus (2.6) in a semi-defined medium was found to be an homopolymer composed of D-glucose. On the basis of monosaccharide and methylation analysis, 1H, 13C, 1D and 2D NMR experiments the polysaccharide was shown to consist of repeating units with the following structure. [sequence: see text]

Structural characterization and hydrolytic degradation of a Zn metal initiated copolymer of L-lactide and epsilon-caprolactone.

A bioresorbable aliphatic polyester was synthesized by bulk copolymerization of a 1/1 M/M L,L-lactide/epsilon-caprolactone mixture using zinc metal as initiator. The actual composition of the copolymer was found to be 1.5/1 as deduced from 1H NMR spectra obtained in DMSO-d6 solutions where higher resolution was obtained as compared with chlorinated solvents. Resonances due to L-lactyl units (L) exhibited triads stereosensitivity, epsilon-oxycaproyl units (C) being sensitive to dyads. Average lengths of both poly(lactic acid) and polycaprolactone sequences were evaluated and showed the presence of rather long PLA blocks. Furthermore, no CLC triad signal was found, suggesting the absence of transesterification rearrangements. 10 x 10 x 2 mm specimens made of the copolymer were allowed to age in isoosmolar pH = 7.4 phosphate buffer at 37 degrees C. Degradation was monitored by various analytical techniques such as SEC, X-ray diffractometry, DSC, and 1H NMR. Data were compared with the behaviour of PCL and PLA homopolymers allowed to age under similar conditions. Crystallinity and composition changes are discussed in terms of preferential degradation in L- and C-containing amorphous domains, crystallized long PLA blocks being much more resistant.