Catherine Chèze

Preparative isolation of polyphenolic compounds from Vitis vinifera by centrifugal partition chromatography

This study deals with a centrifugal partition chromatography developed for the separation of phenolic compounds from Vitis vinifera. EtOAc grape seed extracts were separated using the solvent system hexane-ethyl acetate-ethanol-water (1:8:2:7; v/v) in two fractions: one containing about 75% of flavanol monomers (catechin and epicatechin) corresponding to 18% of crude extract and another fraction B-type dimers (22% of crude extract). From the stalk extracts, we could separate stilbenoid compounds (resveratrol and its oligomers; 12% of crude extract) which were eluted in less than 30 min from flavanols (which required a few hours of additional elution). Using the same solvent system but in different ratios (4:5:3:3; v/v), we isolated the trans-resveratrol (7@1000; 90% purity).

Bisulfite addition to anthocyanins: revisited structures of colourless adducts

Abstract Decolourization of anthocyanins by sulfur dioxide is investigated through the reaction between sodium bisulfite and malvidin 3- O -glucoside. The structural elucidation of the C-4 sulfonate adducts is established by 1 H, 13 C and 33 S NMR spectroscopies.

Prevention of type 2 diabetes induced by high fat diet in the C57BL/6J mouse by two medicinal plants used in traditional treatment of diabetes in the east of Algeria.

AIM OF THE STUDY The preventive effect of the hydro-alcoholic extracts of Artemisia herba-alba Asso (AHA), and Centaurium erythraea Rafn (CE), two medicinal plants used in traditional treatment of diabetes in the north-eastern Algeria, were evaluated in animal models of type 2 diabetic induced with a standardised high fat diet (HFD). MATERIALS AND METHODS Plant extracts were administered orally by gavage at a dose of 2g/kg bodyweight daily for 20 weeks to male C57BL/6J mice fed HFD. Animals were weighed and plasma glucose measured weekly and insulin at the end of study using standard ELISA methods. RESULTS After 6 weeks, blood glucose levels increased in HFD control mice. At end of study (20 weeks) in groups treated with AHA or CE extracts vs. HFD control group there was a significant reduction in mean (+/-SD) fasting blood glucose (respectively 108.0+/-42.0 and 120.4+/-45.1 vs. 183.1+/-19.1mg/dl, p<0.05), triglyceride concentrations (26.9+/-6.7 and 27.9+/-17.8 vs. 48.9+/-12.1mg/dl, p<0.05) and serum insulin levels (1.1+/-1.0 and 0.6+/-0.7 vs. 3.1+/-1.8 ng/ml, p<0.05). Plant extracts also markedly reduced insulin resistance as measured by the homeostasis model assessment (HOMA) compared to HFD controls (AHA: 4.4+/-5.3, CE: 3.0+/-3.3 vs. HFD control 38.3+/-26.6, p<0.05). The plant extracts had no effect on calorie intake or body weight. CONCLUSION AHA had been shown to have a hypoglycaemic effect in diabetes but this is the first demonstration of a preventive effect of AHA and CE on HFD-induced diabetes.

Vasorelaxant effects of grape polyphenols in rat isolated aorta. Possible involvement of a purinergic pathway

The purpose of this study was to investigate the mechanism of the vascular relaxation produced by polyphenolic substances from red wine, with a particular focus on the possible involvement of purinoceptors. With this aim, relaxing responses induced by procyanidin from grape seeds (GSP), anthocyanins, catechin and epicatechin were assessed in rat isolated aortic rings left intact (+E) or endothelium‐denuded (−E). In preparations precontracted with noradrenaline, incubation with NG‐nitro‐l‐arginine methyl ester (100 μm, 30 min) fully inhibited the GSP‐induced relaxations. Concentration–effect curves to these substances (from 10−7 to 10−1 g/L) were determined in depolarized (60 mm KCl) preparations in control condition, after incubation with reactive blue 2 (an antagonist of P2Y purinoceptors, 30 μm), with apyrase (an enzyme which hydrolyses ATP and ADP, 0.8 U/mL) or with α,β‐methylene ATP (an inhibitor of ecto ATPases, 10 μm). In (+E) rings, relaxations (expressed as percentage of initial contraction) were 41 ± 2 and 37 ± 3 for GSP and anthocyanins, respectively. Only modest relaxations (ca. 10%) were observed in (−E) rings, as it was the case for catechin and epicatechin in (±E) rings. Reactive blue 2 or apyrase inhibited the GSP‐ and anthocyanin‐induced relaxations in (+E) rings, while α,β‐methylene ATP shifted to the left the relaxation curves obtained with GSP. These data confirm that modest relaxations observed with catechin and epicatechin are not endothelium‐dependent but that GSP and anthocyanins induce a relaxing effect, which is related to the integrity of the endothelium and the synthesis and release of nitric oxide (NO). Furthermore, the inhibition by apyrase and the increase by ecto‐ATPase inhibition of the GSP‐ and anthocyanin‐induced relaxation suggest that these substances could act via an initial release of nucleotides, which in turn could activate P2Y1 and/or P2Y2 purinoceptors of endothelial cells, trigger the synthesis and release of NO and then lead to relaxation.

DNA triplex stabilization property of natural anthocyanins.

The DNA triplex stabilization property of seven natural anthocyanins (five monoglucosides and two diglucosides) has been measured by the mean of triplex thermal denaturation experiments. We have noticed a difference between the diglucosides that do not modify this melting temperature and the monoglucosides (namely 3-O-beta-D-glucopyranoside of malvidin, peonidin, delphinidin, petunidin and cyanidin) which present a weak but significant stabilizing effect. It appears clearly that the difference between the two series could be due to the supplementary sugar moiety at the 5 position for the diglucosylated compounds, that would make them too crowded to allow interaction with the triplex. Among the monoglucoside series, the most active compounds are the only ones to embody a catechol B-ring in their structure that could be important for such an interaction. The need to have pure and fully characterized compounds to run these measurements, made it possible for us to unambiguously assign the 1H and 13C NMR spectra with the help of 2D NMR experiments. Thus, missing data of compounds not totally described earlier, are provided herein.

Preventive and curative effect of Trigonella foenum-graecum L. seeds in C57BL/6J models of type 2 diabetes induced by high-fat diet

ETHNOPHARMACOLOGICAL RELEVANCE Trigonella foenum-graecum L. (TFG) is traditionally used to treat diabetes in North Africa. we therefore tested the effects of the hydro-alcoholic extract of TFG seeds in a C57/BL6J mouse model of diabetes induced by a standardised high-fat diet (HFD). MATERIALS AND METHODS Plant extracts (2 g/kg daily) were administered orally by gavage at the start of HFD, or after confirmation of established diabetes (17th week), for 20 or 18 weeks, respectively, to male C57BL/6J mice. Animals were weighed; food intake and plasma glucose, lipid profile, insulin and insulin resistance were measured. RESULTS TFG extracts opposed the development of diabetes: compared with untreated HFD mice, TFG-treated HFD mice had lower mean (± SD) plasma glucose (129.3 ± 39.4 vs. 183.1 ± 19.1mg/dL, p<0.05), plasma insulin (1.3 ± 0.8 vs. 3.1 ± 1.8 ng/mL, p<0.05) and triglycerides (18.9 ± 12.9 vs. 48.9 ± 12.1mg/dL, p<0.05), and less insulin resistance as estimated by the homeostasis model assessment (HOMA: 9.7 ± 11.1 vs. 38.3 ± 26.6, p<0.05). In mice with established diabetes, TFG reduced fasting plasma glucose (170.4 ± 24.1 vs. 229.0 ± 20.8 mg/dL, p<0.05), plasma insulin (1.7 ± 1.3 vs. 3.3 ± 14.3 ng/mL, p<0.05) and insulin resistance (HOMA: TFG: 19.2 ± 15.7 vs. HFD control: 38.5 ± 30.3, p<0.05). In addition, administration of TFG extract also caused significant reduction in triglycerides (17.9 ± 9.7 vs. 62.8 ± 18.3 mg/dL, p<0.05) and total cholesterol (1.30 ± 0.20 vs. 1.80 ± 1.10 g/L, p<0.05), and an increase in HDL-cholesterol (1.6 ± 0.2 vs. 1.2 ± 0.1 g/L). The plant extract had no effect on calorie intake or body weight. CONCLUSION TFG extract opposed the development of experimental HFD diabetes in mice, and had an anti-diabetic effect in mice with established diabetes.

Treatment of high fat diet induced type 2 diabetes in C57BL/6J mice by two medicinal plants used in traditional treatment of diabetes in the east of Algeria.

AIM OF THE STUDY Hydro-alcoholic extracts of Centaurium erythraea Rafn (CE), Gentianaceae and Artemisia herba-alba Asso (AHA), Asteraceae, medicinal plants used in traditional treatment of diabetes in north-eastern Algeria, were tested in established type 2 diabetes induced with a standardized high fat diet (HFD) in mice. MATERIALS AND METHODS After confirmation of diabetes (17th week), plant extracts were administered orally by gavage at a dose of 2 g/kg daily for 18 weeks to male C57BL/6J mice fed HFD. Animals were weighed, food intake and plasma glucose measured weekly, insulin and lipid profile at study end. RESULTS At 35 weeks, groups treated with AHA or CE vs. HFD control had a significant reduction in mean (±SD) fasting blood glucose concentrations (143.8±23.9 and 139.5±14.2 vs. 229.0±20.8 mg/dL, p<0.05, respectively), triglyceride (18.9±11.1 and 16.0±6.5 vs. 62.8±18.3 mg/dL, p<0.05), total cholesterol (1.2±0.1 and 1.2±0.3 vs. 1.8±1.1 g/L, p<0.05) and serum insulin concentrations (1.7±0.7 and 0.9±0.7 vs. 3.3±14.3 ng/mL, p<0.05). Plant extracts also markedly reduced insulin resistance as compared to HFD controls (AHA: 15.6±9.1, CE: 9.0±7.7 vs. HFD control 38.5±30.3, p<0.05). The plant extracts decreased calorie intake and had little effect on body weight or HDL-cholesterol. CONCLUSION AHA has already been shown to have a antihyperglycaemic and antihyperlipidemic effect but this is the first demonstration of an effect of AHA and CE on established HFD-induced diabetes.

Sulfur Dioxide Decolorization or Resistance of Anthocyanins: NMR Structural Elucidation of Bisulfite-Adducts

Use of anthocyanins as coloring agents in food is limited, since it is well known that they lose their original color in the presence of nucleophiles. This phenomenon occurs in aqueous alkaline media (OH− addition), but most of all in the presence of bisulfite, commonly used as a preservative. Even though this has been observed for many years, the mechanism is not thoroughly understood. The chalcone form (3), in equilibrium1,2 with the carbinol (2) resulting from hydroxyl addition on the flavylium (1), was postulated. Addition of bisulfite readily occurs, as it does with carbonyls leading to a chalcone-bisulfite adduct.3,4 More recent works, by means of UV-visible,5 kinetic,6,7 and thermodynamic measurements,8 have shown that adducts could result from nucleophilic addition of SO2 either on the C-2 or C-4 carbon of the flavylium, thus refuting the necessity of opening into a chalcone (fig. 1).