Biomedical subjects

Jean-Pierre Monti

Publications and source records attributed to Jean-Pierre Monti.

8 recordsLinked to original sources

PubMed2006

Hopeaphenol: the first resveratrol tetramer in wines from North Africa.

Grapes and wines are now known to constitute a rich source of phenolics such as stilbenes and flavonoids. These compounds have been shown to have cancer chemopreventive activity and potential beneficial effects on cardiovascular diseases thanks to their antioxidant and antiplatelet properties. However, because little is known about African wines and their phenolic compositions, we investigated wine samples from North Africa. A three-step method was used for the fractionation of the Merlot variety wine: column chromatography followed by centrifugal partition chromatography and reversed-phase semipreparative high-performance liquid chromatography (HPLC). Six polyphenolic compounds of the Merlot variety (from Algeria) were isolated and identified by NMR spectroscopy, five of which are known (trans-resveratrol, trans-piceid, trans-epsilon-viniferin, pallidol, and astilbin) and one that is reported for the first time in wine, (+)-hopeaphenol, a stilbene tetramer. Furthermore, these molecules were quantified in 10 commercial wines from North Africa by means of an analytical HPLC system coupled with diode array detection. Differences in concentrations were found ranging in mg/L from 4.6 to 45 (trans-piceid), 0.66 to 3.45 (trans-resveratrol), 0.2 to 1.2 (trans-epsilon-viniferin), 0.2 to 9.2 (pallidol), 0.3 to 3.8 (hopeaphenol), and 10.8 to 24.22 (astilbin). Such a high level of pallidol and astilbin has never been recorded in wine. North African wines may contribute to a significant proportion of dietary intake of stilbene and astilbin, which may have health benefits.

Africa, Northern↗

PubMed2006

Inhibitory activity of stilbenes on Alzheimer's beta-amyloid fibrils in vitro.

Polymerization of the amyloid beta-peptide (Abeta) has been identified as one of the major characteristics of Alzheimer's disease (AD). Thus, finding molecules to prevent the aggregation of Abeta could be of therapeutic value in AD. We describe an original routine in vitro assay to search for inhibitors of Abeta(25-35) fibril formation which uses UV-visible measurements and electron microscopy (EM). In particular, this routine assay was used to examine the effects of stilbenes, a well-known polyphenol class, as inhibitors of Abeta fibril formation. The inhibitory properties of resveratrol (RES), piceid (PIC), resveratrol diglucoside (DIG), piceatannol (PIA), astringine (AST), and viniferin (VIN) were characterized and compared. RES and PIC effectively and dose-dependently inhibited Abeta polymerization while other polyphenols exerted less inhibition. Although the mechanism of anti-amyloidogenic activity is still unknown, these results support the hypothesis that stilbenes could be of therapeutic value in AD.

Algorithms↗

PubMed2006

PVPP-polyphenol complexes: a molecular approach.

In dry white wines, two different forms of instability occur: (i) substantial yellow or yellow-green deposits are observed principally due to flavonol quercetin; and (ii) protein instability leads to protein casse. Polyvinyl polypyrrolidone (PVPP) is used to adsorb phenols from beverages, and bentonite is used to eliminate heat instable protein. However, in both cases, their effects are still largely unknown. This study uses a multitechnique approach to gain a better molecular understanding of the association of polyphenol aglycones with PVPP compared to that of glucosides with PVPP. The work demonstrates, that with aglycones, three forces drive complex formation: hydrophobic interaction, H bonds, and van der Waals bonds. With glucosides, the sugar moiety removes or reduces these driving forces. Thus, if the interaction between proteins and polyphenols is responsible for haze and precipitates, as is classically assumed, PVPP could prevent quercetin sedimentation.

Chemical Phenomena↗

PubMed2006

Two new benzylbenzoate glucosides from Curculigo orchioides.

An extract from in vitro cultures of Curculigo orchioides grown as bulbils in shake flasks, afforded two new glucosides of substituted benzylbenzoate - curculigoside C (3) and curculigoside D (4) - together with two known compounds - curculigoside A (1) and curculigoside B (2). Their structures were elucidated on the basis of spectral evidence, in particular by using 2D NMR methods. Their vasoactive properties were assessed in isolated rat aortic rings.

Animals↗

PubMed2005

New stilbenoid glucosides isolated from Vitis vinifera cell suspension cultures (cv. Cabernet Sauvignon).

Three new monomeric stilbenoid glucosides, (Z)- and (E)-resveratrol 3,5- O-beta-diglucosides (1 and 2, respectively) and (Z)-resveratrol 3,5,4'- O-beta-triglucoside (3), were isolated from an extract of Vitis vinifera cell cultures (Cabernet Sauvignon) together with the known (E)- and (Z)-piceids and (E)- and (Z)-resveratrol 3,4'- O-beta-diglucosides that have already been identified in a Gamay cell culture extract. The structure determinations were based on spectroscopic data analysis.

Cell Culture Techniques↗

PubMed2002

First observation of solution structures of bradykinin-penta-O-galloyl-D-glucopyranose complexes as determined by NMR and simulated annealing.

Polyphenols (tannins) are known for their high propensity to precipitate proteins. They bind most strongly to proteins with a high proline content. Understanding the mechanism of this association is of prime interest because this interaction might induce protein conformational changes that may modify their biological activity. To investigate the interaction, an NMR study was carried out on the binding of a representative polyphenol, penta-O-galloyl-D-glucopyranose, to a nonapeptide hormone, bradykinin (BDK), where proline accounts for 30% of residues. Series of 1D and 2D-NMR experiments were performed. For the first time, a three-dimensional structure of complexes was determined using 2D-NMR experiments and molecular modeling. These structure calculations are a potent tool to understand how the association arises. They clearly show that the interaction is a complex phenomenon where several parameters are involved. The PGG/BDK complexes are formed by multiple weak interactions between peptide side chains and galloyl rings. Proline and arginine are good anchoring points and the glycine gives a certain flexibility in the peptide backbone that allows the polyphenol to approach and interact. Therefore, it is not only the hydrophobic stackings between galloyl rings and proline and hydrogen bonding involving arginine and aromatic rings which are important. The residue sequence and the side chain steric bulk also intervene.

Bradykinin↗

PubMed2002

Carbon-14 biolabelling of wine polyphenols in Vitis vinifera cell suspension cultures.

14C-L-phenylalanine is incorporated into a range of polyphenolic compounds when fed to grape cell cultures. Optimisation of several parameters such as the quantity of precursor applied and the duration of metabolism led to incorporation yields of 15% and to specific activities of 875 mu Ci g(-1) in stilbenes. Purification of the products by several chromatographic steps is reported. Both trans- and cis-resveratrols were easily obtained by enzymatic hydrolysis of their corresponding glucosides, with specific activity of 1200-1400 mu Ci g(-1). The specific radioactivity obtained for all the compounds is suitable for in vivo feeding trials to trace their metabolic fate when consumed by animals and for in vitro activity mechanism studies. Indeed, these polyphenols seem to be implicated in the health benefits associated with regular and moderate wine consumption but little is known about their pharmacokinetics and cellular uptake.

Anthocyanins↗

PubMed2002

Synthesis, and functional properties of a modified human insulin A-chain: implication in a 'mini-insulin' structure determination.

The design and total synthesis of a novel insulin A-chain mutant, analogue 3, is reported. In this compound, the cysteines implied in the two insulin inter-chain disulfide bridges are replaced by two serines (residues Ser(A7) and Ser(A20)) and the intra-A-chain disulfide bridge (residues Cys(A6) and Cys(A11)) is conserved. This A-chain analogue (3) has been tested in three in vitro cell culture assays, using insulin as a reference. The data clearly showed that analogue 3 mimics insulin effects on DNA synthesis, glucose uptake and glycogen synthesis without loss of potency as compared to insulin. To our knowledge, these are the first results showing that an isolated insulin chain displays functional properties similar to those of insulin. The implication of these new findings in insulin structure-function relationships and in a 'mini-insulin' structure determination is discussed.

3T3 Cells↗