CNR - Institute of Neuroscience CNR
Institute of Neuroscience
 

Project

Developing a pharmacology of polyphenols

Summary

Polyphenols have useful biochemical properties, but poor bioavailability. The aim is to synthesise a) pro-drugs providing more efficient absorption and temporary protection against phase II metabolism, b) "mitochondriotropic" compounds and c) anti-tumoural polyphenol-based constructs. The new derivatives are tested in various relevant biological models.

Background

Polyphenols are a vast family of natural compounds exhibiting, at least in vitro, a variety of activities of potential relevance for such major health-care endeavours as protection of the cardiovascular system, improving performance impaired by old age or neurodegeneration, and prevention and therapy of cancer. They are present in many foodstuffs and are mostly studied as "nutraceutics". In our work we are using two popular model polyphenols, quercetin and resveratrol.

 

 

The mechanisms of action of polyphenols are by no means limited to their reactivity as anti- or pro-oxidants. Members of the family are known to modulate signal-transducing proteins ranging from channels to cyclooxygenases. Several biochemical pathways underlying these effects have been identified. Effects on gene expression are important, and in fact much of the antioxidant activity of polyphenols seems to be actually mediated by redox-sensitive transcription factors and enzymes.

The notoriously low bioavailability of these compounds is a major obstacle for their pharmacological exploitation. Since they are ready-made Phase II metabolism substrates, they are rapidly converted by sulfo- and glucuronosyl-transferases in enterocytes into conjugates which are to a large extent re-exported to the intestinal lumen. Liver enzymes then intervene on the molecules which have entered the circulation, administering other rounds of Phase II metabolism.

Project

The goal of the program is to find ways to increase the concentration of polyphenols and their conjugates in the body or at specific locations in the body, considering them as potential pharmacological agents. Three interwined approaches are actively pursued:
Prodrugs. Derivatives are sought in which the polyphenol hydroxyls, the sites of conjugation, are protected during absorption and a period thereafter, regenerating the parent compound through enzymatic action after the crucial initial period.
Mitochondriotropic derivatives. In this case a mitochondria-targeting permeant cation is attached to the polyphenol, determining accumulation in the matrix of mitochondria, a site of intense redox activity. Solubilisation. A recurrent problem is the low solubility in water of polyphenol "aglycones" and their derivatives. We are therefore working to develop precursors incorporating solubilising groups.

 

Methods

Standard organic synthesis methods are used to produce and characterise a variety of derivatives which are checked for stability under conditions mimicking the gastrointestinal tract and in blood. HPLC and LC/MS analysis is then applied to characterise transport and metabolism across the intestinal wall (using explanted rat intestine). Pharmacokinetics are determined in the rat model by intragastric administration followed by blood sampling and analysis.

 

Some results

Mitochondriotropic derivatives do accumulate into the mitochondria of cultured cells as expected (link to avi file). In experiments with isolated mitochondria, quercetin can act as a protective antioxidant or as a permeability transition-inducing prooxidant depending on experimental conditions, particularly the presence of traces of iron or copper ions (link to De Marchi et al., 2009). Its mitochondria-targeted derivatives are cytotoxic when administered to cells in culture at low-µM concentrations, and this effect is much more pronounced on fast-growing cells (Mattarei et al, 2008 and Biasutto et al., 2008). The cytotoxicity of the quercetin derivatives is at least in part due to an action as protonophoric uncouplic agents (Biasutto et al., 2009a).

Pro-drugs bearing protecting groups linked via carboxyester bonds are too easily destroyed by cell esterases to afford the desired protection against metabolism (Biasutto et al., 2009, in press). We are in the process of testing a variety of other chemical bond types to identify more suitable alternatives. A prototype water-soluble resveratrol derivative displayed pharmacokinetics markedly different from those yielded by resveratrol itself (Biasutto et al., 2009b).

Publications

  • Biasutto L, Marotta E, Bradaschia A, Fallica M, Mattarei A, Garbisa S, Zoratti M, Paradisi C (2009) Soluble polyphenols: synthesis and bioavailability of 3,4',5-tri(alpha-D-glucose-3-O-succinyl) resveratrol. Bioorg. Med. Chem. Lett. 19:6721-4.
  • Biasutto L, Sassi N, Mattarei A, Marotta E, Cattelan P, Toninello A, Garbisa S, Zoratti M, Paradisi C (2010) Impact of mitochondriotropic quercetin derivatives on mitochondria. Biochim. Biophys. Acta 1797:189-96.
  • De Marchi U, Biasutto L, Garbisa S, Toninello A, Zoratti M (2009) Quercetin can act either as an inhibitor or an inducer of the mitochondrial permeability transition pore: A demonstration of the ambivalent redox character of polyphenols. Biochim. Biophys. Acta 1787:1425-32.
  • Biasutto L, Marotta E, De Marchi U, Beltramello S, Bradaschia A, Garbisa S, Zoratti M, Paradisi C (2009) Heterogeneity and standardization of phase II metabolism in cultured cells. Cell. Physiol. Biochem. 23:425-30.
  • Mattarei A, Biasutto L, Marotta E, De Marchi U, Sassi N, Garbisa S, Zoratti M, Paradisi C (2008) A mitochondriotropic derivative of quercetin: a strategy to increase the effectiveness of polyphenols. Chembiochem 9:2633-42.
  • Biasutto L, Mattarei A, Marotta E, Bradaschia A, Sassi N, Garbisa S, Zoratti M, Paradisi C (2008) Development of mitochondria-targeted derivatives of resveratrol. Bioorg. Med. Chem. Lett. 18:5594-7.
  • Biasutto L, Marotta E, De Marchi U, Zoratti M, Paradisi C (2007) Ester-based precursors to increase the bioavailability of quercetin. J. Med. Chem. 50:241-53.

Grants

The project is supported by grants from the Fondazione Cassa di Risparmio di Padova e Rovigo, the Italian Association for Cancer Research and the University of Padova

Collaborations

  • Prof. Cristina Paradisi, Dept of Chemical Sciences, University of Padova.
  • Spiridione Garbisa, Dept of Experimental Biomedical Sciences of the University of Padova.
  • Prof. Paolo Caliceti, Dept of Pharmaceutical Sciences, University of Padova.
  • Prof. Antonio Toninello, Dept of Biological Chemistry, University of Padova.

 

PI photo

Mario Zoratti

Contact information

email  E-mail

email  049 8276054

Participating staff

Lucia Biasutto

Andrea Mattarei

Ester Marotta

Nicola Sassi

Alice Bradaschia

Silvia Beltramello