Review Polyphenols: do they play a role in the prevention of human pathologies? H. Tapiero 1 *, K.D. Tew 2 , G. Nguyen Ba 1 , G. Mathé 1 1 Faculté de Pharmacie, Université de Paris, CNRS UMR 8612, 5, rue Jean Baptiste Clément, 94200 Chatenay Malabry, France; 2 Fox Chase Cancer Center, Philadelphia, PA, USA (Received 5 February 2002; accepted 16 February 2002) Summary – Polyphenols are the most abundant antioxidants in our diets. The main classes of polyphenols are phenolic acids (mainly caffeic acid) and flavonoids (the most abundant in the diet are flavanols (catechins plus proanthocyanidins), anthocyanins and their oxidation products), which account for one- and two-thirds, respectively. Polyphenols are reducing agents, and together with other dietary reducing agents, such as vitamin C, vitamin E and carotenoids, referred to as antioxi- dants, protect the body’s tissues against oxidative stress and associated pathologies such as can- cers, coronary heart disease and inflammation. The biological properties, bioavailability, antioxidant activity, specific interactions with cell receptors and enzymes, are related to the chemical structure of polyphenols. It is, therefore, essential to know the nature of the main polyphenols ingested, their dietary origin, the amounts consumed in different diets, their bioavailability and the factors controlling their bioavailability. © 2002 Éditions scientifiques et médicales Elsevier SAS Phenolic acids / Flavonoids / Distribution / Intake / Bioavailability NATURE OF DIETARY POLYPHENOLS The main classes of polyphenols are: phenolic acids (Fig. 1), flavonoids (Fig. 2) and the less common stilbenes and lignans (Fig. 3). The consumption of polyphenol-rich foods or beverages has been reported to play a role in cancers [1-3], stroke [4] and coro- nary heart disease [5-7]. Phenolic acids A major class of phenolic compounds is the hydroxy- cinnamic acids, which are found in almost every plant. The major representative of hydroxycinnamic acids is caffeic acid, which occurs in foods mainly as an ester with quinic acid called chlorogenic acid (5-caffeoylquinic acid; Fig. 1B) [8,9]. Coffee is a major source of chlorogenic acid in the human diet; daily intake in coffee drinkers is 0.5–1 g, while cof- fee abstainers will usually ingest <100 mg/d. Most of the chlorogenic acid from foods will reach the colon and part will enter into the blood circulation [10]. Chlorogenic acid and caffeic acid are antioxi- dants in vitro [11] and they might inhibit the forma- tion of mutagenic and carcinogenic N-nitroso com- pounds because they are inhibitors of the N-nitrosation reaction in vitro [12]. Further, chloro- genic acid can inhibit DNA damage in vitro [13,14]. Therefore, the inverse association between coffee intake and colon cancer in some epidemiologic stud- ies might be explained in part by the chlorogenic acid present in coffee [15-17]. Flavonoids Flavonoids (Fig. 2) are the most abundant polyphe- nols in human diets and represent a subclass of *Corresponding author.Tel.: +33-1-46-83-5814; fax: +33-1-46-83-0613. E-mail address: haimtapiero@aol.com (H. Tapiero). Biomed Pharmacother 2002 ; 56 : 200-7 © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved S0753332202001786/REV