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Cancer Letters 269 (2008) 281–290 www.elsevier.com/locate/canlet

Mini-review

Anthocyanins and their role in cancer prevention
Li-Shu Wang, Gary D. Stoner *
Department of Internal Medicine and Comprehensive Cancer Center, Ohio State University College of Medicine, Columbus, OH 43210, USA Received 14 March 2008; received in revised form 14 March2008; accepted 8 May 2008

Abstract Anthocyanins are the most abundant flavonoid constituents of fruits and vegetables. The conjugated bonds in their structures, which absorb light at about 500 nm, are the basis for the bright red, blue and purple colors of fruits and vegetables, as well as the autumn foliage of deciduous trees. The daily intake of anthocyanins in residents of the United Statesis estimated to be about 200 mg or about 9-fold higher than that of other dietary flavonoids. In this review, we summarize the latest developments on the anti-carcinogenic activities of anthocyanins and anthocyanin-rich extracts in cell culture models and in animal model tumor systems, and discuss their molecular mechanisms of action. We also suggest reasons for the apparent lack of correlationbetween the effectiveness of anthocyanins in laboratory model systems and in humans as evidenced by epidemiological studies. Future studies aimed at enhancing the absorption of anthocyanins and/or their metabolites are likely to be necessary for their ultimate use for chemoprevention of human cancer. Ó 2008 Elsevier Ireland Ltd. All rights reserved.
Keywords: Anthocyanins; Chemoprevention; In vitro;In vivo; Mechanisms

1. Introduction Anthocyanins occur ubiquitously in the plant kingdom and confer the bright red, blue and purple colors to fruits and vegetables such as berries, grapes, apples, purple cabbage and corn. Of potential importance to human health is the relatively high concentration of anthocyanins in the diet. The daily intake of anthocyanins in the U.S. diet is estimated to bebetween 180 and 215 mg whereas,
* Corresponding author. Address: Ohio State University, Comprehensive Cancer Center, Innovation Centre, 2001 Polaris Parkway, Columbus, OH 43240, USA. Tel.: +1 614 293 3268; fax: +1 641 293 5952. E-mail address: gary.stoner@osumc.edu (G.D. Stoner).

the intake of other dietary flavonoids such as genistein, quercetin and apigenin is only 20–25 mg/day [1].Epidemiologic studies suggest that the consumption of anthocyanins lowers the risk of cardiovascular disease, diabetes, arthritis and cancer due, at least in part, to their anti-oxidant and anti-inflammatory activities [2]. In the present review, we highlight recent studies on the cancer preventative activities of the anthocyanins, including results from in vitro cell culture and in vivo animal model tumorsystems, as well as data from human epidemiological studies. Although laboratory studies have provided some clues on the molecular mechanism(s) by which anthocyanins inhibit carcinogenesis, there is still much to be learned. In addition, the relevance of the in vitro

0304-3835/$ - see front matter Ó 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.canlet.2008.05.020

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L.-S.Wang, G.D. Stoner / Cancer Letters 269 (2008) 281–290

studies to the in vivo situation needs to be confirmed in view of the high concentrations of anthocyanins employed in the in vitro studies. 2. Chemistry of anthocyanins

and extent to which the glycosides are attached to the skeleton [4]. 3. Anti-cancer properties of anthocyanins 3.1. In vitro studies

Anthocyanins occur naturally infruits and vegetables as glycosides, having glucose, galactose, rhamnose, xylose or arabinose attached to an aglycon nucleus [3,4]. In contrast to other flavonoids, the anthocyanins carry a positive charge in acidic solution [3]. They are water-soluble and, depending upon pH and the presence of chelating metal ions, are intensely colored in blue, purple, or red. The de-glycosylated or aglycone forms...