Anthocyanin Glycosides from Berry Fruit Are Absorbed and Excreted Unmetabolized by Both Humans and Rats TONY K. MCGHIE,* ,² GARY D. AINGE, ² LAURA E. BARNETT, ² JANINE M. COONEY, ‡ AND DWAYNE J. JENSEN ‡ The Horticulture and Food Research Institute of New Zealand Ltd, Private Bag 11 030, Palmerston North, New Zealand, and The Horticulture and Food Research Institute of New Zealand Ltd, Private Bag 3123, Hamilton, New Zealand Anthocyanins, the red/blue pigments found in plants, are polyphenolic compounds consumed by humans and are part of a normal diet. Recent studies have shown that anthocyanins have substantial bioactivity including antioxidant activity and therefore may have beneficial effects on human health. Anthocyanins are a group of over 500 compounds of diverse structures containing different core phenolic aglycons and conjugated with sugars in a variety of glycosylation patterns. In this study, we have investigated the bioabsorption of 15 anthocyanins with structures containing different aglycons and conjugated sugars extracted from blueberry, boysenberry, black raspberry, and blackcurrant in both humans and rats. Intact and unmetabolized anthocyanins were detected in urine of rats and humans following dosing for all molecular structures investigated, thus demonstrating that anthocyanins with diverse molecular structure and from different dietary sources are bioavailable at diet relevant dosage rates. In addition, the relative concentrations of anthocyanins detected in urine following dosing varied, indicating that differences in bioavailability are due to variations in chemical structure. Our results suggest that the nature of the sugar conjugate and the phenolic aglycon are both important determinants of anthocyanin absorption and excretion in rats and humans. KEYWORDS: Anthocyanins; bioabsorption; human; berry fruit; flavonoid glycosides INTRODUCTION Anthocyanins are the red and blue pigments present in a large number of plant tissues including leaves, flowers, and fruit and therefore are consumed as normal components of the diet. The main dietary sources of anthocyanins include red-colored fruit, some vegetables, and red wine. Dietary consumption has been estimated at up to 200 mg/day, which is higher than for other flavonoids such as quercetin (1-3). Berry fruit in particular accumulate substantial quantities of anthocyanins and are rich dietary sources; single servings of some berry fruit can comprise in the order of 100-300 mg of anthocyanin. Like other flavonoid compounds, anthocyanins have antioxidant activity (4, 5). In addition, anthocyanins have also been reported to have anticancer (6, 7) and antiinflammatory (8) activity. However, despite the relatively high amounts of anthocyanins consumed in the diet and the reported biological activities, little is known about the in vivo biological activity of anthocyanins including bioabsorption and subsequent metabolism. To achieve a biological effect in a target organ or tissue (except for the gastrointestinal tract), bioactive components in the diet must be bioavailable, that is effectively absorbed, transported into the circulatory system, and delivered to the appropriate site. Until quite recently, it was thought that flavonoids, including anthocyanins, were not absorbed from the diet to any significant extent and were therefore biologically inactive. More recent research has now shown that flavonoids (e.g., quercetin glycosides and catechin) are indeed absorbed when consumed as part of the diet (9-11). There is still considerable uncertainty about the precise mechanisms of absorption of dietary phenolic compounds from the gastrointes- tinal tract. It appears that quercetin glycosides are deglycosylated prior to absorption or absorbed through direct interaction with the hexose transport pathway (12, 13) although only glucuronyl quercetin conjugates are present in plasma (14). In contrast, catechin is absorbed directly and without chemical modification but is then extensively metabolized in vivo (15). Recently, a limited number of investigations have shown that anthocyanins, too, are absorbed by humans and rats, albeit apparently by a different mechanism and at lower rates. Absorption of intact anthocyanins has been reported in rats (16, 17) and humans (18-24). Until recently, these investigations were restricted to cyanidin-containing anthocyanins; however, recent papers de- scribe the absorption of both the cyanidin and the delphinidin glycosides of blackcurrant by rats and humans (23) and anthocyanins found in blueberry (24). The mechanism for the absorption of anthocyanins has not been studied but could ² The Horticulture and Food Research Institute of New Zealand Ltd, Palmerston North. ‡ The Horticulture and Food Research Institute of New Zealand Ltd, Hamilton. J. Agric. Food Chem. 2003, 51, 4539-4548 4539 10.1021/jf026206w CCC: $25.00 © 2003 American Chemical Society Published on Web 06/24/2003