What do Spanish olives, berries, the exotic South American fruit açai, purple sweet potatoes and corn have in common? Answer: appreciable amounts of an anthocyanin known as cyanidin-3-glucoside (C3G), and a promise of reduced body fat and improved carbohydrate metabolism.
Anthocyanins are low molecular-weight plant pigments in the flavonoid family that appear to act as light screens, protecting green plant parts from inhibition of photosynthesis and from light-induced oxidative damage.1
Commercial applications of anthocyanins in foods and beverages—they are water soluble and acid stable—have rested primarily upon their utility as natural colourants. Recent in vivo studies have explored the kinetics and magnitude of C3G?s bioavailability and absorption.
Bioavailability of C3G is indeed suggestive of this anthocyanin being able to exert biological effects in vivo. Using a purple corn extract (PCE) with a C3G content of approximately 7 per cent by weight, young male mice were fed diets normal (NF) or high in fat (HF; beef lard), with or without the PCE. The PCE-containing diet provided 0.2 per cent C3G by weight.2 Twelve weeks of feeding showed the HF group that did not receive PCE to have gained a significantly greater amount of body weight, despite the food intakes of both groups on the HF diet not being different.
The average body weight of the NF+PCE group did not differ from the control diet group (no PCE; NF), but regional tissue fat weights showed strong trends of being lesser, although not statistically significant. The average fat weight of regional tissue compartments in the HF+PCE group was significantly lesser than that in the HF group.
The mechanism of PCE?s anti-obesity effects in HF+PCE diets appeared to also transfer to the NF+PCE group.2 The expression of proteins involved in the regulation of fatty acid synthesis and adipose mass expansion were influenced in a manner that would reduce tissue fat accumulation and the attendant increase in circulating pro-inflammatory mediators released by fat cells. Another publication by the same group (from the same PCE study) found that animals fed NF+PCE showed significant elevations in a cytokine produced by fat cells (adiponectin) that enhances insulin sensitivity and fat oxidation.3
Elusive still is confirmatory evidence that C3G alone is the primary mediator. No feeding studies in animals, with pure C3G, appear to have been conducted with the focus of exploring this anthocyanin?s effect on whole body glucose disposal, body lipid accumulation and lipid metabolism. This leaves open the suggestion that other edible fruit/plant crops, which harbour abundant quantities of C3G, are ripe for exploitation as agents added to conventional food and beverage formats with biologically functional relevance to consumers.
One novel C3G source that merits additional exploration is açai, which in one study was shown to contain more than 0.1 per cent C3G in the aqueous fraction of thawed, pasteurized fruit pulp (Amazon Energy).4 Confirmation of metabolic response modification in humans, by ingestion of anthocyanin/C3G-rich products, is awaited.
1. Steyn WJ, et al. Anthocyanins in vegetative tissues: a proposed unified function in photoprotection. New Phytologist 2002; 155:349?61.
2. Tsuda T, et al. Dietary cyanidin 3-O-?-D-glucoside-rich purple corn color prevents obesity and ameliorates hyperglycemia in mice. J Nutr 2003; 133:2125?30.
3. Tsuda T, et al. Anthocyanin enhances adipocytokine secretion and adipocyte-specific gene expression in isolated rat adipocytes. Biochem Biophys Res Comm 2004; 316:149-57.
4. Del Pozo-Insfran, et al. Phytochemical composition and pigment stability of açai (Euterpe oleracea Mart.). J Agric Food Chem 2004; 52:1539-45.