Bioactive berry components: Potential modulators of health benefits

This article focuses on biological activities that have been ascribed to berry antioxidant components other than vitamin C. We illustrate activities of berry polyphenol components, such as anthocyanins, flavonols and tannins, in model systems with potential relevance to cardiovascular health, cancers and glycaemic control. We present evidence that raspberry extracts but not blackcurrant extracts protected nitric oxide bioavailability in ex vivo rat carotid artery models. Nitric oxide is a key regulator of blood vessel dilation and can influence cardiovascular fitness. The raspberry extracts were more effective at lower concentrations than ascorbic acid and were as effective as quercetin metabolites known to be effective in vivo. Raspberry extracts also showed positive effects on platelet aggregation which could have beneficial effects on cardiovascular health. We present evidence that raspberry and cloudberry extracts can inhibit the proliferation of cancer cells grown in vitro and that raspberry extracts are more effective than cloudberry. As the cloudberry extracts are essentially similar in polyphenol composition to raspberry but much lower in anthocyanins and proportionally higher in ellagitannins, this raises questions about previous findings that suggested that ellagitannins were the major antiproliferative agents in raspberry. We screened berry extracts for their ability to inhibit pancreatic -glucosidase activity, a key enzyme in starch digestion and blood glucose control. Raspberry, rowan, lingonberry and pomegranate juice extracts caused significant inhibition whilst strawberry, cloudberry, blackcurrant, blackberry and blueberry caused no inhibition at the concentrations used. A red wine extract significantly increased activity. A comparison of the polyphenol composition of the effective extracts suggests that the active agents may be more complex than previously thought.