Blackberry polyphenols: review of composition, quantity, and health impacts from in vitro and in vivo studies

Blackberries possess marked concentrations of antioxidant polyphenols, most notably anthocyanins, ellagic acid, ellagitannins, epi/catechin, and proanthocyanidins. While the quantity and type of polyphenols can vary, cyanidin-3-O-glucoside (C3G) is consistently the most abundant polyphenol found in blackberries. Though blackberry antioxidants have not demonstrated significant bioavailability or bioaccessibility in their native form, emerging research suggests that antioxidant metabolites, such as protocatechuic acid derived from C3G, may account for some of the in vivo benefits. Cell studies conducted with blackberry phenolic extracts have demonstrated anti-inflammatory, chemopreventive, and neuroprotective effects; whereas, animal models given blackberries have exhibited reduced insulin resistance, attenuated weight gain, and a decrease in inflammatory markers. Blackberry consumption can lead to positive health outcomes. In human health cross-sectional and longitudinal studies, fresh berry consumption has been associated with better long-term insulin resistance, cognitive function, bone density, and cardiovascular function. Research studies, combining in vitro digestion and absorption with targeted cell studies, are being performed to better understand the metabolism and bioactivity of blackberry phenolics. These compounds are not only absorbed by the body, but also can attach to the lining of the digestive tract or be fermented in the colon, contributing to the health outcomes afforded by blackberry consumption.