Flavonoids: Novel food sources and potential health benefits

Today’s health-conscientious consumers are constantly in search of the newest “elixir” to fight aging and disease. Consequently, there has been an increased interest in flavonoids, which are antioxidants found in plants that have been suggested to play a role in the prevention of a variety of diseases, including cancer and heart disease. Dietary sources of flavonoids currently in vogue include berries, teas, red grapes, red wine, citrus fruit, onions, parsley, legumes, and dark chocolate. For example, flavonoids in red wine have been linked to the so-called “French Paradox,” referring to the relatively low incidence of heart disease among the French population despite a traditionally high-fat diet.

Among berries as dietary sources of flavonoids, acai berries contain a variety of flavonoids, including catechin, epicatechin, cyanidin-3-glucoside, and gallic acid. Ripe acai berries are round, grape-sized, dark purple berries with a single large seed. They grow initially as green berries in bundles on the stems of the Euterpe oleraceae palm tree, which is abundant along the swampy river beds of the Amazon River in South America. During July to December, acai berries ripen by turning deep purple, signifying the high content of flavonoids. Compared with other berries such as cranberries and blueberries, acai berries are disproportionately high in antioxidant flavonoids. In fact, the ability of acai berry pulp to scavenge superoxide radicals via induction of the antioxidant enzyme superoxide dismutase is considered to be one of highest among fruits and vegetables. As a result of their potent antioxidant effects, acai berries and their products have also been suggested to have anti-inflammatory and anti-carcinogenic potential.

Another interesting herbal source of flavonoids is rooibos tea. It is a fruity, sweet‑tasting herbal tea made from the leaves and stems of the rooibos plant (Aspalathus linearis), which is indigenous to the mountains of South Africa. Rooibos tea is also referred to as “red tea” because the flavonoids found in rooibos are also pigments that give the leaves and resulting tea a rich, red color. Although rooibos tea is relatively new in the United States, it has been consumed in the Cedarberg mountain region of South Africa for generations. The leaves and stems of rooibos contain high levels of flavonoids, including aspalathin, rutin, and orientin, which have been shown to have significant antioxidant activity. These flavonoids also have been shown to induce apoptosis (spontaneous cell death) of cancer cells, and to reduce DNA damage and lipid peroxidation caused by mutagens in laboratory cultures and in animal studies. Preliminary studies have also suggested that rutin possesses anti-inflammatory activity, strengthens capillaries, and prevents venous edema of the legs due to its antioxidant free‑radical scavenging activity. As a result of these studies, the consumption of antioxidants in rooibos tea has been suggested to prevent free‑radical damage that can lead to cancer, heart attack, and stroke in humans; however, many of these health claims are not well documented.

To substantiate health claims associated with rooibos tea and acai berries, further research—in particular human clinical studies—must be conducted. However, in the meantime, rooibos tea and acai berries are continuously gaining popularity in the United States health food and beverage markets. Eventually, these two relatively recent dietary flavonoid newcomers may become more mainstream flavonoid sources, like red grapes and wine.