Native to South America, particularly the Amazon River and its tributaries and estuaries (J. Agric. Food Chem. 2006;54:8,598-603), the açaí palm (Euterpe oleracea Mart.) has become a subject of great interest in recent years, because its fruit is believed by many to boast significant antioxidant capacity.
Photo courtesy Decio Horita Yokota/Wikimedia Common
The juice and pulp of açaí are popular beverage components in juice blends, smoothies, and other drinks in Central and South America. Mainstream attention, including features on popular U.S. television programs, “has increased interest in the United States in the potential and rumored health effects of açaí. This column will briefly review recent findings regarding this increasingly popular antioxidant-rich plant.
Juicy Benefits
In 2008, investigators studied the antioxidant and anti-inflammatory activities of a commercial juice blend (MonaVie Active) containing açaí as the main ingredient. Anthocyanins, the primary active phenolic components in açaí, were found to be the main antioxidants in the juice, particularly cyanidin 3-rutoside, cyanidin 3-diglycoside, and cyanidin 3-glucoside. In vitro, the antioxidants in the blend were shown to protect against oxidative damage. Polymorphonuclear cells exhibited decreased formation of free radicals and lower migration toward certain proinflammatory chemoattractants.
In vivo, a randomized, double-blind, placebo-controlled crossover trial with 12 healthy participants revealed within-subject increases in serum antioxidants 1 hour and 2 hours after consumption of MonaVie Active, and suppression of lipid peroxidation 2 hours after consumption (J. Agric. Food Chem. 2008;56:8,326-33).
In another study, a four-way crossover clinical trial compared açaí pulp and clarified açaí juice, with applesauce and a nonantioxidant drink as controls. Twelve healthy volunteers were dosed at 7 mL/kg of body weight following a washout phase and overnight fast. The investigators noted that plasma antioxidant capacity increased 2.3- and 3.0-fold for açaí juice and pulp, respectively, 2 hours after consumption of the beverage (J. Agric. Food Chem. 2008;56:7,796-802).
Additional recent research on antioxidant beverages has involved açaí. A study using four tests of antioxidant strength evaluated the relative antioxidant capacities of several polyphenol-rich beverages available on the U.S. market. These beverages included açaí juice, apple juice, black cherry juice, blueberry juice, Concord grape juice, cranberry juice, orange juice, pomegranate juice, red wines, and iced tea (black, green, and white). The in vitro antioxidant capacity of açaí juice was found to be in the middle of the pack, more potent than apple juice, cranberry juice, orange juice, and iced tea. The researchers cautioned, however, that in vitro antioxidant strength does not necessarily translate to in vivo biologic activity (J. Agric. Food Chem. 2008;56:1,415-22).
Anthocyanins
In 2004, investigators studied anthocyanins and other polyphenolic components of açaí in order to identify their contributions to the overall antioxidant profile of the fruit. They also sought to determine the color stability of anthocyanins against hydrogen peroxide at various termperatures. The researchers found that cyanidin 3-glucoside was the prevailing anthocyanin among 16 other polyphenolics in the tropical fruit, and the most influential in terms of its antioxidant capacity. In the presence of hydrogen peroxide, red grape anthocyanins were most stable, with açaí and pigments rich in acylated anthocyanins exhibiting lower color stability in a temperature-dependent fashion. In the presence of ascorbic acid, acylated anthocyanin sources displayed increased color stability. The authors concluded that açaí demonstrated functional characteristics that would be useful in food and nutraceutical products (J. Agric. Food Chem. 2004;52:1539-45).
Subsequently, some of the same researchers studied the effects of açaí polyphenolics on antiproliferation and induction of apoptosis in HL-60 human leukemia cells. They found that the açaí polyphenols indeed lowered leukemia cell proliferation in vitro, and concluded that açaí is a rich source of bioactive polyphenolic compounds (J. Agric. Food Chem. 2006;54:1,222-9).
Fruit Consumption
On the basis of discoveries that açaí fruit exhibits potent antioxidant capacity in vitro, particularly against superoxide and peroxyl radicals, Schauss et al. set out in 2006 to examine the potential health benefits that açaí fruit might impart. They investigated the antioxidant activity of a standardized freeze-dried açaí fruit pulp/skin powder (OptiAcai) in various assays using several sources of free radicals. The researchers found evidence in support of açaí’s antioxidant capacity against superoxide and peroxyl radicals, including strong scavenging of superoxide and the highest antioxidant activity of any food against the peroxyl radical. Mild activity was noted against the peroxynitrite and hydroxyl radicals.
The investigators also performed an assay to assess the inhibition of free radical development in freshly purified human neutrophils, which revealed that the antioxidants in açaí can, at very low doses, penetrate human cells and exhibit oxygen-quenching activity. Finally, the investigators studied the anti-inflammatory and immune bioactivities of açaí components, and observed that the fruit has the potential to inhibit cyclo-oxygenase (COX)-1 and COX-2 (J. Agric. Food Chem. 2006;54:8,604-10).