The Acai Berry for Neurologic Disorders

 

The acai berry is a drupe (fleshy fruit with a pit like a peach) that grows on the Acai palm. The acai palm (Euterpe oleacea) grows in the tropical wetlands of Central and South America. The exocarp, or outer skin of the ripe berry is a deep purple color. In certain Amazonian populations, the acai fruit is a very important component of the diet making up to 42% of the food intake (by weight) (1). The fruit can be eaten by itself or as a component in juice blends, mixed with other foods or as a flavoring.
    The Acai fruit has an unusually large number of food constituents including 19 amino acids, fatty acids (particularly oleic, palmitic and linoleic), protein and carbohydrate (1/3 of its mass is fiber). It contains some minerals and vitamins particularly calcium and vitamin A. Its color as well as a significant component of its medicinal benefit lay in its content of polyphenols.
     Polyphenols are molecules containing more than one phenol ring (circular group of atoms with alternating single and double bonds). In discussing the acai fruit, the most important polyphenols are the flavonoids and condensed tannins. Flavonoids are two phenol (benzene) rings joined by a three carbon bridge. If the three carbon bridge is not closed into another ring you have a class of flavonoids called chalcones. If the three carbon bridge is closed into a third ring you have the other classes of flavonoids called   flavones, flavonols, flavanones, anthocyanidins and isoflavonoids. The reader is referred to the numerous on-line web sites with diagrams of flavonoids. Attaching a sugar molecule to the second ring forms anthocyanins from anthocyanidins. Finally, linking anthocyanidins together form polymers called proanthocyanidins. Over 5000 flavonoids have been dexcribed.
   The anthocyanins in acai impart the deep purple color. The anthocyanin content of about 300mg per 100grams of dried fruit is comparable to the anthocyanin content of blueberries. Numerous anthocyanins exist, depending upon the nature of the side chains hanging from the phenol rings. Cyanidin 3-glucoside and cyanidin 3-rutinoside appear to be the most important anthocyanins in acai. The proanthocyanin content of acai is also similar to that found in blueberries. There are also lesser amounts of other flavonoids in the acai berry (2). It should be noted that much of the research on the acai fruit stems from the work of Alexander Schauss Ph.D. In addition to the publication of over 125 papers and a number of books, Dr. Schauss has held a number of important government and academic positions. In particular, Dr. Schauss has uncovered a number of the unique anti-oxidant properties of the acai fruit related in part to the anthocyanin and proanthocyanin content of the fruit.
   The acai berry contains a number of other important nutrients. It is 52% carbohydrate, 8% protein and 32% fat. 85% of the carbohydrate portion is fiber. In terms of fatty acids, it contains high levels of oleic acid, palmitic acid and linoleic acid. In addition to calcium, vitamin A and a small small amount of iron, 7.59% of the total dry weight are amino acids (3).
   Oxidative stress is a well established pathogenic factor in neurodegenerative disorders(4). In general, oxidation is the loss of electrons by a molecule, atom or ion. Reduction is the reverse, namely a gain in electrons. Although the oxidative mechanisms and the particular reactive oxidative species vary, it is clear that oxidative damage is an essential feature in Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, atherosclerosis and amyotrophic lateral sclerosis (ALS). Oxidative stress occurs in the presence of an imbalance between molecular species seeking electrons and those providing them. Oxidative stress is essential for a number of biological functions such as the killing of bacteria inside white blood cells, signaling between cells and the induction of apoptosis, or programmed cell death. Free radicals are also a natural by-product of energy production in the cellular organelles called mitochondria. In particular, oxygen-centered free radicals are constantly created by several molecular complexes in the electron transport chain in mitochondria. Most important is the superoxide radical, or dioxygen (2 covalently linked oxygen atoms) with an extra electron. Superoxide is quite toxic and is rapidly converted to hydrogen peroxide, H2O2 by an enzyme superoxide dismutase. As hydrogen peroxide is also quite toxic, it is metabolized by an iron containing enzyme in an organelle called the peroxisome to oxygen gas and water. On the other hand, hydrogen peroxide may interact with the pervasive gas in the body, nitric oxide to form peroxynitrite, another dangerous free radical.
   The body’s anti-oxidant system consists of a number of enzymes, two of which are noted above along with vitamins C and E and the carotenoids. Glutathione is another essential intracellular anti-oxidant, reduced rapidly from its oxidized form by glutathione reductase. Co-enzyme Q10 and lipoic acid also have anti-oxidant properties. The minerals copper, zinc, manganese and selenium also serve anti-oxidant functions as does uric acid, the breakdown product of purines which comprise approximately 50% of the bases forming DNA. The polyphenols have variable absorption and have detectable plasma concentration. Studies suggest several anti-oxidant mechanisms of flavonoids. These include the presence of particular carbon double bonds, the stereogeometry favoring intramolecular “hydrogen bonding” and the metal chelating capacity of flavonoids.
   It is well established that oxidation plays a significant role in neurodegenerative process including Alzheimer’s disease, Parkinson’s disease and cerebrovascular atherosclerosis. The Kame project in the state of Washington established a protective role of fruits and vegetables in delaying the onset of Alzheimer’s disease (5). A Finnish study in 2007 revealed that an increased intake of flavonoids was associated with decreased carotid atherosclerosis (6). Questions remain regarding the role of polyphenols in mitigating neurodegenerative disease. These include questions regarding bioavailability in the gut and ability to cross the blood-brain barrier. There is a close relationship between oxidation and inflammation. Polyphenols are know to have anti-inflammatory effects which indirectly will reduce oxidative damage.  In addition to their anti-inflammatory and anti-oxidant effect, polyphenols appear to modify signal transduction. One mechanism is through an effect on protein kinase signaling.  They also appear to alter the transcription of pro-inflammatory genes by affecting the gene transcription factor nuclear factor-kappa B (7). Much more research is required to understand the mechanism and effect of polyphenols (fruits and vegetables) on neurodegenerative disorders.
    Foods vary in their anti-oxidant capacity. The capacity may also vary depending upon the specific free radical. One laboratory method is the ORAC (oxygen radical absorbance capacity) developed at the National Institute on Aging. A fluorescent molecule is mixed with compounds that generate free radicals which degrade the fluorescent molecule. By adding anti-oxidants, this degradation is reduced which, in turn, allows more fluorescence to be measured by a flourometer. Using this method, the anti-oxidant capacity of various foods can be compared. It should be noted that the ORAC method may be most sensitive to peroxyl radicals. It is also important that only dry weight capacities be compared since the water in fresh fruit will significantly increase the weight and the fruit will thereby appear to have a lower anti-oxidant capacity. Values vary from 1.4 for watermelon to 92.6 for wild blueberries (fresh fruit values). For dried fruits, medjool dates have a value of 23.87 and prunes, 85.78. Of interest is that the spice cinnamon had a very high value of 2675 per gram and cocoa 1032. Alexander Schauss, discussed above, published a paper in 2006 showing that the acai berry has the highest know ORAC value for a fruit or vegetable at 1027.
   In summary, the acai berry appears to have an extremely high anti-oxidant capacity, potentially good anti-inflammatory qualities and in addition contains important essential fatty acids and other nutrients. These qualities recommend it for individuals at risk for neurodegenerative disorders or with risk factors for atherosclerotic disease.