Proanthocyanidins contribute the astringent flavor to foods. POA’s are found in a number of foods including blue & bilberries, grapes, cocoa, apples, cranberries, cinnamon, tea, and other herbs and foods
Proanthocyanidins are potent free radical scavengers which relax blood vessels, improving blood flow. They suppress production of a protein emdothelin-1 that constricts blood vessels. They also reduce capillary fragility. In TCM (Traditional Chinese Medicine) one of the factors that contributes to both liver and cardiovascular damage is a concept called Stagnant Blood, where blood flow is inhibited. POA’s normalizes platelet adhesion helping blood flow. In TCM these compounds can be classified as Vitalizing Blood or clearing Stagnant Blood.
Clinically we use Blueberry Extract for a wide variety of vision problems as it improves the light gathering capability of the eye. Bilberry jam which is closely to the blueberry was given to the RAF (Royal Air Force) pilots to improve their night vision in World War II. In TCM we would say that Blueberry Extract Brightens the Eyes. Blueberry Extract also can lower blood sugar, which helps the eyes tremendously in cases of diabetic retinopathy. This illustrates the unique properties of Blueberry Extract as it can help this condition by blood flow to the eyes, lowering blood sugar, as well as a direct action on the eyes themselves.
Blueberries have some similarities to cranberries and this extract is useful for urinary infections, by reducing the ability of bacteria to adhere to the wall of the bladder. The astringent nature with its tannin content is also very helpful in cases of diarrhea.
Blueberry Extract is a potent inhibitor of HCV RNA expression. The Japanese researchers believe the mechanism of action is due to the POA’s binding with proteins that are necessary for viral replication.
A very interesting question is whether proanthocyanidins from different sources vary in antiviral strength. There are many examples of high POA herbs and foods used as antivirals both historically as well as in current research. One of the factors that the Japanese looked at in their research on HCV is that the proanthocyanidins with a polymerization of between 8 – 9 showed the most inhibitory power. Polymerization is the number of repeat units in a molecular chain, which alters the characteristics of that substance. The mDP of the proanthocyandinis from Blueberry Extract was a 7.7, which matches closely with the sweet spot for antiviral strength against HCV.
Obviously there is much research left to do to answer the question of comparing POA compounds.. Previously we have included Grape Seed Extract which is a very high POA product in our REM+. Pycnogenol is a potent POA medicine derived from a Maritime Pine Tree which we used in early days of Hepatitis and HIV treatments, though it is far more expensive than Blueberry Leaf Extracts or Grape Seed Extracts which are both inexpensive starting points.
Another aspect of the Japanese research is that the purified fraction showed a 63 fold increase in inhibitory activity compared with the initial extract. At this point the Alternative Medicine Blueberry Extract is the most potent on the market determined by percentage of proanthocynadidins. This last batch with a minimum of 45% actually tested out at 54%.
Here are the Japanese researchers in their own translated words:
Study Title: Proanthocyanidin from blueberry leaves suppresses expression of subgenomic hepatitis C virus RNA.
Study Abstract: Hepatitis C virus (HCV) infection is a major cause of chronic liver disease such as chronic hepatitis, cirrhosis, and hepatocellular carcinoma. While searching for new natural anti-HCV agents in agricultural products, we found a potent inhibitor of HCV RNA expression in extracts of blueberry leaves when examined in an HCV subgenomic replicon cell culture system. This activity was observed in a methanol extract fraction of blueberry leaves and was purified by repeated fractionations in reversed-phase high-performance liquid chromatography. The final purified fraction showed a 63-fold increase in specific activity compared with the initial methanol extracts and was composed only of carbon, hydrogen, and oxygen. Liquid chromatography/mass-ion trap-time of flight analysis and butanol-HCl hydrolysis analysis of the purified fraction revealed that the blueberry leaf-derived inhibitor was proanthocyanidin. Furthermore, structural analysis using acid thiolysis indicated that the mean degree of polymerization of the purified proanthocyanidin was 7.7, consisting predominantly of epicatechin. Proanthocyanidin with a polymerization degree of 8 to 9 showed the greatest potency at inhibiting the expression of subgenomic HCV RNA. Purified proanthocyanidin showed dose-dependent inhibition of expression of the neomycin-resistant gene and the NS-3 protein gene in the HCV subgenome in replicon cells. While characterizing the mechanism by which proanthocyanidin inhibited HCV subgenome expression, we found that heterogeneous nuclear ribonucleoprotein A2/B1 showed affinity to blueberry leaf-derived proanthocyanidin and was indispensable for HCV subgenome expression in replicon cells. These data suggest that proanthocyanidin isolated from blueberry leaves may have potential usefulness as an anti-HCV compound by inhibiting viral replication.
From press release:
A chemical found in blueberry leaves has shown a strong effect in blocking the replication of the Hepatitis C virus, opening up a new avenue for treating chronic HCV infections, which affect 200 million people worldwide and can eventually lead to cirrhosis and liver cancer.
Among the areas of especially high Hepatitis C incidence is the Miyazaki prefecture of southern Japan, a trend that led Hiroaki Kataoka and colleagues at the University of Miyazaki and elsewhere in Japan on a search for better treatment options. Currently, there is no vaccine for HCV, and though a combination drug regimen can clear HCV infection, this treatment is only about 60% effective on average and poses risks of severe side effects.
Kataoka and colleagues believed that since HCV is localized in the liver and can take 20 years or more to develop into disease, a dietary supplement might help slow or stop disease progression. So they screened nearly 300 different agricultural products for potential compounds that suppress HCV replication and uncovered a strong candidate in the leaves of rabbit-eye blueberry (native to the southeastern US).
They purified the compound and identified it as proanthocyandin (a polyphenol similar to the beneficial chemicals found in grapes and wine). While proanthocyandin can be harmful, Kataoka and colleagues noted its effective concentration against HCV was 100 times less than the toxic threshold, and similar chemicals are found in many edible plants, suggesting it should be safe as a dietary supplement. In the meantime, the researchers now hope to explore the detailed mechanisms of how this chemical stops HCV replication.