Proanthocyanidins are present in the fruits, bark, leaves and seeds of many plants, where they provide protection against predation. At the same time they give flavor and astringency to beverages such as wine, fruit juices and teas.

Proanthocyanidins belong to a class of polyphenols, and are widely distributed throughout the plant kingdom. Most people ingest trace amounts of proanthocyanidins through foods such as red wine and cranberry juice. However, the functional properties of proanthocyanidins have been little understood. The antioxidative activities of proanthocyanidins are much stronger than vitamin C or vitamin E in aqueous systems.

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Proanthocyanidins Intake in Food
Dietary intake of proanthocyanidins has been largely unknown because of the lack of reliable values for their content in foods bur slowly measurements are being made. Grape seed extract provides a concentrated source of polyphenols, most of which are proanthocyanidins. Red wine made from grapes is rich in proanthocyanidins.

Chemistry of Proanthocyanidins
Proanthocyanidins are oligomeric and polymeric end products of the flavonoid biosynthetic pathway. Proanthocyanidins share common properties with other polyphenols, in particular their reducing capacity and ability to chelate metal ions. However, their polymeric nature clearly makes them different. They have a high affinity for proteins and their absorption through the gut barrier is likely limited to the molecules of low polymerization degree and to the metabolites formed by the colonic microflora.

Benefit of Proanthocyanidins
Evidence suggesting that dietary polyphenols, flavanols, and proanthocyanidins in particular offer significant cardiovascular health benefits is rapidly increasing. Proanthocyanidin-rich grape seed extract has preventive actions on diseases such as atherosclerosis, gastric ulcer, large bowel cancer, cataracts and diabetes. In human intervention trials, grape seed extract was shown to have preventive effects on the increase in lipid peroxides in human plasma after exercise and on muscle fatigue after training. The anti-thrombotic effect of proanthocyanidin may be due to a direct inhibitory effect on platelets. One study indicates proanthocyanidins from grape seed may be useful for chloasma.

Proanthocyanidins Research Update
Proanthocyanidins in health care: current and new trends.
Curr Med Chem. 2004 May;11(10):1345-59.
Polyphenolic compounds are widely distributed in higher plants and are an integral part of the human diet. Recent interest in these substances has been stimulated by their potential health benefits, which are believed to arise mainly from their antioxidant activity. In the past years, the antioxidant activity of flavonoids has been studied in detail. An important but often overlooked group of polyphenols is that of the proanthocyanidins. Therefore, the present review is focused mainly on the antioxidant activity of proanthocyanidins and its relevancy in vivo. The three most important mechanisms of their antioxidant action will be discussed, i.e. free radical scavenging activity, chelation of transition metals, and inhibition of enzymes. In addition, the protective role of proanthocyanidins against lipid peroxidation and peroxynitrite, as well as their antimicrobial properties will be discussed. To study the in vivo relevancy of the proanthocyanidin activities, the knowledge of their pharmacokinetic parameters is crucial. Although bioavailability and metabolism data on polyphenols in general and proanthocyanidins in particular are still largely unavailable, the first reports indicate that at least monomers and smaller oligomeric procyanidins are absorbed. There is also considerable scientific and public interest in the important role that antioxidants may play in health care, e.g. by acting as cancer chemopreventive and anti-inflammatory agents and by reducing risk of cardiovascular mortality. Each of these aspects will be discussed, with special attention to the role of proanthocyanidins on apoptosis, gene expression and transcription factors, such as NF-kappa B.

Ingestion of proanthocyanidins derived from cacao inhibits diabetes-induced cataract formation in rats.
Exp Biol Med (Maywood). 2004 Jan;229(1):33-9.
Proanthocyanidins derived from cacao have various antipathophysiological functions. We have tested whether dietary supplementation with proanthocyanidins  prevents cataract formation in rats with diabetes induced by streptozotocin (STZ), using histological, histochemical, and biochemical analyses. Starting at 7 days after the streptozotocin challenge, the animals were fed either a normal diet or a diet containing 0.5% w/w proanthocyanidins  over 10 weeks. There were no significant differences in plasma and urine glucose concentrations, plasma fructose amines, and plasma thiobarbituric reactive substances (TBARS) between the two dietary groups. Antioxidant status as assessed by measuring lipid peroxide production in plasma in response to azocompounds was lower in the STZ-rats fed control diet than in animals fed proanthocyanidins . Opacity was first detected in the lenses of the control dietary group 5 weeks after STZ injection and cataracts had developed in the majority of these animals by 10 weeks. These changes were rarely seen in the STZ/proanthocyanidins  diet group. Histological examinations of the eyes of the STZ-treated normal diet group revealed focal hyperplasia of the lens epithelium and liquefaction of cortical fibers. There were similar but considerably less severe changes in the animals fed proanthocyanidins . Hydroxynonenal (HNE), a marker of oxidative stress, was detected immunohistochemically in the lenses of the STZ-treated normal diet group, but not of those receiving proanthocyanidins . Our findings suggest that proanthocyanidins  inhibits diabetes-induced cataract formation possibly by virtue of its antioxidative activity.

Antioxidant properties of proanthocyanidins of Uncaria tomentosa bark decoction: a mechanism for anti-inflammatory activity.
Phytochemistry. 2005 Jan;66(1):89-98.
Decoctions prepared from the bark of Uncaria tomentosa ( cat's claw ) are widely used in the traditional Peruvian medicine for the treatment of several diseases, in particular as a potent anti-inflammatory agent. Therefore, the main purpose of this study was to determine if the well-known anti-inflammatory activity of cat's claw decoction was related with its reactivity with the oxidant species generated in the inflammatory process and to establish a relationship between such antioxidant ability and its phenolic composition. Thus, our results provide evidence for an antioxidant mechanism underlying the anti-inflammatory activity of cat's claw and support some of the biological effects of proanthocyanidins, more exactly its antioxidant and radical scavenging activities.

Oligomeric proanthocyanidins research coming soon

Proanthocyanidin questions
Q. Do proanthocyanidins help in eyesight?
   A. There are many plant substances that help with vision, particularly carotenoids, and in my opinion proanthocyanidins are likely to play a role.

Q. I am a professor at the University of Pittsburgh. I am interested in knowing if purple Concord grape juice has the same amount of oligomeric procyanidins as Sardinian red wine. I know that some research shows that such darker grape juice does contain some of the same heart healthy compounds as red wine. But I am interested in this specific
compound: oligomeric procyanidins. I have recently read an article which sates that U. K. scientists have identified the specific ingredient in red wine that provides the health benefits as oligomeric procyanidins. The article identified
southwestern French and Sardianian wines as having the highest concentrations of this compound due to the old vines used and the ancient techniques used, such as leaving the seeds and skins on the grapes during processing. This produces a robust, deep red wine. I am a fan of moderate wine consumption. But I would like to know if
Concord grape juice would match the wines from France and Sardinia in terms of oligomeric procyanidins.
   A. We have not seen any research regarding the proanthocyanidin content of French and Sardinian wines. Rather than focusing on the exact amounts of these anthocyanidins and procyanidins, it is best to focus on including a wide range of fruits and vegetables in one's diet, along with small or moderate use of wine and a variety of different fresh fruit and vegetable juices. They each have their own benefit.

Q. The relationship between pycnogenol / grape seed extract (proanthocyanidins) and depression and adhd is confusing to me. First, proanthocyanidins increase nitric oxide levels. Some research suggests that high nitric oxide levels are positively associated with depression and fatigue (links provided below). Second, a new study on pycnogenol and adhd suggested that proanthocyanidins decreased the amount of adrenaline and dopamine in children. Higher levels of dopamine are generally better for depression and adhd (e.g., bupropion, ritalin increase dopamine and NE). This seems to suggest that proanthocyanidins might play a negative role in both depression and adhd. However, many case reports suggest that proanthocyanidins may help adhd and possibly depression (i.e., in menopausal women). The clarification could also be useful for understanding the effects of arginine as well.
   A. Rather than focusing on micro influences of these compounds on specific neurotransmitter levels such as nitric oxide or dopamine, one has to take a more comprehensive overview. The human body is made of countless molecules and substances that influence mood and behavior. The best way to know for sure is to see clinically what happens when a proanthocyanidins are given to humans in terms of mood, energy, clarity of thinking, etc. Otherwise, one can get easily distracted and confused.