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

Proanthocyanidin intake in food and fluids
Dietary intake of proanthocyanidins has been estimated in US adults to be about 100 mg/d, in the order of polymers (30%), monomers (22%), dimers (16%), 4-6 mers (15%), 7-10 mers (11%), and trimers (5%). Three major food sources, tea, legumes, and wines, comprise about half of the PA intake from food and drinks.

Grape seed extract provides a concentrated source of polyphenols, most of which are proanthocyanidins. For the latest research on grape seed extract and its role in disease treatment. Red wine made from grapes is rich in proanthocyanidins. See also information about anthocyanins and a related group of compounds known as anthocyanidins.

Chemistry
Proanthocyanidins are oligomeric and polymeric end products of the flavonoid biosynthetic pathway. They 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 colonic microflora. You may also come across additional substances in this category such as procyanidins, profisetinidins, and prorobinetinidins.

Benefit of proanthocyanidins, medical uses
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 may be due to a direct inhibitory effect on platelets. One study indicates proanthocyanidins from grape seed may be useful for chloasma.

Cancer prevention
Mutat Research 2014. Free radical scavenging, antioxidant and cancer chemoprevention by grape seed proanthocyanidin: an overview.

Prevention of cataracts and vision
Ingestion of proanthocyanidins derived from cacao inhibits diabetes-induced cataract formation in rats.
Exp Biol Med. 2004.
Proanthocyanidins derived from cacao have various disease fighting functions. We have tested whether dietary supplementation with proanthocyanidins prevents cataract formation in rats with diabetes induced by streptozotocin (STZ). 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. Our findings suggest that these substances inhibit diabetes-induced cataract formation possibly by virtue of its antioxidative activity.

Q. Do proanthocyanidins help with eyesight?
   A. There are many plant substances that help with vision, particularly carotenoids, and in my opinion proanthocyanidins play a minor role in visual acuity.

Research
Food Funct. 2014. Grape seed proanthocyanidin extract prevents DDP-induced testicular toxicity in rats.

Proanthocyanidins in health care: current and new trends.
Curr Med Chemistry. 2004.
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.

Content in herbs and plants
These compounds are found in many plants and dietary supplements.

Antioxidant properties of proanthocyanidins of Uncaria tomentosa bark decoction: a mechanism for anti-inflammatory activity.
Phytochemistry. 2005.
Decoctions prepared from the bark of Uncaria tomentosa 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.

Jack Masquelier scientist
Legendary French scientist Jack Masquelier, one of the pioneers in the fields of phytochemistry and human health, died in February 2009 at the age of 86. Dr. jack Masquelier, in 1948, published his doctorate thesis regarding the phytonutrient we know today as oligomeric proanthocyanidins or OPCs. That same year he filed a patent for the industrial method of producing the first botanical product based on OPCs. Based on Dr. Jack Masquelier’s groundbreaking role in the research and development of OPCs-products, their isolation, identification and therapeutic and dietary applications, two botanical products followed. In the 1960s, a botanical medicine based on OPCs isolated from Pinus maritima bark became available, known as the trademarked name Pycnogenol, followed ten years later by an OPCs-based medicinal product manufactured from Vitis vinifera seeds. In France, these medicinal products are still sold today. During the 1980s these complex, but well characterized phytonutrients, were introduced on the natural products market. Today, Masquelier’s OPCs are sold around the world as dietary supplements.

Questions
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.
   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 culinary herbs and spices. They all have their own unique 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. 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 these psychological conditions. 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 proanthocyanidins are given to humans in terms of mood, energy, clarity of thinking, etc. Otherwise, one can get easily distracted and confused.