Resveratrol and OPC – What’s it all about?

Triggered by the so-called French paradox, resveratrol has been the subject of numerous studies since the 1990s. The French paradox consists of the observation that France was one of the countries with the lowest mortality rate from cardiovascular disease at the time - despite extensive and fatty eating habits and high red wine consumption. The polyphenols resveratrol in particular, as well as the oligomeric proanthocyanidins (also OPC), known as grape seed extract, thus became the focus of science, as they can be found in large quantities in red wine.

The harsher the conditions, the higher the OPC content in grapes.

Resveratrol – The Immune System of the Vines

Resveratrol belongs to the large group of secondary plant substances. These are substances that are not essential for plants. However, they still perform important functions for plants, including as colorants or flavorings, and are also of great use to humans as nutrients. Resveratrol, as a so-called phytoalexin, is part of the plant's immune system. It protects the plant from invading microorganisms such as fungi, bacteria or viruses. It has also been observed that red wine vines that are exposed to increased stress from UV radiation secrete increased amounts of resveratrol.

Japanese knotweed is the plant with the highest resveratrol content.

Where is resveratrol found?

The substance was first described in Japan in 1939 by Michio Takaoka. He isolated resveratrol from the medicinal plant Veratrum grandiflorum. The name component -veratr- indicates this origin. The prefix res- comes from resorcinols and -ol is the systematic ending for alcohols. To date, over 70 plant species have been discovered that contain resveratrol. Japanese knotweed has by far the highest resveratrol content. The foods with the highest resveratrol content include grapes, cocoa and peanuts. Peanuts concentrate the substance mainly in their thin, red skin. In grapes, the resveratrol content differs from grape variety to grape variety. Vines that are more at home in difficult weather conditions and are therefore more susceptible to pests contain more resveratrol. The Tannat variety contains the most resveratrol. Two isomeric forms of resveratrol occur in nature - trans-resveratrol and cis-resveratrol. Isomers are molecules with the same molecular formula but different spatial structures, like the left hand and the right hand in humans. Trans-resveratrol is the more stable and therefore the more common form in nature. Synthetic trans-resveratrol can be produced using genetically modified yeast. The European Food Safety Authority (EFSA) has set a maximum daily dose of 150 mg for synthetic trans-resveratrol.

Resveratrol in dietary supplements

Navimol uses resveratrol, which is extracted from Japanese knotweed. The plant, which is native to China, Korea and Japan, is particularly suitable for further processing due to its high resveratrol content. In its home countries, the plant is still used as a medicinal plant in tea infusions. In Europe, Japanese knotweed does not have a very good reputation, especially among botanists: it is considered an undesirable invasive species, i.e. a plant that has been brought into a new habitat by humans and causes damage there. The reason for this is that knotweed can spread extremely quickly via underground rhizomes. Under favorable conditions, the plant can reach a height of three to four meters within a few weeks. The stems of the knotweed resemble those of bamboo, but it forms broad, hand-sized leaves. The strong shade effect of the foliage, together with the dense plant growth, means that knotweed can displace almost all plants in its vicinity. The reputation of Japanese knotweed has been ruined among local plant lovers, although the young shoots of the plant can even be eaten. However, like its relative rhubarb, it tastes very sour. Another nice thing is that the stems of the knotweed can be used to make flutes.

OPCs are mostly obtained from ground grape seeds.

What are Oligomeric Proanthocyanidins (OPC)

The second suspect in the case of the French paradox are oligomeric proanthocyanidins, or OPC for short. Within the polyphenols, they belong to the flavonoids, a group of secondary plant substances that mainly appear as colorants. Plant pigments are not just signaling or attractants. Since they are located in the outermost layer of the plant, they often also have a protective function. They can prevent damage from UV light and ward off invading microorganisms and predators. OPC were discovered in 1948 during a study to determine whether the red peanut skins could be fed to animals. OPC is found not only in peanuts, but also in ginkgo leaves, apples, coconuts, tree bark and, like resveratrol, in grapes. There it is found mainly in the seeds and skins of red grapes. This is why red wine usually contains more OPC than white wine. OPC from grape seed extract is usually used in food supplements. The extract is obtained from grape seed flour, for example using water or ethanol.

External sources:

• Resveratrol – the key to a long life? (Pharmaceutical Journal)
• Resveratrol scavenges reactive oxygen species and effects radical-induced cellular responses. (Leonard SS, Xia C, Jiang BH, Stinefelt B, Klandorf H, Harris GK, Shi X., Biochem Biophys Res Commun. 2003 – English source)
• Safety of synthetic trans-resveratrol as a novel food pursuant to Regulation (EC) No 258/97 (EFSA – European Food Safety Authority – English source)