Anyone who deals with natural antioxidants will inevitably encounter three letters: OPC. Oligomeric proanthocyanidins are secondary plant compounds from the polyphenol family – and they are considered one of the most potent natural antioxidants available. They are particularly concentrated in grape seeds, but also in berries, apple peels, and pine bark. What research knows about them, where OPC naturally occurs, and why the substance has been a focus of science for decades – we explain in this article.
What is OPC – and how was it discovered?
OPC stands for Oligomeric Proanthocyanidins. It is a subgroup of flavonoids, which in turn belong to the large class of polyphenols. In the plant world, these compounds have a protective function: they help the plant protect itself against UV radiation, pests, and oxidative influences.
OPC was discovered in the mid-20th century by French chemist and professor Jacques Masquelier, who first isolated the compound from peanut skins in 1948. Later, grape seeds – more precisely, the extract from the seeds of the grapevine Vitis vinifera – became the focus of research due to their particularly high OPC concentrations.
Today, grape seed extract is one of the most studied plant ingredients in the field of nutritional supplements. OPC is often used synonymously with grape seed extract – correctly speaking: OPC is a component of grape seed extract, but it also occurs in many other foods.
The antioxidant effect of OPC – what research shows
The most well-known property of OPC is its antioxidant capacity. In laboratory studies, its antioxidant potential was rated significantly higher compared to vitamin C – depending on the measurement method, up to several dozen times stronger. Particularly interesting: OPC can regenerate spent vitamin C and synergistically enhances the effect of vitamins A and E.
Another characteristic that distinguishes OPC in research is that it crosses the blood-brain barrier and thus also reaches the central nervous system. However, after absorption, OPC undergoes partial metabolization by intestinal microorganisms, meaning that not the entire amount supplied is available in active form in the blood.
The current state of research shows promising, but not yet conclusively clarified results:
- Vascular health: Several studies indicate a positive influence on blood vessel function, including studies on chronic venous insufficiency (CVI). Registry data published in 2024 point to improvements in oxidative stress markers in observational studies; controlled long-term data are still limited.
- Skin health: Laboratory results and smaller clinical studies investigate the influence of OPC on skin elasticity and protection against UV-induced oxidative stress.
- Cognitive health: Animal studies by the Mount Sinai School of Medicine showed that polyphenols from grape seed extract might delay plaque formation as a precursor to Alzheimer's – human studies are still pending.
Important: In the EU, approved health claims for OPC have not yet been established. Existing research is promising but does not replace medical therapy.
Foods with the highest natural OPC content
OPC occurs in a variety of foods – in very different concentrations. The largest amounts are found in plant seeds and peels, i.e., in parts that are often not eaten in everyday life. The following table provides an overview of the best natural sources:
| Food | OPC Content (Guideline) | Special Feature |
|---|---|---|
| Grape seeds (fresh) | very high (up to 8% of dry weight) | Most concentrated natural OPC source |
| Grape seed extract (standardized) | 40–95% OPC content | Concentrated supplement, laboratory value |
| Red grape skins | high | Additionally contains resveratrol |
| Aronia berries (black chokeberry) | very high | One of Europe's most OPC-rich berry fruits |
| Blueberries / Bilberries | high | Also contains anthocyanins |
| Cranberries | high | Studied for urinary tract health |
| Peanut skins | high | First historical OPC source (Masquelier, 1948) |
| Apple peel (fresh) | medium-high | Only usable with unpeeled apples |
| Cocoa / Dark chocolate | medium-high | Relevant from 70% cocoa content |
| Raspberries | medium | Good everyday source |
| Strawberries | medium | Widely available |
| Green tea | medium | Also contains EGCG (catechins) |
| Hazelnuts | medium | OPC mainly in the brown skin |
| Pine bark (Pycnogenol) | very high | Classic OPC extract from maritime pine |
| Red wine | medium | Contains OPC from grape skins and seeds |
Figures are guidelines; actual contents vary depending on variety, cultivation, and processing.
OPC and Vitamin C – a special duo
OPC does not work alone. The combination with vitamin C is considered particularly beneficial in research: vitamin C demonstrably increases the bioavailability of OPC, and OPC, in turn, can regenerate oxidized vitamin C – the two antioxidants complement each other in their mechanism of action. Those who consume OPC-rich foods or extracts therefore benefit from a simultaneous intake of vitamin C – be it through fresh fruit, acerola, or other natural sources.
OPC as a dietary supplement from Natura Nova
OPC Grape Seed Extract capsules from Natura Nova provide highly concentrated, standardized grape seed extract – manufactured in Switzerland according to GMP standards, laboratory-tested.
OPC from food or as an extract?
A certain amount of OPC can be absorbed through a varied diet with fresh berries, grapes, dark chocolate, and green tea. However, grape seeds are rarely eaten in everyday life, and the OPC concentration in most foods is low compared to standardized extracts.
Standardized grape seed extracts allow for targeted intake. When choosing, attention should be paid to the declared OPC content (not just the polyphenol content), the extraction method, and quality testing by independent laboratories. Products that only claim general polyphenol content do not indicate the actual OPC content.
Individuals taking blood-thinning medication should consult a doctor before use, as OPC can influence the effect of such medications.
Conclusion
OPC is one of the most intensively researched secondary plant compounds. As a natural antioxidant from grape seeds, berries, and pine bark, it shows interesting properties in laboratory studies and smaller clinical investigations – with a special synergistic potential in combination with vitamin C. The evidence is promising but still developing: long-term studies are lacking for many areas of application. A diet rich in colorful fruits and plants remains the most important basis. For targeted supplementation, standardized grape seed extracts offer the most concentrated natural source.
This article is for general information purposes and does not replace medical advice. Dietary supplements are not a substitute for a balanced and varied diet.
Selected studies and sources
Antioxidant properties & mechanism of action
- Sharma AK, Sharma A (2024). Natural Secondary Metabolites. From Nature, Through Science, to Industry. Springer Verlag. — vitalstoff-lexikon.de
- Fan W et al. (2024). Bioactivities and mechanisms of dietary proanthocyanidins on blood pressure lowering: A critical review of in vivo and clinical studies. Critical Reviews in Food Science and Nutrition, 64(11), 3522–3538. — PubMed
- Ye H et al. (2025). Beneficial effects of proanthocyanidins on skin aging: a review. Frontiers in Nutrition. — PubMed / PMC
Vascular health & blood pressure
- Takahashi M et al. (2020). Effects of Grape Seed Proanthocyanidin Extract on Vascular Endothelial Function in Participants with Prehypertension: A Randomized, Double-Blind, Placebo-Controlled Study. — PubMed
- Belcaro G et al. (2024). Improvements in edema and microcirculation in chronic venous insufficiency with Pycnogenol or elastic compression. Angiology, 79(4), 448–454. — PubMed
- Jundishapur Journal of Natural Pharmaceutical Products (2024). Effect of Iranian grape seed extract on blood pressure and lipid profile in type 2 diabetes patients – randomized controlled trial. — Full text (PDF)
Oxidative Stress & COPD
- Tug T et al. (2018). Effect of Oligomeric Proanthocyanidin on the Antioxidant Status and Lung Function of Patients with Chronic Obstructive Pulmonary Disease. In Vivo, 32(4), 753–758. — In Vivo Journal
Cognitive Health & Cell Protection
- NCM / Mount Sinai School of Medicine – Summary on polyphenols from grape seed extract and plaque formation: Wikipedia – Oligomeric Proanthocyanidins
- PMC (2025). Oligomeric Proanthocyanidins Ameliorate Cadmium-Induced Senescence of Osteocytes Through Combating Oxidative Stress and Inflammation. — PMC
Overview & Classification of Evidence
- Nordicoil Editorial / Wehrhan L. (2025). With OPC against oxidative stress: Potential of oligomeric proanthocyanidins. — nordicoil.de
