OPC: Grape Seed, Pine Bark & Antioxidants

Grape seed or pine bark? Once you start looking into OPC, you immediately run into these two raw materials – and into big numbers like "95% OPC" that are hard to make sense of. This guide puts an end to the guesswork and explains what OPC really is, where it comes from and how to recognise quality.

In short: OPC (oligomeric proanthocyanidins) are secondary plant compounds from the flavonoid group. The two most important sources for supplements are grape seeds (the classic, well-studied source) and the bark of the French maritime pine, or pine bark for short (a particularly OPC-rich raw material). Why OPC is often combined with vitamin C and what to watch for when buying, you can read here.

For context: OPC are secondary plant compounds. There are currently no authorised health claims for them in the EU. We describe their origin, properties and quality in neutral terms. Statements about vitamin C refer exclusively to the vitamin.

The key points at a glance

• OPC stands for "oligomeric proanthocyanidins" – a group of secondary plant compounds (flavonoids/polyphenols).
• The main sources are grape seeds and pine bark (French maritime pine).
• OPC is often combined with vitamin C; vitamin C contributes to the protection of cells from oxidative stress.
• Look for the standardised OPC content (e.g. 95%) and a clearly named source.

What is OPC?

OPC is the abbreviation for oligomeric proanthocyanidins – a subgroup of the flavonoids and thus of the secondary plant compounds. These substances belong to the polyphenols, that large family of pigments and protective compounds that give plants their intense colours, among other things. "Oligomeric" means that several identical basic building blocks (catechins) join together to form short chains. These short chains are what is meant by OPC – in contrast to the long, polymeric tannins that taste furry and astringent in the mouth. OPC occurs naturally in many plants, particularly concentrated in grape seeds and in the bark of certain pines. In supplements it is offered as a concentrated, standardised extract.

Why plants produce OPC

OPC is not a random by-product but serves a purpose in the plant: as a secondary plant compound it provides protection – for example against UV radiation, predators and environmental influences. This is precisely why the highest concentrations are found where the plant needs particular protection: in the seeds (the precious offspring) and in the bark (the outer protective layer). This natural concentration makes grape seeds and pine bark the two most productive raw materials for OPC extracts.

There is an interesting side aspect to this: the grape seeds from which high-quality extracts are obtained today accumulate in large quantities as a by-product of wine and grape juice production. What used to be residual material thus becomes a valuable raw material – an example of how plant-based valuable substances can be put to sensible use. In the case of pine bark, the raw material traditionally comes from the French maritime pine in the coastal forests of south-west France. Both sources therefore have a clearly traceable origin, which is helpful for assessing quality.

The main sources: grape seed & pine bark compared

Two sources dominate the market. Both provide OPC but differ in their natural composition.

Because the two raw materials differ in detail, some products combine both sources. Others deliberately rely on a single, clearly defined extract. More important than the origin alone is that the OPC content is transparently standardised and stated.

Extract, standardisation & the 25:1 – what the numbers mean

There are all kinds of technical details surrounding OPC that can quickly become overwhelming on the label. There are two you should be able to decode, because they make the difference between a strong and a weak product:

• The extract ratio (e.g. 25:1): It tells you how much raw material was used for one unit of extract. "25:1" means that 25 parts of starting material were concentrated into one part of extract – an indication of a concentrated raw material.
• The standardisation (e.g. 95% polyphenols): It tells you how high the proportion of the actual valuable substances in the extract is. Only this figure makes products truly comparable.

The reason for standardising: plants are natural products and vary in OPC content depending on variety, soil and harvest year. Through standardisation, a good manufacturer ensures that every batch delivers a defined, consistent content – so that you don't get a lot one time and little the next in the capsule. A product that only states "500 mg grape seed extract" without quantifying the OPC content leaves you in the dark about the decisive point. How to read such information in general is shown in Supplements: how to read the label correctly.

OPC among the plant-based antioxidants

OPC is one of many secondary plant compounds that are popular as antioxidants in supplements – and it is in good company. Anyone interested in OPC will almost inevitably come across related polyphenols and flavonoids that are obtained from other plants and can be classified just as neutrally:

• Quercetin – a flavonoid found in onions and capers, among others.
• Resveratrol – also a grape compound, known from the skin of red grapes.
• Green tea extract (EGCG) – the catechins of green tea.

What actually distinguishes this group and why the term "antioxidant" comes up so often, we explain in a basic way in What are antioxidants? and Free radicals & oxidative stress. What remains important: the same legal restraint applies to these substances as to OPC – we describe origin and properties, not effects.

OPC & vitamin C – why the combination?

Many OPC products also contain vitamin C. The reason is obvious and makes sense from a labelling perspective: vitamin C contributes to the normal function of the immune system, to the reduction of tiredness and fatigue, and to the protection of cells from oxidative stress – these are authorised statements for the vitamin. In addition, vitamin C contributes to normal collagen formation. These statements refer exclusively to the vitamin C it contains, not to OPC. In this way the plant compound and the vitamin complement each other sensibly in one product. You can read more about the all-rounder vitamin C in Vitamin C: effects & daily requirement.

What research is looking into

Proanthocyanidins from grape seed and pine bark are among the longest-studied plant polyphenols of all. Natural-product research is interested above all in their chemical structure, their role as polyphenols and their absorption in the body. To be honest about it: despite this interest, there are currently no authorised health claims for OPC in the EU. That does not mean OPC "can't do anything" – rather that the evidence hurdle required for an authorised health claim has not yet been cleared. That is why we consistently describe OPC in neutral terms: as a high-quality, standardised plant extract.

OPC content, dosage & intake

What matters is not the sheer amount of extract but the standardised OPC content (often 95%). Only in this way can you compare products fairly: "500 mg extract" with an unknown OPC proportion says less than "400 mg extract with 95% polyphenols". OPC is often taken on an empty stomach and ideally not directly combined with milk, since milk protein can bind polyphenols. Stick to the instructions on the packaging. You'll find all the details on practical intake – amount, timing, course or continuous use – in Taking & dosing OPC correctly.

What to look for in terms of quality

• Standardised OPC content (e.g. 95%) clearly stated – not just the "amount of extract".
• Defined source (grape seed and/or pine bark) including the extract ratio.
• Sensible combination – for example with vitamin C for authorised cell-protection statements.
• Lab-tested & made in Germany for traceable standards.
• Clean formulation without unnecessary fillers and additives.

How to spot fillers and additives on the label is shown in Recognising additives & fillers.

An honest assessment

OPC from grape seed and pine bark is a high-quality, well-characterised plant extract and a popular building block of an antioxidant-conscious diet. What OPC specifically does in the body we may not and do not want to promise, because there are no authorised statements for it. For you this means: when buying, don't let yourself be guided by promises of effects and big numbers, but by the transparently stated OPC content and a clean formulation. That way you get reliable quality – which you can then build into your conscious diet, one that OPC complements but does not replace.

Matching products from Scheunengut

You'll find a selection of standardised OPC capsules in the OPC category. We also carry the pure raw materials in the Grape seed and Pine bark categories. If you're looking for the combination with vitamin C, you'll find it in the Vitamin C category. Suitable further reading:

• Taking & dosing OPC correctly
• What are antioxidants?
• Free radicals & oxidative stress
• Quercetin: the flavonoid
• Resveratrol: polyphenol from the grape
• Vitamin C: acerola or synthetic?

Frequently asked questions (FAQ)

Which is better: OPC from grape seed or pine bark?

Both are high-quality OPC sources but differ in their natural composition. Grape seed extract is the classic, well-studied source; pine bark is particularly rich in OPC. Some products combine both. More important than the origin alone is the transparently stated, standardised OPC content.

What exactly does OPC mean?

OPC stands for oligomeric proanthocyanidins, a group of secondary plant compounds from the family of flavonoids or polyphenols. 'Oligomeric' means that several identical building blocks join together to form short chains – in contrast to the long, polymeric tannins.

Why do OPC products often contain vitamin C?

Because the two complement each other sensibly: vitamin C contributes to the protection of cells from oxidative stress and to normal collagen formation – these are authorised statements for the vitamin. No such statements are authorised for OPC itself.

How do I recognise high-quality OPC?

By the standardised OPC or polyphenol content (e.g. 95%), a clearly named source with extract ratio, laboratory testing and a clean formulation without unnecessary additives. A large amount of extract alone is not a mark of quality.