Procyanidin C1 (OPC Trimer · Senolytic · Longevity Research)

Compound	Procyanidin C1 (Epicatechin-(4β→8)-Epicatechin-(4β→8)-Epicatechin; Epicatechin Trimer)
Chemical class	Polyphenol — Proanthocyanidin (B-type trimer; three epicatechin units linked C4β-C8; simplest OPC trimer)
CAS	37064-30-5
Primary source	Vitis vinifera (grape seed — primary commercial source), Theobroma cacao (cocoa), Malus domestica (apple)
Key applications	Senolytic activity; longevity research; skin photoprotection; cardiovascular antioxidant
Claim strength	Moderate (skin/cardiovascular); Emerging (senolytic)
Typical form	Grape Seed Extract Powder 95% OPC (procyanidin C1 as trimer component); specialty grape seed OPC preparations
Buy from Herbuno	Grape Seed Extract Powder 95% - Vitis vinifera → Black Grapes Powder - Vitis vinifera →

Name origin: Procyanidin C1 uses the systematic trimer nomenclature: "C" denotes a trimer (three catechin units); "1" specifies the particular trimer — epicatechin-(4β→8)-epicatechin-(4β→8)-epicatechin, the simplest B-type trimer with three epicatechin units. It is the most abundant trimer in grape seed and cocoa OPC preparations. Traditional use: Procyanidin C1 has no independent traditional medicinal use as a compound — it is a constituent of grape seed and cocoa OPC preparations with the same traditional applications as the broader procyanidin class. Research trajectory: Procyanidin C1 gained significant research attention following a 2021 Nature Metabolism paper (Xu et al., Brigham and Women's Hospital/Harvard) identifying it as a senolytic compound — an agent that selectively eliminates senescent cells ("zombie cells" that accumulate with ageing and drive inflammaging). This senolytic property, if confirmed in human clinical studies, would represent one of the most significant pharmacological findings for any dietary polyphenol — placing procyanidin C1 in the same category as the pharmaceutical senolytics dasatinib and quercetin under active clinical investigation. Commercial source: Procyanidin C1 is available from Herbuno as a component of Grape Seed Extract Powder 95% OPC — it is not separately standardised but is present in the oligomeric fraction of 95% OPC alongside B1, B2, B3, B4, and higher oligomers.

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Evidence for Procyanidin C1 Applications

Senolytic activity (landmark 2021 finding): Xu et al. (2021, Nature Metabolism) screened natural compounds for senolytic activity — the selective elimination of senescent cells while sparing normal cells. Procyanidin C1 demonstrated potent, concentration-dependent senolytic activity in human cell models: at 100 μg/mL, it induced apoptosis in >50% of senescent cells while preserving >90% of non-senescent cells. In aged mouse models, dietary procyanidin C1 administration reduced senescent cell burden in multiple tissues, reduced SASP (senescence-associated secretory phenotype) inflammatory marker levels, and extended median survival. The mechanism involves inhibition of the PI3K/Akt-mTOR pathway (specifically active in senescent cells) and modulation of BCL-2 family anti-apoptotic proteins. Claim strength: Moderate (animal + human cell data); Emerging (clinical).

Skin photoprotection and anti-ageing: In the context of grape seed OPC — where RCT evidence for skin elasticity, hydration, and chloasma reduction is established — procyanidin C1 contributes its trimer-specific collagenase inhibition and UV-induced oxidative damage reduction. Trimer procyanidins have demonstrated greater collagen-protective activity than dimers in some comparative studies, due to improved matrix binding geometry at higher oligomer sizes. Claim strength: Moderate (extract-level).

Cardiovascular antioxidant: Procyanidin C1 inhibits LDL oxidation, reduces platelet aggregation, and improves endothelial function consistent with the broader OPC class. Its contribution within grape seed OPC preparations to cardiovascular RCT outcomes is proportional to its representation in the oligomeric fraction. Claim strength: Moderate (class-level).

Anti-inflammatory: NF-κB inhibition and SASP reduction (in senescent cells specifically) are documented. The anti-SASP activity is particularly relevant to inflammaging — the chronic low-grade inflammation associated with accumulated senescent cells in ageing tissues. Claim strength: Moderate (mechanistic).

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Dosage & Formulator Specification

No human clinical dosing data exist for isolated procyanidin C1. The Nature Metabolism 2021 mouse study used dietary concentrations equivalent to approximately 50–200 mg/kg/day, translating to estimated human equivalent doses of 300–1500 mg/day — at the high end of what typical OPC supplements provide. Whether the senolytic effects observed in mice translate to human biology at achievable supplement doses is a central open question currently under clinical investigation.

Procyanidin C1 is not separately standardised in commercial grape seed OPC preparations. In 95% OPC grape seed extract, procyanidin C1 typically represents 3–8% of the total OPC content by HPLC — delivering approximately 5–15 mg C1 per 200 mg serving of 95% OPC extract. For longevity and senolytic positioning, this is substantially below concentrations studied in animal models; clinical translation data are awaited.

The emerging longevity and senolytic positioning of procyanidin C1 represents a genuinely novel supplement market opportunity — if human clinical data confirm the mouse study findings. Formulators building longevity, healthy ageing, or "senolytic" supplement products may incorporate grape seed OPC and communicate the emerging procyanidin C1 senolytic evidence appropriately (as emerging preclinical and early-stage data, not established clinical benefit). Combination with other evidence-based longevity ingredients (spermidine, fisetin, urolithins, EGCG) is scientifically rational.

Stability and formulation of procyanidin C1 follow the same parameters as the broader OPC fraction. No specific drug interactions are documented for procyanidin C1 beyond OPC class considerations.

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Frequently Asked Questions — Procyanidin C1

What is a senolytic compound and why is procyanidin C1 significant in this category?
Senolytics are agents that selectively eliminate senescent cells — cells that have permanently exited the cell cycle but remain metabolically active, secreting a pro-inflammatory "senescence-associated secretory phenotype" (SASP) that drives tissue ageing, inflammation, and age-related disease. The senolytic field emerged from 2015 work showing elimination of senescent cells extends healthy lifespan in mice. Dasatinib + quercetin (D+Q) is the most clinically studied senolytic combination. Procyanidin C1's 2021 Nature Metabolism identification as a potent, selective senolytic from a natural dietary source is significant because it offers a potential dietary complement to pharmaceutical senolytics with a more accessible safety profile.

How does procyanidin C1 selectively kill senescent cells but not normal cells?
Senescent cells upregulate pro-survival pathways — particularly PI3K/Akt-mTOR signalling and BCL-2 family anti-apoptotic proteins (BCL-2, BCL-XL) — to resist programmed cell death despite their DNA damage burden. Procyanidin C1 inhibits this PI3K/Akt-mTOR pro-survival axis selectively in senescent cells, where this pathway is particularly active, tipping the balance toward apoptosis. Normal cells have lower baseline PI3K/Akt activity and remain below the apoptotic threshold at concentrations effective against senescent cells — providing the differential selectivity observed.

Is procyanidin C1 present in commercially available grape seed OPC supplements?
Yes — procyanidin C1 is a consistent component of grape seed OPC extract, typically representing 3–8% of total OPC content. At 200 mg/serving of 95% OPC grape seed extract, approximately 6–16 mg procyanidin C1 is delivered. This is substantially below the mouse study effective dose equivalent; whether senolytic activity is detectable at these human supplement doses requires clinical study. Grape seed OPC supplements are not currently marketed with specific procyanidin C1 content claims, but this may change as clinical evidence develops.

When might clinical trials of procyanidin C1 for ageing or age-related disease be expected?
Following the 2021 Nature Metabolism publication, research interest in procyanidin C1 as a dietary senolytic has accelerated. As of the HerbIQ knowledge reference date, Phase I safety and pharmacokinetic studies of procyanidin C1 in older adults are a logical next step; no results from completed human trials have been published. The clinical timeline for senolytic supplements is typically 3–7 years from promising animal data to Phase II efficacy results, placing initial human clinical data in the late 2020s.

Related compounds: Procyanidins, Procyanidin B2, Fisetin, Quercetin

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Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.

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