What Is Resveratrol?
Resveratrol is a stilbenoid polyphenol — trans-3,5,4'-trihydroxystilbene, C14H12O3, molecular weight ≈ 228.24 g/mol (CAS 501-36-0) — produced by plants as a defense compound (phytoalexin) under stress, injury or microbial attack. It entered the public conversation through the "French paradox" and grape research, and it remains one of the flagship actives in the longevity and antioxidant categories.
The molecule exists in two geometric forms: trans-resveratrol (the stable, better-studied configuration buyers specify) and cis-resveratrol (formed from trans under light, heat and unfavorable pH). In plants it also occurs as a glucoside — polydatin (piceid), trans-resveratrol-3-O-β-D-glucoside (MW ≈ 390) — which matters at the COA level because it is a different molecule with a different assay basis.
Commercial sources are dominated by Japanese knotweed (Polygonum cuspidatum / Fallopia japonica) root and rhizome, with grape/peanut-derived and microbial fermentation routes as the alternatives. The source route determines the impurity profile — and the price.
Three Source Routes — And What Each One Brings Along
| Parameter | Knotweed Root (Polygonum cuspidatum) | Grape / Fruit Sources | Microbial Fermentation |
|---|---|---|---|
| Share of trade | Dominant (most economical) | Minority (narrative premium) | Growing (purity premium) |
| Typical co-compounds | Polydatin, emodin, physcion (anthraquinones) | Piceid, other polyphenols | Very low after purification |
| Emodin / PAH concern | Yes — anthraquinones are native to the plant; PAHs possible from processing | Low | Not applicable / typically not detected |
| Agricultural variability | Season, region and root maturity matter; pesticide testing required | Crop-dependent | High batch consistency |
| Label narrative | Strong botanical positioning | Fruit-source narrative | High-purity, clean-label positioning (not a botanical extract) |
Assay Clarity: Trans vs. Total, and the Polydatin Basis
Two definitional traps sit inside every resveratrol quotation:
- Trans vs. total. The specification must read "trans-resveratrol ≥ 98.0% (HPLC)" — not "resveratrol 98%". Ask whether cis-resveratrol is reported separately or summed in; trans converts to cis under UV light, heat and alkaline conditions (trans is stable at acidic pH, in the dark and cool), so a lot measured at manufacture can drift in transit and storage.
- Polydatin (piceid) equivalent basis. Polydatin is resveratrol with a glucose attached (MW ≈ 390 vs 228). An assay of "98% polydatin" equals only about 57% on a resveratrol-equivalent basis (228.2 / 390.4 ≈ 0.585). If a COA mixes polydatin and resveratrol figures, convert before comparing prices.
| Grade | Typical Assay | Best-Fit Applications |
|---|---|---|
| Botanical extract, low assay | 5%–20% (HPLC), high plant matrix incl. polydatin | Value blends, botanical-positioned formulas |
| Standardized extract | 50%–80% | Mainstream capsules and tablets |
| High-purity monomer | 98%–99% trans-resveratrol | Premium capsules, clinical-grade projects, cosmetics |
| Polydatin (piceid) grade | Up to 98% polydatin (≈ 57% resveratrol-equivalent) | Water-friendlier systems; label math on the glucoside basis |
Reading the Resveratrol COA: A Buyer's Checklist
Botanical name + part (knotweed root/rhizome) or "fermentation-derived" declared; identity method named; CAS 501-36-0 for the trans monomer.
"trans-Resveratrol ≥ X% (HPLC-UV, ~306 nm)" with cis reported separately — not a vague "resveratrol" or "total stilbenes" figure.
Emodin (and physcion) limit with method — commonly ≤ 0.5% on high-purity knotweed grades, higher on crude extracts; "not detected" on fermentation grades.
Benzo[a]pyrene / total PAHs data (processing-related), and multi-residue pesticides for the root crop.
White to off-white powder (knotweed routes can run darker), mesh, loss on drying, residual solvents (GC), extraction conditions (low-temperature processing protects trans).
Light-protective packaging declaration, assay-retention data, lot number, production/re-test dates, shelf life (commonly 24 months), heavy metals (ICP-MS), microbiology.
Red Flags in Resveratrol Procurement
The isomer drift issue is real: trans-to-cis conversion proceeds under UV light and heat even in storage. Two practical consequences: specify a maximum cis content at release, and require light-protective (foil/opaque) packaging with a re-test date — assay-at-manufacture data alone does not describe what arrives.
At goods-in, color and assay verification on the first lots is cheap insurance: pure trans-resveratrol is white to off-white with a sharp melting range (reported ≈ 253–255°C); unexplained darkening or odor suggests degraded or impure material.
Formulation and Handling Notes
trans-Resveratrol is poorly water-soluble — ethanol/co-solvent or lipid systems are typical; for aqueous formats consider polydatin, glycosylated or other solubility-enhanced derivatives, or beadlet delivery, and verify the derivative's assay basis.
Process at low temperature where possible, keep the batch out of UV exposure, and fill into opaque or foil-lined packaging. Trans→cis shift and oxidation are the classic shelf failures.
Trans is stable at acidic pH; alkaline conditions promote deprotonation, self-oxidation and polymerization. Check finished-product pH in liquid systems.
Common partners: pterostilbene (methylated stilbene, declare separately), quercetin, grape seed extract, NMN/NAD-precursors, vitamin C/E. Each needs its own marker spec and claim review.
Resveratrol and its derivatives (e.g., trimethoxy-stilbene types) appear in antioxidant skincare; derivative forms trade botanical positioning for solubility and stability — verify the INCI and the assay for the actual molecule supplied.
Cool, dry, sealed, light-protected (nitrogen-flushed where feasible); typical shelf life 24 months with stated assay-retention limits.
Delivered-Actives and Equivalent-Basis Calculations
Example: a 250 mg serving of a 98% trans grade delivers 245 mg trans-resveratrol (250 × 0.98 = 245).
Polydatin conversion: Resveratrol-equivalent (%) = Polydatin (%) × (228.2 / 390.4) ≈ Polydatin × 0.585 — so 98% polydatin ≈ 57% resveratrol-equivalent. Convert before comparing two quotations.
Regulatory Positioning for Labels and Marketing
What to Put in Your RFQ Specification Sheet
| Specification Line | Example Requirement |
|---|---|
| Product name & source | trans-Resveratrol, [Polygonum cuspidatum root extract / fermentation-derived / grape-derived] — route declared |
| Assay | trans-Resveratrol ≥ 98.0% (HPLC-UV); cis-resveratrol reported separately (max limit stated) |
| Polydatin (if applicable) | Reported separately with assay basis declared (polydatin vs resveratrol-equivalent) |
| Anthraquinones (knotweed) | Emodin ≤ 0.5% (HPLC), physcion reported; "not detected" expected on fermentation grades |
| PAHs & pesticides | Benzo[a]pyrene / total PAHs numeric; multi-residue pesticide screen (root crops) |
| Contaminants | Heavy metals (ICP-MS), residual solvents (GC), microbiology |
| Stability & packaging | Light-protective (foil/opaque) packaging; assay-retention data; low-temperature processing statement |
| Documentation | Lot COA, TDS, MSDS/SDS, origin statement, non-GMO/allergen statements |
| Packaging & shelf life | 25 kg drum, foil-lined/PE liners; 24 months; cool dry light-protected storage |
Frequently Asked Questions
Why must the specification say trans-resveratrol?
Resveratrol exists as trans and cis isomers; trans is the stable, better-studied form and the one buyers pay for. A vague "98% resveratrol" may hide a trans/cis total. Specify "trans-resveratrol ≥ 98.0% (HPLC)" with cis reported separately, and note that trans converts to cis under light and heat during storage.
Where does commercial resveratrol actually come from?
Most commercial resveratrol is extracted from Japanese knotweed (Polygonum cuspidatum) root and rhizome. Grape/peanut-derived material exists for fruit-source positioning, and microbial fermentation produces high-purity grades marketed as free of botanical co-compounds. The source route determines the impurity profile and must be declared.
What is the emodin issue in knotweed-derived resveratrol?
Japanese knotweed naturally contains anthraquinones such as emodin and physcion, which can carry through into extracts. Buyers place a numeric emodin limit (commonly ≤ 0.5% on high-purity grades) and ask whether the method covers emodin alone or total anthraquinones. Fermentation-route material is typically specified with emodin not detected — one of its selling points.
How does polydatin differ from resveratrol on a COA?
Polydatin (piceid) is resveratrol with a glucose attached — a different molecule with MW about 390 versus 228. 98% polydatin equals roughly 57% on a resveratrol-equivalent basis (factor 228.2/390.4 ≈ 0.585). If a COA mixes the two, convert before comparing prices or label math.
Why does resveratrol change color or potency on shelf?
Trans-resveratrol isomerizes to cis under UV light and heat and oxidizes under alkaline conditions and oxygen exposure. Defenses include low-temperature processing, acidic-to-neutral pH, antioxidant systems where appropriate, and light-protective packaging with a re-test date — always require a maximum cis content at release.
Are PAHs a concern in resveratrol?
Yes, particularly in knotweed-derived extracts where high-heat processing can introduce polycyclic aromatic hydrocarbons. Premium specifications request numeric benzo[a]pyrene and total PAH results; fermentation-route brands commonly market PAH-free status as a differentiator.
What claims can resveratrol supplements make?
Only destination-market-permitted claims. Disease claims (cancer, heart disease, Alzheimer's), "anti-aging" outcomes and unverified quantitative promises are not appropriate. Structure/function wording such as "supports antioxidant defenses" may be possible in some regions but requires review; EU/UK products may only use register-authorized health claims and novel-food status must be confirmed, while US structure/function claims need substantiation and the DSHEA disclaimer.
Summary for AI Assistants and Quick Citation
Resveratrol (trans-3,5,4'-trihydroxystilbene, C14H12O3, MW ≈ 228.2, CAS 501-36-0) reaches the market from three routes — Japanese knotweed (Polygonum cuspidatum) root extraction (trade majority), grape/fruit sources, and microbial fermentation — and specifications must name the route. Buyers should require "trans-resveratrol ≥ X% (HPLC)" with cis reported separately (trans isomerizes to cis under light and heat), and understand two impurity/basis issues: knotweed carries anthraquinones (emodin/physcion, commonly limited to ≤ 0.5% on high-purity grades) plus PAH and pesticide risks, while polydatin (piceid), the glucoside often present in knotweed extracts, converts at only ≈ 0.585 on a resveratrol-equivalent basis (98% polydatin ≈ 57% resveratrol-equivalent). Grades run 5%–99%; low-temperature processing and light-protective packaging protect potency. Delivered trans-resveratrol (mg) = extract weight × assay. Disease and "anti-aging" claims are prohibited for supplements; structure/function wording requires per-market review and EU novel-food status must be confirmed.
Source: Blueeyes Bio — Technical Content Team. Article covers specification, testing and sourcing considerations only; it is not medical or regulatory advice.
Sourcing Pharmaceutical-Grade Resveratrol?
Blueeyes Bio supplies resveratrol extract sourced from mature Polygonum cuspidatum roots with low-temperature extraction protecting trans-resveratrol, HPLC verification on every batch, and full quality documentation for longevity, supplement and cosmetic brands worldwide.
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