Japanese Knotweed Extract 20–50% Resveratrol

Japanese knotweed extract comes from the rhizome of Polygonum cuspidatum, the tall perennial grown as a commercial stilbene source, and not from its leaves or stems. Ethanol extraction takes up resveratrol, its glucoside and the anthraquinones of the rhizome, and the liquor is dried to a light brown powder.

The grade range is 20–50% resveratrol by HPLC, and the primary grade is the 50% end. The powder is 80 mesh and insoluble in water. The 20% grade keeps a fuller extract profile for blends, while the 50% grade carries more resveratrol per gram for compact capsules and tablets.

SKU: BOT-STX-0014 Category: Standardized Extracts Tags: Bars & Bakery, Ethanol Extracted, Japanese Knotweed, Polyphenols, Root & Rhizome, Softgels & Oil Fills, Standardized Extracts, Stilbenes

Resveratrol Standardization & Grades

Resveratrol is a stilbene, a two-ring phenolic compound joined by a double bond, and Japanese knotweed rhizome is a major commercial plant source of it. The rhizome holds much of its resveratrol as the glucoside polydatin, with the free aglycone as a smaller fraction. The extract is standardized to the resveratrol figure that buyers search for. Polydatin, emodin and tannins are present at the same time, but resveratrol is the compound that can be quantified against a pure reference standard, which is why it defines the grade of this Japanese knotweed extract. The botanical name Polygonum cuspidatum is also listed in current botanical databases as Reynoutria japonica; the trade uses the first name for this rhizome.

Grade	Assay & Method	Where It Fits
20% Resveratrol	HPLC	Blended drink powders and gummy premixes
50% Resveratrol	HPLC	Compact capsules and tablets

Grade choice follows dose and the wish to keep co-extracted material. The 50% grade carries two and a half times the resveratrol of the 20% grade per gram, which suits capsules and tablets with a limited fill weight. Resveratrol content rises from the 20% to the 50% grade at the cost of the other rhizome solids, so the lower grade stays closer to the whole-rhizome profile. The 20% grade is a fuller extract, with more of the glycosides, tannins and anthraquinones that travel with resveratrol in the rhizome. Japanese knotweed is also supplied as a 10:1 ratio extract without a marker figure, the Polygonum Cuspidatum Extract Powder, and the purified compound is listed as Resveratrol 99%. The anthraquinone Emodin 95–98% is a separate purified compound from the same rhizome.

Resveratrol Analysis & Purity Risks

Both grades are measured by HPLC, which separates resveratrol from polydatin and from the other phenolics of the rhizome and quantifies the resveratrol peak against a reference standard. A UV reading adds every stilbene and phenolic that absorbs near the same wavelength, so a UV total and an HPLC resveratrol figure describe different things and cannot be converted into one another. The basis matters as well, because a figure for free resveratrol is not the same as a figure that counts polydatin after hydrolysis.

The sample is dissolved in ethanol, filtered and run on a reversed-phase column with UV detection near the absorption maximum of trans-resveratrol. The peak is identified by retention time and spectrum against the standard. Only the named peak is counted. Polydatin, tannins and other solids stay outside the figure, so a lot at 50% resveratrol still contains a large share of other material.

A chromatogram of the extract shows polydatin as an early, larger peak, resveratrol later, and the anthraquinone group after them. The balance of these peaks is part of the identity of a Japanese knotweed lot, since any step that splits the glucoside raises free resveratrol at the expense of polydatin.

Purity risks follow from the chemistry of the rhizome. Anthraquinones such as emodin and physcion are natural co-extractives of Japanese knotweed, so a trace of them marks the plant source and belongs in the fingerprint, not in a defect list. The common name also covers giant knotweed, Reynoutria sachalinensis, and the hybrid Bohemian knotweed, which are different taxa, so a fixed rhizome part and a stated species are the first identity check. Resveratrol turns from the trans form to the cis form in light. For that reason the assay names the trans isomer.

Typical Specifications

Specification Item	Product Information
Latin Name	Polygonum cuspidatum
Plant Part	Root & Rhizome
Processing	Ethanol Extraction
Compound Class	Polyphenols
Common Name	Japanese Knotweed, Hu Zhang
Ingredient Type	Standardized Extract
Marker Compound(s)	Resveratrol (stilbene)
Primary Grade	50% Resveratrol (HPLC)
Available Grades	20% · 50% Resveratrol (HPLC)
Appearance	Light Brown powder
Solubility / Dispersibility	Insoluble in Water
Quality Parameters
Moisture (LOD)	≤5.0%
Total Ash	≤5.0%
Particle Size	80 mesh
Heavy Metals	Lead ≤2 ppm · Arsenic ≤1 ppm · Cadmium ≤1 ppm · Mercury ≤0.1 ppm
Microbiology	TPC ≤1,000 cfu/g · Yeast & Mold ≤100 cfu/g · E. coli Negative · Salmonella Negative/25 g
Shelf Life	24 months in unopened original packaging, cool and dry storage

Applications by Grade

50% Grade for Compact Capsules

The 50% grade reaches a resveratrol target in a small fill, which suits hard capsules. Fill weight needs a check at each lot change, since a resveratrol-rich lot packs differently from a glycoside-rich one. The light brown powder is fine and cohesive. A glidant helps hopper flow, and a dry room limits sticking at the filling station.

50% Grade in Tablet Blends

Tablets take the 50% grade with a dry binder and a disintegrant, because the water-insoluble powder is slow to wet. Run a hardness and disintegration trial on the full blend, and protect the compacts from light during storage.

20% Grade in Drink Powders

The lower grade is used in stick packs and drink powders where more bulk per dose is acceptable. Because the powder is insoluble in water, the mix needs a suspension aid or a thickener, and the drink will show a light brown haze.

20% Grade in Gummy Premixes

Gummies carry the 20% grade when a mild flavor matters more than a small fill. Disperse the powder in the sugar or pectin syrup after the main cook, and keep the hold short so that heat does not darken the color.

20% Grade in Bar Premixes

Bar premixes use the 20% grade because the brown powder blends into nut and cereal bases without the bitter edge of a concentrated dose. Add it to the dry fraction before the binder so that the insoluble particles distribute evenly, and expect a slight darkening of pale bars.

50% Grade in Oil Suspensions

Softgel and oil-based fills use the 50% grade as a milled suspension. The fine, light brown solid does not dissolve in oil either, so particle size and a suspending wax decide whether the fill stays uniform.

Technical & Quality Considerations

The extract is a light brown powder, insoluble in water and soluble in ethanol, so it dissolves in water-based systems only as a fine suspension. Free resveratrol is sensitive to light and to alkaline conditions, and it darkens when exposed to both over time. Polydatin is more stable, which is one reason the glucoside-rich 20% grade holds its color better in a clear-pack drink mix than a resveratrol-rich lot does.

Taste is mildly bitter and astringent and the odor is faint and woody, so Japanese knotweed extract is easy to mask in flavored bases. The anthraquinones add a yellow-brown tint, which shows in pale tablets and clear gels.

For capsules and tablets, sieve the powder before blending to break up the soft agglomerates that fine plant powders form, and fold it into a portion of the carrier ahead of the final mix. Check fill weight at each lot change, since the 50% grade packs more densely than the 20% grade. Tablet hardness should be checked after storage, because small amounts of moisture change how the powder compacts.

In liquid systems, add a wetting agent to the dry blend before water is introduced, then use high-shear mixing so that the powder does not float or form lumps. Keep the drum closed and shielded from light, and compare each lot with a retained sample for color and for the pattern of the chromatographic peaks.

Packaging & Commercial Supply

Essencefield supports product evaluation, formulation trials, commercial orders, and ongoing ingredient supply. Packaging, storage, and shipping arrangements are determined by product characteristics, order quantity, stability requirements, and destination-market needs.

Supply Item	General Information
Sample	Available upon request for formulation, testing, and supplier evaluation
Order Quantities	100 g · 1 kg · 5 kg · 25 kg · 100 kg · 500 kg · Bulk
Sample Lead Time	Typically 5–7 days after sample confirmation
Production Lead Time	Typically 15–30 days after order and specification confirmation
Packaging	Suitable protective inner packaging with bags, cartons, drums, or other appropriate outer packaging
Storage	Store in tightly sealed, suitable protective packaging in a cool, dry environment. Protect from moisture, heat, and direct sunlight. Specific storage conditions follow the approved product specification.
Documentation	COA · Product Specification · TDS · SDS · Applicable declarations (as applicable)

Final order quantities, lead times, packaging, documentation, and shipping arrangements are confirmed according to the selected product and commercial requirements.