ZHICHENG BIO
How to buy bulk fisetin: five questions that separate one “98%” from another
Botanical source, related flavonoids, urushiol, quercetin interference, and writing a spec where no monograph exists.
The short answer
Two drums of fisetin both certified “98% by HPLC” can differ in botanical source, in which related flavonoids are present, in whether urushiol was tested at all, and in whether the assay method can separate fisetin from quercetin — and none of those differences appear in the 98% figure. Because no pharmacopoeial monograph exists for fisetin in USP, EP, ChP or JP, there is no default standard to fall back on: the specification is whatever buyer and supplier write down. Zhicheng Bio supplies bulk fisetin from Shanghai and agrees that document before the first batch.
- Question 1 — What plant?
- Ask for the species on the CoA. Cotinus coggygria Scop. is the mainstream Chinese source; Rhus verniciflua and R. succedanea are used in Korea and Japan. This is a regulatory and allergen question, not a botanical curiosity
- Question 2 — Urushiol tested?
- Rhus species are in the same family as poison ivy. Korea writes “urushiol not detected” into its standard. A Rhus-sourced material whose CoA has no urushiol line is a material whose allergen risk was never measured
- Question 3 — Which related flavonoids, individually?
- Fisetin is roughly 5% of a Cotinus heartwood extract, against fustin at about 22% and sulfuretin at about 14%. Fustin is fisetin's dihydro analogue with near-identical polarity and UV — so ask for fustin, sulfuretin, butin and taxifolin reported as separate lines, not aggregated into one “other flavonoids” total
- Question 4 — Does the method resolve quercetin?
- Fisetin and quercetin differ by one hydroxyl, and fisetin has been used as an internal standard in quercetin assays. Quercetin is also a common co-formulated ingredient. A method not shown to resolve the two is not fit to release a blend
- Question 5 — Against what standard?
- There is no USP, EP, ChP or JP monograph for fisetin. Agree the specification, the test methods and the acceptance limits in writing before production, or you are buying against an undefined word
- What a price alone tells you
- Very little. Public listings for 98% material have appeared around US$5,400/kg, but published purification patents self-report only 85–90% before final refining — the step from 90% to 98% is where the cost sits, because fustin is chemically so close
Why the source plant is a commercial question, not a botanical one
Fisetin is a naturally occurring flavonol in the public domain — there is no compound patent to license and no exclusivity to buy. The barriers in this supply chain sit elsewhere, and the first of them is the raw material.
The mainstream Chinese route extracts smoke tree heartwood, Cotinus coggygria Scop., grown in Shaanxi, Sichuan and Yunnan, where fisetin runs at roughly 1% of the raw material. The Korean and Japanese route uses Rhus verniciflua or R. succedanea. Both are Anacardiaceae, and that family brings two problems with it that a buyer inherits.
The first is enzymatic. Anacardiaceae raw material carries its own laccase and polyphenol oxidase, and a granted Chinese process patent states plainly that this enzyme degrades phenolic flavonoids in exposed material. The loss happens during comminution, drying and storage — before extraction begins. That is why the same botanical raw material yields very differently at different plants, and it is why the same patent's central claim is to spray an oxidase inhibitor onto the material at the grinding step. If you are qualifying a supplier, this is a sharper question than asking about their extraction solvent.
The second is allergenic, and it applies specifically to Rhus-sourced material.
Urushiol: the line that is either on the certificate or is not
Rhus verniciflua is the lacquer tree, in the same family as poison ivy, and urushiol is the sensitiser responsible. Documented de-toxification approaches exist — thermal pre-treatment at 120–140 °C, and fungal fermentation have both been reported to remove it — so this is a solvable problem, not a disqualifying one.
What matters commercially is that it is measured and reported. Korea's standard for this material requires fustin above 13.0%, fisetin above 2.0%, and urushiol not detected. If you are offered Rhus-sourced fisetin and the certificate of analysis carries no urushiol line, the correct inference is not that the material is clean. It is that nobody looked.
The related-flavonoid profile, and why aggregation hides the problem
Published HPLC-DAD composition of a Cotinus heartwood ethanol extract gives fustin at 22.1 ± 0.8%, sulfuretin at 14.4 ± 0.4%, butin at 9.3 ± 0.4%, fisetin itself at 5.0 ± 0.4%, taxifolin at 2.0 ± 0.3% and butein at 0.8 ± 0.3%. The target compound is a minor component of its own raw material, and its most abundant neighbour is its own dihydro analogue.
Fustin's polarity and UV behaviour are close enough to fisetin's that separating the two is the dominant cost in moving a batch from 90% to 98% purity. It is also why the commercially cleverest synthetic route is semi-synthesis — dehydrogenating the abundant fustin into fisetin, covered by a granted US patent — which turns the principal impurity into product.
A certificate that reports “other flavonoids ≤ 2.0%” as a single figure conceals which of these is present and at what level. For a formulator, that matters: your analytical method has to be shown to resolve whatever is actually in the drum, and your stability programme has to account for it. Ask for the four named lines separately.
Writing a specification where no monograph exists
For most amino acids, a buyer can point at a pharmacopoeial monograph and be done. For fisetin there is nothing to point at — no USP, EP, ChP or JP monograph exists. Every clause is therefore negotiated, which is a burden and also an opportunity, because you can specify the things that actually matter to your process rather than inheriting a generic list.
A workable minimum: assay by HPLC with the method shown to resolve quercetin and fustin; botanical species named; the four related flavonoids reported individually; urushiol tested and reported on any Rhus-sourced lot; residual solvents; heavy metals against the limits of your destination market; microbiology; and loss on drying. Add particle size only if your dose form needs it, and be aware that published aqueous solubility values for fisetin disagree by more than tenfold, so measure solubility in your own vehicle rather than copying a number from a supplier page.
Then, before you commit to a dose form or a label, read the oral exposure guide. The specification decides what is in the drum; that guide covers what reaches plasma, which is a different question with a published answer.
Buying from Zhicheng Bio
Zhicheng Bio supplies bulk fisetin from Shanghai, China, on a made-to-order basis, with the botanical source declared on the certificate, related flavonoids reported individually, and urushiol tested on Rhus-sourced material. Zhicheng Bio publishes no list price for this grade — it is quoted per project against a stated quantity, destination and Incoterm.
Full identity data, specification structure, analytical notes and the reference list are on the fisetin product page. To start a quotation, send the quantity, destination country and the Incoterm you want quoted.
Frequently asked
What should a fisetin certificate of analysis contain?
Assay by HPLC with a method shown to resolve quercetin and fustin; the botanical species of the source material; the related flavonoids fustin, sulfuretin, butin and taxifolin reported individually rather than as one total; urushiol tested and reported on any Rhus-sourced material; residual solvents; heavy metals against your destination market's limits; microbiology; and loss on drying. There is no pharmacopoeial monograph for fisetin, so these are agreed in writing rather than inherited from a standard.
Which plant does bulk fisetin come from?
Mainstream Chinese material is extracted from smoke tree heartwood, Cotinus coggygria Scop., where fisetin is about 1% of the raw material. Korean and Japanese material commonly uses Rhus verniciflua or R. succedanea, which requires urushiol removal and testing. Semi-synthetic routes that dehydrogenate fustin into fisetin also exist and are covered by a granted US patent.
Why is fisetin expensive relative to other flavonoids?
Because it is a minor component of its own raw material — roughly 5% of a Cotinus heartwood extract against 22% fustin — and because fustin, its dihydro analogue, has nearly identical polarity and UV behaviour. Separating the two is the dominant cost between 90% and 98% purity. Published purification patents self-report finished content of only 85–90%, which indicates where the difficulty lies.
Is there a pharmacopoeial standard for fisetin?
No. No monograph for fisetin was found in USP, EP, the Chinese Pharmacopoeia or JP. The specification and test methods are therefore agreed between buyer and supplier in writing before the first batch.
This page describes raw-material sourcing and specification. It is not a health claim and not medical advice. Last updated 2026-07-31.