Updated November 2026. Chemistry, food figures and UK label wording checked on 6 November 2026. Verve makes Quercetin + Fisetin 1000mg Capsules, described near the end.
Quercetin and fisetin are flavonols, a type of flavonoid: plant compounds with the formulas C15H10O7 and C15H10O6. Fisetin is quercetin with one fewer hydroxyl group. Quercetin is in onions, kale, apples and, above all, capers. Fisetin is in strawberries, apples and persimmons in far smaller amounts, and most supplement labels name the smoke tree, Cotinus coggygria, as its source. Quercetin dihydrate, a common label form, is about 89% quercetin by weight, so "equivalent to 500mg of quercetin" means about 560mg of the dihydrate (our calculation). The labels we read state 400mg to 1,000mg of quercetin and 100mg to 800mg of fisetin a day, and say to check with a doctor first if you are pregnant, breastfeeding, taking medication or have a medical condition. There are no authorised health claims for either in Great Britain, so this guide describes the compounds and the label, not effects.
The short answer
- Both are flavonols. Quercetin is C15H10O7 (mass 302.24); fisetin is C15H10O6 (286.24), quercetin minus one oxygen atom.
- Quercetin foods: capers (about 234mg per 100g raw), onions (45mg), kale (23mg), apples (4mg, mostly in the skin).
- Fisetin foods: strawberries are the richest at about 16mg per 100g. Most supplement labels name smoke tree extract.
- Dihydrate is not all quercetin. 500mg of quercetin dihydrate holds about 447mg of quercetin (our calculation).
- No authorised GB health claims exist for either. A label can tell you dose, form, purity and allergens, nothing else.
- From Verve: Verve Quercetin + Fisetin, 500mg of quercetin and 500mg of fisetin per capsule, one a day, every batch independently lab-tested for purity, with the certificate for your batch on request, and made in the UK.
What quercetin and fisetin are
The Linus Pauling Institute at Oregon State University describes flavonoids as "a large family of over 5,000 hydroxylated polyphenolic compounds". Flavonols are one of six main subclasses and the most widespread in the diet. The institute lists quercetin among them, and fisetin is a flavonol too.
| Compound | Formula | Mass | Other names |
|---|---|---|---|
| Quercetin | C15H10O7 | 302.24 | 3,3',4',5,7-pentahydroxyflavone; CAS 117-39-5 |
| Quercetin dihydrate | C15H10O7·2H2O | 338.27 | Quercetin with two water molecules; CAS 6151-25-3 |
| Fisetin | C15H10O6 | 286.24 | 3,3',4',7-tetrahydroxyflavone; 5-deoxyquercetin; CAS 528-48-3 |
The numbers in the names mark where hydroxyl (OH) groups sit. Quercetin has five. Fisetin lacks the one at position 5, hence "5-deoxyquercetin", and weighs 16 less, one oxygen atom.
Where quercetin is found
| Food | Quercetin per 100g | Source |
|---|---|---|
| Capers, raw | 233.84mg | USDA |
| Capers, canned | 172.55mg | USDA |
| Onions | 45.0mg | Dabeek and Marra |
| Kale | 22.6mg | Dabeek and Marra |
| Apples, raw, with skin | 4.01mg | USDA |
| Apples, raw, without skin | 1.05mg | USDA |
USDA is the USDA Database for the Flavonoid Content of Selected Foods, Release 3.3 (2018). Dabeek and Marra is Table 1 of a 2019 review in Nutrients, drawn from the USDA database and Phenol-Explorer. The review says most quercetin in plants is bound to sugars, as in rutin (quercetin-3-O-rutinoside), and that in apples it sits mainly in the peel. Single figures are a guide: the USDA's data for canned capers range from 45mg to 520mg per 100g.
Where fisetin is found
A 2019 review in Frontiers in Chemistry (Grynkiewicz and Demchuk) lists strawberries, apples, persimmons, grapes, onions, kiwi and kale, "albeit in low concentration". Strawberries are the richest at 160μg per gram, about 16mg per 100g on our conversion. The review puts average intake from food at about 0.4mg a day. On its strawberry figure, 500mg of fisetin is in about 3kg of strawberries (our calculation).
Most fisetin labels we read give the smoke tree, Cotinus coggygria, as the source. It takes its name from its smoke-like flowers. The same review says fisetin was first isolated in 1833 from "venetian sumach (Rhus cotinus L.)", which World Flora Online lists as a synonym of Cotinus coggygria. A 2021 review in Frontiers in Pharmacology (Antal and colleagues) lists fisetin, quercetin and myricetin among the flavonols in its heartwood. Time Health and The Health Project state 98% fisetin from Cotinus coggygria.
How UK labels state the amounts
Quercetin dihydrate and "equivalent to"
Quercetin dihydrate is quercetin crystallised with two molecules of water. Anhydrous quercetin has no water. Using NIST masses for quercetin (302.24) and water (18.02), quercetin is about 89.3% of the dihydrate by weight and water 10.7%. This is our calculation.
| What the label says | Quercetin it contains (our calculation) |
|---|---|
| 500mg quercetin dihydrate | About 447mg |
| 1,000mg quercetin dihydrate | About 893mg |
| Quercetin dihydrate equivalent to 500mg quercetin | 500mg, from about 560mg of dihydrate |
| 500mg quercetin (anhydrous) | 500mg |
| "400mg of quercetin", from quercetin dihydrate | 400mg if the figure is quercetin; about 357mg if it is the dihydrate |
The last row is real wording: DoNotAge's Pure Quercetin, as listed by the UK retailer Healf, says "Each capsule contains 400 mg of quercetin" and "pure quercetin dihydrate", without saying which the 400mg is. The rule: "equivalent to" or "providing" means the figure is quercetin. A bare "x mg quercetin dihydrate" means multiply by 0.89.
Fisetin as a percentage of smoke tree extract
"Smoke Tree Extract (98% Fisetin)", as The Health Project writes it, means the brand states 98% of the extract's weight is fisetin; 100mg of fisetin then needs about 102mg of extract (our calculation). Compare the fisetin figure, not the extract weight. If a label gives an extract weight with no percentage, you cannot tell the fisetin content. Naturecan's page gives "Fisetin 100mg" with no plant or percentage.
Added vitamin C, bromelain and rutin
Some quercetin products are blends. Solgar's Quercetin Complex with Ester-C Plus gives, per two capsules, 500mg quercetin, 500mg vitamin C, 50mg bromelain (2000 GDU/g) and 10mg rutin, among others, and suggests two servings a day. Nutravita's adds 80mg vitamin C (100% NRV), 50mg bromelain from pineapple and 10mg rutin to 500mg quercetin.
- Rutin is quercetin bound to a sugar. It has its own line and is not part of the quercetin figure.
- Bromelain is an enzyme from pineapple. GDU per gram measures its activity, not its weight.
- Only vitamin C has an NRV, so the others show a dash (see what NRV means). The NHS says less than 1,000mg of vitamin C a day from supplements is unlikely to cause any harm. Solgar at two servings gives 1,000mg, so add up vitamin C across everything you take.
Typical label doses
Quercetin, per day on the pages we read: 400mg (Naturecan), 500mg (Nutravita, Charava, Verve) and 1,000mg (Solgar at two servings). DoNotAge states 400mg per capsule with no daily number. Fisetin: 100mg (Naturecan, The Health Project), 100mg to 200mg (Time Health), 250mg (Charava), 500mg (Verve) and 800mg (DoNotAge's international site). These are label statements, not recommendations. No reference intake exists for either.
Purity and certificates of analysis
A certificate of analysis (CoA) is the laboratory report for one batch. Naturecan links a certificate issued by Power Health for both products. Time Health's heavy metals report covers its brown rice flour, not the fisetin. When you get a certificate, check the batch number against your pack; that the assay names the compound ("quercetin dihydrate 98%" is not "quercetin 98%"), or for fisetin gives its percentage of the extract and the plant name; a water result near 10.7% for a dihydrate; heavy metals (lead, arsenic, cadmium, mercury); microbiology; and residual solvents for an extract. A purity figure without a certificate is a claim, not a result. Storage lines vary: Solgar says "Store in a cool, dry place"; most pages, Verve's included, give none.
Who should check with a doctor first
Verve's product page uses this wording: consult your doctor before use if you are pregnant, breastfeeding, taking medication or have a medical condition. Not suitable for children. Keep out of reach of children. Some labels go further: Naturecan says quercetin "is generally not recommended for use by pregnant women, those on certain existing medications or children unless specifically advised by a healthcare professional", and Charava and Nutravita say not for anyone under 18.
What do quercetin and fisetin do?
There are no authorised health claims for quercetin or fisetin on the Great Britain nutrition and health claims register. No UK brand, including Verve, may tell you what they do for your health, and this guide does not. What can be said is above: two flavonols one oxygen atom apart, sold as quercetin dihydrate and smoke tree extract. Anything more on a product page is the brand's wording, not an authorised claim.
Verve Quercetin + Fisetin 1000mg Capsules
Verve's label table is one line: "Quercetin + Fisetin Complex", 1000mg per serving, NRV not established. The split is in the description: fisetin at 500mg from smoke tree extract, and quercetin dihydrate equivalent to 500mg of quercetin. The page does not state the fisetin percentage of the extract. One capsule a day with water; 30 capsules. Verve lists it as gluten free, dairy free, soy free, vegetarian and vegan. Not suitable for children; check with your doctor first if you are pregnant, breastfeeding, taking medication or have a medical condition. Every batch is independently lab-tested for purity; the certificate of analysis for your batch is available on request from hello@vavaverve.com. Details are on the Quercetin + Fisetin 1000mg Capsules page. Verve's other single-compound capsules are in its capsule range, and UK quercetin labels are compared in best quercetin supplement UK.
Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle. Do not exceed the recommended daily dose.
Quercetin and fisetin: your questions
Is fisetin the same as quercetin?
No, but they are close. Both are flavonols, and fisetin is quercetin without the hydroxyl group at position 5, so it is also called 5-deoxyquercetin. Quercetin leads in capers and onions; fisetin in strawberries, at far lower levels.
Which foods are highest in quercetin?
Capers, at about 234mg per 100g raw in the USDA flavonoid database. Onions follow at about 45mg and kale at about 23mg per 100g. Apples hold about 4mg per 100g with the skin and 1mg without.
What does "quercetin dihydrate equivalent to 500mg quercetin" mean?
The capsule holds enough quercetin dihydrate to supply 500mg of quercetin: about 560mg of the dihydrate, which is about 11% water. "500mg quercetin dihydrate" gives about 447mg of quercetin (our calculations).
How much quercetin or fisetin is in a UK supplement?
The labels we read state 400mg to 1,000mg of quercetin a day and 100mg to 800mg of fisetin. Verve's capsule states 500mg of each. There is no reference intake for either.
What do quercetin and fisetin do?
No health claim for either is authorised in Great Britain, so no UK brand may say what they do, and this guide does not. They are plant flavonols: quercetin in capers, onions and kale, fisetin in strawberries and smoke tree wood.
How we checked
Chemistry: NIST Chemistry WebBook (quercetin, water); Fisher Scientific's catalogue (fisetin, quercetin dihydrate), as PubChem was not available to us. Percentages, extract weights and food equivalents are our calculations. Flavonoid classes: Linus Pauling Institute flavonoids page. Foods: USDA Database for the Flavonoid Content of Selected Foods, Release 3.3 (2018); Dabeek WM and Marra MV, Nutrients 2019;11:2288. Fisetin: Grynkiewicz G and Demchuk OM, "New Perspectives for Fisetin", Frontiers in Chemistry 2019. Smoke tree: Antal DS and colleagues, Frontiers in Pharmacology 2021; World Flora Online. Vitamin C: NHS. We found no NHS page on quercetin or fisetin. Labels: Verve's product page and data; uk.naturecan.com; nutravita.com; charava.co.uk; timehealth.co.uk; donotage.org; Solgar and DoNotAge quercetin via Healf; The Health Project via discount-supplements.co.uk. No prices are compared. All read on 6 November 2026. Verve makes Quercetin + Fisetin 1000mg Capsules.
