Ask five suppliers for “sulforaphane powder 10%” and you can receive five materials that share a label and little else. One is free sulforaphane measured directly by HPLC. Another is a broccoli seed extract standardized to glucoraphanin, the precursor, sold under the sulforaphane name. A third pairs glucoraphanin with an enzyme and quotes the sulforaphane it could form. The percentage only means something once you know which molecule was measured, by which method, and what the other 90–95% of the powder is.
A 5% or 10% sulforaphane powder should mean 5 or 10 g of free sulforaphane per 100 g, quantified by HPLC against a sulforaphane reference standard. The rest is a carrier system that protects an unstable molecule. Choose 10% when capsule or tablet fill weight is the constraint, and 5% when you need more blending volume.
What Does 5% or 10% Mean on a Sulforaphane Powder Specification?
On a correctly written specification, the percentage is the mass of free sulforaphane (SFN) per 100 g of finished powder. The problem is that three other ingredient types are routinely offered under the same search term, and their percentages describe different things.
| Ingredient type | What the % measures | Sulforaphane present on delivery | Main buyer question |
|---|---|---|---|
| Free sulforaphane powder (e.g. 5%, 10%) | Free SFN by HPLC | Yes, already formed | Carrier system and storage stability |
| Glucoraphanin-standardized broccoli seed extract | Glucoraphanin (GR), the glucosinolate precursor | No | How much converts after ingestion |
| Glucoraphanin plus active myrosinase | Usually GR; sometimes the SFN the blend can form | No, forms on contact with water | Enzyme activity and moisture control |
| Microencapsulated low-dose SFN (e.g. 1%) | Free SFN by HPLC | Yes | Dose per gram versus handling convenience |
The distinction matters because conversion is not guaranteed. In a human study, glucoraphanin taken without active myrosinase was recovered in urine as sulforaphane metabolites at about 10% of the dose on average, with wide variation between people; supplying active myrosinase raised that to almost 40%[1]. A powder that already contains free sulforaphane removes that conversion step from the formula. We cover the chemistry of the two molecules in our glucoraphanin and sulforaphane comparison; this article stays with specifications.
How Free Sulforaphane and Glucoraphanin Are Measured
Free sulforaphane and glucoraphanin are quantified by different HPLC methods, and the chromatogram behind a COA shows which one was used. Sulforaphane has no strong UV chromophore, so direct HPLC-UV methods read it at short wavelengths of about 202–210 nm, where background is higher and sensitivity lower; plasma methods often add a derivatization step for that reason[2]. Glucoraphanin is a glucosinolate, built on a thioglucose unit and a sulfate group, and is analyzed with glucosinolate methods. The reference method for glucosinolates in rapeseed, ISO 9167, separates individual glucosinolates by HPLC after an on-column desulfation step[3].
Sulforaphane 10% HPLC Chromatogram
Glucoraphanin 13% HPLC Chromatogram
Our two in-house methods illustrate the difference. Free sulforaphane is read by HPLC with a diode-array detector at 201 nm, with the sulforaphane peak at about 11.9 min. Glucoraphanin is read at 226 nm on a separate method, with its peak at about 7.9 min. Both are quantified against their own reference standards.
Analyte: sulforaphane, an isothiocyanate. Detection near 200 nm because the molecule absorbs UV weakly. Reference standard: sulforaphane. Our method: 201 nm, peak at about 11.9 min.
Analyte: glucoraphanin, a glucosinolate. Analyzed intact or after desulfation, depending on the method. Reference standard: glucoraphanin. Our method: 226 nm, peak at about 7.9 min.
Before approving a sulforaphane powder supplier, ask for three things with the COA: the chromatogram, the identity of the reference standard, and the detection wavelength. A “sulforaphane” result calibrated against a glucoraphanin standard, or a single total-isothiocyanate figure, is not a free sulforaphane assay.
Broccoli seed extract, batch SC260907, produced September 2026. Sulforaphane: 5.2 g/100 g against a specification of not less than 5.0 g/100 g, by in-house HPLC method. Moisture: 6.0% (GB 5009.3). Aerobic plate count and coliforms: below 10 CFU/g in all five samples (GB 4789.2, GB 4789.3).
5% vs 10% Sulforaphane vs 13% Glucoraphanin: Molar Equivalence
Comparing grades by weight percentage hides the chemistry, because glucoraphanin is roughly 2.5 times heavier than the sulforaphane it releases. Each molecule of glucoraphanin can yield at most one molecule of sulforaphane, so the fair comparison is in micromoles. Using molecular weights calculated from the molecular formulas (sulforaphane C6H11NOS2, 177.3 g/mol; glucoraphanin C12H23NO10S3, 437.5 g/mol, or 475.6 g/mol as the potassium salt often used as a standard):
| Grade | Assay basis | µmol per gram | Sulforaphane per gram |
|---|---|---|---|
| 1% sulforaphane, microencapsulated | Free SFN | 56 | 10 mg, already formed |
| 5% sulforaphane | Free SFN | 282 | 50 mg, already formed |
| 10% sulforaphane | Free SFN | 564 | 100 mg, already formed |
| 13% glucoraphanin | GR (free acid or potassium salt basis) | 273–297 | 48–53 mg theoretical maximum at 100% conversion |
On paper, a 13% glucoraphanin extract and a 5% free sulforaphane powder carry about the same molar potential; only the sulforaphane powder delivers it without a conversion step.
The gap between theoretical and realized yield has two causes. The first is enzyme availability: without active myrosinase, conversion depends on gut bacteria and varies widely from person to person[1]. The second is the hydrolysis route. Plant epithiospecifier protein (ESP) diverts glucosinolate breakdown toward nitriles instead of isothiocyanates, and nitriles were the most abundant hydrolysis products in a survey of cabbage accessions[4]. A free sulforaphane grade is assayed after conversion, so the number on the COA already reflects the molecule you are paying for. Published intake ranges are discussed separately in our review of sulforaphane amounts per day.
Why Free Sulforaphane Powder Needs a Carrier System
Pure sulforaphane is an unstable oil, and that instability has long been the main obstacle to manufacturing and distributing it[5]. Heat in a watery environment is the main threat. A 2023 kinetic study notes that sulforaphane degradation starts at about 40 °C in aqueous systems; in its own tests, encapsulation lowered first-order degradation rate constants by roughly one order of magnitude across 37–70 °C[6].
Cyclodextrin complexation is the route most used in powders. In the examples of a stabilized-sulforaphane patent, alpha-, beta- and gamma-cyclodextrin complexes all outperformed uncomplexed sulforaphane. Alpha- and beta-cyclodextrin complexes kept about 90% of their theoretical load after 150 days frozen, but only about 40–45% after 150 days at 40 °C in open containers[5]. Complexation slows degradation; it does not make heat exposure safe.
Our 5% and 10% grades use a combination of beta-cyclodextrin, maltodextrin and resistant dextrin. Beta-cyclodextrin forms inclusion complexes with sulforaphane, while the two dextrins dilute and coat the complex so the powder flows and blends. The 5% grade carries more dextrin per gram and is formulated for sealed storage at ambient temperature, cool, dry and away from light. Storage conditions and retest dates are stated on each batch COA, including for the 10% grade.
How Our Sulforaphane Powder Is Produced
We make free sulforaphane from broccoli seed, a concentrated source of glucoraphanin, and convert it before standardization rather than leaving conversion to the finished product.
Broccoli seed
Seed of Brassica oleracea var. italica supplies the glucoraphanin.
Enzymatic conversion
Glucoraphanin is hydrolyzed with myrosinase from red cabbage, an enzyme ingredient we also supply as a freeze-dried powder.
Carrier complexation
The sulforaphane is complexed with beta-cyclodextrin and combined with maltodextrin and resistant dextrin.
HPLC release
Each batch is released on its free sulforaphane result, moisture and microbiology.
Choosing Between 5% and 10% Sulforaphane Powder
Both grades contain the same molecule in the same carrier system, so the choice is about fill weight and blending volume, not quality. Work back from the sulforaphane content you intend to declare per serving.
Half the fill weight of the 5% grade for the same sulforaphane content. Suits capsules and tablets where size limits the formula, and multi-ingredient products that need room for other actives.
More carrier per gram, which spreads the active more evenly in powder blends, stick packs and larger tablets. Formulated for ambient storage, which simplifies warehousing.
Whichever sulforaphane powder grade you use, add it late in the process and keep it out of hot, wet steps. Wet granulation with heated drying, hot-fill beverages and baking all expose the molecule to the heat-and-water conditions that drive degradation[6]. Direct compression, dry blending and capsule filling are the safer routes. A 1% microencapsulated grade is also available for formulas that need a very low inclusion level.
Specifications for all grades, including glucoraphanin-standardized broccoli seed extract, are on our broccoli seed extract product page, where you can request a batch COA and chromatogram.
Frequently Asked Questions
Is sulforaphane powder the same as broccoli seed extract?
Not always. Both come from broccoli seed, but a sulforaphane powder contains free sulforaphane already formed and is assayed for it, while a standard broccoli seed extract is usually standardized to glucoraphanin, the precursor. Check which molecule the COA reports before comparing offers or doses.
How can I tell if a COA reports free sulforaphane or glucoraphanin?
Ask for the chromatogram, the reference standard and the detection wavelength. A free sulforaphane assay is calibrated against a sulforaphane standard and read at a short UV wavelength, around 200 nm in direct methods. A glucoraphanin assay uses a glucoraphanin standard and a separate glucosinolate method.
Is 10% sulforaphane powder better than 5%?
It is more concentrated, not better. Both grades hold the same molecule in the same carrier system. The 10% grade halves fill weight for a given sulforaphane content, which helps in capsules and tablets. The 5% grade gives more blending volume and is formulated for ambient storage.
What is in the rest of a 5% sulforaphane powder?
In our 5% and 10% grades, the balance is a carrier system of beta-cyclodextrin, maltodextrin and resistant dextrin. Beta-cyclodextrin complexes the sulforaphane, and the dextrins dilute the complex so the powder flows and blends evenly. Our 5% grade specification limits moisture to 7.0% or lower.
How should sulforaphane powder be stored?
Keep it sealed in its original packaging, cool, dry and away from light, and reseal opened containers promptly. Sulforaphane degrades faster with heat and moisture, so avoid warm warehouses and humid filling rooms. The storage condition and retest date for each batch are stated on its COA.
Does a 13% glucoraphanin extract equal 5% sulforaphane?
Only on paper. By moles, 13% glucoraphanin could form about 48 to 53 mg of sulforaphane per gram if conversion were complete, close to a 5% sulforaphane powder. In practice, conversion depends on active myrosinase and individual gut bacteria, so realized yield is usually much lower.
References
[1] Fahey JW, Holtzclaw WD, Wehage SL, Wade KL, Stephenson KK, Talalay P. Sulforaphane bioavailability from glucoraphanin-rich broccoli: control by active endogenous myrosinase. PLoS ONE. 2015;10(11):e0140963. https://doi.org/10.1371/journal.pone.0140963
[2] Shin KO, Park K. A newly developed HPLC-UV/Vis method using chemical derivatization with 2-naphthalenethiol for quantitation of sulforaphane in rat plasma. Molecules. 2021;26(18):5473. https://doi.org/10.3390/molecules26185473
[3] International Organization for Standardization. ISO 9167:2019 Rapeseed and rapeseed meals: Determination of glucosinolates content, method using high-performance liquid chromatography. Geneva: ISO; 2019. Standard, not peer-reviewed; scope summary consulted via the Swiss national standards body listing, full text not reviewed. https://connect.snv.ch/en/iso-9167-2019
[4] Oloyede OO, Wagstaff C, Methven L. Influence of cabbage (Brassica oleracea) accession and growing conditions on myrosinase activity, glucosinolates and their hydrolysis products. Foods. 2021;10(12):2903. https://doi.org/10.3390/foods10122903
[5] Dagan ID, Frisbee AR, Newsome PW, Baudet MP. Stabilized sulforaphane. US Patent 7,879,822 B2. Granted February 1, 2011. Patent, not peer-reviewed. https://patents.google.com/patent/US7879822B2/en
[6] Zambrano V, Bustos R, Arozarena Y, Mahn A. Optimization of a microencapsulation process using oil-in-water (O/W) emulsion to increase thermal stability of sulforaphane. Foods. 2023;12(20):3869. https://doi.org/10.3390/foods12203869
