Wholesome in bulk™ Milk Thistle Seed Extract Powder
Bulk ingredient prices vary with supply and order size. Please complete the quote request form with the ingredient, package size, and quantity you need. We'll email you a current quote.
Explore our bottled supplements
Bulk Milk Thistle Seed Extract for Supplement Manufacturing
Milk thistle extract is a dry powder made from the seeds of Silybum marianum (L.) Gaertn., a thistle in the daisy family. It is standardized to silymarin, a group of flavonolignans, measured by UV or HPLC. We supply it in bulk to supplement brands, contract manufacturers, and formulators. You can request testing documents and samples on the quote form.
A seed extract with a named marker and a published standard
Milk thistle extract is specified by one marker group, silymarin, and the method used to measure it. A European pharmacopoeia monograph also defines the makeup of a refined extract. That gives buyers and quality teams a clear basis for comparing lots.
Silymarin as the marker
Silymarin is the combined name for the seed's flavonolignans: silibinin A and B, isosilibinin A and B, silicristin, and silidianin. Specifications state a minimum silymarin content for each lot.
The method is part of the grade
The most widely listed grade is 80% silymarin by UV. HPLC grades count the named flavonolignans one by one, so the same lot gives a different figure by each method. Read the method next to every percentage.
A pharmacopoeia reference
The European Pharmacopoeia's refined and standardized extract sets silymarin at 30 to 65%, expressed as silibinin, with fixed shares for each flavonolignan group. Some buyers use it as a reference for HPLC grades.
Stated extraction solvents
Refined extracts are made with ethyl acetate, acetone, ethanol, or methanol, alone or with water. The solvent shapes the extract's profile, so it belongs on the spec sheet.
Light, fine powder
Milk thistle extract is usually a light yellow to tan powder with a bitter taste. Standard grades disperse poorly in water, which is why capsules and tablets are the usual formats.
A field crop with known origins
Milk thistle is grown as a field crop. Supplier pages name Argentina, China, and Germany among the main producing countries, so ask for the country of harvest on each lot.
Where formulators use milk thistle extract
This extract suits measured dry formats where fill weight is controlled, including:
- Capsules
- Compressed tablets
- Softgels, as a suspension in oil after trials
- Single ingredient powders
- Multiple ingredient botanical blends
- Stick packs and sachets
- Private label programs
Plan fill weights from the confirmed assay and method on each COA. An 80% UV extract and an HPLC graded extract are not interchangeable gram for gram, so recalculate your serving math whenever you change grade or method.
What to check before you buy milk thistle extract
Two powders sold as 80% silymarin can differ in method, solvent, plant part, and contaminant profile. Review these points together, and ask for lot documents before you approve a supplier.
Species and plant part
Confirm Silybum marianum seed (fruit) on both the specification and the certificate of analysis (COA). Some listings say whole plant, which does not match a seed extract.
Assay method and basis
Ask whether silymarin is measured by UV or HPLC, and on a dry or as is basis. For HPLC grades, ask for the silibinin and isosilibinin results as well as the total.
Identity fingerprint
An HPTLC or HPLC fingerprint against a reference standard confirms milk thistle. It also shows the expected flavonolignan pattern.
Solvent and residues
Confirm the extraction solvent for each lot. Extracts made with ethyl acetate, acetone, or methanol need residual solvent results under USP <467>.
Mycotoxin screen
Milk thistle is a field crop, and field molds can leave mycotoxins on the seed. Ask for aflatoxin results plus a wider screen for Fusarium and Alternaria toxins, such as T-2, HT-2, zearalenone, and enniatins.
Metals, pesticides, and microbes
Check heavy metals by ICP-MS, pesticide residues, and microbial limits by USP methods. Compare each limit with your own finished product specification.
UV versus HPLC: Approve the grade and the method together. A move between a UV grade and an HPLC grade is a change of material. Give it its own specification, sample approval, and label math.
Typical specification for milk thistle extract
These values reflect the common 80% silymarin grade. Final figures come from the specification sheet and COA for your lot. NLT means not less than, and NMT means not more than.
| Parameter | Specification | Method |
|---|---|---|
| Botanical source | Silybum marianum (L.) Gaertn., seed (fruit) | HPTLC or HPLC fingerprint |
| Appearance | Light yellow to yellowish brown fine powder | Visual |
| Silymarin | NLT 80.0% | UV |
| Silibinin A and B plus isosilibinin A and B | NLT 30.0% | HPLC |
| Extraction solvent | Ethanol, or ethyl acetate | Supplier declaration |
| Residual solvents | Meets USP <467> | GC |
| Particle size | NLT 95% through 80 mesh | USP <786> |
| Loss on drying | NMT 5.0% | USP <731> |
| Total ash | NMT 5.0% | USP <561> |
| Lead | NMT 3.0 ppm | ICP-MS |
| Arsenic | NMT 1.0 ppm | ICP-MS |
| Cadmium | NMT 1.0 ppm | ICP-MS |
| Mercury | NMT 0.1 ppm | ICP-MS |
| Aflatoxins | B1 NMT 5 ppb; total B1, B2, G1, G2 NMT 20 ppb | LC-MS/MS or HPLC |
| Other mycotoxins | T-2, HT-2, zearalenone, and enniatins reported on the COA | LC-MS/MS |
| Pesticide residues | Meets USP <561> | GC-MS and LC-MS |
| Total aerobic count | NMT 10,000 cfu/g | USP <2021> |
| Yeast and mold | NMT 1,000 cfu/g | USP <2021> |
| E. coli and Salmonella | Negative in 10 g and 25 g | USP <2022> |
| Shelf life | 24 to 36 months, unopened | Stability data |
Quality standards for milk thistle extract
Milk thistle extract has its own monograph in both the USP-NF and the European Pharmacopoeia. Both define silymarin by HPLC as the sum of six named flavonolignans, which gives buyers a shared yardstick.
USP Powdered Milk Thistle Extract
The USP-NF monograph covers extract made from defatted fruit with suitable solvents. Silymarin must read 90.0 to 110.0% of the labeled amount by HPLC at 288 nm. It is calculated as silybin on the dried basis. Loss on drying is NMT 5.0% after 2 hours at 105 °C.
A fixed flavonolignan profile
USP and the European Pharmacopoeia set the same shares of total silymarin. Silychristin plus silydianin make up 20 to 45%, silybin A plus B 40 to 65%, and isosilybin A plus B 10 to 20%. Silybin is also spelled silibinin. A lot outside these ranges does not match the monograph profile, even if its total looks right.
How identity is confirmed
In USP identity test A, a TLC plate shows silybin as a green blue fluorescent zone near Rf 0.5. Silychristin appears near 0.25 and taxifolin as a red orange zone near 0.3. Test B matches the HPLC retention times of all six flavonolignans to the USP reference standard. DNA methods suit whole seed, since a refined extract keeps little intact DNA.
Seed powder has its own limits
Whole seed powder is a separate article from the extract. The USP monograph for powdered milk thistle requires NLT 2.0% silymarin on the dried basis. The European Pharmacopoeia fruit monograph sets a minimum of 1.5%, expressed as silibinin.
Authenticity guidance
The botanical adulterants program run by ABC, AHP, and NCNPR (BAPP) issued a milk thistle extract bulletin in October 2020. It reviews the lab methods QA teams use to confirm silymarin content. An HPLC profile with all six flavonolignans is the practical check. A UV total cannot show which compounds make up the figure.
Contaminant limits to build on
USP <2232> sets component limits of 0.5 µg/g for lead and cadmium. It sets 1.5 µg/g for inorganic arsenic and total mercury, for products with an intake of up to 10 g a day. Smaller daily amounts can meet the chapter's daily limits at higher per gram levels. No US or EU rule sets mycotoxin limits specific to milk thistle. Buyers write their own, using LC-MS/MS screens that cover Fusarium and Alternaria toxins.
Sourcing and processing practices for milk thistle extract
Most quality differences in milk thistle extract start in the field or in the extraction plant. These practices give QA teams specific points to ask about and verify.
Qualify each crop year
Mycotoxin levels on milk thistle seed can change a lot from one harvest to the next. One crop year's results do not cover the next. Ask for mycotoxin results tied to the harvest year of your lot.
Know the defatting step
The fruit holds 20 to 30% fatty oil, so it is defatted before extraction. Makers often use hexane for this step, then extract with acetone, ethanol, ethyl acetate, or methanol. When hexane is used, ask for a GC result against the 290 ppm limit listed under USP <467>.
Ask for the extract ratio
Dry extracts take 20 to 70 kg of fruit for each kilogram, depending on solvent and target assay. One large European maker states 25 kg of seed per kg of its 80% UV grade. A ratio well outside the usual range for the stated assay deserves a question.
Limit heat in water based steps
Silymarin compounds break down in hot water. At pH 5.1, the half life of silychristin fell from 58.3 minutes at 100 °C to 6.2 minutes at 160 °C. Extraction in ethanol alone at 140 °C showed no loss, and losses grew as the water content rose.
Control microbes after extraction
Solvent extraction and drying leave few field molds behind, so later handling and packing matter most for microbial counts. Some grades state heat and pressure sterilization, with no ethylene oxide and no irradiation. Ask which method was used and keep that statement in the lot file.
Match the pesticide panel
Pesticide screens on milk thistle products have found pirimiphos-methyl, malathion, chlorpyrifos, carbendazim, and piperonyl butoxide. Check that your supplier's multiresidue method covers these, along with the panel under USP <561>. Some grades cite the AOAC 2007.01 multiresidue method.
Formulator tips for milk thistle extract
Use these points when you set label amounts, fill weights, and incoming tests. Most figures below come from USP monographs and published supplier sheets.
- Set the label figure on the method your finished product lab will use. If that lab runs HPLC, buy on an HPLC result, not on the UV grade name.
- Expect a gap between methods. One supplier lists the same grade as NLT 80% silymarin by UV and NLT 40% by HPLC. A label amount set on UV can read low on an HPLC check of the finished capsule.
- Plan capsule fill from bulk density. Supplier sheets give 0.30 to 0.60 g/mL, so 500 mg of extract needs about 0.8 to 1.7 mL of fill volume. Ask for tapped density too; one sheet lists 0.40 to 0.80 g/mL.
- If your capsules will state USP compliance, run the monograph dissolution test early. It uses paddles at 100 rpm in 900 mL of pH 7.5 phosphate buffer with 2% sodium lauryl sulfate. The limit is NLT 75% of the labeled silymarin dissolved in 45 minutes.
- Check for a carrier. Some 80% grades contain 1 to 10% maltodextrin from corn, which you will need to declare on the label.
- For liquids and wet granulation, keep hot water steps short. Ethanol based steps hold the flavonolignan profile better than water based steps at the same heat.
- Do not swap in a branded phospholipid complex grade gram for gram. These grades are specified as 29.7 to 36.3% silybin by HPLC, so the label amount and the test method both change.
- Set an incoming test plan. Run identity and HPLC assay on every lot, plus a multi mycotoxin LC-MS/MS screen for each new crop year or supplier. Recheck HPLC assay and loss on drying (NMT 5.0%) before you use stock past its retest date.
Helping shoppers read a milk thistle label
Brands and their customer service teams field the same label questions again and again. These answers stick to what the ingredient is and how it is labeled.
What the label line means
A typical line reads milk thistle extract (Silybum marianum) (seed), standardized to 80% silymarin. USP labeling asks for the Latin name and the plant part. The seed is botanically a fruit, so either word can appear.
How to read the percentage
Multiply the extract amount by the percentage to get silymarin per capsule. 250 mg of extract at 80% gives 200 mg of silymarin. A note such as "via UV" or "by HPLC" tells you how the figure was measured. The two methods give different numbers for the same powder.
Independent quality programs
Programs such as the USP Dietary Supplement Verification Program and NSF/ANSI 173 certification check finished products against their labels and contaminant limits. USP also publishes monographs for milk thistle capsules and tablets. A capsule made to that monograph states silymarin in mg per capsule.
Normal look, taste, and home storage
The powder inside a capsule is light yellow to brownish and tastes bitter. Color can vary a little from lot to lot. Keep the bottle tightly closed in a cool, dry place away from light, which matches the USP storage wording.
Storage and handling for bulk milk thistle extract
Botanical extracts hold their color and assay when they stay sealed, dry, and out of light. These steps keep the powder in good condition between production runs.
Keep it sealed
Close the inner liner after each use and press out the air. Extract powders pick up moisture from the air and can cake when left open.
Store cool and dry
Keep bags off the floor in a dry room, away from heat sources. Follow the temperature range on the spec sheet.
Keep away from light
Leave the powder in its original opaque packaging. Light and heat can shift color and assay over time.
Rotate stock
Record the lot number and retest date for each bag. Send older lots to production first.
Milk thistle extract buyer FAQ
Quick answers to the questions procurement and quality teams ask most.
What is the difference between 80% silymarin by UV and by HPLC?
UV and HPLC measure silymarin in different ways, so the same lot gives different results. UV reads the whole sample's response at one wavelength, while HPLC separates and counts each named flavonolignan. Compare quotes only when they use the same method.
Is milk thistle extract made from the seed or the whole plant?
Standardized milk thistle extract is made from the seed, which botanically is the ripe fruit with its tuft of hairs removed. Leaf and whole plant material are different products. Make sure the spec sheet and COA both say seed or fruit.
What solvent is used to make milk thistle extract?
Common solvents are ethanol, ethyl acetate, and acetone, sometimes mixed with water. The European Pharmacopoeia also allows methanol for its refined extract. Ask for the solvent and residual solvent results for each lot.
Is silymarin water soluble?
No, standard silymarin extract disperses poorly in water. That is why most formulators use it in capsules, tablets, and softgel suspensions. Water dispersible grades are also sold, so run trials before you switch.
Should milk thistle extract be checked for mycotoxins?
Yes. Milk thistle is a field crop, and mycotoxins from field molds are a known quality topic for the seed. Ask for aflatoxin results and a wider screen that covers Fusarium and Alternaria toxins.
Is there a USP monograph for milk thistle extract?
Yes. The USP-NF includes a Powdered Milk Thistle Extract monograph, with separate monographs for capsules and tablets. It sets silymarin at 90.0 to 110.0% of the labeled amount by HPLC, fixed shares for three flavonolignan groups, and loss on drying at NMT 5.0%.
How much extract do I need for a 160 mg silymarin label amount?
You need 200 mg of an 80% grade, before any overage. Divide the label amount by the assay: 160 mg divided by 0.80 equals 200 mg. Base the label on the same assay method your finished product lab uses, because UV and HPLC give different figures.
What documents can I get with an order?
A certificate of analysis (COA) and a specification sheet ship with every order. An allergen statement and a safety data sheet may also be available, depending on the lot in inventory. Contact us to request them.
Can I get a sample before a bulk order?
You can request one by choosing sample options on the quote form. We will confirm availability, size, and timing.
Request a quote for bulk milk thistle extract
Tell us the grade, assay method, quantity, and timing. We will reply with current pricing. Select testing documents and sample options on the quote form.
Order Milk Thistle ExtractBulk orders: Choose a pack size above, or use the quote form for larger volumes, testing documents, and sample options. We serve supplement brands, contract manufacturers, product developers, and formulators.
This bulk ingredient is sold for further manufacturing and formulation. The information on this page describes the ingredient and how commercial buyers evaluate it. It is not medical advice. Each finished product brand is responsible for its own labeling and product claims.
