Ashwagandha Extract Withanolides: A Buyer's Spec Sheet for Supplement Makers

The number is the weight share of withanolides, a family of steroid-like plant compounds, in the extract, as found by one analytical method. Without the method, the plant part and the way the total is calculated, one supplier's percentage cannot be compared with another's.

The arithmetic is simple. A 5% extract carries 5 g of withanolides per 100 g, which is 50 mg per gram. A 2.5% extract carries 25 mg per gram. A 1 kg lot at 5% holds 50 g of withanolides, and a 2.5% extract needs 2 kg to hold the same amount (hypothetical numbers, arithmetic only). If the assay is wrong, every downstream calculation is wrong too.

Why aren't ashwagandha extract withanolide claims directly comparable?

Claims differ in plant part, in which compounds are summed, and in assay. The United States Pharmacopeia (USP) monograph for ashwagandha root dry extract covers extract made from the dried mature root with methanol, alcohol, water or mixtures of these. It sets a floor of not less than 2.5% withanolides, calculated on the dried basis as the sum of withanolide aglycones (calculated as withanolide A) and withanolide glycosides (calculated as withanoside IV). Listings above that floor can still come from a different plant part, a different marker set or a different assay, so the percentage alone does not rank quality.

The authors of a 2024 analytical study make the same point: a reported "total" is a sum of the compounds the lab chose to quantify, and withanosides are glycosides, not free withanolides.Total withanolides, withanolide glycosides and withaferin A: what should the COA report?

Ask whether the figure is a total, a sum of named withanolides, or withanolide glycosides (the sugar-linked forms) reported separately. The USP definition above adds aglycones and glycosides together, so a COA that follows it should show both groups and name the standard used for each: withanolide A for aglycones, withanoside IV for glycosides. Ask for withaferin A as its own line.

We recommend asking for the calculation basis in writing, because the same chromatogram can yield different totals depending on which peaks are summed.

Yes. Write "root only" as its own line, because the withanolide profile differs by plant part and a total percentage can hide the difference. The USP monograph above covers root material.

As of October 2026, India's Food Safety and Standards Authority (FSSAI) advisory of 16 April 2026 says ashwagandha leaves, in crude, extract or any other form, are not permitted in foods, health supplements and nutraceuticals under Indian regulations; only root and root extracts are allowed. A Ministry of Ayush letter of 15 April 2026 gives the same root-only direction for Ayush drugs and products and addresses manufacturers, exporters and sellers. The Ministry cites higher levels of reactive withanolides, particularly withaferin A, in leaves. Confirm how these rules apply to your destination market and ask the supplier for written root-only confirmation.

Withaferin A can work as a screening signal. In the 2024 retail study, withaferin A and withanolide A gave peaks of similar size, which the authors read as root-like; they cite earlier work in which a leaf-containing fraction showed a withaferin A to withanolide A signal ratio above 10. Treat this as a screening signal, not proof, and confirm plant part with your lab.

Write "not less than X% withanolides, dried basis, by HPLC," and require the method and reference standards on the COA. Choose X from your formula. The USP root dry extract monograph sets the 2.5% floor. 5% is an example seen on supplier spec pages; confirm the level with your QA team. A higher percentage is not a quality measure on its own.

If a carrier such as maltodextrin is in the powder, the percentage is calculated on total powder weight, so ask for the loading level. For example, 5% on a powder that is 30% carrier means the native extract is about 7% (our arithmetic: 5 divided by 0.70).

HPLC (high-performance liquid chromatography) separates the compounds in a sample before a detector measures each one. A UV-only (ultraviolet, spectrophotometric) assay without that separation reads total absorbance, so other compounds that absorb light can be counted as withanolides. That is why a UV-only number is not enough for potency. HPLC with UV detection, as used in the 2024 study at 227 nm with named reference standards, is a different thing and is acceptable.

Require on the COA: the column and detection wavelength, the reference standards, the calculation basis (dried basis) and the method source. Have your QA team read the method in the current USP-NF (United States Pharmacopeia and National Formulary) monograph for ashwagandha root dry extract and ask the supplier which version it follows. For how HPLC works in general, see our pharmaceutical API quality testing guide. It covers pharmaceutical APIs, not botanical markers.

Require the botanical name Withania somnifera, an HPTLC (high-performance thin-layer chromatography) fingerprint compared with a reference, and your own identity test. A fingerprint shows a pattern of bands, so identity and potency are separate questions.

The Food and Drug Administration's dietary supplement rule requires that you "conduct at least one appropriate test or examination to verify the identity" of a dietary ingredient, unless FDA grants an exemption on petition under 111.75(a)(1)(ii) (21 CFR 111.75). A supplier COA can be relied on for other specifications only after the supplier is qualified, and it must show methods, limits and actual results. For what a COA can and cannot prove, see our guide to what a supplier's COA can and can't prove under 21 CFR Part 111.

Authenticity needs more than a percentage. One 2024 study of 10 retail finished supplements labeled as ashwagandha root extracts found plant fragments and starch granules in the extracts it examined, which a properly made extract should not show. Identity testing and an HPLC assay are both needed. Microscopy is a low-cost addition.

Require a numeric result per lot for elements, pesticides, residual solvents and microbial counts, with the method named beside each; the lines themselves are in the spec box and the RFQ table. A pass with no number cannot be audited later.

For elements, USP <2232> sets daily-exposure limits for supplements labeled to USP-NF standards: 5 µg per day for lead, 5 µg per day for cadmium, 15 µg per day for inorganic arsenic and 15 µg per day for total mercury (confirm against the current official chapter).

Converting to a parts per million (ppm) limit depends on your daily amount of ingredient: limit in µg per g equals the daily limit in µg divided by grams of ingredient per day.

For illustration only, a hypothetical 5 µg per day limit at 2 g per day of ingredient is 2.5 µg per g. The chapter also lists concentration limits in µg per g for products taken at 10 g per day or less; check the current official chapter in USP-NF.

Supplier spec pages do not agree with one another: for mercury, one bulk-supplier page lists 0.1 ppm and another 0.5 ppm. These are supplement limits, not drug-product permitted daily exposures (PDEs); for the PDE-to-limit math, see ICH Q3D elemental impurities. Confirm the current chapter and your limits with your QA team.

For pesticides, residual solvents and microbial counts, specify them per your lab's validated method or USP general chapters.

The physical lines and microbial counts in the spec box are the ones buyers most often leave off, and each does a job. Loss on drying (LOD, the weight lost on drying; see what loss on drying means on a COA) matters because withanolides are reported on a dried basis. Mesh size and bulk density decide blending and flow, and ash gives a rough check on inorganic content. Put numbers on all of them, and check each against a numeric COA result with its method named.

For orientation only, one bulk-supplier spec page for a 5% extract lists loss on drying not more than 5%, ash not more than 10%, 90% through 60 mesh, bulk density of 0.30 to 0.60 g/ml, total plate count not more than 10,000 cfu/g, yeast and mold not more than 250 cfu/g, and E. coli and Salmonella negative. Another page lists loss on drying not more than 10%, and an older USP text for powdered ashwagandha root extract lists not more than 6.0%; check the current monograph. These are examples, not recommendations. Set your limits with your QA team.

Request the extraction solvent, any carrier or excipient, and allergen status. The USP monograph describes extraction with methanol, alcohol, water or mixtures, so the solvent drives which residual solvent line you need. A carrier dilutes the extract, so ask whether the withanolide percentage is reported with or without it.

What is the difference between an extract ratio and a standardized extract?

An extract ratio such as 10:1 describes how much raw root went into a unit of extract. A standardized extract is one where a marker is measured and held to a limit. A ratio says nothing about withanolide content. The 2024 study tested the claim that extracts were more than 10-fold concentrated against powdered root. In the 2024 study of 10 retail finished supplements, measured withanolides were consistent with powdered root rather than a more-than-10-fold concentrated extract.

Check three things: the lot number matches your shipment, every line names a method, and every result is a number against a stated limit. The table below uses hypothetical values to show where to look for an ashwagandha extract COA.

Verify incoming lots yourself because a label percentage is a claim, not a measurement. One study of 10 retail finished supplements labeled as ashwagandha root extracts found that none met their label claims. Eight claimed 5% withanolides and two claimed 2.5%, yet measured withanolides averaged about 0.13% in the results (the abstract rounds this to about 0.15%) (Thalhamer et al., Exploration of Foods and Foodomics, August 2024). Our arithmetic: for the eight products claiming 5% (50 mg per gram), a 0.13% average (1.3 mg per gram) is about 38 times lower; for the two claiming 2.5% it is about 19 times lower.

The study covers finished supplements, not ingredient suppliers, and cannot be generalized to them. What it supports is narrower: a label percentage is a claim, and microscopy plus HPLC-UV can test it cheaply. We recommend testing the first lots from any supplier, and any lot after a change in source, lot or process, against your spec.

Copy this table into your RFQ and fill in the limits with your QA team. Limits are left blank for you to set; the reference points in brackets are examples from published sources, not recommendations.

A CAS (Chemical Abstracts Service) number identifies a substance, not a grade. It does not fix the plant part, the standardization level or the test method, so each of those must be written as its own line (see what a CAS Registry Number means). Whether your product raises a new dietary ingredient question is a separate decision.

Send us an RFQ using the table above. Our Aarise Supplement APIs list includes Ashwagandha Extract under CAS 90147-43-6.

A quote request should include the product or CAS number, quantity, destination, grade or purity, documents to request, payment terms and Incoterms (international delivery terms). Tell us the specification you need, and we confirm product by product what is available. Documents to request are the COA, specification and SDS/MSDS where applicable. We support sample or evaluation quantities for qualified B2B buyers, subject to the product and its availability. Pricing and quantities are confirmed in the quotation.

Reach us through our contact page, by email at sunil@aarisepharma.com, or by WhatsApp at +91 9899783330.

For ashwagandha extract withanolides, the spec is the control: plant part, a named HPLC method, an identity test, numeric contaminant lines and a lot-matched COA.

Written by the Aarise Pharmaceuticals technical content team. Last updated: October 28, 2026.