What Are Withanolides, and What Does 5% Mean?

Withanolides are a group of naturally occurring compounds found in ashwagandha (Withania somnifera). Extract makers measure them to standardise their product from batch to batch. '5% withanolides' means 5% of the extract's weight is withanolides, so 500 mg of a 5% extract contains 25 mg.

What withanolides are

Withanolides are steroidal lactones, a family of plant compounds named after the Withania genus where they were first identified. More than a hundred different withanolides have been isolated from ashwagandha, and the plant also contains other compounds such as alkaloids, amino acids and sugars.

The amount in any batch of ashwagandha depends on where and how the plant was grown, which part of the plant is used, and how it is processed. That variation is the reason extract makers measure withanolides at all.

They are the compounds most often measured in ashwagandha research, so they have become the standard marker of consistency.

How to read a withanolide percentage

A percentage on the label describes the extract, not the whole capsule. Multiply the extract weight by the percentage to get the milligrams of withanolides.

For example, 500 mg of extract at 5% gives 25 mg of withanolides. 300 mg at 5% gives 15 mg. 600 mg at 2.5% also gives 15 mg.

This is why two products with different percentages can deliver a similar amount. Where you can, compare the milligram figure rather than the percentage.

If a label gives a percentage but not the extract weight, or the extract weight but not the percentage, you cannot work out the milligrams. Our guide on when to take ashwagandha covers timing and daily routine.

Read: when to take ashwagandha.

Why the testing method matters

Withanolides can be measured in different ways. HPLC, or high-performance liquid chromatography, separates and measures individual compounds. Older gravimetric methods weigh a whole fraction of the extract and can give higher readings because they pick up other material too.

So a figure of 5% by HPLC and a figure of 5% by a gravimetric method may not mean the same thing. Reputable branded extracts state the method. KSM-66, for example, is standardised to at least 5% withanolides measured by HPLC, according to published trial reports and supplier information: HerbalGram summary.

Why a higher percentage is not automatically better

Some extracts advertise 10% withanolides or more. These are usually made with different solvents, or include leaf as well as root. A higher percentage means more withanolides per milligram, but it is a different extract with a different overall profile.

Root-only versus root-and-leaf is worth checking. Traditional use has centred on the root, and pharmacopoeia monographs cover the root. Many branded extracts, including KSM-66, are root-only.

Research done on one extract does not automatically apply to another. If a product refers to studies, check that they used the same extract at a similar amount.

Root, leaf and withaferin A

Withaferin A is one specific withanolide. Ashwagandha leaf tends to contain more of it than the root, which is one reason the plant part on a label matters. Supplier information for root-only extracts such as KSM-66 notes that they contain low levels of withaferin A compared with extracts that include leaf.

Some European regulators accept only the root of ashwagandha in food supplements. If a label does not say which part of the plant is used, ask the brand before you buy.

Withanolide figures also depend on storage. Keep any herbal supplement sealed, cool and dry, and use it before the date on the pack.

Questions to ask of any ashwagandha label

Which part of the plant is used: root, leaf or both?

How much extract is in each capsule, and how many capsules make the daily amount?

What percentage of withanolides is stated, and which testing method was used?

Is it a named, branded extract, or a generic one?

Our quality review goes through these points with examples.

Read: what to check in an ashwagandha supplement.

Hyoomen's figures

Hyoomen KSM-66 Ashwagandha states 500 mg of extract with 25 mg of withanolides per capsule.

See Hyoomen KSM-66 Ashwagandha.

Frequently asked questions

Are withanolides the only important part of ashwagandha?

No. Ashwagandha contains many compounds. Withanolides are simply the most commonly measured marker.

Is 5% withanolides standard?

It is a common standard for root extracts such as KSM-66. Other extracts are standardised to different levels.

Do all labels show withanolides?

No. Plain root powders often do not. If it is not stated, you cannot compare the amount.

What is withaferin A?

It is one specific withanolide. Leaf contains more of it than root, which is one reason labels state the plant part.

Important

This article is general information, not medical advice. Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle. If you are pregnant, breastfeeding, taking any medication or under medical supervision, speak to your GP or pharmacist before taking a supplement. Do not exceed the stated recommended daily dose.