Extract Ratio, DER and Standardisation: Reading the Numbers on a Botanical Specification

Three numbers appear on botanical specifications and are treated as if they meant the same thing. One describes how much plant went in, one describes what the material was adjusted to, and one describes a measurement of a named compound. Suppliers quote whichever of the three is most flattering to the material, and buyers compare them across quotations as though they were interchangeable. They are not. This guide sets out what each number is measuring, how the two assay conventions differ, and how to write a specification that leaves less room for a favourable reading.

Three ways of describing strength

It helps to start with the question each convention is answering. An extract ratio answers “how much plant material went into this?”; it is a process description, and a material sold as 10:1 is claiming that ten parts of dried plant material produced one part of extract, which says nothing directly about the concentration of any particular compound. A DER — drug extract ratio, the term used in pharmacopoeial monographs — answers the same question in a more structured way, and distinguishes between a native extract and an extract that has been adjusted; it is the closest thing the industry has to a defined convention. A standardisation figure answers “what content has this material been adjusted to?”, describing the result of blending or diluting a lot to a declared content of a named compound; it is a product property rather than a process description.

A single material can carry all three statements at once — a native extract of a stated DER, standardised to a stated marker content — and a specification that gives only one of them is incomplete rather than concise. An extract ratio such as 10:1 answers how much dried plant material produced the extract, and leaves out the content of any compound, the extraction solvent, and whether the ratio was calculated on dried or on fresh material. A DER such as 4:1 native applies the same question through a defined convention that separates native from adjusted extracts, and it is still not a strength statement, so a high DER does not imply a high content of a marker. A standardised content such as 80% silymarin says what the lot was adjusted to, and therefore what a gram delivers, but not the extraction ratio, the carrier, or the method by which the content was measured.

Extract ratio: the number most often read too generously

The ratio is a mass relationship, and it is affected by everything that happened between the field and the drum. A more efficient extraction produces more extract from the same plant, which lowers the ratio for an identical material. A wetter raw material raises the apparent ratio. A second extraction pass on the same marc adds yield and changes the figure again.

The practical consequences are three. First, ratios are not comparable between suppliers unless the extraction method and the basis of calculation are the same, which is rarely documented. Second, a higher ratio is not a strength claim: a 20:1 material can contain less of a named compound than a 5:1 material, because concentration and yield are different properties. Third, a ratio quoted for a blend of two or more plants — common in multi-herb products — is very often a composite figure that cannot be verified for any single component.

Where a ratio is quoted, the useful questions are what plant part was used, whether the figure is calculated on dried material, what solvent was used, and whether it refers to a native extract or to the finished, standardised powder. The last of these is the one most often glossed over: a ratio calculated on a concentrated native extract and the same ratio printed on a drum of carrier-diluted powder are two different claims.

DER: the same idea, with a convention attached

The drug extract ratio, as described in pharmacopoeial monographs, expresses the relationship between the quantity of herbal material and the quantity of extract obtained. Its value is not that it reveals more than a plain ratio, but that it comes with defined categories. Two distinctions matter in practice. The first is between a native extract — the material as obtained by extraction, without adjustment — and an extract that has been adjusted or standardised after extraction; a DER quoted for a native extract is a process statement, while the same figure quoted for a standardised product is a statement about the starting material that may or may not reflect what is in the drum.

The second is between conventions that express the ratio on the total extract and those that tie it to a constituent or a class of constituents. Where an extract has been adjusted to a defined content of a marker — often by adding or removing material, or by blending lots — the relationship between plant input and finished output is no longer a simple ratio, and the specification should say so rather than printing a figure that implies otherwise. The value of the convention for a buyer is that it forces the question of which extract the ratio refers to; ask for that clarification in writing, and the number becomes usable.

Standardisation: a different kind of claim entirely

Standardisation describes the adjustment of a lot to a declared content of a named compound, usually by blending or by dilution onto a carrier. It is the figure that determines how much of the active you receive per kilogram, and therefore the figure that matters most for dosing and for cost comparison.

Two things about it are routinely missed. The first is that the marker may not be the active: standardisation is often carried out against a compound that is convenient to measure rather than against the compound responsible for the material’s commercial function, which means two materials standardised to the same figure can behave differently in application. The second is that the standardisation figure is only as meaningful as the method behind it, which is the subject of the next section. Where a specification carries both a ratio and a standardisation figure, the standardisation figure is the one to buy on, and the ratio is best treated as a process note.

The two assay conventions that cannot be compared

This is the trap that costs buyers the most, because both numbers are printed as percentages and both look like content. Spectrophotometric methods, usually ultraviolet, measure a class of compounds together: a total flavonoid or total polyphenol figure produced by UV is a sum, calibrated against a reference standard, and it includes everything in the material that absorbs at the chosen wavelength. It is fast, inexpensive and useful for routine control, but it is not a measure of a single compound. Chromatographic methods, usually HPLC, separate and quantify individual compounds, so a silibinin figure by HPLC, or a single ginsenoside figure by HPLC, is a specific measurement of a specific molecule.

The two are not convertible. A material sold as a stated content of a flavonoid class by UV and the same material sold as a stated content of one compound by HPLC can carry numerically different figures for the same drum, and neither supplier is wrong. What is wrong is a specification that names a percentage without naming the method, or a comparison between two quotations that used different methods.

Where both are available, the practical approach is to require one convention for the purchase specification and to ask for the other only as supplementary information, so that incoming material is tested the same way every time. Where the marketing claim on the finished product depends on a single compound, the chromatographic figure is the one to standardise against.

Where the numbers touch the label

The terminology does not stay in the purchasing department: several commercial claims are built from these figures, and the way they are expressed is constrained. An extract ratio can be used in a product name in some markets and is restricted in others. A standardised content claim has to be supportable by the method named, and a claim that says “standardised to 80%” without naming the compound is not verifiable. Where a material is described as concentrated or as a specific multiple of the fresh plant, that claim is usually constrained by the destination’s labelling rules, and the definition of what the multiple refers to may be narrower than the supplier’s usage.

The safe approach is to decide the label wording before the specification is settled, then require the analytical data that supports that wording. Doing it in the other order produces a specification that cannot back the label the brand has already designed.

What to write into the purchase specification

State the plant part and the species, since neither the ratio nor the content means much without them. State the extract ratio or DER and, explicitly, whether it refers to the native extract or to the delivered standardised powder. State the marker or marker family the material is standardised to, the content, the method and the basis — as-is or dried. State whether the assay is a class measurement or a single-compound measurement. State the reference standard used for calibration where that matters, and the specification revision the material is measured against. And state the carrier identity and ratio where the standardisation figure was reached by dilution, since that is the other half of the strength story. Used together, those lines make a specification that can be checked rather than negotiated at each shipment.

Frequently Asked Questions

Is a 10:1 extract stronger than a 5:1 extract?

Not necessarily. The ratio describes how much plant material produced the extract, not how much of any compound is present. A 5:1 material can be standardised to a higher content of the marker than a 20:1 material, and the standardised content is the figure that describes strength.

What does DER mean on a specification?

Drug extract ratio, the convention used in pharmacopoeial monographs to express the relationship between the quantity of herbal material and the quantity of extract. Its practical value is that it forces a distinction between a native extract and an extract that has been standardised or adjusted after extraction.

Why does the same plant give different extract ratios from different suppliers?

Because the ratio reflects the extraction method as much as the plant. Solvent, number of extraction passes, temperature, and whether the figure is calculated on dried or as-received material all change it. Without that context, ratios from two suppliers are not comparable.

Can I compare a UV assay with an HPLC assay?

No. The UV figure measures a class of compounds together while the HPLC figure measures a named compound, so the same drum can carry different numbers under the two conventions. Choose one convention for your specification and use it consistently, and name the method whenever a figure appears.

Does a higher extract ratio cost more?

It often does, because a higher ratio implies more raw material per kilogram of extract. But it is not a reliable indicator of value: the material that delivers a higher content of the marker you need is the better buy, whether its ratio is high or low, and for many extracts the higher ratio also brings a higher price without a corresponding increase in the compound you are buying.