Picture a turmeric extract that passes every routine test. The HPTLC fingerprint shows the curcuminoid bands. The HPLC assay finds curcumin at the declared percentage. The IR spectrum matches.
And the curcumin did not come from turmeric.
That is not a hypothetical I made up. It is one of the cases in a 2023 review from the Botanical Adulterants Prevention Program, Botanical Ingredient Forensics by Gafner and co-workers in the Journal of Natural Products. Its subject is exactly this: how adulterated botanical ingredients are prepared so that they pass the methods labs commonly use.
Why a correct result can be the wrong answer
Most identity and assay methods for botanicals look for a marker compound: curcumin in turmeric, rutin and other flavonoids in ginkgo, berberine in goldenseal. If the marker is there at the right level, the method passes.
The review calls this one of the hardest frauds to detect: “the fortification of a botanical extract with a pure or highly purified chemical marker”. Its examples include synthetic curcumin added to turmeric extracts, rutin added to ginkgo leaf extracts, and ellagic acid added to pomegranate peel extracts.
The analytical problem is simple to state. The method is measuring the right molecule. It is just the wrong source.
Which methods turmeric fraud can fool
The review includes a table of botanicals, their adulterants, and the methods “at risk of being deceived”. For turmeric it lists two cases:
| Adulteration | Methods at risk |
|---|---|
| Whole extract with undeclared excipients | HPTLC, HPLC-UV/vis, HPLC-MS |
| Curcumin replaced or topped up with synthetic curcumin | HPTLC, HPLC-UV/vis, HPLC-MS, IR, NIR, Raman, NMR |
That second row covers nearly every routine technique in a QC lab. The same table lists rutin-rich extracts in hawthorn and ginkgo against a similar range of methods, and other Actaea species substituted for black cohosh against HPTLC and HPLC-UV.
How labs catch it
The review describes several signs, and they are worth knowing because some are available in an ordinary chromatography lab.
The curcuminoid pattern. Natural turmeric contains curcumin together with demethoxycurcumin and bisdemethoxycurcumin. Synthetic curcumin is curcumin alone. The review lists “the absence or low concentrations” of demethoxycurcumin and bisdemethoxycurcumin as a sign of fortification. An HPLC method that separates and reports all three curcuminoids can show this; a method that reports only total curcuminoids, or only curcumin, may not.
Synthesis byproducts. The review cites Girme and co-workers, who found a byproduct of the common curcumin synthesis route (from vanillin and acetylacetone) in four of 16 commercial turmeric samples bought in India. A byproduct that has no business in a plant extract is strong evidence.
Carbon-14. Molecules made from fossil-fuel starting materials contain essentially no carbon-14; molecules built by a living plant contain modern levels. Measuring carbon-14 by mass spectrometry separates the two. The review cites You and co-workers, who found that 5 of 14 “all-natural” turmeric supplements sold in the USA contained curcumin made from fossil-fuel-derived starting materials. This is specialist work, not a routine QC test, but it answers the question directly.
Both of those studies are reported here through the review; I have not read them in the original.
What this means for NHP identity testing
In Canada, an NHP specification must include identity for each medicinal ingredient, and a finished product’s identity must conform to its reference material (Health Canada, FPS form user guide, Table 1). The question is which test proves identity for that ingredient.
For botanicals with known adulteration, I would build the identity test around the adulterant:
- Find out what the ingredient is adulterated with. The Botanical Adulterants Prevention Program publishes bulletins and laboratory guidance documents for this purpose.
- Ask whether your method can see that adulterant. A turmeric method that reports curcumin only cannot see synthetic curcumin. One that reports the three curcuminoids separately has a chance.
- Add an orthogonal method for high-risk ingredients. A fingerprint plus a quantitative profile, or a chemical method plus a species method for raw material.
- Treat a supplier’s certificate of analysis as a claim to verify, especially for ingredients on the adulteration lists.
- Have a plan for a failure. The same programme published a best-practice SOP for the disposal or destruction of defective botanical ingredients, including a decision tree and supply-chain contract language.
Peak purity on a diode array detector will not help with this particular fraud, by the way. Synthetic and natural curcumin have the same spectrum. I wrote about what PDA peak purity can and cannot see.
Sources
- Gafner S, Blumenthal M, Foster S, Cardellina JH II, et al. Botanical ingredient forensics: detection of attempts to deceive commonly used analytical methods for authenticating herbal dietary and food ingredients and supplements. J Nat Prod 2023; 86(2):460–472. doi:10.1021/acs.jnatprod.2c00929. The Girme and You studies are cited from this review.
- ABC-AHP-NCNPR Botanical Adulterants Prevention Program. Best Practices Standard Operating Procedure for the Disposal / Destruction of Irreparably Defective Articles, October 2022.
- Health Canada. Finished product specifications form user guide, Table 1 (identity).
If you test botanical ingredients and are not sure your identity method would catch the known adulterants, tell me the ingredient on LinkedIn and I will tell you what I would add.
Common questions
- How is turmeric adulterated?
- Two ways described in the botanical adulteration literature are undeclared excipients in whole extracts and the undeclared addition of synthetic curcumin to turmeric extracts.
- Can HPLC detect synthetic curcumin in turmeric?
- A standard HPLC assay measures curcumin, and synthetic curcumin is the same molecule, so the assay can pass. The 2023 Botanical Ingredient Forensics review lists HPTLC, HPLC-UV, HPLC-MS, IR, NIR, Raman and NMR as methods that synthetic curcumin can deceive. HPLC can still give a clue through the ratio of curcumin to demethoxycurcumin and bisdemethoxycurcumin, or by detecting synthesis byproducts.
- What are the signs of synthetic curcumin in a turmeric extract?
- Absent or low demethoxycurcumin and bisdemethoxycurcumin, which occur in natural turmeric, and impurities from the chemical synthesis. One study cited in the review found a synthesis byproduct in four of 16 commercial turmeric samples bought in India.
- How does carbon-14 testing detect synthetic curcumin?
- Molecules made from fossil-fuel starting materials contain essentially no carbon-14, while molecules from living plants contain modern levels. Measuring carbon-14 by mass spectrometry can distinguish them. A study cited in the review found that 5 of 14 'all-natural' turmeric supplements sold in the USA contained curcumin made from fossil-fuel-derived starting materials.
- Is one identity test enough for a botanical NHP?
- For botanicals with known adulteration, often not. A test that measures one marker compound can be fooled by adding that compound. The identity method should be chosen for the known adulterants of that ingredient, and a second, orthogonal method is often needed.