There is something fishy about Acacia rigidula supplements

There’s probably a problem with all slimming supplements that contain Acacia rigidula. Almost half of the products containing Acacia rigidula actually contain a synthetic amphetamine analogue that does not occur in nature. And the other half, well…
There’s probably a problem with all slimming supplements that contain Acacia rigidula. Almost half of the products containing Acacia rigidula actually contain a synthetic amphetamine analogue that does not occur in nature. And the other half, well…

When governments across the world banned the use of Ephedra sinica in slimming supplements, and supplements manufacturers went in search of an alternative, they discovered DMAA. And when governments blacklisted DMAA, the industry discovered Acacia rigidula.

According to an American study done in 1998, extracts of Acacia rigidula contain impressive amounts of stimulants in equally impressive concentrations. [Phytochemistry, Volume 49, Issue 5, 5 November 1998, Pages 1377-1380.] The table below comes from that study.


As you can see, the analysis shows that Acacia rigidula contains amphetamine and methamphetamine, both of which are marketed as recreational drugs. The 1998 study, and the increasingly popularity of slimming supplements with Acacia rigidula, prompted researchers at the American FDA to take a closer look at Acacia rigidula. And at supplements containing extracts of this plant of course. The results were published in the Journal of Pharmaceutical and Biomedical Analysis.

USA Today, a newspaper that had already had a critical eye on the supplements industry for several months, reported on the publication and it became world news. [USA Today 18-11-2013] Nine diet supplements contain amphetamine-like compound was the title of the article.

The article in USA Today actually doesn’t do justice to the content of the publication. The article argues not only that some of the products claiming to contain Acacia rigidula actually contain a synthetic amphetamine analogue, but also that there may something wrong with all supplements claiming to contain Acacia rigidula.

The researchers analysed samples of Acacia rigidula. A simplified version of the results is shown below. Click here for the complete table. The researchers found no trace of amphetamines. That’s not so surprising: as far as biochemists know, amphetamine is not a substance that occurs in nature. The 1998 study is the only report of analysts having found amphetamine in a natural product.



The FDA researchers did find phenethylamine, tyramine and tryptamine.

The researchers then bought 21 supplements containing Acacia rigidula extracts and analysed them too. At this point they made a number of discoveries. The table below is simplified. Click on it for the complete version.


In 9 of the 21 supplements they examined, the researchers found – mainly substantial – amounts of beta-methylphenethylamine. This is a substance that bears a striking resemblance to amphetamine, and is not found in nature. Going by the amounts, manufacturers must have added it intentionally to the supplement. Someone using supplements 1 and 9, if they were to take the maximum recommended dose, would ingest 146 and 67 mg beta-methylphenethylamine respectively and 148 and 23 mg phenethylamine respectively.

The researchers then trawled the literature for information on the synthetic amphetamine analogue, and found no human studies. They did come across a few animal studies from the first half of the twentieth century. These would suggest that beta-methylphenethylamine is about 30 to 50 percent as effective as good old amphetamine. [[J. Am. Chem. Soc. 53(1931) 1875–1879.] [Ind. Eng. Chem. 37 (1945) 149–151.]

But the products that don’t contain beta-methylphenethylamine are not completely kosher either. The main active ingredient in these is phenethylamine. Phenethylamine is a naturally occurring substance, and is found in Acacia rigidula. But Acacia rigidula contains other substances that are conspicuously absent in the supplements. The same goes for the supplements containing the synthetic beta-methylphenethylamine. The researchers assume therefore that none of the 21 preparations they studied contain any extracts of Acacia rigidula.

It looks as though many Acacia rigidula supplements contain the synthetic phenethylamine. The researchers found high quantities, especially in the supplements that did not contain the amphetamine analogue beta-methylphenethylamine. If you take the maximum recommended dose of supplements 10 and 11, then you’d be consuming 809 and 552 mg phenethylamine daily.

Determination of selected biogenic amines in Acacia rigidula plant materials and dietary supplements using LC-MS/MS methods.

Pawar RS, Grundel E, Fardin-Kia AR, Rader JI.


Extracts of Acacia rigidula leaves are used in weight-loss products sold in vitamin shops and over the internet with little or no published data about their potential biological effects. In our chemical investigations on authenticated A. rigidula plant material, we established a rapid and sensitive LC-MS/MS method for the quantitative determination of several phenethylamine, tyramine and tryptamine derivatives. Stable isotopically labeled compounds were used as internal standards for quantitative analysis. We found total calculated contents of 6 biogenic amines in A. rigidula leaf of 18.6 and 32.9?g/g. The content of selected amines in 21 dietary supplements labeled as containing A. rigidula was determined by a second LC-MS/MS method. Our study revealed significant differences in the amine profiles of authenticated plant materials and dietary supplements. ?-Methylphenethylamine, a non-natural compound, was found in 9 of the 21 dietary supplement products. ?-Methylphenethylamine was found at levels of 960-60,500?g/g while phenethylamine was found at levels of 710-171,620?g/g. ?-Methylphenethylamine is a positional isomer of amphetamine and our results showed that it can be misidentified as amphetamine during LC-MS analysis. An independent GC-MS analysis was used to confirm the presence of ?-methylphenethylamine and the absence of amphetamine in dietary supplements labeled as containing A. rigidula. This study demonstrates that confirmations by independent analytical methods are essential to verify findings of unusual or unexpected compounds in dietary supplements.

Published by Elsevier B.V.

PMID: 24176750 [PubMed – in process]