Recently we received an email from an organization called “Consumers Advocate.org”. They stated that they had performed a quality test on multiple brands of essential oils, including a brand that we carry called “NOW”. The report/web page stated that several of the Essential Oils they tested from NOW were adulterated.

Their report is located here: https://www.consumersadvocate.org/essential-oils

We contacted NOW directly and asked that they review the information that “Consumers Advocate.org” compiled and get back with us. NOW responded with a lengthy testing explanation and rebuttal of the comments stated by “Consumers Advocate.org”.

 

We realize the information below is quite complicated and scientific in nature. The important key takeaways from this are:

 

• NOW brand takes its testing very seriously; so serious that they took the time to respond specifically to the comments made by “Consumers Advocate.org” and provided the reference information to back it up.

• The NOW scientific testing of their products directly contradicts the information posted by “Consumers Advocate.org”.

• NOW brand scientists provided exact testing details and reference to help show the thoroughness and validity of their testing.

• Its very important to trust the companies you partner with and clear communication with them is key.

• Sometime information found on the internet can be misleading. A good rule of thumb is to contact the manufacturer of a product to obtain the most accurate information.

• We are very pleased to be a re-seller of NOW brand products and consider them to be a trusted/valuable partner to Life Thyme Botanicals in our mission to help peoples journey to wellness.

 

Here is the response from NOW brand:

 

At NOW® we take assurance of the quality and purity of our essential oils very seriously. We have made long-term investments in the instrumentation and the professional staff necessary to guarantee the identity, purity, and quality of our essential oils.

NOW regularly assesses the quality of our essential oils through evaluation of their purity and identity to protect our retailers and consumers, and ensure they are getting the product they paid for. We utilize numerous physical or physiochemical techniques which include instrumental testing such as Refractive Index, Optical Rotation, Specific Gravity, Gas Chromatography Mass Spectrometry (GC-MS) and Inductively Coupled Mass Spectrometry (ICP-MS) as well as organoleptic evaluation, which focuses on appearance and odor.

NOW has reviewed APRC’s evaluation of our oils, and we can attest that the oils meet NOW’s specifications and are not adulterated.
Specifically, in response to the evaluation of NOW’s peppermint oil

“This peppermint oil has been adulterated with menthol and menthyl acetate”:

• Menthol result reported by APRC is 43% (Now in-house specification: 32% – 49%, ISO Norm non US: 32% – 49%, ISO Norm US: 36% – 46%)
• Menthyl acetate result reported by APRC is 6.5% (Now in-house specification: 1.7% – 9%, ISO Norm non US: 2% – 8%, ISO Norm US: 3% – 6.5%)

 

“This peppermint sample has a reduced or missing key biomarkers”:

• Viridiflorol is not detected but it is also not required as a biomarker per NOW in-house specification, nor per both ISO Norms.
• Sabinene hydrate is detected at 0.15% (NOW in-house specification: Traces – 2.9%, ISO Norm non US: 0.5% – 2%, ISO Norm US: 0.5% – 2.3%)
• Germacrene D (compound is misspelled in the APRC comment section) is detected at 0.19% (is not required as biomarker per NOW in-house specification, nor per ISO Norm).

 

The Technical Team at NOW agrees that detection of adulteration in an essential oil is challenging; however, our expertise and resources allow us often decipher the sophistication of adulteration methods. The most logical adulteration of peppermint essential oil is with cornmint oil. In that case, detected isopulegol levels rise above the European Pharmacopoeia limit of <0.20%. The isopulegol determined in the sample tested by APRC was at 0.11%.

For more information regarding the detection of 3-p-menthene, menthane, pinane, (Z)-menthan-4-ol and 2,2-dimethylcyclohexyl acetate in peppermint essential oil, please refer to the reference information below.

Regarding the testing results of NOW’s lavender essential oil, our technical team was surprised to see so many synthetic compounds detected by the APRC lab. The presence of multiple byproducts of different processes to synthesize linalyl acetate is rather unachievable. All essential oils at NOW undergo comprehensive tests and if ANY synthetic material is detected, the material is rejected immediately. We cannot confirm the APRC compound identification legitimacy; however, here are a couple of observations NOW® Technical Team made regarding the APRC report:

• When tetrahydrolinalyl acetate is present, dihydrolinalyl acetate should be detected as well (process of synthesis of linalool from acetylene).
• Plinyl acetate is present, if acetylated linalool is obtained from pinene (in this case di/tetrahydrolinalyl acetate should not be detected due to different synthesis path)
• Please see the additional information regarding detection of plinyl acetate, tetrahydrolinalyl acetate (Z) and (E)-linalool oxide acetate in lavender essential oil: In the reference section below.

 

Reference:

Updated on June 26, 2019 – see in green below

 

Caveat

Here are our findings/observations on some of the compounds indicated as markers of adulteration. Bear in mind throughout that we always apply the same analysis criterion to these proofs – these compounds should be indicative of adulteration beyond doubt. In other words, a marker must be reasonably tied to a synthetic route and hardly confounded with a natural occurrence.

 

3-p-Menthene

3-p-Menthene is typically a very minor constituent and therefore often goes unnoticed. At PhytoChemia, we already found it in Boswellia dalzielii (whose samples came directly from a research group), pine oils (including some distilled locally), junipers, and a couple of other frankincenses. It also is frequently reported in various plants in literature: 

• Santolina oblongifolia (doi: 10.1080/10412905.2008.9699424), 
• Cyperus prolixus (doi: 10.1080/10412905.2008.9699418), 
• Artemisia pedemontana (doi: 10.1016/S0305-1978(02)00082-0), 
• Satureja hortensis (doi: 10.1080/10412905.2002.9699754), etc. 

We do not see why this would be a marker for anything. From a structural point of view, it is a very “regular” and legitimate monoterpene.

 

Menthane and pinane 

Menthane and pinane isomers are, in our experience, not widely common sights, but also not particularly worrying. They are just small compounds that can easily escape detection. We observe menthane regularly in eucalyptus, tea tree, oregano, mint and white camphor – bearing in mind eucalyptus and white camphor are not known to be adulterated, typically. It has also been reported naturally in e. g. Protium (doi: 10.1080/10412905.2012.751055), Artemisia oliveriana (doi: 10.1002/ffj.1919), or Hibiscus cannabinus (doi: 10.1021/jf0101455). Pinane is also regularly reported in essential oil studies, for example in Premna latifolia (doi: 10.1080/14786419.2010.511620), a South African lavender (doi: 10.1002/ffj.1093), or Cupressus nootkatensis (doi: 10.1177/1934578×1000500529).

 

(Z)-Menthan-4-ol 

(Z)-Menthan-4-ol is one of the products of hydroxylation of menthane (known as menthanols), which can proceed in a few ways according to literature. A Chinese group used a catalyst in 2014 to generate a mixture of menthanols from menthane (doi: 10.1016/j.catcom.2014.09.039). (Z)-Menthan-4-ol is a noticeable secondary product according to the patent, while the main products of the reaction are alpha- and beta-dihydroterpineols. But to make sense, the objective of the reaction should be to obtain menthol, which in this case accounts for only 0.3% of the obtained product. In 2015, a German group published a similar approach of menthane hydroxylation, but using P450 enzymes to conduct the reaction, yielding 40% menthol (doi: 10.1016/j.tet.2014.11.067). This would make a bit more sense, except that such a recent publication (the authors themselves note an “exploratory” approach) would hardly in our opinion have lead to vast amounts of commercially available menthol by 2018 (considering batches currently on the market have probably been purchased last year), keeping in mind that menthol is already cheaply available from other well-established processes. Interestingly, a third, older study (doi: 10.1016/S0040-4020(01)96644-X) has conducted the same transformation by exposing menthane to light and peroxide, mimicking an accelerated process of oxidation as could realistically happen in a plant or to an essential oil over time. Therefore, in our opinion, one cannot rule out that menthanols could simply arise from oxidative degradation of menthane, which in turn is known to occur naturally.

 

In addition, we have already observed some menthanols in a Canarium sp. resin we have distilled ourselves, so these can occur naturally – although probably always in small amounts. In our opinion, (Z)-menthan-4-ol is just one of those possible isomers that can be encountered following this logic.

 

2,2-dimethylcyclohexyl acetate

We will admit we do not get how 2,2-dimethylcyclohexyl acetate is relevant of anything. It is an odd constituent, but there are barely 7 references to it overall on SciFinder (which is a quite thorough database of chemical papers), mostly pertaining to theoretical studies of molecular configurations. We do not see how this structure would fit in a menthol synthesis, or in fact in any useful synthesis.

 

2,6-diisopropylanisole

2,6-diisopropylanisole is a bit puzzling. We suspect it is not the proper identification, otherwise it would not make much sense from a structural point of view (the anisole core bears a methoxy group, which is unrelated to any useful synthetic approach to menthol or thymol – so this probably is an isomer). Posing anyhow that this would be the signal of a side-product in synthetic thymol used to prepare menthol, we do not see well how this substance would make it through the further steps (reduction, esterification, fractional distillation) required to obtain the menthol from the thymol and not be discarded, keeping in mind it is a heavier (significantly higher boiling point) and less polar/more bulky constituent than menthol/thymol due to the extra isopropyl group.

 

Dehydromintlactone

Dehydromintlactone (and its parent structure mint lactone) are natural constituents of peppermint. See Näf, R., & Velluz, A. (1998). Phenols and lactones in Italo-Mitcham peppermint oil Mentha × piperita L. Flavour and Fragrance Journal, 13(3), 203–208. (doi:10.1002/(sici)1099-1026(199805/06)13:3<203::aid-ffj725>3.0.co;2-0 – note that the compound is presented under its formal name rather than dehydromintlactone, and is structure 12 of the paper). The adulteration claim on this basis is questionable. For those with a good memory, isomintlactone (also reported in that paper and structurally related) was postulated as potentially the real identification of the ethyl vanillin in the DoTERRA vs Young Living peppermint saga a couple of years ago, both having a similar ions in their mass spectra.

 

Plinyl acetate and tetrahydrolinalyl acetate 

Plinyl acetate and tetrahydrolinalyl acetate are not questioned, being part of lists of compounds commonly recognized as problematic in oils (we do not here endorse or not their observation in the oils, just making a statement on the compounds themselves).

 

(Z) and (E)-linalool oxide acetates (furanoid or pyranoid form not specified) 

(Z) and (E)-linalool oxide acetates are pointed out as markers for adulteration in almost all challenged lavenders. We fail to see the validity of this point of view. Linalyl acetate can undergo the exact same process (which has nothing to do with the presence of an acetate) as linalool, and develop into linalyl acetate oxides just like linalool yields linalool oxides. Although this process increases with the oil’s age, oxides are also expected in fresh oils. We sadly do not have access to the full texts, only the abstracts, but here are two references we found in that regard:

 

Mazza, G. (1998) Clary sage aroma: 1. Identifications of volatile compounds of flower tip oil and alcoholic infusions. Science des Aliments, 8(4), 489-510.

 

Abstract: The arom. compn. of clary sage (Salvia sclarea) flower tips was investigated by gas chromatog. and mass spectrometry.  One-hundred and seventy volatile components were detected, including 38 hydrocarbons, 43 alcs., 11 esters, 21 carbonyl compds., 21 (ep)oxido-compds., 3 acetals, 2 ethers, 2 furans, and 2 acids.  A total of 150 components were identified, 99 of them for the 1st time and the most meaningful qual. and quant. differences between essential oil and alc. infusion were shown. Myrcene, β-caryophyllene, and germacrene-D are the main hydrocarbons of the essential oil; in the aged oil, the 1st tended to increase, while the other 2 diminish so greatly that they disappear.  Among the oxygenated compds., linalool and linalyl acetate provide greater contribution to the aroma, both in the oil and in the alc. infusion. The presence of many oxidn. products of linalool and linalyl acetate in aged essential oils is also pointed out; indeed many diols and (ep)oxides are found, among which the trans-3,7-dimethyl-1,5-octadien-3,7-diol, the trans-3-acetoxy-3,7-dimethyl-1,5-octadien-7-ol, the trans-furanlinalool oxide, the cis-furanlinalool oxide, and the 2 isomers of epoxy-linalyl acetate are the most abundant.  Finally, the mass spectra of unidentified compds. are reported.

 

The article (written in French) was obtained on June 26, 2019. Giacomo Mazza has studied two essential oils of clary sage. The fresh oil did not contain “acétoxy-trans-oxyde furannique de linalol” and “acetoxy-cis-oxyde furannique de linalol” (peaks 49 and 55 from his table), which refer to (Z) and (E)-linalool oxide acetates; in a four-years-old oil, both compounds showed up in trace amounts, defined by the author as less than 0.10%. Mazza also comments that “À cause de la plus grand stabilité des deux isomères de l’acétate d’époxylinalyle acétate (pics 88 et 89), il est fréquent de les trouver dans les vieilles huiles aussi, à concentrations élevées; seulement une partie de ces deux époxydes (pics 88 et 89) se cyclise lentement pour donner les oxydes correspondants (pics 49, 55, 58 et 60).” [translated: Because of the greater stability of the two isomers of epoxylinalyl acetate (peaks 88 and 89), it is frequent to encounter them in old oils too, at high concentrations; only a fraction of these two epoxides (peaks 88 and 89) cyclizes slowly to yield the corresponding oxides (peaks 49, 55, 58 and 60).” Peaks 58 and 60 are the pyranoid forms of the oxides.

This last sentence clearly indicates that Mazza considers that the linalool oxide acetates slowly develop naturally over time in clary sage oil (which is rich in linalyl acetate).

 

Mazza, G. (1987) Oxidations of monoterpenes in essential oils. Essenze, Derivati Agrumari, 57(1), 5-18.

 

Abstract: Essential oils of mandarin, bergamot, and sage were analyzed by gas chromatog.-mass spectrometry after various periods of aging (up to 4 yr), and the oxidn. products were detd.  Data are tabulated on the amts. of the oxidn. products of monoterpenes and of the O-contg. compds. Mechanistic oxidn. schemes are presented.

 

Then SciFinder (which we have used for this reasearch) gives us a list of molecules included in the paper, which comprises linalyl acetate and its two oxides. We currently are trying to get copies of these papers.

 

Both linalyl acetate oxides have also been reported in several studies, for example traces in ylang-ylang (doi: 10.1002/ffj.3106), in bergamot (Hifnawy, M. S., Azzam, S. M., Sabry, O. M. M. (2004) Essential oils, pectins, tannins and lipids of certain Citrus species growing in Egypt, Bulletin of the Faculty of Pharmacy (Cairo University), 42(2), 177-192), in coriander macerated in wine (Mazza, G. Ubigli, M. (2001) Chemical and sensorial effects of the addition of black elder flower and coriander seed extracts to muscat wines, Rivista di Viticoltura e di Enologia, 54(4), 25-35), etc. Even 12% of it was reported in Tanacetum dumosum (although the study is not of the highest quality, we will admit: doi 10.1080/14786419.2014.971319). Overall, these compounds seem to be perfectly naturally explanable.

 

Conclusion

With the exception of the plinyl ester and dihydrolinalyl ester, all compound noted as adulteration marker can be found naturally in small amount in essential oil, said amount is the same amount as those found in the report given to us for analysis. Therefore, we cannot conclude that these compounds are indication of adulteration with synthetics material at the level shown.

 

Laboratoire PhytoChemia, June 21, 2019

Last update: June 26, 2019