In which I am confused about maple syrup and plasticiser precursors.

As I noted below on the last ‘What Am I?’ post, I was following a paper in J Chem Ed with the chemical composition of Maple Syrup.  This paper was a summary of other analytical chemistry papers.  When I was sketching out the components (generally I look up the Smiles or InChI strings and generate the structures in Symyx draw from them rather than trying to draw them all myself), I noticed that one was 2-ethyl hexanol.    The paper was by Ball, http://pubs.acs.org/doi/abs/10.1021/ed084p1647.

Now, as this is the 23rd ‘What Am I?’, I’m starting to have a better appreciation for what looks right in terms of certain substances.  2-ethyl hexanol didn’t look right for Maple Syrup, particularly not in the context of table 4 in the paper:

Screenshot of partial table 4 from http://pubs.acs.org/doi/abs/10.1021/ed084p1647 taken without permission.

Now, as you can see there are lots of compounds that sound similar, such as the collection of pyrazine derivatives and the compounds based around benzene rings.  2-ethyl-1-hexanol, when I came to draw it, looked very different.  

I usually scan the Wikipedia entry for the molecule, particularly for such complex substances, looking for the compounds that will give the greatest hint towards the identity.  Some of the compounds that I did put in the post below clearly stated in the Wikipedia entry that they were obtained from natural sources such as maple trees. But this one doesn’t.  http://en.wikipedia.org/wiki/2-Ethylhexanol In fact, it says:

“It is produced on a massive scale as a precursor to plasticizers, some of which are controversial as potential endocrine disruptors.”

This is one of the common plasticisers, Bis(2-ethylhexyl)phthalate, used in PVC and other things.  Apparently it is metabolised to mono-ethylhexylphthalate, which would seem to imply that 2-ethyl-1-hexanol might be produced through simple ester cleavage.

I don’t have access to the original analytical chem papers from which the data in table 4 came, but I’m wondering if the presence of this compound was from degraded plasticiser in either labware or a storage bottle (or some plastic during the production process) rather than a naturally occurring substance.    On the other hand, it is apparently found in some fruit (source: http://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+1118) .

As a footnote, I did also stumble across this paper: L.G. Valerio Jr. et al.  Toxicology and Applied Pharmacology 222 (2007) 1–16 as found at http://elec.polytech.unice.fr/~rgautier/SiteWebEPUTOX/Articale2.pdf .  It states (table 1, page 5) that 2-ethyl-1-hexanol is a metabolite of safrole (found in black pepper, basil, sassafras).

Structure of safrole, source: http://en.wikipedia.org/wiki/Safrole

Now, I’m a little confused as to how safrole gets  metabolised to 2-ethyl-1-hexanol: anyone got any ideas? It seems…well..a little improbable (but I’m no biological chemist, so know little about metabolism).

As a second footnote, there are a few links here talking about toxicity.  At no point am I stating that this compound, present in extremely tiny amounts in the sample of maple syrup that was analysed, is risky to health.  The data cited in these papers are relatively old and probably don’t reflect current methods of production (if the compound comes from production), or storage (if the compound comes from storage).

 

 

 

 

 

 

2 thoughts on “In which I am confused about maple syrup and plasticiser precursors.

  1. Here in the US, pure maple syrup is stored in glass (or occasionally ceramic) bottles. I’ve never seen it store in any plastic containers, although I certainly haven’t been everywhere. In contrast, the cheaper syrups that are only 2% maple syrup and the rest HFCS and flavorings are always stored in plastic squeeze bottles. I never have looked to see what they are made of (I’ll try and stop by a grocery store later today), but PVC is certainly a possibility.

    I am having a difficult time accessing the article right now (or anything else on the ACS site), but does this seem like a possibility?

  2. As a synthetic organic chemist, I can tell you this is a small – but annoying – problem. It’s funny you blog about this now. Just yesterday, I was trying to analyze the byproducts of a synthesis I was running by 1H NMR (very common for organic chemists). There was this extra product I couldn’t identify, and I was about to chalk it up to ‘unknown degradation product.’ Then I noticed another 1H NMR from a completely different reaction which had the same signals.

    After staring befuddled for a while, it finally hit me – plasticizer leaching from plastic somewhere as I was running my reaction. Sure enough, the reference 1H NMR for bis-(2-ethylhexyl) phthalate matched my byproduct 1H NMR exactly.

    Plastics are used in lines feeding inert gas to reaction flasks, and the most common solvents are often stored in 500-mL plastic wash bottles for ‘grab-and-go’ use. Now I get to spend today taking NMR of solvents from all my plastic sources to see which bottle I need to replace.

    As for the maple syrup, my guess is the plasticizer leeched from their solvent bottles or plastic containers manipulating or storing their samples waiting for analysis.

    Derek Lowe blogged about this a while back, and I might venture a guess that this is where the safrole ‘metabolite’ comes from, too (though that’s just a guess based on being burned before).

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