Menthol - Sean McDonald

Image — Mint Chocolates [1].

Menthol is a compound found on the leaves of several different types of plants, but it is mainly found on its namesake, mint plants.  The organic compound provides a unique ‘cooling’ sensation, as it interacts with neurons that it comes in contact with [2].  Because of this effect,  menthol is found in numerous household products ranging from throat lozenges, topical creams for pain treatment, and even cigarettes [2; 3; 4].  Moreover, menthol can be used as a fragrance added to perfumes and vapour rubs for decongestion. 

Luckily, menthol is safe for close contact and consumption as many of its uses are found in items consumed or applied to skin.  Specifically,  2500 mg/kg is required to kill 50% of a population (LD50) of rats when fed menthol [5].  For perspective, this LD50 is less than table salt (3000 mg/kg) but higher than Tylenol (1944 mg/kg) [6; 7].

Due to its diverse applications, industry was required to move away from steam distillation of mint plants and utilize complex chemical reactions [2].  In fact, the 2001 Nobel Prize in Chemistry was given to Ryoji Noyori, a chemist who used the element rhodium in a complex chemical reaction in order to synthesize various chemicals including the same menthol compounds used in products mentioned above [8].

However, in a world where Ryoji Noyori had discovered his method for menthol synthesize, surely the price for menthol would much higher than it currently is.  Therefore, other compounds may be needed to replace its use.  One such compound is pectin, due to its ability to cover membranes in our mouth for instance, thereby relieving pain [3].  Interestingly, certain throat lozenge brands even offer menthol-free lozenges that use pectin as a replacement [4].  Similarly, there have been talks in Europe and the USA to ban the use of menthol in cigarettes.  This seems curious, but apparently, many smokers would not be able to handle the robust flavour of normal cigarettes.  In fact, 39% of smokers polled by the periodical NewScientist claim that they would quit smoking, whereas the remainder would either switch to non-menthol cigarettes (36%), or they would resort to the blackmarket for menthol cigarettes (25%) [4].

 REFERENCES

[1] Pazmandi, Krisztina. 50087511_6faec30936_o.jpg. 2010. Pics4Learning. 7 Dec 2013

<http://pics.tech4learning.com>

[2] Galeotti, M. et al. (2002). Menthol: a natural analgesic compound. Neurosci. Lett. 322(3),

145-8.

[3] Halls Breezers. (October 24, 2013). Retrieved from:

http://www.gethalls.com/products/halls_breezers/halls_breezers_df

[4] Carter, L. (2013). Menthol cigarettes: Stub out these seductive smokes. NewScientist. 21 

October 2013. Retrieved from: http://www.newscientist.com/article/mg22029390 

.100-mentholcigarettesstub-outthese-seductive-smokes.html#.UmrGyCSSWMM

[5] Inchem.org (2005). Menthols (Screening information data set – SIDS).  www.inchem.org/documents/sids/sids/MENTHOLS.pdf‎

[6] Sodium chloride. CSID:5044, http://www.chemspider.com/Chemical Structure.5044.html (accessed 18:48, Oct 24, 2013).

[7] Paracetamol. CSID:1906, http://www.chemspider.com/ChemicalStructure.1906.html               (accessed 18:55, Oct 24, 2013).

[8] Colacot, TJ. (2002). 2001 Nobel Prize in chemistry. Platinum Metals Review. 46(2), 82-83.