Caution, Hot Subject!

Benoit Roger, Ph. D.

Laboratoire Phytochemia is proud to be a sponsor of the hot sauce festival ”Saguenay en Feu” that will take place in Chicoutimi on May 25-26! A good occasion for us to talk a bit about the chemistry of Chili pepper and by extension of some molecules that confuse our senses.

It has already happened to almost all of us to taste some food that was a bit too spicy for ours taste buds and feel this strong feeling of heat or even burn. Then we blush and we have a few drops of sweat that appear on the forehead. Indeed, the Chili pepper (Capsicum frutescens and others species) is one of these plant that has mastered the art of confusing our senses. It contains some molecules named capsaicinoids (capsaicin, dihydrocapsaicin, nordihydrocapsaicin, etc…) that feature the characteristic to activate our TrpV1 heat receptors (transient receptor potential vanilloid 1).

Figure 1. TrpV1 receptors

These receptors that spontaneously activate when in presence of temperature above 43 °C, are located on sensitive nerves in the mouth but also on all mucous membranes and all over the skin. This is not the case for our taste receptors that are only located on the tongue and the palate. When capsaicinoids enters in contact with these receptors, they ”inform” the body of an excess of heat and it responds with sweat and blush (peripheral vasodilation), even if the body temperature stays almost unchanged.

To characterize the intensity of the sensation generated by this kind of molecules we use the Scoville scale. Pure capsaicin scores 15 000 000 on Scoville scale, meaning that is must be diluted 15 000 000 times to be undetectable. Although capsaicin is very active and it is considered as a reference, other molecules also activate heat receptors. We can mention shogaol and gingerol from ginger that score 160 000 and 60 000 respectively and piperine from black pepper that scores 100 000 on Scoville scale. Others compounds, resiniferatoxin and tinyatoxin from an african cactus-like plant (Euphorbia poissonii) score 1000 and 320 times capsaicin score on Scoville scale. Better not touch its latex !

Figure 2. The most actives compounds on TrpV1 and Euphorbia poissonii Pax.

Allyl isothiocyanate from mustard and Wasabi activate the same receptors TrpV1 but this little sulfurous compound also activate another related receptor named (TrpA1), it produces a similar sensation albeit a bit different.

Camphor also activate the heat receptors TrpV1 but it simultaneously activate the cold receptors (TrpM8) producing a sensation of cold and heat at the same time. Menthol finaly, that produce a well known sensation of cold, you gessed it, activate cold receptors TrpM8 but not the heat receptors TrpV1. Besides these three last molecules are much more small and volatiles than previous ones allowing them to also participate to the flavour (all the sensations we feel when we eat) by their odor.

               Figure 3. Others molecules that activate heat receptors, cold receptors or both.

But let’s come back to the Chili pepper. It does not only contain capsaicinoids but also carotenoids and glycosylated flavonoids known for their health benefits, vitamin C (about 5 times more than orange) and vitamin E, a powerful antioxidant. It also been shown to be interesting for diabetes by reducing the quantity of insulin need for blood glucose regulation following a spicy meal. Local application of capsaicinoid has also been demonstrated to be useful to sooth arthritic pain and some skins ailment. Some cancer where the cells are over-expressing TrpV1 receptor are also sensitive to the compounds. 

To conclude, if you are a fan of hot sauces, feel free to come to Saguenay en Feu to taste what the numerous exhibitor will have prepared for you. Remember that pepper is first and foremost a sensation experience. If there is at least one thing that we can take out from the chemistry of these compounds, and that is confirmed by experimentation, is that when something is too spicy the first reflex of taking a cold glass of water may not be the best option. Cold water may diminish the burning sensation but will not stop it. Capsaicin posses a long carbon chain that turn it almost insoluble in water but very soluble in oil and grease. You are better drink whole milk in small sip, the fat from the milk does a better job at “washing away” the capsaicin.

Photos credits

TrpV1 receptor : http://www.nibb.ac.jp/en/press/2011/07/15.html

Chili pepper : www.freepik.com/free-photo/chilli-isolated-on-white_1038257.htm

Euphorbia Poissonii Pax : worldofsucculents.com

References

http://www.chm.bris.ac.uk/motm/chilli/capsaicin.htm

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