Aromatherapy Workbook. Shirley Price

to coumarins, are noted for their hazards in connection with sunbathing. They are photosensitizers and should not be used immediately before going into the sun or onto a sunbed (see chapter 6). Bergaptene, found in bergamot oil (not a terpene and sometimes spelt without the final ‘e’), is the best-known example.

      Two hours after applying complete bergamot oil (see folded oils – chapter 2) suitably diluted in a carrier, there is no longer a great risk of adverse reactions due to the sun; by that time the oil is safely absorbed into the bloodstream.¹⁴

      Ethers (Not to be confused with esters)

      Here we have yet another component which occurs but rarely in essential oils and can be confusing. Like phenols and phenolic ethers, the properties of ethers are anti-depressant, anti-spasmodic and sedative.

      Conclusion

      An essential oil is always a complex cocktail of many different naturally occurring components; there are several different kinds of terpenes, alcohols, phenols, ketones, esters and so on in each oil, and these vary from harvest to harvest and plant to plant. The actions of any whole essential oil are difficult to forecast from this complicated make up; I repeat, there is no direct simple relationship between the chemical constituents and the therapeutic qualities (or even the hazards) of an essential oil.

      No one in the aromatherapy world understands or knows everything to do with essential oils, so take heart! There is also no way in which a book like this can cover each constituent known of every single oil, but simply by being acquainted with the main constituent families you may be able to see some sort of pattern emerging in relation to therapeutic effects.

      There are, nevertheless, some essential oils whose chemical constituents do not seem to conform to their expected pattern and are the ‘black’ (or sometimes perhaps, the ‘white’!) sheep of their family. There are also trace elements which show up on a gas-liquid chromatograph (see chapter 2), but have so far not been identified – these too must surely play an important part in the eventual effect of the final chemical ‘cocktail’.

      The above points (plus climate and soil variants) may help to explain why no document or book lists every minor chemical, or even gives the same proportions of the major ones. It would take years to research and would take up many volumes! (Guenther’s well-respected reference work on essential oils comprises six thick volumes, without including any therapeutic effects!)

      May I suggest that if you have found this chapter (so far) a bit difficult, yet you wish to understand it, you come back to it later. Read it again up to the isoprene unit, perhaps drawing the molecules as you go along, moving on to each new chemical family only when you fully understand how the previous one was formed.

      Perhaps you already knew it all, or have neither the wish nor the need to pursue the intricacies of these simple to use and wonderful liquids! In either case I hope you found it interesting.

      Electrical Classification of Essential Oils

      The therapeutic effects of the different chemicals we have been looking at can be shown by charting the reaction of essential oils and their components to electricity and water. There has been a lot of work done in France by Franchomme, based on investigations begun by Vincent and Mars, to determine the polarity of each chemical constituent in order to discover whether these follow an overall pattern. It presents a fascinating concept and has given very interesting results.¹⁵

      When essential oil molecules are sprayed between two electric plates (one positively charged and one negatively charged) they will be attracted either to one plate or the other. This attraction stems from the chemical components, each of which has either a negative or a positive charge. Opposites attract, so negative components go towards the positive plate and vice versa. When a component from one chemical family is sprayed between the plates, it is attracted either to the negative or the positive plate. Aliphatic aldehydes (chain based), esters and ketones are attracted towards the negative plate; alcohols, aromatic aldehydes (ring based), monoterpenes, oxides, phenols and phenolic ethers towards the positive one; the sesquiterpenes, lactones and coumarins are neutral and are not attracted – some are slightly more negative – others more positive. See Figure 3.23.

      FIGURE 3.23: Movement of alcohol molecules

      Essential oils are slightly soluble in water – this is due to the hydrophilic (soluble) or hydrophobic (insoluble) factor of each chemical family. Alcohols, all aldehydes, phenols, ketones, lactones and coumarins are soluble to some degree; monoterpenes and sesquiterpenes are insoluble, as are most of the esters; oxides and phenolic ethers fall in the middle, as do a relatively small proportion of the esters. See Figure 3.24.

      With a four-way grid like this, it is easy to see which constituents from the essential oils are cooling and which are warming; which are calming and which are stimulating (Figure 3.25).

      See how top and bottom, left and right, and opposite quadrants, complement each other; using a combination of these opposites, essential oils can be selected to treat the whole person. Franchomme’s approach is that there is a relationship between the chemical components and the effects – if you know the chemical constituents it gives at least an idea of the effect of an essential oil containing these. I am told that he and his colleagues have carried out many clinical experiments in French hospitals to verify his work.

      

      FIGURE 3.24: Polarity and solubility of individual components of essential oils (adapted from grid originated by Roger Jallois and published in Aromathérapie Exactement)

      There is much work being done and more yet to be done on these fascinating creations of nature, essential oils. Even though I have only touched the tip of the iceberg, I trust I have awakened in you a desire to utilize the information in it to the good of your own health and, if you are an aromatherapist, of that of your clients.

      

      FIGURE 3.25: Basic effects of individual constituents

      TABLE 1: Chemical Constituents of Essential Oils and their Effects

      TABLE 2: Some Chief Chemical Constituents of Essential Oils

      This table simply gives an idea of a few of the chemicals in selected essential oils and is not meant to be comprehensive.

TABLE 3: List of Oils with Common Name, Latin Name and Plant Family

Common Plant name and Latin name	Family	Page
Angelica (Angelica archangelica)	Apiaceae	62
Aniseed (Pimpinella anisum)	Apiaceae	66
Basil (Ocimum basilicum)	Lamiaceae