Plant essential oils

What are they?

Essential oil is the thin layer that remains on the surface of the distilled plant water (called "hydrolat"). Essential oils are obtained by distilling plants by steam. To use them in aromatherapy, only steam can be used, and it is expressly prohibited to extract them with solvents. Although we call them "oils", they are not real lipids, however they resemble oils in the sense that, when you touch them, they have the same unctuous feel.

Which part of the plant is it from?

Essential oils can be distilled from roots, stems, leaves, barks, flowers, fruits or seeds, depending on the part of the plant that contains the active ingredients. There are exceptions where different parts of the plant have different activities, for example in citrus fruits: Oranges, lemons, tangerines and grapefruits provide three different essential oils with three different activities, depending if they come from their peels (squeezing), their leaves (petitgrain) or their flowers (nerolí).

Why are essences so powerful?

Firstly it is important to note how much essential oil can be extracted from the plant. The following list shows how much essential oil could be approximately obtained from 1.000 kg of several plants:

Essential oils Quantity in kg.
Basil Oil 1 kilo
Star Anise Oil 25 kilos
Cinnamon Oil 1 kilo
Bay Oil 30 kilos
Marjoram oil 5 kilos
Peppermint Oil 25 kilos
Orange Oil 15 kilos
Oregano Oil 10 kilos
Parsley oil 5 kilos
Thyme Oil 20 kilos

This data is not exact, but pretty close, and gives us an idea for example, that when we use a kilo of basil oil, we are actually using 1.000 kg of the plant.

Because they are highly concentrated, we have to consider that, for example, the use of thyme essential oil would not be the same as having a thyme soup (even though thyme soup is still effective).

Plants: magic or true?

After seeing the previous point, does anybody still doubt the power of plants?. In France, for example, there are ten Faculties of Pharmacy with Phytotherapy departments. All developed countries' pharmacopoeias contain monographies of plants. Nowadays, the German E Commission, or the European Scientific Cooperative of Phytotherapy (ESCOP), based in Exeter (England), of which all European countries are members, including Spain, represented by the Spanish Society of Phytotherapy, are aware of the power of plants for healing, and the necessity of regulating it.

Moreover, Social Security in countries like France, Switzerland and Germany are considering dispensing plant extracts, and in some countries, on medical prescription.

In Spain, plants or their derivatives are 25% of the ingredients in medicines sold in pharmacies, and 16% as plant or extract alone.

Moreover, the World Health Organization (WHO), which has its own monographs, estimated that medicinal plants are the only means of treatment for 80% of the world's population (1997).

Plant essential oils


Pharmacodynamic action of plant oils.

Plant essential oils are complex mixtures of active ingredients; some of them having more than 200 components (the typical example is eucalyptus). As in all chemical compounds, the active principles follow the relationship chemical structure-pharmacodynamic action, and thus their activity can be classified according to their chemical classification.

The major biochemical families found in EO are: alcohols, ketones, terpenic aldehydes, aromatic aldehydes, esters, ethers, terpenes and oxides.

Alcohols include: alcohols, phenols and sesquiterpenols

  • Alcohols and phenols are excellent broad spectrum antibacterials, as well as superb virucidals and fungicides.
  • Phenols have a remarkable skin and intestinal antiparasitic activity. They are immune stimulants.

Aldehydes are of two types: aromatic and terpenic.

  • Aromatic aldehydes have identical properties and side effects as phenols.
  • Terpenic aldehydes have antalgic, anti-inflammatory and soothing properties.
  • Aldehydes exhibit better skin tolerance than phenols; even though it is still necessary to dilute them at 5% in topical applications.

Terpenic oxides are excellent expectorants and antivirals. They are also mucolytic and antibacterial. Essential oils which are rich in oxides are immunomodulators.

Ethers are molecules which have an exceptional antispasmodic action, and simultaneously also have an analgesic and antiviral activity.

Terpenes are volatile substances responsible for general stimulation. They are useful in chronic inflammatory processes. Likewise, they act as a decongestive in the respiratory and lymphatic systems.

Ketones and lactones are the most difficult aromatic molecules to handle.

Esters are volatile substances with great antispasmodic activity, a potent anti-inflammatory action, and an effective sedative. Their toxicity is low, almost zero. They are used for inflammatory and nerve disorders.

All plant oils have bactericidal activity at high concentrations, so here we have quoted only those bactericides which have high activity at low concentrations.

It is also common that the same oil shows more than one pharmacodynamic activity, due to the diversity of their constituents, and it would be therefore up to the formulator to design the product for its concrete application.

Presence of resistances

Resistances to plant oils have not been shown. Furthermore, most prestigious specialists are under the opinion that plant oils, as natural products, have been exposed in nature against bacteria, viruses, fungi, parasites, for millions of years, and nothing suggests that resistance can be created by their use or application.

Aceites Esenciales de plantas


Some historical background

Vegetable oils and resins have been in use since ancient times; no one can dispute their effectiveness as a way of preserving mummies, as many of them are more than 4,000 years old. The Arabs were the main medical prescribers of plant essential oils for therapeutic use. Ignorance in the Middle Ages and in the Modern Age in Europe made them fall into disuse, until microbiologists in the late nineteenth and early twentieth century were using them, quoting for example:

• 1881 Robert Koch, studying the action of the essence of turpentine (Pistacia terebinthus) on anthrax.

• Chamberland, studied the activity of the essences of oregano, cinnamon and cloves on Bacillus anthracis.

• Martindale showed that oregano oil is the most potent known antiseptic, 25.76 times more active than phenol.

• 1930, Rideal and Walker set the phenol coefficient.

Ignorance in the Middle Ages and in Modern times have delayed the therapeutic use of essential oils. Subsequently, modern microbiologists such as Koch, Pasteur, Chamberland, created a short revival, -short because the discovery of penicillin and other antibiotics slowed its development-. Although we consider them essential right now, their use is being questioned because they show resistances.

Aromatherapy should be developed. Modern techniques of analysis and clinical protocols, identical to those of synthetic products, will offer a new therapeutic arsenal, with the application of natural products based on proven scientific facts. Furthermore, the undiscovered floras in emerging countries like China, India or Brazil, will be the reservoir, and the hope for medicine in the future.

Author: Pedro Peñalver