Mode of action of aromatic molecules
The activity of an essential oil is bound to the biochemical structure of their components. The mechanism of action of these volatile molecules can be expressed in different ways.
1. Direct action
- On pathogen micro-organisms
- On a given physiologic pathway or function
- On a given metabolism
Numerous aromatic molecules exert a direct and specific biochemical activity on pathogen micro-organisms. They have a specific toxicity, causticity that lead to physico-chemical modifications of the outer membrane of micro-organisms, accounting for the bacteriostatic and/or bactericidal activity of essential oils.
A lot of scientific research has been made in the last decades on the intime mechanism by which essential oils exert their antimicrobial activity. As already mentioned the privileged target is the outer bacterial membrane in which some polypeptic structures are disrupted, leading to a progressive weakening of the bacterial cell wall (formation of "blebs"). Once the integrity of the outer bacterial membrane has been damaged the bacteria becomes highly sensitive to the natural body defence systems but can also become non-viable by loss of cytoplasmic material (formation of protoplams).
The essential oil of tea tree has become one of the prides of Australia. For this reason a lot of scientific research has been made on this essential oil in order to understand its mechanisms of action on bacteria and other micro-organisms (fungi, yeasts ...). Beside the direct effect on the micro-organism cell wall the essential oil of Melaleuca alternifolia has been shown to alterate the transmembranar potassium transport, the glucose metabolism and the ATP metabolism. All these factors are key-elements of the energetic metabolism of the micro-organisms, which becomes no more efficient and rapidly leads to bacterial death.
So far it has not been demonstrated that essential oils can have a direct effect on the division process of micro-organisms or on protein synthesis, as synthetic antibiotics do by acting on the DNA -> RNA translocation or by interfering with mRNA traduction into peptides.
But the fact that one of the main targets of volatile compounds is the outer membrane of micro-organisms also explains why essential oils are anti-viral. They can attack the proteic viral membrane and thereby inhibit viral replication and viral migration. This particular property combined with the immunostimulating effect of essential oils account for their great anti-viral action against a broad range of viruses (herpes virus, influenza, .....)
Some aromatic molecules are so close to naturally synthesized compounds or naturally occurring molecules in the human body that they can mimic the structure and the function of hormones. They are called hormone-like terpenes, present in hormone-like essential oils.
Example: Sclareol (found in the essential oil of clary sage (Salvia sclarea) shows a great structural analogy with estrogens and can therefore be useful in many hormone-dependent pathologies such as amenorrhea.
Other aromatic molecules have a direct effect on neuroreceptors and neurotransmitters.
- Sympathomimetic action : basil, lemon, sage, pine, mountain savory
- Sympatolytic action : lavender, ylang-ylang, spike lavender, angelica
- Parasympathomimetic : clove, oregano, rosemary, exotic verbena
- Parasympatholytic : cajeput, cypres, tarragon, hyssop, thyme
2. An indirect action
Essential oils can act on biological processes, or by modifying the general and/or local "ground*" thanks to their energetic activity:
(* The term "ground" refers to the French word "Terrain" ; some specialists prefer to use the word "Diathesis" referring to all the factors predisposing someone to be sensitive to a given disease)
- supply of electrons (negativation)
- capture of electrons (positivation)
- supply of protons (acidification)
Negatively charged aromatic molecules are soothing, easing, anti-inflammatory and antispasmodic and are useful in :
- post-traumatic and post-surgery pains
- stress, anxiety, insomnia, pessimism
- physical asthenia
- asthma, hay fever
- gastric laziness, colitis, dyspepsia, constipation
- ringing in the ears
- general weakness
- high blood pressure, tachycardia, heart palpitations
- irritability, severe headache, migraine
- eczema, itching, hives
- bowel spasms
- troubles of the liver and the gall bladder
Positively charged aromatic molecules can either capture electrons, or supply protons. In the first case they act contrarily to the previous ones. In the second case they strengthen the vital energy, accounting for their tonic power. The aromatic molecules rich in H+ ions promote a loss of the blood pH (acidification) and allow therefore to fight against blood alkalosis, first metabolic step leading to numerous health troubles and organic disturbances : viral and microbial infections, severe asthenia, cancers, multiple sclerosis, ... thanks to their informational functions:
- Exogenous (olfaction)
- Endogenous (neurologic, endocrine function)
Through their high diffusibility and volatility aromatic molecules act directly, when inhaled, on the olfactive cortical areas. This phenomenon leads to chain reactions reactivating weakened biological or physiological pathways. The study of the therapeutic effects of volatile compounds through their binding with neuro-olfactive receptors is called "Aromachology".