Essential Oils - Terpenes Flashcards
(18 cards)
What are Terpenoids (essential oils?)
- A large group with many important pharmacological properties.
- Highly concentrated, easily absorbed through skin and affect CNS via olfactory receptors.
- Soluble in alcohol, oils and fats, and only
- slightly in water.
- Slowly evaporate if left exposed, for example, placing a drop of oil on blotting paper.
- Water soluble saponins: triterpene and the steroidal glycosides.
What are their composition?
Vary according to season, time of day, growing conditions, geographic and genetic factors.
Total essential oil content in plants is often less than 1%.
Distinct chemotypes: e.g. thyme chemotype (ct) linalool and thyme ct thymol.
Often isomers - (+)-carvone smells of caraway. (-)-carvone smells of spearmint.
How are they extracted from plants?
- Steam distillation- Volatile compounds in the steam. Often the oil is slightly modified and produces new compounds e.g. chamazulene from matricin.
- Solvent extraction - As in myrtle, Myrtus communis. Immersed in a solvent until dissolved and then evaporated to give the absolute.
- Enfleurage - Oil extraction from flowers or petals. Scentless fatty oil base, using a cold or hot process.
How are they antimicrobial?
Many are antiseptic/antimicrobial against bacterial, fungal and viral plant infections.
Effective against microbial resistance - because they have an absence of specific cellular targets, Large number of different essential oils in one plant.
Excretion of essential oils via the lungs or urine creates mild antimicrobial activity.
* Juniper and buchu are used for urinary tract infections
* Thyme is used in respiratory infections.
* Volatile oils are used to treat intestinal pathogens, bacterial and other infections.
* Tea tree essential oil has bactericidal activity against oral and dental pathogenic micro-organisms.
How are they antifungal?
Studies have shown efficacy against herpes simplex virus and enveloped viruses
Non-enveloped (naked) viruses are not affected by essential oils.
How are they spasmolytic?
Useful in functional gastrointestinal problems
Traditional use of carminatives: spasmolytic
activity relieves colic, relaxes sphincters and assists in expulsion of intestinal gas.
* EO of peppermint, sage and rosemary relax sphincter of Oddi
* Peppermint most active and also used in IBS.
* Relaxant effects on tracheal smooth muscle
* Roots of angelica, Angelica archangelica, clove and elecampane, Inula helenium
How are they expectorant?
Hot lemon drink for respiratory infections: some EOs are inhaled while drinking. Inhalation of essential oils into the
lungs may exert a direct antimicrobial activity.
Clinical trials of myrtol
Standardised, derived from pine, lime and
eucalyptus. 3 monoterpenes: (+)-alpha-pinene, d-limonene and 1,8-cineole. Expectorant and mucolytic for acute/chronic bronchitis, COPD and sinusitis.
What are their CNS effects?
- Sedative activity - Clinical trial using 1,8-Cineole, in eucalyptus, was effective in decreasing anxiety.
- Stimulant activity - Inhalation and oral doses of rosemary oil increased locomotor activity in
vivo. - Analgesic - Mainly monoterpenes, e.g. peppermint oil or menthol topically for headache and joint pain. Clove and lavender oils are local anaesthetics; in clinical trials, rosemary essential oil has been beneficial in pain management in combination with analgesic drugs.
Lavender and rosemary essential oil
Participants given math tests were more relaxed and alert after aromatherapy using Lavender, Lavandula angustifolia. and rosemary, Rosmarinus officinalis.
What are their effect on the kidneys?
Effect on kidneys
Some essential oils are traditionally used as diuretics because they act as ‘kidney
irritants’.
EO terpenes used orally shown some promise in dissolving small kidney stones.
How are they toxic?
Pennyroyal, tansy and parsley have been used
as abortifacients but have no direct
stimulating action on the uterine muscle, and
inhibit uterine contractions. The action seems
due to general poisoning or gastrointestinal
irritation.
Tea tree oil cases noted of contact dermatitis: oxidation is the likely cause.
How are they undertood via functional groups - Monoterpenes and Sesquiterpenes?
Monoterpenes - Diverse characteristics - linalool is acyclic (no ring), monocyclic Ð pulegone and bicyclic Ð thujone.
Sesquiterpenes - Derived from the 15-carbon precursor farnesyl pyrophosphate. Tend to be antihistaminic, antiallergic and anti-inflammatory.
Chamazulene in yarrow and wormwood. Chamazulene and precursor matricin (chamomile), achillicin and achillin
Antiinflammatory
Antibacterial
Wound healing.
Examples are a-caryophyllene (=humulene) in
hops. Beta-caryophyllene in cloves and
sage. Zingiberene in turmeric and ginger.
How are they undertood via functional groups - Hydrocarbon volatile oils and alcohol volatile oils?
Hydrocarbon volatile oils - Contain only carbon and hydrogen, e.g. pinene and limonene.
Pinene in turpentine oil. Used as a rubefacient or liniment for rheumatic disease. Also in black
pepper.
Very active against bacteria but not against fungi except dill.
Alcohol volatile oils - Acyclic, monocyclic or dicyclic, end in ‘ol’
* Tend to be Antimicrobial
* Terpinen-4-ol in Tea Tree - Ideal skin disinfectant due to activity against a wide range of microorganisms (Gram-positive bacteria and Gram-negative bacteria, and fungi).
* Topically effective in acne patients and in recurrent cold sores, Herpes labialis.
* Antibacterial mouthwash, reduced Methicillin-resistant Staphylococcus aureus (MRSA) levels and fungal infections in the mouth and on skin
* Alpha-terpineol: antibacterial and antifungal.
* Menthol from mint, geraniol, linalool, citronellol, borneol, zingibero
How are they understood via functional grounds - Aldehydes?
- Terpenoids with a double-bonded oxygen and a hydrogen attached directly to carbon.
- Names end in ‘al’ as in citral, geranial and citronellal.
- Can produce skin sensitisation and irritation, but are not toxic.
- Some are antimicrobial or antiviral; often calming, antiinflammatory
- Citral, a mixture of geranial, neral and citronellal
- Cinnamaldehyde, vanillin (vanilla, benzoin, peru balsams) found in cinnamon, orange, lemon and citronella oil.
How are they understood via functional grounds - Phenol volatile oils?
A hydroxyl group attached to a benzene ring (terpene alcohols)
Antimicrobial, tend to be irritant or
even toxic
Eugenol, a phenylpropanoid is found
in clove.
Thymol (monoterpene phenol) and carvacrol is
* Antibacterial, inhibit Gram-positive bacteria better than Gramnegative bacteria and have broad-spectrum activity.
* Expectorant, antimicrobial, anthelmintic, antispasmodic and antifungal.
* Dermal and mucous membrane irritant, needs careful use: tincture is safer.
How are they understood as functional groups - Phenylpropanoids and Phenolic Ethers?
Phenylpropanoids - Saffrole in sassafras: isolated it is irritant and toxic.
Myristicin in nutmeg, black pepper, carrot, parsley and dill, toxic in high doses, inducing nausea, delirium and hallucinations.
Phenolic ethers - Contain an oxygen atom between carbon and the benzene ring.
Anethole found in aniseed and fennel
How are they understood as functional groups - Oxide volatile oils?
- Oxide volatile oils - An oxidised derivative of other monoterpene compounds, e.g. cineole and ascaridole.
- Cineole (1.8- cineole or eucalyptol) - Major constituent of eucalyptus and rosemary. Expectorant and mucolytic. Active against E. coli and grampositive organisms, antifungal. Cytotoxic against human cancer cells (liver, breast)
- Eucalyptus oil - Cineole-rich oils are preferred where the expectorant property is needed.
Activity against several organisms for upper respiratory tract infections. Immune stimulatory, antiinflammatory, antioxidant,
analgesic, and spasmolytic.
How are they understood as functional groups - Ketones?
- More active and toxic than alcohol.
- Wound-healing, mucolytic, antibacterial, cholagogue and choleretic.
- Camphor - Topically antipruritic and anti-infective.
Monocyclic terpene ketones include
Menthone, carvone, piperitone
Pulegone (+)-pulegone, from pennyroyal - Repels mosquitos and fleas. Highly toxic to cats. Emmenagogue and possible abortifacient.
Large doses can be hepatotoxic and fatal if taken internally.
Diosphenol in buchu
Thujone - Neurotoxic (only small amounts present in absinthe.) Antimicrobial, anthelmintic and insecticidal; convulsions from high doses in vivo. Toxic and contraindicated in pregnancy. Non-toxic ketones include carvone in caraway seed, Carum carvi and spearmint.
How are the understood as functional groups - Ester Volatile oils?
- Contain two oxygens attached to a carbon,
- Lavender oil - Contains linalool and ester linalyl acetate. Most esters are gentle, nonirritant, sedative and antispasmodic, for example lavender, roman chamomile and bitter orange oils.
- Linalool (in vivo) - Affects autonomic nervous system, stimulating parasympathetic gastric nerve while inhibiting sympathetic innervation of adrenal glands and adipose tissue.
- Methyl salicylates - Found in wintergreen. Esters (important in the flavour): stimulant, carminative and stomachic. Induces phase II liver enzymes responsible for detoxifying carcinogens. Used clinically to dissolve cholesterolcontaining gallstones, reducegastric
hyperacidity in GORD and support intestinal peristalsis. - (+)-limonene - Peel with the outer rind for cancerpreventative effects along with other monoterpenes and flavonoids.
