Terpenoids

Question 1

What are terpenoids (terpenes?)

Answer 1

Terpenoids (terpenes)
* First identified in turpentine (distilled pine oleoresin).
* A large group of compounds
* Oil- and/or alcohol-soluble: many are found in essential oils, resins and oleoresins.
* There are also some which are water soluble: saponins (triterpene and steroidal glycosides).

Question 2

Whay are they so named?

Answer 2

Naming of terpenoids is based on multiples of 10 carbons (this is the same of two isoprene units, a breakdown of terpenoids).
* Monoterpenes (C10H16), two 5-carbon units for example, limonene, geraniol, borneol and thujone.
* Sesquiterpenes (sesqui = 1 ½), bisabolol.
* Diterpenes (di = two sets of ten), resins as resin acids.
* Triterpenes (tri = 3 sets of tens), saponins.
* Tetraterpenes, carotenoids.
* Plant steroids, phytosterols derived from terpenoid precursors.

Question 3

What are their metabolic pathways?

Answer 3

Terpenoid metabolic pathways
* Mevalonate (MVA) pathway
* Methylerythritol
4-phosphate (MEP) pathway

Question 4

How are they found in essential oils?

Answer 4

Essential oils
* Usually contain mono- and sesquiterpenes.
* Not all mono- and sesquiterpenes are volatile in steam:
* For example the iridoids, sesquiterpene lactones, irregular monoterpenes.
* Essential oils are often isomers - mirror image of each other but different biological function.
* (+)-carvone smells of caraway.
* (-)-carvone smells of spearmint.
* Also some phenylpropanoids (polyphenols): eugenol in clove and cinnamaldehyde from cinnamon.

Variation
* Essential oil concentration and composition can vary in the same plant - depending on the season, time of day, growing conditions, geographic and genetic factors. So can have very different actions!
* Distinct chemotypes eg Thymus vulgaris ct (chemotype) linalool, Thymus vulgaris ct thymol
* The total essential oil content of plants is less than 1%

Question 5

How do you extract them?

Answer 5

• Distillation
• Expression
• Solvent extraction
• Enfleurage

Question 6

What is their antiseptic activity?

Answer 6

• Many essential oils have antiseptic/antimicrobial activity
• They usually don’t have a specific cellular targets.
• Range of volatile constituents in one plant cuts microbial resistance
• Lipophilic: so they can penetrate and disrupt cell membranes.
• Damage to cell wall and membrane leads to leakage of macromolecules and lysis

Question 7

How are they used for antimicrobials, anti fungals or antivirals?

Answer 7

Antimicrobial/antifungal constituents
* Tea tree essential oil is bactericidal and antifungal.
* Lemon grass, some Thymus species
* Linalool, antibacterial.
* Citral and geraniol, antifungal.

Carvacrol can be used as an antiviral
* Effective against herpes simplex virus
and enveloped viruses.
* Essential oil affects the viability of
the free virus, probably by interfering with the envelope.

Question 8

How are they used for UTIs?

Answer 8

Internal use of juniper and buchu for UTIs
* EOs: antimicrobial effects in the body.
* Infusion and essential oil of juniper berries as well as terpinen-4-ol in vivo: initial antidiuretic effect, but diuretic after repeated doses.
* Terpenes are used orally, as have some promise in dissolving small kidney stones.
* No nephrotoxic effects provided high quality oil is used.
* Metabolised forms excreted in urine.

Question 9

How are they used for gut parasites?

Answer 9

• Oregano oil has been used for gut parasites
• Oil of oregano (orally) subjects with a positive stool test for certain parasites in intestines,
  Blastocystis hominis, Entamoeba hartmanni and Endolimax nana: reduction in pathogens and improvement in gastrointestinal symptoms.

Question 10

How are they used as antispasmodics?

Answer 10

• Many have spasmolytic and carminative activity
• Relaxant effects in functional gastrointestinal problems and tracheal smooth muscle in vivo for example Angelica archangelica root, clove and elecampane root.
• Some EOs can be used as carminatives: they relax sphincters and assist in the expulsion of intestinal gas and have spasmolytic activity
• Peppermint essential oil, spasmolytic activity confirmed clinically and is used irritable bowel syndrome
• Care needs to be taken as it

Question 11

How are they used as analgesics?

Answer 11

Analgesic
* Analgesic effects: chemical diversity of
essential oils, different mechanisms of action.
* Topical peppermint oil or menthol: Activation of sensory neurons, affects GABA receptors and sodium ion channels resulting in analgesia.
* Rosemary essential oil beneficial in the
management of pain, in combination with analgesic drugs.
* Also clove oil for tooth pain - rub on your gums

Question 12

How are they used as expectorants?

Answer 12

Expectorants
* Certain essential oils and herbs rich
in essential oils are expectorants.
* Biphasic effect: high concentrations
of essential oils suppressed
respiratory tract fluid and mucin
release
* Whereas lower doses (on the
threshold of detection by the nose)
had a pronounced stimulatory effect.

Question 13

What interesting research has there been?

Answer 13

Clinical trial with myrtol
Pine, Pinus species, lime, Citrus aurantifolia
and Eucalyptus globulus, monoterpenes (+)-
α-pinene, d-limonene and 1,8-cineole.
* Found to be expectorant, mucolytic antioxidative, antiinflammatory, antibacterial and bronchospasmolytic.
* Improved mucociliary clearance in
patients with COAD (COPD?)
* Useful for acute and chronic infections of
the upper and lower respiratory system.

Lavender as a relaxing and sedative EO
* Lavender EO inhalations and herb infusions enhance sleep, decrease anxiety and improve cognition.
* Clinically effective in sub-threshold anxiety disorder.
* Clinical trial, 1,8-Cineole (Eucalyptus spp., tea tree and sage, Salvia lavandulifolia) also anxiolytic.
* Linalool in vivo stimulated the parasympathetic gastric nerve, inhibiting sympathetic innervation of the adrenal
glands and adipose tissue, suppressing breakdown of lipids and enhancing appetite.

Nervous system: sedative versus stimulant
* Stimulant activity: rosemary EO increased locomotor
activity in vivo.
* Lavender and rosemary EO: Reduced test-taking stress. More alert, working faster on maths test.
* Lavender: increased beta power, suggesting
drowsiness, less depressed, reported feeling
relaxed, maths computations faster and more
accurate.
* Rosemary: decreased frontal alpha and beta
power, suggesting increased alertness, lower
state anxiety scores, reported feeling relaxed,
alert; faster but not more accurate.”