Volatile Oils Composition and Terpenoid Removal

Study Notes

Volatile oils are complex mixtures of organic compounds.
The main categories of compounds include hydrocarbons, oxygenated compounds, aromatic benzenoids, and compounds containing sulfur or nitrogen.
Oxygenated compounds are responsible for the characteristic odor of volatile oils.

Volatile oils with high percentages of terpenoids are prone to rapid deterioration due to oxidation and polymerization.
This deterioration results in a turpentine-like odor and decreased aroma.
The terpenoid hydrocarbons are less soluble in low-strength alcohols and readily resinify.
Terpeneless oils are more stable, more soluble in low-strength alcohols, and require smaller amounts to achieve the same aroma strength.
The process of removing terpenoid hydrocarbons is expensive.
Several methods for removing terpenoid hydrocarbons include fractional distillation under reduced pressure, column chromatography on silica gel, and selective extraction with dilute alcohol followed by distillation.

Hydrocarbons are unoxygenated constituents found in volatile oils.
They are mainly classified as acyclic mono- and sesquiterpenoids, alicyclic mono- and sesquiterpenoids, and aromatic hydrocarbons.

Acyclic Monoterpenoid Hydrocarbons:
- Myrecene is found in oils of hops and bay.
- Ocimene is present in basil oil.
Acyclic Sesquiterpenoid Hydrocarbons:
- Farnesene is found in citronella oil and is considered the sesquiterpene analogue of myrecene.
- Sesquicitronellene is another example of an acyclic sesquiterpenoid hydrocarbon.

Monoterpenes:
- Monocyclic monoterpenoid hydrocarbons include limonene, dipentene, and p-cymene.
- Bicyclic monoterpenoid hydrocarbons include various derivatives based on carane, pinane, bornane, and thujane.
Sesquiterpenes:
- Monocyclic sesquiterpenoid hydrocarbons include zingiberene, which is the main constituent of ginger oil.
- Bicyclic sesquiterpenoid hydrocarbons include cadalene and β-cadinene.
- Tricyclic sesquiterpenoid hydrocarbons include santalene, found in sandalwood oil.

d-Limonene: Present in citrus oils such as orange, lime, grapefruit, bitter orange, mandarin, and bergamot oils.
l-Limonene: Found in turpentine oil.
Dipentene: A racemic form of limonene found in turpentine oil, lemon grass, pepper, nutmeg, neroli, fennel, and turpentine.
Uses of Limonene and Dipentene:
- Flavoring agents for cosmetics, soaps, and pharmaceuticals.
- Substitutes for orange oil preparation.
- Antiflatulence and antispasmodic properties when used with other volatile oil constituents.
Toxicity: Skin irritant and sensitizer.

Parent Classes:
- Carane, Pinane, Bornane, Fenchane, Thujane (Camphane).
Derivatives:
- Sabinene: Found in savin oil.
- α- and β-Pinenes: Major components of turpentine oil.
- Derivatives of Pharmaceutical Importance:
  - Sobrerol (Pinol Hydrate): A mucolytic agent used in cough mixtures formed by auto-oxidation of α-pinene.
  - α-Pinene: Incorporated in Bilichol cap for bile therapy and acts as a cholagogue.

p-Cymene:
- Found in a variety of essential oils, including lemon, sage, thyme, oregano, lavender, nutmeg, and cinnamon.
- Often an artifact formed during hydro distillation.
- Prepared by fractional steam distillation.
- Used for scenting soaps.
Azulene Derivatives:
- Highly conjugated, colored compounds found in pigments of mushrooms, guaiac wood oil, and marine organisms.
- Occur as colorless precursors called pro-azulenes.
- Isolated through adduct formation with mineral acids.
- Exhibit anti-inflammatory and anti-ulcerative effects.
Chamazulene:
- Found in chamomile oil.
- Contributes to the blue color of chamomile oil.
- Used in cosmetics as an anti-inflammatory and mild antiulcerative agent.
- Chamomile oil is used for gastrointestinal disturbances and has spasmolytic properties.
Guaiazulene:
- Found in guaiacum wood oil.
- Formed by dehydrogenation of guaiacum wood oil.

Chamazulene is used in cosmetic preparations for its anti-inflammatory and mild antiulcerative properties.
Chamomile oil is used for managing gastrointestinal disturbances and possesses spasmolytic properties.
The ulcer-protective effects of chamomile oil are primarily attributed to its bisabolol and bisabolol oxide content.