Volatile Oils: Identification and Uses

• Volatile oils are also called ethereal or essential oils and are odorous principles in plants.
• Volatile oils evaporate at room temperature, are immiscible with water.
• Fresh volatile oils are colorless and oxidation and resinification occurs upon air exposure, leading to darkening.
• Store volatile oils in cool, dry places in tightly stoppered amber glass containers to prevent oxidation.

Biosynthesis

• Volatile oils are produced through the shikimic acid pathway or the acetate-mevalonic acid pathway.
• Shikimic acid pathway leads to aromatic amino acids like tyrosine and phenylalanine.
• Intermediates like gallic acid contribute to phenolic compounds.

Structures

• Glandular hairs are found in Lamiaceae.
• Modified parenchymal cells are found in Piperaceae.
• Oil tubes (vittae) are found in Apiaceae.
• Lysigenous or schizogenous cavities are found in Pinaceae and Rutaceae.

Chemical and Physical Properties

• High refractive indices and are often optically active.
• Classified as terpene derivatives or aromatic compounds based on their biosynthetic origin.
• Volatile oils have two portions: eleoptene (liquid, like eucalyptol or eugenol) and stearoptene (solid, like menthol or thymol).

Methods of Extraction

• Distillation through water, water and steam, or direct steam distillation.
• Expression involves mechanical extraction, especially for citrus oils.
• Ecuelle method involves puncturing oil glands in citrus fruits.
• Enfleurage uses fats to absorb oils from flower petals.
• Enzymatic hydrolysis releases glycosidic volatile oils like mustard oil.

Classes of Volatile Oils

• Hydrocarbon
• Alcohol
• Aldehyde
• Ketone
• Phenol
• Phenolic ether
• Oxide
• Ester

Hydrocarbon Volatile Oils

• Turpentine Oil or Spirits of Turpentine: volatile oil distilled from the oleoresin of Pinus palustris (Fam. Pinaceae) and other Pinus species.
• It yields terpene oils exclusively and is an odorless liquid which becomes disagreeable as the oil ages or is exposed to the air.
• Rectified Turpentine Oil: turpentine oil rectified by distillation from an aqueous solution of sodium hydroxide and is an expectorant.
• Terpin hydrate or terpinol: formed by nitric acid action on rectified turpentine oil in the presence of alcohol and used as an expectorant.
• Plant of origin is Pinus palustris.

Alcohol Volatile Oils

• Peppermint consists of the dried leaf and flowering top of Mentha piperita (Fam. Labiatae) and menthol.
• Peppermint Oil is the volatile oil distilled with steam from the fresh over ground parts of Mentha piperita (Fam. Labiatae), rectified by distillation and neither partially nor wholly dementholized.
• Peppermint is used as a flavor for confections.
• Japanese Peppermint oil or Mentha arvensis oil is obtained by steam, distillation where this oil is higher in menthol but inferior in flavor to peppermint oil and is solely a menthol source.
• Menthol or Menthan-3-ol is an alcohol from mint oils or prepared synthetically.
• It is used as topical antipruritic, counterirritant, antiseptic, and a stimulant.
• Plant of origin is Mentha arvenis, when applied at 0.1-1% dilates the blood vessel and when taken in small doses as a carminative.

Aldehyde Volatile Oils

• Cinnamon or Saigon cinnamon is from Cinnamomum loureirii (Fam. Lauraceae) or from the dried bark of Cinnamon where its oil is used as in flavoring and also carminative, pungent aromatic and has antiseptic properties:
• Lemon Peel is the fruit of Citrus limon and its peel the outer yellow rind, and is used as a flavoring agent, a stimulant, and a stomachic.

Ketone Volatile Oils

• Ketones occurring in volatile oils may be divided into monocyclic terpene ketones (menthone, carvone, pipertone, pulegone, and Diosphenol).
• Dicyclic Ketones - camphor, fenchone, thujone.
• Camphor is a ketone obtained from Cinnamomum camphora (Fam Lauraceae) or produced synthetically.
• It is a topical antipruritic, rubefacient, and anti-infective employed at 1 to 3% in preparations for use on the skin.
• Spearmint - consists of the drief leaf and flowering top of Mentha spicata (common spearmint) or M. cardiaca (Scotch spearmint) (Fam Labiatae).
• Spearmint is a flavor and is known for its carminative properties
• Spearmint Oil - A flavor known for its carminative properties that is used to a considerable extent in the chewing gum industry

Phenol Volatile Oils

• Thymol is a phenol obtained from thyme oil from Thymus vugaris or other plant oils, where the oil is an antifungal and antibacterial agent at 0.1 to 1%.
• SN: Thymus vulgaris (thyme); Monarda punetata (horsemint); Monarda didyma (tea); Carum copticum (ajowan)
• Clove is the dried flower bud, Eugenia caryophyllus and its components eugenol acetatem and B-caryophyllen are known for their properties.
• Clove oil is also used as a toothache remedy given it possess antiseptic, counterirritant, and carminative properties
• Eugenol or 4-allyl-2- methoxyphenol - a dental analgesic applied topically to dental cavities.

Phenolic Ether Volatile Oils

• Nutmeg is the dried, ripe seed of Myristica fragrans that is deprived of its seed coat and is useful that is a useful agent for controlling diarrhea associated with certain carcinomas.
• Nutmeg Oil is from Myristica fragrans and is a flavoring agent known for its properties.

Oxide Volatile Oils

• Eucalyptus oil is a dried, scythe-shaped leaf of Eucalyptus globules and the oil it carries has a characteristic aromatic, somewhat camphoraceous odor and a pungent, spicy, cooling taste.
• Eucalyptus oil is a flavoring agent often used as an antiseptic, diaphoretic, and expectorant.
• Cineole or eucalyptol is from eucalyptus oil and is a flavoring agent with similar properties to eucalyptus oil.

Ester Volatile Oils

• Gaultheria Oil: is a consists of the dried leaves of Gaultheria procumbens
• Methyl Salicylate- the pharmaceutic found with gaultheria oil, wintergreen oil, betula oil, or sweet birch oil

Test your knowledge of volatile oils, their sources (like Pinus palustris and Mentha piperita), and their uses. Questions cover distinguishing characteristics, chemical classes (like menthol), storage conditions, and biosynthetic pathways related to volatile oil production.