E. Cineole
Synonyms Eucalyptol; Cajeputol.
Chemical Structure 1, 8-Epoxy-p-menthane.
Occurrence It is the chief constituent of oil of eucalyptus obtained from the leaves of Eucalyptus globulus Labill (Family: Myrtaceae) and other species of Eucalyptus. It also occurs largely in a variety of plants, namely: Acorus calamus L., (Araceae); Aloysia triphylla Britton (Family: Verbenaceae)-Lemon Verbena; Artemisia vulgaris L., (Family: Asteraceae)-Mugwort, Carline Thistle; Chamaemelum nobile (L.) All (Family: Asteraceae)-Roman Camomile, English Camomile, Camomile, Cinnamomum verum J.S. Presl (Family: Lauraceae)-Ceylon Cinnamon; Crocus sativus
L., (Family: Iridaceae)-Saffron, Saffron crocus; Croton eleutheria Sw. (Family: Euphorbiaceae-Cascarilla; Illicium verum Hook. f. (Family: Magnoliaceae)-Star-Anise, Chinese Anise; Juniperus communis L. (Family: Cupressaceae)-Common Juniper; Juniperus sabina L. (Family Cupressaceae)-Sabine, Savin; Laurus nobilis L., (Family: Lauraceae)-Bay, Grecian Laurel, Green Bay; Melaleuca
leucadenron L. (Family: Myrtaceae)-Cajeput; Pimenta diocia (L.) Merr. (Family: Myrtaceae)-Allspice, Jamaica Pepper, Clove Pepper; Rosmarinus officinalis L. (Family: Lamiaceae)-Rosemary; Salvia sclarea L., Family: Lamiaceae)-Clary, Muscatel Sage; Tanecetum vulgare L., (Family: Asteraceae)-Tansy; Umbellularia californica (Hook and Arn.) Nutt.-California Bay, California Laurel, California Sassafras.
Isolation Cineole may be isolated from Eucalyptus oil, which contains this ingredient to the extent of 80% by any one of the following four methods, namely:
Method I: Fractional Distillation. It may be obtained from fractional distillation under vacuo and
the colourless liquid is collected over powdered anhydrous sodium sulphate. The clear oily substance is obtained finally in the pure crystalline form by chilling it (mp + 1.5°C).
Method II: Addition Products with Halogen Acids (HCl, HBr). It forms addition compounds with HCl and HBr as: C10H18O.HCl and C10H18O . HBr, from which the pure cincole may be regenerated conveniently.
Method III: Addition Product with Resorcinol. It forms an addition compound with 50% (w/v) solution of pure resorcinol as [(C10H18O)2.C6H6O2] having mp 80-85°C, from which cineole may be regenerated easily.
Note This reaction may eater for the separation of cineole from essential oils having a high cineole content (more than 50-60%), otherwise the volatile oil must first be fractionated.
Method IV: Addition Product with Phosphoric Acid. Cineole readily forms addition product with phosphoric acid as: [C10H18O.H3PO4] having mp 84°C, that may be decomposed by hot water.
Note This method is also utilized for the estimation of cineole in volatile oils in v/v percentage.
Characteristic Features It is a colourless liquid having a camphor-like odour. It possesses a spicy and cooling taste. Its physical characteristics are: d2525 0.921-0.923, bp 176-177°C, mp + 1.5°C, n20D 1.455-1.460, flash point (closed-up) 48°C. It is almost insoluble in water but miscible with alcohol,
chloroform, ether, glacial acetic acid and oils.
Cineole forms addition compounds with resorcinol and phosphoric acid, that are found to be fairly stable, having mp 80-85°C and 80°C respectively.
It is not attacked by ordinary reducing agents, such as: glucose etc.
Identification
1. Cineole may be characterized by a host of derivatives/addition compounds obtained from pure chemical substances, for instance: halogen acids, resorcinol, phosphoric acid, orthocresol etc.
2. Microchemical Test of Cineole: A drop of pure cineole or a drop of Eucalyptus oil or a few drops of an alcoholic extract of eucalyptus leaf, is made to react with a drop of 5% (w/v) solution of hydroquinone on a microscopic slide and subsequently examined under a low-power microscope one may observe either colourless prisms or rhomboid crystals.
However, an identical treatment with a 50% (w/v) solution of resorcinol gives rise to beautiful leaf-like crystals.
Uses
1. It is used quite extensively in pharmaceutical preparations both meant for internal and external utilities, such as:
Internal usage—as a stimulating expectorant in cases of chromic bronchitis
External usage—as a mild antiseptic, anaesthetic in cases of inflammatory conditions.
2. It is also employed in room-sprays, hand lotions and all types of cosmetic formulations.
3. It is invariably used as a pharmaceutical aid i.e., flavouring agent.
