One of the world’s oldest healers, confirmed by modern science for its prevention of infection and indigestion and used as an essential oil in aromatherapy.

1. Introduction
Cinnamomum zeylanicum, commonly known as cinnamon, cassia, Ceylon cinnamon and Saigon cinnamon is a spice belonging to the Lauraceae family (1). Cinnamon oil is available from both the bark and the leaf via water or steam distillation (14).

2. History
Cinnamon has been continually used since ancient times, and was one of the oldest and most valuable items in the spice trade (10,14,13). Cinnamon grew originally in southern Asia, namely Ceylon (now Sri Lanka) (14). Ancient Chinese herbals mention it as early as 2700 B.C. as a treatment for fever, diarrhoea, and menstrual problems. It was used in a similar way by India’s ancient Ayurvedic healers (1). In traditional Chinese medicine, cinnamon was seen as a cure-all and most recipes include cinnamon. It was used as a nerve tranquilliser and tonic, and considered good for depression and a weak heart (14).

The spice is mentioned in the bible on several occasions and was included in the holy ointment of Moses (10). In Exodus, God told Moses to take myrrh, cinnamon, olive oil and bulrushes with him from Egypt (14).
The Egyptians used cinnamon as a medicine and as incense and in their ever-popular ‘kyphi’, a blend of 16 aromatic compounds (6,10,12). It was added to the embalming mixtures for the mummification process by the Egyptians (1,10,14) as well as used to minimise the outbreak of epidemics (14). The spice was also considered valuable enough to be presented to the temple as a gift (10).

The Arab traders, who kept its origins a secret, (6,10,14,16) supplied the spice to the Greeks and Romans (14). The Arabs valued cinnamon as they considered it to be a symbol of wealth and they used to anoint the sacred vessels used in their religious ceremonies (10). The Greeks came to value cinnamon for its stomachic and antiseptic properties (13). In ancient Rome, mourners’ burnt cinnamon in funeral pyres in order to cover the scent of burning flesh (16) and it was also included in their famous perfume ‘Susinum’ (13).

Most often, however, the spice found its primary use as an additive to food, and in the Middle Ages it was a status symbol of Europe’s elite (16). Those who could obtain cinnamon used it in Hippocras (a tonic drink made of sugared wine in which cinnamon, ginger and cloves have been infused), pastries and curing meats (7).
The quest for the coveted cinnamon was pursued so enthusiastically that it was the principal incentive of the Portuguese in discovering the route around the Cape to India and Ceylon. The Dutch, who took control of Ceylon in the mid-seventeenth century, monopolised the cinnamon trade for over 150 years (14).

In 1796, the English arrived on Ceylon, thereby displacing the Dutch from their control of the cinnamon monopoly. By the middle of the nineteenth century, the market in Europe was larger and more democratic than it had been in the Middle Ages, when only the ruling elite could afford spices in large quantities. Production of cinnamon reached 1000 tonnes a year, after a lower grade quality of the spice became acceptable to European tastes. By that time cinnamon was being grown in other parts of the Indian Ocean region and in the West Indies, Brazil and Guyana. Not only was a monopoly of cinnamon becoming impossible, but the spice trade overall was diminishing in economic potential. Eventually coffee, tea, chocolate and sugar dominated cinnamon and other spices in the European market (16).

3. Distribution
The Cinnamon is a tree growing in tropical regions. Several species of Cinnamomum provide commercial cinnamon, but the best comes from the Ceylon Cinnamon tree: Cinnamomum zeylanicum. A native of China, Western India and Sri Lanka, the Cinnamon tree was introduced into several tropical countries, including Madagascar, the West Indies, Malaysia (11), the East Indies, the Antilles and Java (7). Despite the many places cinnamon may be obtained from, the most sought after bark comes from Sri Lankan plantations (11).

4. Description
The Cinnamomum zeylanicum tree is a tropical evergreen that grows up to 15 metres high, with strong branches and thick scabrous bark with young shoots speckled greeny-orange (2). When the trees are six to eight years old, the bark is removed in long strips and left to dry in the hot sun. These strips are rolled into tubes, the ‘quills’ familiar as the culinary spice (14).
Cultivation demands a great deal of rain, light, rich soil and a high temperature of around 25oC on average. Gathering takes place in winter with the increase in atmospheric moisture and increased sap production allowing easier decortication(11).
Commonly, the cuttings, chips or broken twigs/inner bark are used for distillation with a yield of 0.6% (volume) of volatile oil. The leaves can also be distilled and provide a volatile oil yield in excess of 1.8% (volume), but they provide a very different essential oil from the bark (11), which can be seen in the next section titled Chemical compounds.
The following pictures are of the Cinnamomum zeylanicum plant (17).

5. Chemical compounds
The main constituents are generally linalool, benzaldehyde, cinnamic aldehyde, eugenol, pinene (terpene) and benzyl benzoate (7,13,14,18). The list below demonstrates the difference in the chemical composition of the essential oils obtained from the bark and the leaf of the Cinnamomum zeylanicum tree (18).

Main component, %
Bark Leaf
-pinene 0.2-0.6 0.2-1.0
-cymene 0.6-1.2 0.4-1.2
Cinnamaldehyde 74-75 1.3-2.0
Eugenol 0.8 70-96
Cinnamyl acetate 5.0 0.8-1.7
Caryophyllene 1.4-3.3 1.9-5.8
Benzyl benzoate 0.7-1.0 2.7-3.5

By looking at the chemical compositions of the two oils in this table we can see that the two compounds that stand out are Cinnamaldehyde and Eugenol, with the bark oil containing a higher percentage of the former compound and the leaf oil containing a higher percentage of the latter compound. This is actually what gives the oils their slightly differing properties, as can be seen later on.

6. Toxicology
According to Michael Castleman (1991), author of ‘The Healing Herbs’, in its powdered form culinary amounts of cinnamon are non-toxic, though allergic reactions are possible and that cinnamon oil may cause redness and burning on the skin. Used internally, it can cause nausea, vomiting, and possibly kidney damage. He advises not to ingest cinnamon oil (1). Interestingly enough, Schnaubelt (5) suggests that whilst cinnamon bark and cinnamon leaf are strong allergenic agents, and have been found to provoke skin sensitisation in approximately 5% of the population when topically applied, it is preferable that these oils are used internally as they are less problematic (5).

In other readings it has been suggested that cinnamon bark oil is a dermal toxin, irritant and sensitiser and should never be used on the skin (2,14). Tisserand (13) also states that cinnamon (though does not distinguish between the bark or leaf) oil should not at all be used on the skin. The compound that causes skin sensitisation and irritation is cinnamic aldehyde (5) and since the bark oil contains a very high percentage of this compound it renders the oil unfriendly to the skin.
Tisserand and Balacs (9) state that d-limonene and eugenol appear to reduce the skin sensitisation caused by cinnamic aldehyde. This may indicate that they act as quenchers (Personal opinion). They also reported that undiluted cinnamon oil (type unspecified) has caused severe burns in an 11-year-old boy after remaining in contact with the skin for 48 hours, after a vial broke in his trouser pocket. They also go on to say that if cinnamon bark were used externally, a maximum use level of 0.1% would be recommended. Oral use might be feasible, but only if the oil is well tolerated (9).

Lawless (2) and Battaglia (14) also suggest that cinnamon leaf oil is relatively non-toxic. Lawless goes on to state that it may be a possible irritant due to the cinnamic aldehyde content (2).

Tisserand and Balacs (9) reported that eugenol has been shown to cause liver damage in mice whose livers have been depleted of glutathione and recommend that people with impaired liver function do not ingest cinnamon leaf oil. They have also reported that eugenol has anti-platelet activity due to an anti-prostaglandin action. Therefore, they suggest that people with blood-clotting disorders and those taking anticoagulant drugs should avoid eugenol rich essential oils, with cinnamon leaf being one of them. Tisserand and Balacs (9) have also found that when tested at 10% (w/w), cinnamon leaf oil produced no irritation in a closed-patch test on human subjects. Lawless (2) suggests avoiding cinnamon leaf oil during pregnancy.
Both cinnamon leaf and cinnamon bark oils are reported to be mucous membrane irritants (2,9).

LD50: Cinnamon leaf oil – 2.7g/kg (oral) rat; >5g/kg (dermal) rabbit.
Cinnamon bark oil – 3.4g/kg (oral) rat; >0.7g/kg (dermal) rabbit. (18)
The LD50 levels for oral and dermal tolerance suggest that cinnamon bark oil is better tolerated for indications where ingestion of cinnamon is required and that the cinnamon leaf oil is better for topical applications.

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