1 The lavenders (true, lavandin and spike) (Figs. 7.3, 7.4, 7.5)

Figure 7.3 Lavender. A good-quality French lavender, true lavender Lavandula angustifolia. This shows a high linalyl acetate content (33.29%) and low camphor content (0.21%). This oil would meet the ISO standards.

Courtesy of Jenny Warden, Traceability.

Figure 7.4 Lavender. This shows the GC analysis for spike lavender (Lavandula latifolia). The camphor level is high and that of linalyl acetate is low.

Courtesy of Jenny Warden, Traceability.

Figure 7.5 Lavender. Analysis of Lavandula hybrida, showing a composition that is intermediate between the true lavender and spike lavender.

Courtesy of Jenny Warden, Traceability.

Lavender is a long-established essential oil, with a legendary folk tradition. The use of ‘just lavender’ is very misleading. The true lavender is from Lavandula angustifolia (also called Lavandula officinalis, Lavandula vera). This is divided into other subspecies Lavandula delphinensis and Lavandula fragrans. Lavandula angustifolia Miller is a lavender grown in France and is the only one recognized in the French Pharmacopoeia. Combined with the existence of many chemotypes, this gives an indication of the many possibilities for variation in the oil.

True lavender species grow at high altitudes (above 600 metres) on dry, limey soil from plants distinguished by small flower heads and no side shoots from the main stem.

Spike lavender comes from the Lavandula latifolia or Lavandula spica species. These grow at much lower altitudes, are easier and cheaper to cultivate and give high yields of oil. The main country of origin is Spain.

Lavandin is produced by a hybrid plant Lavandula intermedia or Lavandula hybrida, which was bred by crossing the true lavender (Lavandula angustifolia) with spike lavender (Lavandula latifolia). Lavandin is sometimes called ‘bastard lavender’. Hybrids are widespread in horticulture, where they are bred to produce plants with the desired properties of the parents. The lavandin plants are easier to grow at lower altitudes (400–600 metres), yielding almost twice as much oil as the true lavender plant. Again, this is economically favourable and lavandin essential oil is particularly useful for the cosmetic and fragrance industries.

Chemically, all forms contain linalyl acetate, linalool and 1,8-cineole, along with many other compounds. Further analysis of each type reveals their differences in amounts of chemical components. The situation is illustrated by comparing published data for principal constituents and then seeing how these are reinforced by an actual GC chromatogram. This is shown in Table 7.1; the main figure is the published data while figures in brackets are those taken from the GC analysis of actual oil samples (cis– and trans-ocimene are minor hydrocarbon components, but are included as they are often used as markers for the authenticity of lavender oils). In all cases the amounts of compounds in the hybrid (Lavandula intermedia) are in between those of the true (Lavandula angustifolia) and the spike (Lavandula latifolia).

Table 7.1 Composition data (%) for lavender oil

The true lavender (Lavandula officinalis) shown in the chromatogram is high in linalyl acetate, conforming to the ISO standard composition range of 25–45% and linalool ISO standard of 25–38%. True lavenders also may have between 5% and 30% lavandulyl acetate; the GC for this sample shows quite a low value of 3.55%. Also characteristic of true lavender, the amounts of camphor and the oxide 1,8-cineole are low, but are increased in the other species. High ester and alcohol content makes this a desirable aromatherapy choice as it is gentle with no known contraindications.

For the spike (Lavandula latifolia) lavender the analysis shows a much lower acetate content and a high natural camphor and 1,8-cineole level. This makes it useful for respiratory infections, as an insecticide and for muscular pain. However, it must be used cautiously as it is a more vigorous oil.

The hybrid (Lavandula intermedia) lavender shows an intermediate composition between the true and spike for all major components. Ester content is lower and camphor content higher than in the true lavender. It is generally considered to be an inferior essential oil as it was initially bred for the perfumery industry. However, it has been attributed with many therapeutic applications with rare contraindications when used correctly.

Another type of lavender, Lavandula stoechas, is less commonly encountered. It has a very high camphor content (15–30%), which necessitates cautious handling. Its main component is fenchone (45–50%), a terpenoid ketone, which, although a ketone, is considered nontoxic, nonirritant and nonsensitizing.

2 Clary Sage (Salvia sclarea)

Several different chemotypes occur according to their geographical region of growth. They are mainly Mediterranean regions but also USA, Russia, Morocco and France. The essential oil has a heavy fragrance with herbal and nutty tones and pale green/yellow to clear colour. The odour can be attributed to the major component the ester linalyl acetate that can be present as up to 75% of the total composition. Also present alcohol linalool (up to 26%), terpenes β-caryophyllene (up to 3%), germacrene (up to 4%), neryl acetate (up to 1.7%). Box 7.1 shows a certificate of analysis which gives a more comprehensive insight to the chemical composition. Therapeutic applications are linked to antidepressive, spirit lifting and creative stimulating actions on the mind. Reputed to act as an antispasmodic and emmenagogue, and promoting the female hormone oestrogen it is used to ease PMS (pre-menstrual syndrome) and encourage and ease labour. Also used for respiratory conditions including asthma and for a range of skin conditions associated with greasy complexions such as acne, boils and dandruff. Although considered to be nontoxic, nonirritant and nonsensitizing it should be avoided during pregnancy.

3 Marjoram (Origanum marjorana)

Sweet marjoram is a pale yellow oil with a warm, camphoraceous and spicy odour. Its main components are alcohols terpinen-1-ol-4 (14–20%), thujan-4-ol (4–13%), linalool (2–10%), α–terpineol (7–27%), hydrocarbon monoterpenes sabinene (2–10%) β-myrcene (1–9%), β-terpinolene (1–7%), α-pinene (1–5%), α–terpinene (6–8%), ester geranyl acetate (1–7%) and aldehyde citral (4–6%). Box 7.2 shows a GC analysis report. A versatile oil with many claimed therapeutic properties. Often called a comforting oil. Applied to the mind in situations of stress and grief where it calms and relaxes. For the body it is considered warming, analgesic, and antispasmodic suitable for muscle and joint pains. Also acting on the respiratory system for asthma and bronchitis, on the digestive system as a carmative relieving cholics and constipation and in skincare for bruising and chilblains. Considered a safe nontoxic, nonirritating and nonsensitizing essential oil but should be avoided during pregnancy.

4 Rosemary (Rosmarinus officinalis)

Figure 7.6 Typical supplier’s GC analysis data. Rosemary. Analysis of Rosmarinus officinalis.

Courtesy of Jasbir Chana, Phoenix Natural Products Ltd.

Rosemary has been used for a long time with extensive applications for culinary and medical purposes. Rosmarinus officinalis is the species used for the production of the essential oil.

Typically listed chemical components are:

There are three principal chemotypes: verbenone, 1,8-cineole and camphor-borneol. These are examples of variation due to the climate they are grown in and are also called cultivars. The names of the cultivars are not Latinized and appear after the species name, often within quotation marks. For example, Lavandula angustifolia ‘Maillette’ is a type of lavender named after its originator. For rosemary the cultivars are named after their country of origin. As a consequence of this, the verbenone is also called French, the 1,8-cineole is called Tunisian and the camphor-borneol is called Spanish. A comparison of these in terms of their amounts of main components is shown in Table 7.2.

Table 7.2 Main components (%) of three cultivars of Rosmarinus officinalis

The essential oil has many beneficial effects and applications in aromatherapy for skin and hair care, as an antirheumatic, antispasmodic and calmative, for complaints of the respiratory, circulatory and digestive systems and for nervous disorders. The camphor type is best suited to the musculoskeletal system, and the 1,8-cineole for pulmonary congestion and efficient functioning of the liver and kidneys, with the verbenone being a safe nonirritant essential oil for skin and hair treatments.

Rosmarinus officinalis essential oil is usually regarded as nontoxic, nonsensitizing and nonirritant when used in sufficient dilution. It may cause dermatitis in hypersensitive individuals and there is some evidence to suggest it should not be used during pregnancy, by epileptics, or by those with high blood pressure. A material safety data sheet from an oil supplier (Box 7.3) shows the type of information available for a Spanish Rosmarinus officinalis. The sample conforms to the data in the table for the Spanish but also has compounds that would fit the ranges given for Tunisian.

Figure 5.6 also shows an IR spectral analysis of Rosmarinus officinalis.

5 Thyme (Thymus vulgaris)

The main species are believed to originate from the wild type Thymus serphyllum, with the majority of oils coming from the Thymus vulgaris or common thyme species. However, there are over 150 species of the genus Thymus including Thymus vulgaris (common or red), Thymus zygis (Spanish), Thymus serphyllum (wild), Thymus mastichina (Spanish marjoram) and Thymus capitatus (Spanish oregano). Thyme belongs to the plant family Labiatae, whose members are easily hybridized: that is, there is interbreeding of different species, making it difficult to define species and subspecies. Exact botanical classification of the essential oil is also difficult and there are wide variations and conflicting data on the constituents for each species depending on the source of the information. Coupled with the fact that thyme is probably the aromatic plant with the most diverse range of chemotypes, these factors contribute to a very complex and often contradictory situation for these essential oils.

White thyme is not complete or natural, but is usually an adulterated and compounded oil made up of fractions of pine oils, rosemary, eucalyptus and red thyme, or it may be origanum with p-cymene, pinene, limonene and caryophyllene.

When considering the composition of the natural, whole essential oils, the environment the plants are grown in is an important factor in determining the chemical composition. Altitude is a significant factor in determination of chemotype. In general the gentler, alcohol chemotypes high in linalool, geraniol, thujanol-4 and α-terpineol are associated with growth at altitudes between 1000 and 1200 metres. They are called sweet thymes and owing to their high alcohol content are generally considered safe to use in a variety of conditions. This is in contrast to the phenolic chemotypes high in compounds such as carvacrol and thymol. These are called red thymes, and are extracted from plants growing at lower altitudes, usually close to the Mediterranean sea. The phenolics act as powerful antiseptics and need to be used with extreme care as they may cause skin irritation.

A ‘typical’ analysis of major components of these contrasting chemotypes for T. vulgaris shows this difference (Table 7.3). Typical analysis is again difficult to define, so ‘representative’ analysis might be a better description.

Table 7.3 A representative analysis (%) of phenolic and alcohol chemotypes (CT) of Thymus vulgaris

There are many published therapeutic uses of the thyme oils. Linalool CT, with very low phenol content, is attributed properties such as reviving, strengthening nerves and aiding concentration by stimulation of the cerebral regions of the brain. It is considered to be an immuno-stimulant and safe for use with children. The high ester content also contributes to its application as an antispasmodic for dry coughs.

In contrast the thymol CT varies widely with the alcoholic CTs in both olfactory and therapeutic properties. Thymol CT is also attributed immuno- stimulant action but it is strongly antiseptic and is used for infectious conditions like colds, coughs and bronchitis. It is also recommended for its warming analgesic properties for treatment of rheumatism, arthritis and sciatica. It stimulates the digestive and cardiovascular systems and may help raise the blood pressure.

The GC analysis (Fig. 7.7) shows a commercial white thyme with a high percentage of the phenols thymol (55.8%) and carvacrol (2.07%). This contrasts with that of sweet thyme (Fig. 7.8) with no phenolic compounds present and alcohols terpineol-4 (13%), α-terpineol (12.37%) and borneol (5.95%) making up a total of 31.34% for this particular sample.

Figure 7.7 Thyme. A typical white Spanish thyme, showing the presence of thymol. Thymol has a retention time of 56.381 min and makes up 55.58% of the oil in this GC analysis of this particular sample.

Courtesy of Jenny Warden, Traceability.

Figure 7.8 Thyme. A typical sweet thyme, showing no thymol present.

Courtesy of Jenny Warden, Traceability.

6 Peppermint (Mentha piperita)

There are numerous species of mint including peppermint, Mentha piperita, spearmint, Mentha spicata, and cornmint, Mentha arvensis. Mentha piperita is actually a hybrid species bred from spearmint Mentha spicata and watermint Mentha aquatica. They all contain subspecies and chemotypes. Mints have a long tradition of culinary, fragrance, cosmetic and therapeutic applications.

Typical composition would be: menthol (27–51%), menthone (13–32%), isomenthone (2–10%), 1,8-cineole (5–14%), methyl acetate (2–4%), methofuran (2–12%), limonene (0.5–6%), pinenes (1.5–4%), germacrene (2.1–4.3%) and pulegone (0.1–1%). Box 7.4 shows a GC analysis for Mentha piperita.

Therapeutic uses are widespread as peppermint has a skin toning effect and is most effective for digestive disorders such as indigestion and flatulence; it stimulates cardiovascular and lymphatic systems, works on ligaments for joint and muscle pain and has local antiseptic properties.

Most aromatherapy books state that peppermint is nontoxic, nonirritant when diluted and possibly sensitizing owing to its menthol content. It is often advised to use it in moderation. However, it should be used with caution and is contraindicated for use with babies and young children. The high menthol content has been shown to cause breathing problems in infants. It is irritant to mucous membranes and may exacerbate skin irritations and contact dermatitis. External use necessitates a concentration of not more than 3%. Internal use should be under the direction of a qualified medical practitioner, medical herbalist or pharmacist and is beyond the scope of aromatherapy.