Lavender: Lavandula angustifolia Mill. and Lavandula pedunculata (Mill.) Cav.
By Samantha Frangos
Lavandula angustifolia Mill. and Lavandula pedunculata (Mill.) Cav. (Lamiaceae) can be found in the medicinal herb spiral of the Mecklenburgh Square Garden. Commonly known as lavender, these species are renowned for the production of lavender essential oil used in aromatherapy, perfumes, cosmetics, food processing and medicines. Lavender’s traditional uses largely influence scientific and medical research today. Historical and anecdotal uses of lavender across England and Europe include scents for linens, headache relief and antimicrobial applications. The known active constituents and possible mechanisms of action are explored in vivo and in vitro, as well as lavender’s efficacy as an aromatherapeutic agent. The unmistakable aroma of lavender’s essential oil is largely used today for the relief of anxiety, restlessness and irritability.
Lavandula angustifolia Mill. Lavandula angustifolia Mill. Lavandula pedunculata (Mill.) commons.wikimedia.org
There are 32 known species of Lavandula grown around the world (Lis-Balchin, 2003). Two of these types of lavender can be seen on the lower level of the medicinal herb spiral in the Mecklenburgh Square Garden, located in the north-east corner. These are Lavandula angustifolia Mill. and Lavandula pedunculata (Mill.) Cav., (a subspecies of Lavandula stoechas L.); English lavender and Spanish Lavender respectively. The genus Lavandula falls within the Lamiaceae, or mint family. Lavender is a shrub-like plant that grows 1-3 feet high and flowers during the spring and summer, but its leaves remain a silver- green year-round (Royal Horticultural Society [RHS], 2015). Both species have purple flowers growing at the end of long stems. Spanish lavender can be differentiated from English lavender by its small violet flowers with long tufts of bright colored petals at the end of the stalk. It is for this reason that L. pedunculata, is generally grown as an ornamental plant (McCoy, 2007). Lavender is native to the mountains of southern Europe, making it hardy and easy to grow in gravel gardens (Adam, 2006). Therefore, the rock spiral in the garden makes for the perfect location to grow these two lavender species. Spanish Lavender is not as hardy as English lavender and should be treated as an annual. Both require well-drained soil, and should be located in a sunny and sheltered position. To encourage flowering, remove all dry flower stalks at the end of the summer, and trim the stalks by about 2 centimeters in the spring (RHS, 2015).
Historical and Modern Uses
For centuries, lavender has been used for ailments ranging from panic attacks and palpitations, to paralytic limbs. The most widely cultivated species in the genus Lavandula is Lavandula angustifolia Mill., or English Lavender. It is the main species cultivated for the production of lavender oil, which is used in aromatherapy today. The name Lavandula is said to come from the Latin word, ‘lavare’, meaning ‘to bathe’, for the Romans used lavender, among other herbs, to perfume their baths (Lis-Balchin, 2003). Several classical physicians in England and around Europe have used species of Lavandula in a variety of ways, the oldest and most common association being cleanliness. In the time of King Edward VI (1547-53), lavender was boiled in water and used for washing clothes, shirts and sheets (Lis-Balchin, 2003). John Parkinson, the herbal apothecary to King James I in the early 1600’s wrote that lavender was ‘useful for the senses, and should be used for scenting linen, clothes, gloves and leather’, as well as recommended it for ‘pains in the head and brain’ (Lis-Balchin, 2003). Lavender oil was first distilled in the still rooms of 16th Century England, however it was during Victorian times that lavender began to gain popularity as a scent across the country. The famous Eau de Cologne produced by Yardley in 1834 was based on lavender oil. Yardley of London, established in 1770 is one of the world’s oldest established perfumeries and English lavender is still sold as one of their original scents.
In 1931, Maude Grieve, a respected herbalist in England, wrote a book entitled “A Modern Herbal”, which detailed the uses and cultivation of over 800 medicinal herbal plants, some of which can be found in the Mecklenburgh Square Garden today. In this book, she advises lavender oil to be useful for the treatment of headaches via the anointment of the temples and forehead, as well as an external massage for paralysed limbs (Lis-Balchin, 2003). Grieve also wrote that the fermentation of hot lavender in a bag and application to the body can ease local pains, and the gargling of distilled lavender water is useful for hoarseness and loss of voice (1931). The antiseptic power of lavender oil was also being explored in France; it was seen as useful for sores, ulcers burns and bites (Grieve, 1931). The French perfumer Renee Gattefosse was said to have applied pure lavender essential oil on a severe burn, in order to observe its analgesic (pain relieving) and healing activity (Denner, 2009).
Modern uses of lavender differ only slightly from its classical roots. Today, it is mainly cultivated for its essential oils, which are used in perfumery, cosmetics, food processing and aromatherapy products. Some of the modern indications for the internal use of lavender as a tea or supplement are mood changes that result in restlessness and insomnia, nervous intestinal discomfort, and treatment of irritable stomach (Denner, 2009). The essential oil is used in both aromatherapy massage and as a rubefacient, which improves circulation to the skin (Denner, 2009). Medical and scientific research is currently testing the efficacy of the historical claims made for the uses of lavender. This includes in vitro, in vivo and clinical studies to unearth the mechanism of action behind lavender’s antimicrobial, anxiolytic (anti-anxiety) and spasmolytic (anti-spasmodic) properties.
Phytochemistry
English lavender and larger hybrids are commercially important and are grown to produce large quantities of oil used in perfumes, aromatherapy and cooking. The annual production of lavender oil via steam distillation has been upwards of 462 tons per year since 1992 (Lis-Balchin, 2003). It is for this reason a majority of the phytochemistry known about lavender is based on its essential oil, which is made of compounds known as terpenes. The major phytochemical constituents of lavender essential oil are linalool, its acetic ester linalyl acetate, cis-ocimene and lavandulyl acetate (Lis-Balchin, 2003). The acetic esters are what give lavender the pleasant aroma it is known for (McCoy, 2007). In addition to these 4 major components there are over 100 minor constituents in lavender oil, with their quantities depending on the location of the plant. Apart from the essential oil, characteristic triterpenoid compounds, ursolic and oleanoic acid, have been found in the leaves of several lavender samples (Lis-Balchin, 2003).
Important constituents of lavender leaves are flavanoids, the majority of which are flavone glycosides. Simple flavone glycosides have been detected in L. angustifolia, and L. pedunculata, including luteolin and apigenin. Flavanoids located in the flowers are the chemical components that give the flowers their colouring. The main pigmented compounds found are malvidin and delphinidin. Coumarin has also been found in volatile oil extracts of the Lavandula genus (Lis-Balchin, 2003).
Scientific Evidence:
Lavender Oil as a Spasmolytic: As a result of its industrialization and large- scale production, most pharmacological and clinical testing has been done using lavender essential oil only. Therefore the active constituents studied in the majority of literature published are linalyl acetate and linalool. Although linalyl acetate is seen in greater proportion to linalool in lavender oil, it is believed that linalool is the active constituent (Prashar et al., 2004). A clearly defined mechanism of action of these constituents has not yet been determined, however research is being conducted on the neurotransmitters in the sympathetic nervous system (Denner, 2009). When activated during stress, the sympathetic nervous system experiences a rise in neurotransmitter cyclic adenosine monophosphate (cAMP). Some studies have shown that linalool acts to inhibit this increase in ways similar to known anticonvulsant and anti-anxiety drugs in vitro (Elisabetsky et al., 1995). cAMP also regulates other channels that play a role in neuromuscular transmission. Two studies investigated linalool and linalyl acetate’s local anesthetic activity in vitro and in vivo (Denner, 2009). Both studies were able to display that these constituents of lavender oil may play a role in the central nervous system sedative and anticonvulsive effects (Ghelardini et al. 1999; Re et al. 2000).
Lavender Oil as an Antimicrobial: Lavender oil has been found to be active against many species of bacteria and fungi, including some infections that have become resistant to antibiotics (Cavanagh and Wilkinson, 2002). Last year, a study explored the antimicrobial effects of lavender oil on a multi-drug resistant Escherichia coli (E. coli) strain (Yap et al., 2014). Results showed that lavender essential oil was active against piperacillin-resistant E. coli. It has also been shown to have in vitro activity against methicillin- resistant Staphylococcus aureus (MRSA) and vancomycin- resistant Enterococcus faecalis (VRE) (Cavanagh and Wilkinson, 2002). These results are important in sight of the imminent issue of antibiotic resistance (Yap et al., 2014). Despite the promising antimicrobial activity of lavender oil in vitro, no convincing in vivo study has been reported, and human clinical trials are limited (Cavanagh and Wilkinson, 2002).
Lavender Oil as an Anxiolytic: Some in vivo animal studies have shown encouraging results regarding the anti-anxiety and sedative effects of lavender oil. One study investigated the inhalation effects of lavender oil on gerbils and exposure to the lavender odor had a similar effect as the anxiolytic drug diazepam (Bradley et al. 2006). Another group explored the sedative activity of lavender oil and its main constituents linalyl acetate and linalool after inhalation in mice. The mice displayed a significant decrease in activity after exposure to lavender oil during baseline activity and also after being injected with caffeine. Increased levels of linalool in the blood suggest that this relaxing effect is due to the lavender oil (Buchbauer et al., 1991). The relevance of these studies to humans is poor however, seeing as the doses as well as the exposure routes of lavender inhalation differs from laboratory rodent to human (Cavanagh and Wilkinson, 2002).
Clinical Evidence:
Lavender Oil taken Orally: A recently licensed product: Clinical efficacy of lavender oil in humans is difficult to evaluate, as a result of questionable methodology, lack of transparency, and non-standardized essential oil preparations (Denner, 2006). Recently however, a chemically very well characterized lavender oil preparation has been licensed in Germany as an herbal medicinal product for the treatment of restlessness associated with anxiety (Uehleke et al., 2012). Although it is relatively new, it has been shown to be a highly effective preparation. A 6 week study compared the efficacy of this product against a known anxiety medication Lorazepam. Anxiety symptoms were diminished to a similar extent by both substances (Woelk and Schlafke, 2009). The safety of lavender oil was demonstrated as it showed no symptoms of drowsiness and no risk of potential drug abuse whereas after the use of Lorazepam, patients seem to feel a “hangover effect” (Woelk and Schlafke, 2009). In clinical study done in 2012, 50 patients with post traumatic stress and related disorders showed improvements in symptoms such as restlessness, anxiety and sleep disturbances, with the only side effects being minimal gastrointestinal complaints (Uehleke et al., 2012). Most recently in 2014, researchers are working to determine the mechanism of action of this preparation on the receptors in the human brain using molecular and structural neuroimaging (Baldinger, 2014). The results of the study suggested that the serotonin receptor in the brain was possibly involved in its anxiolytic effects (Baldinger, 2014).
Lavender Oil in Aromatherapy: In addition to the internal use of lavender, efficacy studies on the aromatherapeutic effects of lavender oil are widely published. In a placebo controlled clinical trial, the inhalation of lavender oil was tested in the treatment of migraine headaches (Sasannejad et al. 2012). The results of the study suggested that the inhalation of lavender oil was an effective and safe treatment in the acute management of migraines, however this effect should be verified in a larger group of patients (Sasannejad et al. 2012). In a study testing the effects of inhaling lavender oil in the treatment of mild insomnia, patients showed great improvement, especially those suffering from milder insomnia. A third study tested the effect of lavender on the anxiety of pre-operative patients (Braden et al. 2009). Controlling for baseline anxiety and pain, the experimental group had significantly lower anxiety than the standard care group, suggesting that lavender oil is a simple intervention that can improve patient satisfaction pre-operatively (Braden et al. 2009).
It is important to keep in mind that the outcomes of lavender oil aromatherapy trials do not always contain convincing evidence as a result of poor methodological approches. Lavender inhalation trials are difficult to manage because it is hard to assure that all groups have received a consistent level of lavender odour; when attempting replication, this is not easy to control (Perry et al. 2012). Publication bias, especially in the field of alternative medicine is another limitation to consider when reading these results.
Cautions and Interactions
According to the Medicines and Healthcare Regulatory Agency (MHRA) Traditional Herbal Medicinal Product (THMP) scheme, there is only one registered product that includes lavender oil. This THMP is called Weleda Arnica Massage Balm. It is indicated for the relief of rheumatic and muscular pain, backache, stiffness and minor sprains (MHRA, 2012). This indication however is based on traditional use only, and the lavender oil is not considered to be the active ingredient in the product. The traditional herbal registration scheme does not require any clinical proof of the efficacy of the product; it is however guaranteed to be of good quality. Since it is the only THMP with lavender granted registration by the MHRA, it is not guaranteed that other sources of lavender are not adulterated. Some well-known adulterants are synthetic linalool and linayl acetate, fractions of other oils such as rosemary or rosewood, and lavandin oil. Lavandin oil is produced from a cross breed of L. angustifolia and Lavandula latifolia Medik., and is mixed into lavender oil because it is much cheaper and more abundant. These are things to consider when purchasing lavender oil for use.
On a positive note, reviewing the current data suggests that the use of lavender oil is generally safe. There are a few gastrointestinal effects of lavender being taken orally, however these were reported as minimal or mild by the researchers (Perry et al. 2012). The long- term gastrointestinal effects have yet to be assessed. Lavender should be used with caution when applying it directly to the skin undiluted because it is a powerful allergen (Perry et al. 2012). A report in 2003 demonstrated that lavender oil is cytotoxic to human skin cells in vitro (Prashar et al. 2004). Concentrated lavender oil been shown to cause acute contact dermatitis in some cases (Prashar et al. 2004). It is also recommended to avoid ingesting lavender whilst pregnant or breastfeeding (Perry et al. 2012). There are no known reports of lavender interacting with any prescription medications, however because of its relaxing qualities it is not recommended for use with any sedative-type medications such as CNS depressants and narcotics (Hawkins, 2007).
The genus Lavandula has been used historically for centuries, and its traditional uses are still relevant in today’s age of modern medicine. Its long medical use proves it to be a safe, calming alternative to the stresses of London. Regardless of all of the positive medicinal effects that lavender can offer, it is indeed a wonderful smelling herb and a fantastic part of the Mecklenburgh Square Garden. If you happen to be in the garden, rub the leaves of lavender gently in between your fingers to enjoy its scent!
DISCLAIMER
This essay is not intended to advise or recommend herbs for medicinal or health use. This information is for educational purposes only and should not be considered as a recommendation or an endorsement of any particular medical or health treatment. The use of any such product should be based on the appropriate advice of a health care professional or based on the information available in the patient information leaflets (i.e. for THR products). The information provided should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. Please call 999 for all medical emergencies.
© Samantha Frangos MSc student
Centre for Pharmacognosy and Phytotherapy
UCL School of Pharmacy, Univ. London
29 – 39 Brunswick Sq. London WC1N 1AX
Samantha Frangos is currently working on her masters in pharmacognosy and phytotherapy at the UCL School of Pharmacy in London. If you have any further questions please do not hesitate to contactSamantha though the CONTACT FORM on this website.
Works Cited