Other activities and effects

A protective effect by aerial parts of lavender flowers against enzyme-dependent lipid peroxidation is described by Hohmann et al. (1999). Plant volatile oils have been found to exert certain beneficial effects on the human body in maintaining the level of polyunsaturated acids (PUFAs), to protect them from becoming oxidised (Deans et al., 1995). These EOs show a greater anti-hydrolytic effect than commercial preservatives, such as BHT, on butter, thus reducing its oxidation (Singh et al, 1998). Linalool, on the contrary, showed only marginal inhibitory effects, even at high concentrations, on lipid peroxidation of PUFA's (Reddy et al, 1992). Natural concentrations of some EOs were examined for effects on the system lipid-peroxidation-antioxidant-defense and lipid metabolism in 150 patients with chronic bronchitis. Lavender oil promoted normalisation of the level of total lipids and the ratio of total cholesterol to its a-fraction (Siurin, 1997). Inhalation of lavender oil volatiles, had no effect on the content of cholesterol in the blood, but reduced its content in the aorta and reduced also the incidence of atherosclerotic plaques in the aorta, that is these EOs are said to produce an angioprotective effect (Nikolaevskii et al., 1990).

Linalyl acetate, a prominent constituent of the EO of Hedyosmum brasiliense, is used on account of its analeptic and febrifuge characteristics (Gabriel et al., 1998). Anti-inflammatory properties and peripheral analgesic effects are also attributed to this monoterpenic ester (Moretti et al.,

1997). The local anaesthetic activity of the EO obtained from L. angustifolia Mill. was studied by in vivo tests on the rabbit conjunctiva and in vitro in a rat phrenic nerve-hemidiaphragm preparation (Ghelardini et al, 1999). The authors found that the EO, as well as the main constituents, linalool and linalyl acetate, were able to reduce drastically in a dose-dependent manner, the electrically evoked contractions of the rat phrenic-hemidiaphragm. In the rabbit conjunctival test these odorants allow a dose-dependent increase in the number of stimuli necessary to provoke the reflex, thus confirming in vivo the local anaesthetic activity.

As a potent radical scavenger, lavender oil is used as a component in topical formulations to relieve the pain associated with rheumatic and musculo-skeletal disorders (Billany et al., 1995). The influence of inhalation of terpenic volatiles on the blood pressure in human subjects was investigated and found that immediately after the end of the jogging tour, these EO-volatiles lessened the raised systolic blood pressure rapidly to normal values (Suzuki et al., 1994; Romine et al, 1999). A hypoglycemic effect caused by linalool in normal and streptozotocin-diabetic rats was described by Afifi et al. (1998). Linalool leads also to a hepatic peroxysomal and microsomal enzyme induction in rats (Roffey et al, 1990; Chadba et al, 1984). A choleretic and cholagogic activity of Bulgarian lavender oil as well as of a mixture of linalool and a-terpineol was found (Peana et al, 1994; Gruncharov, 1973).

Periodontal diseases can be treated with a mixture of EO's, among them lavender oil (Yamahara et al, 1994; Sysoev et al, 1990). An immunotoxicity assessment of food flavouring ingredients indicated that the majority of the compounds tested did not modulate the cellmediated or humoral immune response (Gaworski et al., 1994). Linalool was shown to penetrate the ex-vivo porcine oral mucosa in Franz' cells very easily (Ceschel et al, 1997). Lavender oil is suitable for prevention and treatment of decubitus ulcers as well as of insect bites, athletes foot and skin rash (Hartwig, 1996; Karita, 1996). This oil can also be used for the topical treatment of acne and dilated pores and for the prevention of facial scarring and blemishes of the face and body (Anon, 1997a,b). The EO of lavender is also a component of a mixture which is suitable as a hair growth stimulant and for the treatment of Alopecia areata (Betourne, 1995; Hay et al,

1998). Lavender oil also reduced somewhat the perineal discomfort after childbirth when added to the bath water, probably on account of its antiseptic and healing properties, but side effects were recorded (Cornwell et al, 1995; Dale et al., 1994).

A series of papers describe the use of EOs as skin penetration enhancers, especially for the transdermal absorption of various drugs and medicaments: Nifedipine and lavender oil (Thacharodi et al, 1994), metoprolol and ( + )- /(_)-linalool (Kommuru et al, 1999), propanolol (Kunta et al, 1997), ketoprofen and linalool (Kommuru et al, 1998) and azidothymidine and linalool (Kararli et al, 1995).

Enhancement of the growth of plants, for example, cultures of vegetables such as radish, kidney beans and lettuce, by applying linalool vapours is claimed in a Japanese patent application (Sato et al., 1995). Some papers deal with the olfactory sense in behavioural discrimination of volatiles by the honey bee Apis mellifera (Lozano et al., 1996; Sandoz et al, 1995; Pham-Delegue et al, 1993; Akas et al, 1992).

A review, especially on Oleum spicae ( = the EO of lavandula latifolia), reports on the treatment of bronchial diseases as well as of chronic arthritis and also as an adjuvant treatment with antibiotics (Fröhlich, 1968). Another review about lavender oil covers all interesting facts from chemistry to uses of this natural product (Tewari et al., 1987). Toxicological aspects of linalool are reviewed by Powers et al. (1985). A very informative review mainly on the Lavandula species cultivated in the southern part of France, the Provence, furnishes valuable details on the harvesting and EO-composition but nearly nothing about its use in medical treatments (Galle-Hoffmann, 1997).

The best review so far - at least to the opinion of the author of this article - is given by Schmidt (1996). The mere title of his paper 'a lavender oil is a lavender oil — or perhaps not at all?' already points in the direction of this review. Schmidt covers the history, lavender species, cultivation, quality, the analysis of this EO, the problem of the linalool enantiomers and adulteration of the oil, toxicity, market and usage in perfumery. Finally, two other articles on lavender and lavender oil should be mentioned, published in the same issue of the above-mentioned journal (Collin, 1996; Häringer, 1996).

Lavender oil increased the response rate during the alarm period in a dose-dependent manner in the same way as diazepam, indicating that it has an anticonflict effect in ICR mice using the 'Geller-type-conflict-test' (Umezu, 2000). Enantiomeric stereospecificity of (R)-(—)-linalool or (S)-( + )-linalool) evoked different odour perception and responses not only with chiral dependence but also with task dependence when administered to subjects both before and after 10 min of physical work. The (R)-(—)-linalool gave a more positive response to the sensory test and also produced a greater decrease in beta waves after work in comparison with that before work. This is in contrast to the case of mental work, which resulted in a tendency for agitation accompanied by an increase in beta waves of the EEG (Sugawara et al., 2000). Inhalation of lavender oil furnished evidence for a possible correlation between alpha 1 activity (alpha 1 (8-10 Hz) of EEG at parietal and posterior temporal regions) and subjective evaluation as it was significantly decreased under odour conditions in which subjects felt comfortable and showed no significant change when subjects felt uncomfortable (Masago et al., 2000). As a decrease of alpha-wave activity means higher attentiveness, these results seem to be contradictory to the many findings of relaxation, sedation, etc., discussed in this chapter. In experiments to clarify the anticonvul-sive mechanisms of linalool, its effects on binding of [3H]MK801 (NMDA-antagonist) and [3H]muscimol (GABAA-agonist) to mouse cortical membranes showed a dose dependent non-competitive inhibition on the antagonist binding but no effect on the muscimol binding suggesting that the anticonvulsant mode of action of linalool includes a direct interaction with the NMDA receptor complex and no direct interaction with the GABAA-receptors, although changes in GABA-mediated neuronal inhibition or effects on GABA release and uptake cannot be ruled out (Silv-Brum et al., 2001a). Linalool also inhibits the binding of [3H]glutamate and [3H]dizocilpine to brain cortical membranes and significantly reduces potassium-stimulated glutamate release as well as glutamate uptake, but not interfering with basal glutamate release (Silva-Brum et al, 2001b). An interesting diagnostic method in brain research uses linalool to determine how odour processing is altered in patients with unilateral supratentorial brain tumours. Patients with right-sided lesions showed distinct deficits in a discrimination task after stimulation of the right and left nostril. In contrast, patients with left-sided lesions only had an attenuation of correct reactions after left-sided stimulation. The first patients group showed bilateral impairment, thus supporting the importance of the right hemisphere in olfaction (Daniels et al., 2001). Linalool showed not only marked sedative effects at the CNS, including hypnotic, anticonvulsant and hypothermic properties, but also an inhibitory effect on the acetyl-choline release and on the channel open time in the mouse neuromuscular junction which demonstrates a local anaesthetic action either on the voltage or on the receptor-activated channels (Re et al, 2000).

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