Cytotoxicity of lavender oil and its major components to human skin cells

Abstract.  Lavender ( Lavandula angustifolia ) oil, chiefly composed of linalyl acetate (51%) and linalool (35%), is considered to be one of the mildest of known plant essential oils and has a history in wound healing. Concerns are building about the potential for irritant or allergenic skin reactions with the use of lavender oil. This study has demonstrated that lavender oil is cytotoxic to human skin cells in vitro (endothelial cells and fibroblasts) at a concentration of 0.25% (v/v) in all cell types tested (HMEC-1, HNDF and 153BR). The major components of the oil, linalyl acetate and linalool, were also assayed under similar conditions for their cytotoxicity. The activity of linalool reflected that of the whole oil, indicating that linalool may be the active component of lavender oil. Linalyl acetate cytotoxicity was higher than that of the oil itself, suggesting suppression of its activity by an unknown factor in the oil. Membrane damage is proposed as the possible mechanism of action.     

Anti-inflammatory activity of linalool and linalyl acetate constituents of essential oils

Linalool and linalyl acetate are the principal components of many essential oils known to possess several biological activities, attributable to these monoterpene compounds. In this work, we evaluated individually the anti-inflammatory properties of (-) linalool, that is, the natural occurring enantiomer, and its racemate form, present in various amounts in distilled or extracted essential oils. Because in the linalool-containing essential oils, linalyl acetate, is frequently present, we also examined the anti-inflammatory action of this monoterpene ester. Carrageenin-induced edema in rats was used as a model of inflammation. The experimental data indicate that both the pure enantiomer and its racemate induced, after systemic administration, a reduction of edema. Moreover, the pure enantiomer, at a dose of 25 mg/kg, elicited a delayed and more prolonged effect, while the racemate form induced a significant reduction of the edema only one hour after carrageenin administration. At higher doses, no differences were observed between the (-) enantiomer and the racemate; a further increase in the dose of both forms did not result in an increased effect at any time of observation. The effects of equi-molar doses of linalyl acetate on local edema were less relevant and more delayed than that of the corresponding alcohol. These finding suggest a typical pro-drug behavior of linalyl acetate. The results obtained indicate that linalool and the corresponding acetate play a major role in the anti-inflammatory activity displayed by the essential oils containing them, and provide further evidence suggesting that linalool and linalyl acetate-producing species are potentially anti-inflammatory agents.     

Repellency of lavender oil and linalool against spot clothing wax cicada,Lycorma delicatula (Hemiptera: Fulgoridae) and their electrophysiological responses

This study was performed to investigate the repellent effect of 5 μl doses of ten essential oils (bergamot, chamomile, clary sage, fennel, lavender, lemongrass, majoram, peanut, pennyroyal, and peppermint) against Lycorma delicatula 4th nymphs using an olfactometer. Only lavender oil exhibited significant repellency. We then tested 10, 5, 2.5, and 1 μl doses of lavender oil against the nymphs and females of L. delicatula. The oil showed significant repellency at 10 and 5 μl, although the latter is less potent to 1st instar nymphs. At the lavender oil dose of 2.5 μl, only 3rd and 4th instar nymphs and females were significantly affected. None of the stages tested were affected by 1 μl. Chromatographic and mass spectrometric analyses of lavender oil detected linalool (42.2%), linalyl acetate (49.4%), terpinen-4-ol (5.0%), and caryophyllene oxide (3.4%). Among the four main components, only linalool showed repellency to all instar nymphs and females. No synergism was detected. Antennae of all instar nymphs and females showed electrophysiological responses only to linalool. In field studies using linalool, 4th nymphs and adults were highly repelled at a dose of 30 μl of lavender oil. The effect differed according to test plot and treatment dose.     

Inhaled linalool-induced sedation in mice

Linalool is a monoterpene often found as a major component of essential oils obtained from aromatic plant species, many of which are used in traditional medical systems as hypno-sedatives. Psychopharmacological evaluations of linalool (i.p. and i.c.v.) revealed marked sedative and anticonvulsant central effects in various mouse models. Considering this profile and alleged effects of inhaled lavender essential oil, the purpose of this study was to examine the sedative effects of inhaled linalool in mice. Mice were placed in an inhalation chamber during 60 min, in an atmosphere saturated with 1% or 3% linalool.Immediately after inhalation, animals were evaluated regarding locomotion, barbiturate-induced sleeping time, body temperature and motor coordination (rota-rod test). The 1% and 3% linalool increased (p<0.01) pentobarbital sleeping time and reduced (p<0.01) body temperature. The 3% linalool decreased (p<0.01) locomotion. Motor coordination was not affected. Hence, linalool inhaled for 1 h seems to induce sedation without significant impairment in motor abilities, a side effect shared by most psycholeptic drugs.     

Essential oil of lavender inhibited the decreased attention during a long-term task in humans

This study examined the effects of odors on sustained attention during a vigilance task. Two essential oils (lavender and eucalyptus) and two materials (l-menthol and linalyl acetate) were compared with a control. The increase in reaction time was significantly lower with lavender than with the control. The results suggest that the administration of lavender helped to maintain sustained attention during the long-term task.     

Anosmia does not impair the anxiolytic-like effect of lavender essential oil inhalation in mice

AimThe inhalation of Lavandula angustifolia (lavender) essential oil has anxiolytic-like effects in animal models and humans, but its mechanism of action is still not fully understood. The inhalation of essential oils can induce anxiolytic effects through the central nervous system (e.g., lung absorption and bloodstream transport) or stimulation of the olfactory system and secondary activation of brain regions. Thus, the main objective of the present study was to evaluate whether the perception of lavender essential oil aroma, when inhaled, is necessary to obtain its anxiolytic-like effects in mice tested in the marble-burying test.Main methodsAnosmia was induced by irrigating the nasal cavity with zinc gluconate + zinc acetate so that the mice could not detect odors in the olfactory discrimination test. The marble-burying test was used to evaluate the anxiolytic-like effects of inhaled lavender essential oil.Key findingsAnosmia did not interfere with the anxiolytic-like effect of lavender essential oil inhalation in the marble-burying test at concentrations of 2.5% (number of marbles buried: vehicle, 4.7 ± 1.0; zinc, 6.2 ± 2.2; p > 0.10) and 5% (number of marbles buried: vehicle, 3.4 ± 0.8; zinc, 4.3 ± 0.9; p > 0.10). Lavender essential oil at a concentration of 0.5% was ineffective.SignificanceThese results suggest that olfactory system activation is unlikely to participate in the anxiolytic-like effect of lavender essential oil inhalation.     

Essential Oil of Lavender Inhibited the Decreased Attention during a Long-Term Task in Humans

This study examined the effects of odors on sustained attention during a vigilance task. Two essential oils (lavender and eucalyptus) and two materials (l-menthol and linalyl acetate) were compared with a control. The increase in reaction time was significantly lower with lavender than with the control. The results suggest that the administration of lavender helped to maintain sustained attention during the long-term task.     

Volatile oils ofIlucium floridanum andI. parviflorum (Illiciaceae) of the southeastern United States and their potential economic utilization

The essential oil from leaves and branches of cultivatedIllicium floridanum is dominated by 22.53 ± 2.23% linalool and 13.93 ± 1.61% linalyl acetate. The essential oil from leaves and branches of cultivated I. parviflorum is dominated by 68.14 ± 0.88% safrole, 13.18 ± 1.01% linalool, and 11.89 ± 0.87% methyl eugenol. Besides the Lauraceae and Piperaceae, the Illiciaceae is another natural source of safrole.     

Essential oil composition and variability of Thymus lotocephalus and Thymusxmourae

The composition of the essential oils of four populations of Thymus lotocephalus G. López and R. Morales and one population of T.xmourae Paiva and Salgueiro, two endemic taxa from Portugal, was investigated mainly by GC and GC-MS. Txmourae is a natural hybrid between T. lotocephalus and T. mastichina (L.) L. subsp. donyanae R. Morales, which essential oil was analysed for the first time. In its oil, it was possible to find compounds of both parents, which could enable us to confirm its intermediate status between those two taxa. 1,8-Cineole and borneol were the main constituents in the essential oil of T.xmourae, whereas linalool, geranyl acetate and 1,8-cineol were the major ones in T. lotocephalus. Intermedeol was also an important constituent in the oils of both taxa. Nevertheless, the volatile oils of the four populations investigated of T. lotocephalus showed important differences among the main constituents. In order to study their infraspecific variability, the results obtained in the analysis of individual plants were submitted to a Principal Component and Chemometric Cluster Analyses. Five types of essential oils were found: linalool, 1,8-cineole, linalool/1,8-cineole, linalyl acetate/linalool and geranyl acetate.     

Diversity of essential oil glands of clary sage (Salvia sclarea L., Lamiaceae)

The Lamiaceae is rich in aromatic plant species. Most of these species produce and store essential oils in specialised epidermal oil glands, which are responsible for their specific flavour. Two types of glands producing essential oil and possessing different morphological structure can be found in Salvia sclarea : peltate and capitate glands. The content of single oil glands from different positions on the plant (corolla, calyx and leaf) were sampled using an SPME fibre and analysed by gas chromatography in order to study variability of the essential oil composition. It was found that the composition of terpenoids is quite variable within an individual plant. Capitate oil glands mainly produce three essential oil compounds: the monoterpenes linalool and linalyl acetate, and the diterpene sclareol. Peltate oil glands, however, accumulate noticeable concentrations of sesquiterpenes and an unknown compound (m/z = 354). Furthermore, the oil composition varies within each gland type according to the plant organ. Linalool and linalyl acetate are characteristic substances of flowers, whereas the sesquiterpenes occur in higher proportions in leaves. Even within one gland type on a single leaf, the chemical variability is exceedingly high.     

Antimicrobial activity of essential oils isolated from Portuguese endemic species of Thymus

AIMS: Thymus species are wild species mostly found in the arid lands of Portugal. Possible antimicrobial properties of Thymus essential oils have been investigated. The chemical composition of the essential oils and the antimicrobial activity of Thymus mastichina (L) L. subsp. mastichina, T. camphoratus and T. lotocephalus from different regions of Portugal were analysed. METHODS AND RESULTS: Hydrodistillation was used to isolate the essential oils and the chemical analyses were performed by gas chromatography (GC) and GC coupled to mass spectrometry. The antimicrobial activity was tested by the disc agar diffusion technique against Candida albicans, Escherichia coli, Listeria monocytogenes, Proteus mirabilis, Salmonella spp. and Staphylococcus aureus. Pure linalool, 1,8-cineole and a mixture (1 : 1) of these compounds were included. Linalool, 1,8-cineole or linalool/1,8-cineole and linalool/1,8-cineole/linalyl acetate were the major components of the essential oils, depending on the species or sampling place. The essential oils isolated from the Thymus species studied demonstrated antimicrobial activity but the micro-organisms tested had significantly different sensitivities. CONCLUSIONS: The antimicrobial activity of essential oils may be related to more than one component. SIGNIFICANCE AND IMPACT OF THE STUDY: Portuguese endemic species of Thymus can be used for essential oil production for food spoilage control, cosmetics and pharmaceutical use. Further studies will be required to elucidate the cell targets of the essential oil components.     

Effects of variety and growth year on the essential oil properties of lavender (Lavandula angustifolia Mill.) and lavandin (Lavandula x intermedia Emeric ex Loisel.)

Essential oil (EO) properties of six L. angustifolia (LA) and two L. x intermedia (LI) cultivars were evaluated during summer harvest periods of 2017 and 2018, The cultivars were grown in Dörgicse, Hungary. According to our results, the essential oil (EO) content was highly dependent on the varieties in both experimental years (2017: p < 0.0001 and 2018: p < 0.0001). In 2017, the EO content values of LI accessions were all higher than those of the LA cultivars. However, in 2018, the mean EO content value of ‘Budakalászi’ (LA) (8.2 mL/100g) exceeded that of ‘Grosso’ (LI) (7.7 mL/100g). The EO of ‘Mailette’ (LA) and ‘Budakalászi’ (LA) contained the highest linalool proportions (52.9% and 47.0%) while ‘Beate’ (LA) showed the lowest (18.1%); and this latter variety was richest in linalyl-acetate (58.9%). LI varieties produced lower linalyl acetate and total ester ratios in comparison to the LA cultivars. Concerning EO composition, only the UK varieties ‘Hidcote Blue’ (LA) and ‘Munstead’ (LA) met the requirements of the Ph. Eur.This study provided evidence that the effect of growth year on the EO content was significant only in two varieties out of the eight. However, in the more rainy year 2018, the accumulation of linalool and linalyl acetate was significantly affected in several cases, where linalool proportions decreased and linalyl acetate ratios increased.     

苦橙叶精油化学成分及抗炎作用研究

为探究苦橙叶精油的抗炎作用。实验采用气相-质谱联用法(GC-MS)分析精油成分,并建立脂多糖(LPS)诱导RAW 264.7细胞炎症模型,用Griess法检测一氧化氮(NO)含量评价其体外抗炎作用,随后进一步通过巴豆油致小鼠耳肿胀模型和鸡蛋清致小鼠足肿胀模型评价其体内抗炎作用。结果表明苦橙叶精油成分以酯类、醇类物质为主;25μg/mL浓度能显著抑制RAW 264.7细胞NO的释放;中浓度苦橙叶精油能明显减轻小鼠耳肿胀程度;低、中、高浓度苦橙叶精油均对小鼠足肿胀模型有炎症缓解作用,并于肿胀前期呈浓度依赖性。以上实验证明苦橙叶精油在体外和体内具有一定抗炎作用。     

Effects of essential oil inhalation on objective and subjective sleep quality in healthy university students

Aromatherapy with essential oils is one of the most popular complementary medical tools for improving sleep quality. However, only a few reports have objectively measured the effects of essential oils on sleep. Here, we used objective and subjective measures to analyze the effects of the essential oils of lavender (Lavandula angustifolia) and sweet orange (Citrus sinensis) on the sleep quality of healthy university students. The participants were monitored for 15 consecutive nights as they inhaled lavender oil and sweet orange oil, in a crossover design. Their sleep was monitored objectively by actigraphy, and total sleep time (TST), sleep efficiency, sleep latency, and wake after sleep onset (WASO) were analyzed. Their sleep was analyzed subjectively using Oguri–Shirakawa–Azumi (OSA) sleep inventory scores. Inhalation of an essential oil improved sleep measures only in participant whose sleep quality was poor in the control condition. Lavender seemed more effective than sweet orange in objective measures, especially in improving sleep latency. In the subjective sleep analysis, the essential oils improved sleep maintenance, dreaming, and sleep length in subjects who had poor sleep quality. Sweet orange seemed more effective than lavender in the subjective sleep measures. The difference between the two oils suggests that expectancy bias had little effect on the hypnotic effect of lavender on objective sleep. Although no obvious effect was observed in good sleepers, the inhalation of lavender oil could be effective for helping poor sleepers improve objective sleep quality.

     

植物油对大鼠应激性胃粘膜损伤的保护作用

将大鼠捆缚后置于4℃冰箱3h,造成应激性胃粘膜损伤,损伤程度用损伤指数表示:(1)在应激前3h 用0.5、1.0、2.Oml 的花生油灌胃,使损伤指数从对照的18.8—22.6降为6.8—7.0,P<0.01,但当花生油用量降至0.25ml 时,其保护作用不明显;(2)在应激前0.5、1.5、2.5和3.5h用1.0ml 花生油灌胃,也均有保护作用,(3)菜籽油或油酸有类似花生油的抗胃粘膜损伤作用,而且油酸的作用比花生油更显著,但30%甘油却无效;(4)将1.0ml 花生油注入空肠,具有与灌胃相似的保护作用;(5)在大鼠应激前1.5h 肌注消炎痛(10mg/kg),并不能阻断花生油的保护作用。以上结果表明,花生油等植物油能够通过其脂肪酸成分作用于小肠而产生对抗应激性胃粘膜损伤的作用。这种保护作用的机理不明,但似与前列腺素无关。     

Comparative effects of Pro-Leu-Gly-NH2 and cyclo(Leu-Gly) administered orally on the development of tolerance to the analgesic effect of morphine in the rat

Comparative effects of Pro-Leu-Gly-NH2 (MIF) and cyclo(Leu-Gly) (CLG) administered orally at different stages of chronic morphine treatment on the development of tolerance to the analgesic effect of morphine in the rat were determined. Male Sprague-Dawley rats were implanted with either 6 placebo or morphine pellets during a 7-day period. Implantation of morphine pellets resulted in the development of a high degree of tolerance as evidenced by a decrease in the analgesic response to morphine. Administration of CLG (8 and 16 mg/kg/day) on day 5, 6 and 7 of implantation inhibited the development of tolerance to morphine but 4 and 32 mg/kg doses had no effect. Further, CLG (2 mg/kg/day for 7 days) inhibited the development of tolerance but higher doses (4 and 8 mg/kg) had no effect. MIF (26 and 52 mg/kg) administered orally on the last three days of the implantation schedule inhibited the development of tolerance to morphine. MIF (6.5 mg/kg/day for 7 days) inhibited the development of tolerance but the higher doses had no effect. Concurrent administration of MIF (6.5 mg/kg) and CLG (2 mg/kg) for seven days failed to inhibit the development of tolerance. A single dose of MIF or CLG administered a day before the assessment of tolerance did not affect the morphine tolerance. Thus, even after a significant degree of tolerance to morphine had developed, neuropeptides like MIF and CLG given orally, in appropriate doses, can inhibit development of tolerance to morphine and restore the analgesic effect of morphine.     

A Study on Chemical Components of Essential Oils from Citrus bergamia and Its Close Relatives and Its Taxonomy

Citrus bergamia Risso. is a rare perfumery plant. Taxonomists have different views on the taxonomy of C. bergamia. Chemical components of leaf and peel essential oils from C. bergamia, and its close relatives, C. limon, C. aurantifolia and three varieties of C. aurantium, were analyzed by GC and GC-MS. The analytical result shows that the chemical compositions of the leaf essential oils from C. bergamia are basically the same as those from three varieties of C. aurantium. Their main components are linalool (29.19-39.75% )and linalyl acetate (24.73-30.24% )etc., and contents of other components are also similar. But their peel essential oils are different. The peel essential oils from C. bergamia contain less limonene (29.94%) than those from C. aurantium (92.55-94.31% ) and less beta-pinene (3.00%) and y-terpinene(3.48% )than those from C. limon or C. aurantifolia (respectiyely 9.16% and 10.42% ) . The peel essential oils from C. bergamia contain not only as much linalool (22.20%) and linalyl acetate (32.66%)as those in the leaf essential oils from C. aurantium, but also as much limonene(29.94% )as that in the peel essential oils from C. limon or C. aurantifolia . The contents of limonene are close to those of the essential oils from C. aurantifolia. This result shows that C. bergamia may be a natural hybrid between C.aurantium and C. aurantifolia, as proposed by Sinclair W. B.     

An esterase is involved in geraniol production during palmarosa inflorescence development

Total incorporation of exogenously administered [2-14C]acetate into essential oil of palmarosa (Cymbopogon martinii) was found to be relatively higher than that of either [U-14C]sucrose or [U-14C]glucose during inflorescence development. Among the major essential oil constituents, biogenesis of geranyl acetate was much higher than that of geraniol. Alkaline hydrolysis of [14C]labeled geranyl acetate revealed that the majority of the label incorporated into geranyl acetate was present in the geraniol moiety, indicating that only newly synthesized geraniol gets acetylated to form geranyl acetate. Geranyl acetate cleaving esterase (GAE) activity followed a similar pattern during both in vivo and in vitro inflorescence development, with maximum activity at immature inflorescence stages, suggesting the involvement of GAE in geraniol production during inflorescence development. Five esterase isozymes (Est-A to E) were detected in the enzymic fraction of palmarosa inflorescence and all showed GAE activity, with Est-B being significantly increased during inflorescence development. The role of GAE in geraniol production and improving the palmarosa oil quality is discussed.     

Investigations of animal blood samples after fragrance drug inhalation by gas chromatography/mass spectrometry with chemical ionization and selected ion monitoring.

The fragrance compounds linalool (1) and linalyl acetate (2) could be detected, identified and quantified (1: 7-9 ng ml-1; and 2: 1-2 ng ml-1 and 4-5 ng ml-1 as free linalool) in blood samples after inhalation in animal experiments (mice) by gas chromatography/mass spectrometry (GC/MS) with chemical ionization (CI) (ammonia); selected ion monitoring (SIM) mode (1: m/z 81, 137 and 154; 2: 47, 57 and 137) and GC/flame ionization detection (FID). The inhalation of these monoterpenes in concentrations of 5 mg l-1 air leads to a significant reduction of the motility of the test animals down to 30-40% with respect to the control group.