Antibacterial activity of essential oils from Cymbopogon: inter- and intra-specific differences

The influence of the genetic background of a plant on the antibacterial activity of essential oil derived from it was investigated. Essential oils from six distinct strains of Cymbopogon were tested against eighteen bacteria. Interspecific and intra-specific differences were evident in the antibacterial activity of the essential oils derived from the the six Cymbopogon strains.     

Composition and antibacterial activity of the essential oils of Helichrysum rupestre and H. ambiguum growing in the Balearic Islands (Part III)

The chemical compositions of the essential oils obtained from the aerial parts of Helichrysum rupestre and H. ambiguum were analysed by GC and GC/MS. From the forty-five identified constituents representing 90.21% and 93.90% of the two oils, respectively, manoyl oxide, dodecanal, nonanal, p-cymene, alpha-pinene, and 2,4,6-tris(1,1-dimethylethyl)benzoic acid, were found to be the major components. Furthermore, the oils were tested against six Gram (+/-) bacteria and it was found that one of them exhibited significant antibacterial activity.     

Development of vegetable extracts by microencapsulation

The microencapsulation of essential oils offers protection against oxidation and evaporation, and allows the concurrent utilization of several vegetable extracts. Complex coacervation methods have been described for essential oils. Even though microencapsulation involves wrapping the essential oils in shells, some difficulties arise in the process of stabilizing the essential oils: oil may be lost by evaporation and partial dissolution in the water-gelatin phase and this will vary with the type of essential oil being encapsulated. In order to investigate the efficacy of the gelatin-polyphosphate methods we analysed their essential oil microcapsules peppermint and rosemary, in particular their granulometric size distribution, oil content (%) and encapsulation yield (%). In addition the essential oils were analysed by GC before and after microencapsulation so as to investigate the loss of their components during the process.     

Antibacterial and antifungal activity of aromatic constituents of essential oils

Five aromatic constituents of essential oils (cineole, citral, geraniol, linalool and menthol) were tested for antimicrobial activity against eighteen bacteria (including Gram-positive cocci and rods, and Gram-negative rods) and twelve fungi (three yeast-like and nine filamentous). In terms of antibacterial activity linalool was the most effective and inhibited seventeen bacteria, followed by cineole, geraniol (each of which inhibited sixteen bacteria), menthol and citral aromatic compounds, which inhibited fifteen and fourteen bacteria, respectively. Against fungi the citral and geraniol oils were the most effective (inhibiting all twelve fungi), followed by linalool (inhibiting ten fungi), cineole and menthol (each of which inhibited seven fungi) compounds.     

A review of the literature surrounding the research into aromatherapy

Whilst nurses in the UK are increasingly introducing aromatherapy into their practice, the research surrounding its use is still in its infancy. This position is in contrast to other parts of Europe such as France, where aromatherapy has been incorporated into areas of medical practice for some time, and is supported by increasing numbers of research papers. More recently, studies have been undertaken into the absorption of the essential oils, their therapeutic properties and the antimicrobial activity of certain oils. These studies will be reviewed, along with an evaluation of the studies undertaken in the UK into the use of aromatherapy with patients.     

Using essential oils in professional practice

As the use of aromatherapy within a health care setting has grown so rapidly in recent years, and will continue to do so, the need for suitable training has become apparent. No health service can afford the risk of having staff who are inadequately trained in the practice of aromatherapy using essential oils incorrectly on those in a state of ill-health, especially if the essential oils used are not to a standard suitable for therapeutic use. Training to an acceptable level in aromatic therapy is essential for safety and effectiveness. Knowledge of the nature and make-up of essential oils, their effect on the body and the emotions, and how, when, and where to apply them is imperative in order for them to be beneficial to a patient's health. Contraindications to certain oils, patients, or treatment have also to be thoroughly understood, and the dosage employed is related to some extent to the standard of training undertaken.     

On the essential oil of green algae. III. The oils of some Chlorella mutants (author''s transl)]

The stability against mutation of essential oil formation in the genus Chlorella is similar to that of hydrogenase. Both characters are therefore of special value in Chlorella taxonomy. All the 21 mutants of C. fusca C-1.1.10 produce essential oils, but only a few of them produce proazulenes. Two mutants of C. kessleri C-1.1.12 produce essential oils and proazulenes like the wild type.     

The potential effectiveness of essential oils as a treatment for headlice, Pediculus humanus capitis

Essential oils of aniseed, cinnamon leaf, red thyme, tea tree, peppermint, nutmeg, rosemary, and pine were tested in vitro against lice, Pediculus humanus. All the oils except for rosemary and pine were found to be effective in the laboratory when applied in an alcoholic solution and followed by a rinse the following morning in an essential oil/vinegar/water mixture. Peppermint and nutmeg were only used as a blend rather than as individual oils. Problems of solubility and toxicity are discussed, as are possible mechanisms of action. Phenols, phenolic ethers, ketones, and oxides (1,8-cineole) appear to be the major toxic components of these essential oils when used on lice. Aldehydes and sesquiterpenes may also play a role.     

Chemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides

The major components of commercial New Zealand essential oils of Leptospermum scoparium (manuka) and Kunzea ericoides (kanuka) are identified. In the manuka oil, monoterpenes are present at low levels (< or = 3%). Sesquiterpene hydrocarbons are predominant (> or = 60%) and include groups possessing cubebene/copaene, elemene, gurjunene/aromadendrene, farnesene/ caryophyllene, selinene, calamenene and cadinene skeletons. Oxygenated sesquiterpenes and triketones are present (< or = 30%). The antimicrobial activity of the manuka oil was associated with a fraction containing three major and three trace triketones, two of the latter were previously unreported. Kanuka oil was characterized by high levels of alpha-pinene (> 50%) and lower levels (< 10%) of viridiflorol and viridiflorene. GC-MS and GC-FID detector responses to the same components were noticeably different for some major components, including the triketones. Non-commercial manuka oils from different sites differed widely in composition and could be separated into four groups by the presence and levels of distinctive components. The density and refractive index of manuka and kanuka oils were closely correlated with the total sesquiterpene levels. The density of the commercial manuka oil was closely correlated with the level of the triketones. Simple density measurements enabled discrimination between the commercial oil and oils from other sites, and prediction of antimicrobial activity.     

Studies on the essential oils in Ligusticum chuanxiong Hort. of different habitats and species

Constituents of the essential oils obtained from Chuanxiong, Yungxiong, Fuxiong, Xixiong and "Chuanxiong" of Japan were analysed by GC-MS. Ninety-six compounds including ligustilide, etc. were identified. Their percentages in the oils were given.     

A potential role for angiotensin II-induced vascular endothelial growth factor expression in the pathogenesis of diabetic nephropathy?

The relationship between sensory quality of carrots and their contents and composition of essential oils and total sugars as influenced by nitrogen fertilization was investigated. Carrots (Daucus carota L.) of the variety 'Nanthya' F1 (S&G Sandoz Seeds) were grown in Weihenstephan 1996 with three levels of inorganic nitrogen fertilization (3 levels in 4 replications). Medium- and higher-boiling flavour-components were extracted as essential oils and separated gas-chromatographically (GC-FID). Lower-boiling flavour-components were taken from the headspace and analysed chemosensorially. The human sensory assessments were performed by an untrained panel of 300 people (students and employees of the TU München)--these results were compared with those of the chemical analyses. Carrots with lower nitrogen application were found to taste more intensive, more fruity, sweeter and better and at the same time less bitter and less earthy. They had higher contents of total sugar and a higher percentage of dry matter. Fertilization with nitrogen does not only affect the quantity but also the composition of the essential oils. The taste intensive was positively correlated with the quantity of essential oils, the taste sweet was positively correlated with the content of total sugars. It was possible to differentiate the carrots from each other by chemo-sensorial headspace analyses according to their N-fertilization levels.     

Nepetalactone: a new opioid analgesic from Nepeta caesarea Boiss

The essential oils of Nepeta species including Nepeta phyllochlamys P. H. Davis, N. nuda L. ssp. nuda, and N. caesarea Boiss. have been screened by use of the tail-flick and tail immersion (52.5 degrees C) methods. Of the species studied, only N. caesarea showed significant analgesic activity, besides marked sedation, which was also blocked by naloxone, indicating involvement of opioid receptors. Moreover, it was only active on mechanical, not thermal, algesic response which suggests specificity for specific opioid receptor subtypes, excluding mu-opioid receptors. Because 4a alpha,7alpha,7a alpha-nepetalactone is the main component of the essential oil of N. caesarea, and is present at very high levels (92-95%), it is concluded that 4a alpha,7alpha,7a alpha-nepetalactone is the active principle and has a specific opioid receptor subtype agonistic activity.     

Microencapsulation in yeast cells

A method for encapsulating high concentrations of essential oils into bakers' yeast (Saccharomyces cerevisiae) is described. The process involves mixing an aqueous suspension of yeast and an essential oil, which allows the oil to pass freely through the cell wall and membrane and remain passively within the cell. Oil droplets sequestered within the cell were clearly visible using confocal microscopy. Transmission electron microscopy demonstrated that the cell wall and membrane remain intact during the process. Cells quickly lost viability during the process and it appeared unnecessary for the cells to be viable for the process to occur. Encapsulated oil was recovered from the cells using a water/ethanol extraction procedure and analysed by gas chromatography. No significant differences were noted between encapsulated and unencapsulated oil profiles. The rate of permeation of oil into the yeast cells was found to increase significantly at higher temperatures due to the phase transition of the lipid membrane. The rates at which different essential oils permeated the cell varied considerably due to variations in terpene chemistry. The encapsulation of straight chain hydrocarbons highlighted the effects of molecular size, shape and the presence of hydroxl groups on the process. The process occurs by passive diffusion as a result of hydrophobic flavour components partitioning into the cell membrane and intracellular lipid. This paper briefly reviews the patented literature and reports some of the initial observations of the transport mechanisms involved during the accumulation of essential oils by yeast cells.     

GC-MS analysis of essential oils from pericarps of Illicium brevistylum A. C. Smith and I. jiadifengpi B.N. Chang

The chemical constituents of essential oils from the pericarps of illicium brevistylum and I. Jiadifeng pi were analyzed. Sixty-six compounds have been identified by GC-MS, of which limonene and linalool are higher in content. The essential oil of I. brevistylum has been found rich in 1, 8-cineole and terpinen-4-ol.     

GC-MS analysis of essential oils from the pericarps of Illicium majus Hook.f.et. Thoms. and I. micranthum Dunn

The chemical constituents of essential oils from the pericarps of Illicium majus and I. micranthum were analyzed. Seventy-two compounds have been identified by GC-MS, of which safrole, linalool and limonene are higher in content.     

Analysis of the DNA content in Bowen''s disease

Marketing of medicinal plants and phytotherapeutic products is spreading all over the world. In order to assess the commercialization of medicinal plants and phytotherapeutic products in the State of Minas Gerais, we identified and tested for the presence of adulterants and active ingredients in 27 samples of chamomile. All the samples consisted of Matricaria recutita flowers, but they were badly fragmented, a result of excessive handling and poor preservation. All samples contained contaminants, and insects were observed in 63% of the samples sold in drugstores. Only 50% of the samples in each group had the essential oils needed to produce antiinflammatory activity. Flavonoids and other phenolic constituents with a spasmolytic effect were detected in only 20% of the samples from each group. Results with chamomile indicated the poor quality with which medicinal plants and phytotherapeutic products are marketed and confirm the need for surveillance of such products in Brazil.     

Essential oils analysis. I. Evaluation of essential oils composition using both GC and MS fingerprints

The chemical nature of essential oils makes them suitable for analysis using a gas chromatography-mass selective detector (GC-MSD). Mass spectra (MS) libraries can not be used as unique and absolute criteria for the identification of chromatogram peaks. The wide variety of MS of the libraries, recorded in different conditions, can lead us to erroneous results. In order to increase the reliability of the analytical results, we used as identity criteria, both GC fingerprints resulted from the relative retention indices (RRI) and the recorded MS of the separated compounds. The two criteria have been quantified by their correlation with the standards. A new parameter called global composition evaluation index (I(GCMS)), which resulted from a well-balanced average of the two criteria, has been defined. Because the comparison of the results of the MS with databases is more accurate than the RRI, we considered that the ratio of the two criteria must be at least GC:MS 1:2. A database containing RRI of about 600 components, widely found in essential oils composition and separated on HP-5 column, was created. Two macros based on the Microsoft Excel spreadsheet were also created. The program offers the best 20 matches of each compound with the combined MS and RRI library. The composition of Romanian Acorus calamus L. essential oil was established and the results were compared with those obtained by 'classical' methods.     

Free fatty acid fractions from some vegetable oils exhibit reduced survival time-shortening activity in stroke-prone spontaneously hypertensive rats

Previously, we demonstrated that several vegetable oils that included low-erucic rapeseed oil markedly shortened the survival time (by approximately 40%) of stroke-prone spontaneously hypertensive (SHRSP) rats as compared with perilla oil, soybean oil, and fish oil. We considered that a factor other than fatty acids is toxic to SHRSP rats, because the survival time-shortening activity could not be accounted for by the fatty acid compositions of these oils. In fact, a free fatty acid (FFA) fraction derived from lipase-treated rapeseed oil was found to be essentially devoid of such activity. A high-oleate safflower oil/safflower oil/perilla oil mixture exhibited a survival time-shortening activity comparable to that of rapeseed oil, but the activity of this mixed oil was also reduced by lipase treatment. A partially hydrogenated soybean oil shortened the survival time by approximately 40%, but a FFA fraction derived from lipase-treated partially hydrogenated soybean oil shortened it by 13% compared with soybean oil. Fatty acid compositions of the rapeseed oil and a FFA fraction derived from lipase-treated rapeseed oil were similar, but those of hepatic phospholipids of rats fed the oil and FFA were slightly but significantly different. These results support the interpretation that the survival time-shortening activity exhibited by some vegetable oils is due to minor components other than fatty acids, and that an active component(s) were produced in or contaminated soybean oil during the partial hydrogenation processes.     

Reduction of protein volume and compressibility by macromolecular cosolvents: dependence on the cosolvent molecular weight

The role of dietary fatty acids in the regulation of carnitine palmitoyltransferase (CPT) activity has been shown in liver but their role in the regulation of tumour CPT activity in vivo is unknown. The present study investigated the effects of several oils, given as dietary supplements, upon the activity of CPT I and II in the Walker 256 rat tumour and the inhibition or stimulation of tumour growth. CPT I activity was markedly inhibited by soya oil, rich in linoleic acid (70% inhibition vs control). CPT I mRNA expression was not inhibited by any of the oils studied, indeed soya oil caused a marked increase (132% vs control) in expression. These results suggest that soya oil can modulate, in vivo, the beta-oxidative pathway of tumour tissue and further supports the hypothesis of tumour CPT I regulation by polyunsaturated fatty acids.     

Trans-fatty acids and health

Trans fatty acids are formed by partial hydrogenation of vegetable and marine oils or by bacterial activity in the rumen of ruminants. Main dietary sources are margarine, meat, milk fat and bakery products. Unsaturated fatty acids in the trans form have a more straight structure than their cis counterparts. They therefore have properties more like saturated fatty acids. Trans fatty acids may compete with essential fatty acids for elongating and desaturating enzymes and thereby interfere in the formation of eicosanoids. Trans fatty acids in the diet will increase LDL-cholesterol but to a lesser degree than the saturated fatty acids C12-C16. They also decrease HDL-cholesterol and increase Lp(a). By these unfavorable effects on blood lipids it may be expected that they will increase the risk of coronary heart disease. This has been confirmed in some, but not all, epidemiological studies. Provided the diet contains sufficient amounts of essential fatty acids there are no strong indications that trans fatty acids may have other unfavorable effects on health. Over time the intake of trans fatty acids has decreased considerably in Norway (from a mean of about 15 g/day in 1958 to about 4 g/day actually). The health effects of such an intake must be considered minor compared to an eight to ten fold higher intake of saturated fatty acids.