Pure Essential Oil Research Articles

Application of essential oils of thyme as a natural preservative in leather tanning

The aim of this study was to investigate the possibility of using essential oils of Thymus vulgaris as an alternative preservative for chromed leather. The differences between the chemical composition of commercial and pure essential oils of thyme were determined. It was observed that these differences have an influence on the antibacterial activity of essential oils. Gram-positive bacteria were found to be more sensitive to the essential oils of thyme than Gram-negative bacteria. The bacteria Pseudomonas aeruginosa had a low sensitivity to the action of the selected essential oils of thyme, but the leather samples treated with the essential oils of thyme remained resistant to the action of these bacteria. As the main result of this study, it was concluded that the essential oil of thyme could be used as a preservation agent in the leather tanning industry. The leather preserved with 2-(thiocyanomethylthio)benzothiazole had weaker protection after four weeks compared to the samples treated with the essential oil of thyme when the amount of the used essential oil was not less than 3% of the wet-blue mass. The essential oil of thyme was the more active component in the mixture of essential oil and synthetic biocide used for the preservation of leather.

Antifungal activity of essential oils against wood degrading fungi and their applications as wood preservatives

Essential oils were screened for their antifungal activity against common wood inhabiting fungi. Subsequently, two pure essential oil extracts, eugenol and cinnamaldehyde, were evaluated for their efficacy on radiata pine wood durability. During the in vitro screening trial, variability in the tolerance of the tested fungi towards the selected essential oil was apparent. However, wood durability test on wood confirmed the antifungal activity of eugenol and cinnamaldehyde but highlighted the leaching (when exposed to wet conditions) of these compounds from treated wood. Blocks treated with 3% w/v eugenol without exposure to wet conditions had <1% weight loss when exposed to all three test fungi, Oligoporus placenta, Coniophora puteana and Antrodia Xantha. However, blocks which were exposed to water showed weight losses in the range of 13·4–23·1%. This study identified eugenol and cinnamaldehyde as potentially benign wood preservatives for treatment of timber not exposed to wet conditions.

Green synthesis of para-Menthane-3,8-diol from Eucalyptus citriodora: Application for repellent products

A simple and efficient method was developed for the synthesis of para-Menthane-3,8-diol (PMD), a well-known repellent active against mosquitoes, from Eucalyptus citriodora essential oil by a treatment of citric acid in a biphasic medium (H2O/essential oil). The E. citriodora contains as main component (+)-citronellal (74% in the present case), which cyclises (Prins reaction) to form cis/trans PMD isomers. As an example, an emulsion containing an aqueous solution of 7% citric acid and E. citriodora oil at 50°, conducted after 15 h stirring to 82% conversion of (+)-citronellal with a selectivity of 80% with the remaining presence of monoterpenes and sesquiterpenes in the medium. Investigations of lasting protection on human volunteers are carried out using a cage test bioassay protocol and Aedes aegypti mosquitoes. At 20% in iPrOH, the new reaction mixture showed a complete protection of 303 min compared to 22 min with the pure essential oil. The modified oil was compared with N,N-diethyl-m-methylbenzamide (DEET), the most popular active used in repellent formulations. Thermogravimetric analyses (TGA) of E. citriodora, the modified oil, PMD, DEET, and (+)-citronellal were performed and showed a slow evaporation rate for PMD and DEET as well as for the modified oil, which may explain their long lasting protection action.

Fumigant Toxicity of some Essential Oils on Adults of some Stored-Product Pests

Plant materials with insecticidal properties have been traditionally used for generations in some parts of the world. In this study, fumigant toxicity of some essential oils extracted from Rosmarinus officinalis L., Mentha pulegium L., Zataria multiflora, and Citrus sinensis (L.) Osbeck var. hamlin on adults of stored-product pests, including Tribolium castaneum, Sitophilus granarius, Callosobruchus maculatus, and Plodia interpunctella were investigated. Pure essential oils were used in glass vials for the bioassay. LC50 values of Citrus sinensis var. hamlin against T. castaneum, S. granarius, and C. maculatus were 391.28, 367.75, and 223.48 µL L -1 air after 24 h, 362.40, 20.45, and 207.17 µL L -1 air after 48 h, respectively. Furthermore, LC50 values of the fumigant test of C. sinensis and M. pulegium essential oils against S. granarius were 0.038 and 367.75 µL L -1 air after 24 h, 0.025 and 320.45 µL L -1 air after 48 h, respectively. On the other hand, LC50 values of R. officinalis and Z. multiflora on P. interpunctella moths were 0.93 and 1.75 µL L -1 after 24 h. Results showed that among tested essential oils, C. sinensis var. hamlin had good fumigant toxicity on T. castaneum, S. granarius, and C. maculatus. In addition, M. pulegium essential oil was stronger than C. sinensis var. hamlin on S. granarius. Results also indicated that both Z. multiflora and R. officinalis had fumigant toxicity on P. interpunctella adults. In summary, results indicated that these essential oils have good fumigant toxicity on stored-product pests.

Repellent Effects of the Insecticide Based on Porous Starch and Fennel Essential Oil against &lt;i&gt;Tribolium confusum&lt;/i&gt;

The insecticidal effects of the insecticide based on the mixture of porous starch and fennel essential oil was investigated. Its insecticidal activity and its mortality on adults of Tribolium confusum were evaluated. Moreover, the production methods used in the evaluation was studied. Fennel essential oil was put into the porous starch with glycerin and ethyl acrylate. Non-woven was chosen as the substrate, and ethyl acrylate as adhesives. Then the new insecticide was made. According to the fumigant toxicity and persistent of the new insecticide, the insecticidal effect of the insecticide was analyzed. Tribolium confusum mortality was dose dependant and after 4-day exposure the insecticide was more toxic than the pure fennel essential oil. There was, however, a highly significant loss of toxicity after 24 and 48 h following treated with essential oil and insecticide, respectively. The fennel essential oil evoked moderated repellent action and high fumigant toxicity (LD50 = 0.030μL/cm3) against adults of Tribolium confusum.

Antifungal activity of essential oil from fruits of Indian Cuminum cyminum

The essential oil of fruits of Cuminum cyminum L. (Apiaceae), from India, was analyzed by GC and GC-MS, and its antifungal activity was tested on dermatophytes and phytopathogens, fungi, yeasts and some new Aspergilli. The most abundant components were cumin aldehyde, pinenes, and p-cymene, and a fraction of oxygenate compounds such as alcohol and epoxides. Because of the large amount of the highly volatile components in the cumin extract, we used a modified recent technique to evaluate the antifungal activity only of the volatile parts at doses from 5 to 20 µL of pure essential oil. Antifungal testing showed that Cuminum cyminum is active in general on all fungi but in particular on the dermatophytes, where Trichophyton rubrum was the most inhibited fungus also at the lowest dose of 5 µL. Less sensitive to treatment were the phytopathogens.

The Essential Oil Composition of Ajuga chamaecistus Ging. subsp. tomentella Rech. f.

The essential oil obtained from the aerial parts of Ajuga chamaecistus Ging. subsp. tomentella Rech. f..was analyzed by using GC and GC-MS. Forty four compounds representing 95.13 % of the oil were identified. The main ones were thymol (34.45 %), exo-fenchol (15.58 %), β-pinene (8.26 %), 1-octen-3-ol (5.92 %), α-terpineol (3.88 %), 2-hexanol (3.85 %), α-thujene (2.66 %), and α-pinene (2.54 %). The oil was rich in oxygenated monoterpenes. Antibacterial activity of the essential oil was determined using disc diffusion method against both Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. The experiments showed that the pure essential oils had no antibacterial activity against Gram-positive and Gram-negative bacteria at 25 μl/disc.

Antimicrobial activity of extracts from Tamarindus indica L. leaves

Tamarindus indica L. leaves are reported worldwide as antibacterial and antifungal agents; however, this observation is not completely accurate in the case of Cuba. In this article, decoctions from fresh and sun dried leaves, as well as fluid extracts prepared with 30 and 70% ethanol-water and the pure essential oil from tamarind leaves were microbiologically tested against Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Pseudomona aeruginosa and Candida albicans. Aqueous and fluid extracts were previously characterized by spectrophotometric determination of their total phenols and flavonoids, while the essential oil was chemically evaluated by gas chromatography/mass spectroscopy (GC/MS). Experimental data suggest phenols as active compounds against B. subtilis cultures, but not against other microorganisms. On the other hand, the essential oil exhibited a good antimicrobial spectrum when pure, but its relative low concentrations in common folk preparations do not allow for any good activity in these extracts.

Antioxidant and antibacterial activities of eugenol and carvacrol‐grafted chitosan nanoparticles

Essential oils are known to possess antimicrobial and antioxidant activity while chitosan is a biocompatible polymer with antibacterial activity against a broad spectrum of bacteria. In this work, nanoparticles with both antioxidant and antibacterial properties were prepared by grafting eugenol and carvacrol (two components of essential oils) on chitosan nanoparticles. Aldehyde groups were first introduced in eugenol and carvacrol, and the grafting of these oils to chitosan nanoparticles was carried out via the Schiff base reaction. The surface concentration of the grafted essential oil components was determined by X-ray photoelectron spectroscopy (XPS). The antioxidant activities of the carvacrol-grafted chitosan nanoparticles (CHCA NPs) and the eugenol-grafted chitosan nanoparticles (CHEU NPs) were assayed with diphenylpicrylhydrazyl (DPPH). Antibacterial assays were carried out with a representative gram-negative bacterium, Escherichia coli (E. coli) and a gram-positive bacterium, Staphylococcus aureus (S. aureus). The grafted eugenol and carvacrol conferred antioxidant activity to the chitosan nanoparticles, and the essential oil component-grafted chitosan nanoparticles achieved an antibacterial activity equivalent to or better than that of the unmodified chitosan nanoparticles. Cytotoxicity assays using 3T3 mouse fibroblast showed that the cytotoxicity of CHEU NPs and CHCA NPs were significant lower than those of the pure essential oils.

Antibacterial activity of aromatic plants essential oils from Serbia against the Listeria monocytogenes

The purpose of this study was to examine the effectiveness of selected essential oils for the control of the growth and survival of pathogenic bacteria Listeria monocytogenes ATCC 19112 and Listeria monocytogenes ATCC 19115, which are of significant importance in food hygiene. Essential oils extracted from Salvia officinalis L., Rosmarinus officinalis L., Majorana hortensis Moench., Thymus vulgaris L., Carum carvi L., Pimpinella anisum L. and Coriandrum sativum L. were evaluated. Antibacterial activity was done by the disk diffusion method in the presence of pure essential oils and four suspensions in alcohol. The best results obtained with Thymus vulgaris and Majorana hortensis essential oils, which were acting microbicidaly on both observed strains of Listeria monocytogenes, even in the small concentration. Because some of the essential oils were highly inhibitory even in small quantities to selected pathogenic bacteria, they may provide alternatives to conventional antimicrobial additives in foods. .

Impact of cinnamon oil-enrichment on microbial spoilage of fresh produce

Abstract Cinnamon (Cinnamomum zeylanicum L.) oil (ranging between 25 and 500 ppm) was tested for antifungal activity against Colletotrichum coccodes, Botrytis cinerea, Cladosporium herbarum, Rhizopus stolonifer and Aspergillus niger in vitro. Oil-enrichment resulted in significant (P Industrial relevance The data presented in this work suggest that the use of pure cinnamon essential oil is an innovative and useful tool as alternative to the use of synthetic fungicides or other sanitation techniques in storage/packaging. Oil enrichment may reduce disease development with a major contribution to limiting the spread of the pathogen by lowering the spore load (spore production) in the storage/transit atmospheres as well as the use of essential oil as an alternative food preservative. The effectiveness (oil concentration) of the oil depends on the target pathogen. The effects of natural compounds on individual microorganisms (fungi and bacteria), both responsible for spoilage and food-borne pathogens, as well as the minimum concentration to gain effectiveness without affecting fresh produce quality and storage deserve further research.

Insecticidal effects of the powdery formulation based on clay and essential oil from the leaves of Clausena anisata (Willd.) J. D. Hook ex. Benth. (Rutaceae) against Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae)

The bioefficacies of essential oil and aromatized clay powder based on the mixture of clay and essential oil extracted from Clausena anisata were evaluated for their insecticidal activities and their effects on progeny production of Acanthoscelides obtectus. Contact toxicity assayed by coating on bean grains showed that these chemicals caused significant mortality of the test insect. Beetle mortality was dose dependant and after 2-day exposure the aromatized clay powder was more toxic (LD50 = 0.069 mu l/g grain) than the pure essential oil (LD50 = 0.081 mu l/g grain). There was, however, a highly significant loss of toxicity after 24 and 36 h following treatment with essential oil and aromatized powder, respectively. Both aromatized clay powder and pure essential oil considerably reduced the F-1 progeny insect production. The essential oil evoked moderated repellent action and high fumigant toxicity (LC50 = 0.093 mu l/cm(3)) against adults of A. obtectus. These results suggest that the clay powder could be used to stabilize the essential oil to increase its efficacy for use as an alternative to synthetic insecticides.

Acaricidal efficacy of Origanum onites L. essential oil against Rhipicephalus turanicus (Ixodidae)

Essential oils that were extracted by steam distillation from Origanum onites L. from northwest Turkey were analyzed using an Agilent GC-MSD system. Carvacrol was the major component (64.3%) of the oil. Both pure commercial carvacrol and essential oil at concentrations of 1.5%, 3.2%, 6.25%, 12.5%, 25%, 50%, and 100% (v/v) were tested for their effects against engorging Rhipicephalus turanicus, which were collected from cattle breeding in the region. Pure carvacrol killed all the ticks following 6 h of exposure, while 25% and higher concentrations of the oil were completely effective in killing the ticks by the 24th-hour post-treatment (p < 0.05). The concentrations of 6.25% and 12.5% killed all the ticks by day 2. Lethal concentrations for 50% (LC(50)) and 90% (LC(90)) of 2.34% and 7.12%, respectively, were detected 24 h post-treatment. These findings indicate that the essential oil of O. onites L. has potential to be utilized at reasonable concentrations to control tick infestations.

Antifungal activity of lemongrass (Cympopogon citratus L.) essential oil against key postharvest pathogens

Abstract Lemongrass ( Cympopogon citratus L.) oil (ranging between 25 and 500 ppm) was tested for antifungal activity against Colletotrichum coccodes , Botrytis cinerea , Cladosporium herbarum , Rhizopus stolonifer and Aspergillus niger in vitro. Oil-enrichment resulted in significant ( P C. coccodes , B. cinerea , C. herbarum and R. stolonifer with the effects dependent on oil concentration. However, lemongrass oil (up to 100 ppm) accelerated spore germination for A. niger . Work is currently focussing on the mechanisms underlying the impacts of essential oil volatiles on disease development with a major contribution to limiting the spread of the pathogen by lowering the spore load in the storage/transit atmospheres as well as the use of essential oil as an alternative food preservative. Industrial relevance The present study suggests that the use of pure lemongrass essential oil is an innovative and useful tool as alternative to the use of synthetic fungicides or other sanitation techniques in storage/packaging. Oil enrichment may reduce disease development with a major contribution to limiting the spread of the pathogen by lowering the spore load (spore production) in the storage/transit atmospheres as well as the use of essential oil as an alternative food preservative. The effectiveness (oil concentration) of the oil depends on the target pathogen. The effects of natural compounds on individual microorganisms (fungi and bacteria), both responsible for spoilage and food-borne pathogens, as well as the minimum concentration to gain effectiveness without affecting fresh produce quality and storage deserve further research.

Skin Penetration of Terpenes from Essential Oils and Topical Vehicles

The purpose of this study was to evaluate the in vitro cutaneous penetration of five terpenes--linalool, linalyl acetate, terpinen-4-ol, citronellol and alpha-pinene--applied in pure essential oils or in dermatological formulations (o/w emulsion, oily solution or hydrogel) containing 0.75 % w/w of the essential oils. Different skin absorption was observed depending on the type of the vehicle and terpenes' log P values. Cutaneous accumulation of terpenes is several times higher when they are applied in pure essential oils than in topical vehicles. Penetration of terpinen-4-ol to the skin was better from an oily solution (approximately 90 microg/cm (2)) than from an emulsion (60 microg/cm (2)). No penetration of linalyl acetate from topical vehicles into viable skin was observed, but also for this terpene penetration to the upper layers of the stratum corneum was 2-times higher when an oily solution was used. In contrast, the cutaneous absorption of linalool was the same from both vehicles (50-60 microg/cm (2)). The skin penetration of alpha-pinene was not traceable when it was applied in an oily solution. Only a small amount (approximately 5 microg/cm (2)) of this terpene was determined in viable skin after application as a hydrogel. Citronellol applied in a hydrogel penetrated into all skin layers in a total amount of 25 microg/cm (2), while no penetration into viable skin layers after application of an oily solution was noted. Only citronellol permeated into the acceptor medium.

Supercritical fluid extraction of essential oils: Results of joint research

Peppermint, creeping thyme, and sage herbs, as well as yarrow flowers were extracted with supercritical and liquid carbon dioxide at 9-13 MPa and 25-60?C. Two extraction periods were distinguished except in the case of thyme extraction. Almost pure essential oil was extracted in the first, fast period. The extraction was retarded in the second period controlled by essential oil-matrix interaction, and waxes and water prevailed over the essential oil in the extract. To estimate the effect of essential oil-vegetable oil interaction during the extraction of essential oils from seeds, the limonene + vegetable oil + CO2 equilibrium was investigated using thermodynamic modeling. Changes in the composition of the essential oil in the extracts are demonstrated on the example of sage oil. Compared to hydro distillation, the extracts contained less monoterpenes, the most volatile components, because the separation of the extract from gaseous ??2 in the cold trap was incomplete. The yield of sesqui- and di-terpenes in the extracts, however, was higher than their yield by hydrodistillation. The extraction of sage essential oil was most efficient at 13 MPa and 50?C, when the yield of diterpene manool was more than two times higher than its yield by hydrodistillation.

Sensory and instrumental evaluation of sweet marjoram (Origanum majorana L.) aroma

The present study investigates the composition of volatile constituents and sensory characteristics of sweet marjoram (Origanum majorana L.) grown in Lithuania. Hydrodistillation, simultaneous distillation–solvent extraction, static headspace and solid phase microextraction methods were used for the isolation of aroma volatiles. Terpinen-4-ol, α-terpineol, γ-terpinene, α-terpinene, cis-sabinene hydrate and p-cymene were the major constituents in sweet marjoram. The differences in the composition depending on the isolation techniques were quite considerable. A sensory panel performed sensory analysis of the ground herb, pure essential oil and the extract, and aroma profiles of the products were expressed graphically. The changes of the odour profiles of marjoram during isolation in many cases can be linked to the odour characteristics of pure compounds present in marjoram. Copyright © 2005 John Wiley & Sons, Ltd.

Antimicrobial Activity of Chitosan Films Enriched with Essential Oils

ABSTRACT: Antimicrobial and physicochemical properties of chitosan films and chitosan films enriched with essential oils (EO) were determined in vitro and on processed meat. Antimicrobial effects of pure EO of anise, basil, coriander, and oregano, and of chitosan-essential oil films against Listeria monocytogenes and Escheri-chia coli O157:H7 were determined by an agar diffusion test. The antibacterial effects of the EO were similar when applied alone or incorporated in the films. The intensity of antimicrobial efficacy was in the following order: oregano > > coriander > basil > anise. The chitosan films and chitosan-oregano EO films were applied on inoculated bologna samples and stored 5 d at 10 °C. Pure chitosan films reduced L. monocytogenes by 2 logs, whereas the films with 1% and 2% oregano EO decreased the numbers of L. monocytogenes by 3.6 to 4 logs and E. coli by 3 logs. Pure chitosan films were 89 μm thick, whereas addition of 1% and 2% oregano EO increased thickness to 220 and 318 μm, respectively. During application on bologna discs, the films absorbed moisture, resulting in the final thickness of 143, 242, and 333 μm, respectively. Addition of oregano essential oil into the chitosan films decreased water vapor permeability, puncture and tensile strength, but increased elasticity of the films. The films have the potential to be used as active biodegradable films with strong antimicrobial effects.

The use of natural antifungal compounds improves the beneficial effect of MAP in sweet cherry storage

Sweet cherry shows severe problems for commercialisation mainly due to incidence of decay and a fast loss of sensory quality, both for fruit and stem. A package has been developed based on the addition of eugenol, thymol, menthol or eucalyptol (pure essential oils) separately to trays sealed with polypropylene bags to generate a modified atmosphere (MAP). In addition, cherries in MAP (without essential oils) were selected and served as controls. All cherries were stored during 16 days at 1 °C and 90% RH. Steady-state atmosphere was reached after 9 days of cold storage with 2–3% of CO 2 and 11–12% of O 2 with no significant differences between treated and control, with the exception of eucalyptol, in which significant increases in CO 2 and decreases of O 2 were obtained. When fruit quality parameters were determined, those treated with eugenol, thymol or menthol showed benefits in terms of reduced weight loss, delayed colour changes and maintenance of fruit firmness compared with control. Stem remained green in treated cherries while they became brown in control. However, cherries packaged with eucalyptol behaved even worst than control cherries, with generation of off-flavours, loss of quality and stem browning. Finally, the microbial analysis showed that all essential oils reduced moulds and yeasts and total aerobic mesophilic colonies by 4- and 2-log CFU compared with control, respectively. In conclusion, the use of MAP in combination with eugenol, thymol or menthol is an effective tool on maintaining cherry fruit quality and reducing the occurrence of decay. Industrial relevance The data presented in this work suggest that the use of pure essential oils (eugenol, thymol or menthol) in combination with modified atmosphere packaging (MAP) is an innovative and useful tool as alternative to the use of synthetic fungicides in fruits and vegetables, especially for those which are highly perishable and have a short shelf-life, as cherries. These compounds have been included in the list of generally recognized as safe (GRAS) compounds by FDA. As far as we know, this is the first paper dealing on the use of natural antifungal compounds and MAP and that these combined technologies confer benefits in fruit storage and retailing, with reduction in spoilage microorganisms, maintenance of cherry quality attributes and extension of shelf-life. The effects of these natural compounds on individual microorganisms, both responsible for spoilage and food-borne pathogens, as well as the minimum concentration to gain effectiveness deserve further research.

Specific Selection of Essential Oil Compounds for Treatment of Children’s Infection Diseases

Preparations with essential oils and their dosages applied in the therapy of children’s infectious diseases are well documented. In contrast, information is only sparingly available about uses of isolated pure essential oil compounds for the treatment of such infections. To find out safe antimicrobials from essential oils, microbiological inhibitory data of children pathogens were combined with oral and dermal acute toxicity data to calculate oral and dermal therapeutical indices (TI). The superiority of antibiotic drugs became obvious following calculating oral TIs of antimicrobials from higher plants, which suggests that oral administrations of essential oil compounds are not suitable to cure severe infections. A few selected compounds from higher plants show moderate effectiveness against gram-positive bacteria, yeast and fungi, but not gram-negative bacteria. Topical application or inhalation of selected compounds for the treatment or additional treatment of mild infections is reasonable.