Antifungal and Herbicidal Effects of Fruit Essential Oils of Four Myrtus communis Genotypes

The chemical composition of the essential oils isolated by hydrodistillation from the fruits of four selected Myrtus communis L. genotypes from Turkey was characterized by GC‐FID and GC/MS analyses. 1,8‐Cineole (29.20–31.40%), linalool (15.67–19.13%), α‐terpineol (8.40–18.43%), α‐pinene (6.04–20.71%), and geranyl acetate (3.98–7.54%) were found to be the major constituents of the fruit essential oils of all M. communis genotypes investigated. The oils were characterized by high amounts of oxygenated monoterpenes, representing 73.02–83.83% of the total oil compositions. The results of the fungal growth inhibition assays showed that the oils inhibited the growth of 19 phytopathogenic fungi. However, their antifungal activity was generally lower than that of the commercial pesticide benomyl. The herbicidal effects of the oils on the seed germination and seedling growth of Amaranthus retroflexus L., Chenopodium album L., Cirsium arvense (L.) Scop ., Lactuca serriola L., and Rumex crispus L. were also determined. The oils completely or partly inhibited the seed germinations and seedling growths of the plants. The findings of the present study suggest that the M. communis essential oils might have potential to be used as natural herbicides as well as fungicides.     

Chemical Composition and Biological Activities of Tunisian Cupressus arizonica Greene Essential Oils

The chemical composition of the essential oils obtained by hydrodistillation of leaves, stems, and female cones of Cupressus arizonica Greene , grown in Tunisia, was studied by GC‐FID and GC/MS analyses. Altogether, 62 compounds were identified, 62 in the leaf oil, 19 in the cone oil, and 24 in the stem oil. The cone and stem oils were mainly composed by monoterpene hydrocarbons (96.6 and 85.2%, resp.). In the leaf oil, the total sesquiterpene fraction constituted 36.1% and that of the monoterpene hydrocarbons 33.8% of the total oil composition. The three oils were evaluated for their in vitro herbicidal activity by determining their influence on the germination and the shoot and root growth of the four weed species Sinapis arvensis L., Lolium rigidum Gaudin , Trifolium campestre Schreb ., and Phalaris canariensis L. At the highest doses tested (0.8 and 1.0 mg/ml), the leaf essential oil inhibited either totally or almost completely the seed germination and the shoot and root growth of S. arvensis and T. campestre. The oils were also tested for their antifungal activity; however, their effects on the fungal growth were statistically not significant.     

Essential oils of catmint (<Emphasis Type="Italic">Nepeta meyeri</Emphasis> Benth.) induce oxidative stress in early seedlings of various weed species

The essential oils from the aerial parts of catmint (Nepeta meyeri Benth.) were analyzed by hydrodistillation with GC–MS. Fourteen compounds were identified in the yellowish essential oil of the plant, representing more than 99.07% of the oil, of which the major components were found to be 4aα,7α,7aβ-nepetalactone (83.4%) and 4aα,7α,7aα-nepetalactone (8.83%). The oils were characterized by relatively high content of oxygenated monoterpenes, and were tested on the germination and antioxidative systems in early seedlings of seven weed species (Amaranthus retroflexus L., Bromus danthoniae Trin., Bromus intermedius Guss., Chenopodium album L., Cynodon dactylon L., Lactuca serriola L., and Portulaca oleracea L.) and autotoxicity. The essential oil of N. meyeri inhibited seed germination by more than 50% in three weed species (B. danthoniae, B. intermedius, and L. serriola) when applied at a concentration of 0.01%. When the same oils were applied at 0.02% concentration, the inhibition of germination was more than 70% in two weeds (C. album and C. dactylon) and was 100% in four weeds (A. retroflexus, B. danthoniae, B. intermedius, and L. serriola). The essential oils increased CAT activity in all the weed species and decreased SOD activity, except in A. retroflexus. POX activity did not exhibit a revealing situation in the weed species tested. The essential oils increased the level of lipid peroxidation and hydrogen peroxide (H₂O₂) concentration in all the weeds studied. Our results show that the essential oils of N. meyeri have an important phytotoxic effect on seed germination and, consequently, seedling growth by exhausting antioxidative system of the weeds. The phytotoxic activity of the essential oils may be attributed to their relatively high content of oxygenated monoterpenes, especially 4aα,7α,7aβ-nepetalactone. It can be suggest that the essential oils of N. meyeri have the potential to be used as a bioherbicide.     

Phytotoxic effects of Lantana camara, Eucalyptus camaldulensis and Eriocephalus africanus essential oils in weeds of Mediterranean summer crops

The essential oil composition of Lantana camara, Eucalyptus camaldulensis and Eriocephalus africanus was analyzed by means of GC and GC–MS and bioassayed in order to determine their activity against Amaranthus hybridus and Portulaca oleracea. E. camaldulensis essential oil, with spathulenol as the main compound, was the most effective, completely inhibiting germination and seedling growth on both weeds. The essential oil of E. africanus, rich in artemisia ketone, showed activity similar to that of E. camaldulensis on A. hybridus, but it was not so effective against P. oleracea, and L. camara essential oil, with high percentages in sesquiterpene hydrocarbons, also showed higher phytotoxic activity against A. hybridus, inhibiting its germination and seedling length; however, it showed no effect against P. oleracea germination, whereas was effective in significantly reducing its seedling growth at all concentrations assayed. The results suggest the possible use of these essential oils as natural herbicides.     

Chemical Composition and Allelopathic,Phytotoxic and Pesticidal Activities of Atriplex cana Ledeb. (Amaranthaceae) Essential Oil

The chemical composition and allelopathic, phytotoxic and pesticidal activities of Atriplex cana Ledeb . (Amaranthaceae) essential oil were investigated. Nineteen compounds were identified via GC/MS, representing 82.3 % of the total oil, and the most abundant constituents were dibutyl phthalate (21.79 %), eucalyptol (20.14 %) and myrtenyl acetate (15.56 %). The results showed that volatile organic compounds (VOCs) released by A. cana significantly inhibited seedling growth of Amaranthus retroflexus L. and Poa annua L., and 80 g of fresh stems and leaves of A. cana in a 1.5 L airtight container almost completely suppressed the seed germination of both plants. Meanwhile, 5 μg/mL essential oil completely inhibited the seed germination of A. retroflexus, Medicago sativa L., P. annua and Echinochloa crusgalli L. Pesticidal testing revealed that the essential oil had strong behavioral avoidance and lethal effects on Aphis pomi DeGeer . Five microliters of essential oil/Petri dish treatment resulted in an 84.5 % mortality rate after 12 h, and the mortality rate reached nearly 100 % after 48 h. This report is the first one on the chemical composition as well as the biological activity of the essential oil of A. cana, and our results indicate that the oil is valuable in terms of being further exploited as a bioherbicide/insecticide.     

Chemical Composition and Antimicrobial and Allelopathic Activity of Tunisian Conyza sumatrensis (Retz.) E.Walker Essential Oils

Conyza sumatrensis (Retz.) E.Walker (Asteraceae) is a spontaneous annual herb, fairly widespread throughout Tunisia, which has rarely been studied or valued in any sector. Essential oils were obtained by hydrodistillation of different parts (flower heads, leaves, stems, and roots) of C. sumatrensis plants, which were collected in autumn (November 2007) at the flowering stage in the area of Monastir, Tunisia. In total, 98 compounds, representing 88.1–99.3% of the oil composition, were identified by GC‐FID and GC/MS analyses. The root essential oil was distinguished by its high content in acetylenes (matricaria ester, 4 ; 74.3%), while those from flower heads and leaves were dominated by oxygenated sesquiterpenes (61.1 and 50.3%, resp.). The oils of C. sumatrensis from Tunisia belonged to a matricaria ester/caryophyllene oxide chemotype. All the oils were evaluated for antibacterial, antifungal, and allelopathic activities. The results indicate that the leaf oil exhibited significant in vitro antibacterial activity against Enterococcus faecalis, Staphylococcus aureus, and Proteus mirabilis and that the C. sumatrensis oils isolated from the aerial parts presented high mycelia‐growth inhibition of Candida albicans and the filamentous fungi tested. Moreover, the essential oils of the different plant parts inhibited the shoot and root growth of Raphanus sativus (radish) seedlings. Indeed, the inhibition of the hypocotyl growth varied from 28.6 to 90.1% and that of the radicle from 42.3 to 96.2%.     

Chemical composition of Thuja orientalis L. essential oils and study of their allelopathic potential on germination and seedling growth of weeds

The chemical composition of essential oils isolated by hydrodistillation from needles and cones of Thuja orientalis L. was analysed by gas chromatography-flame ionisation detection and gas chromatography–mass spectrometry. Twenty-one compounds were identified; quantitative differences, mainly, between cone and needle oils were observed. Both oils were rich in monoterpene hydrocarbons and the major constituents were α-pinene (64.2 and 49.3%, respectively, in cones and needles), β-phellandrene (6.7–9.6%) and α-cedrol (3.9 and 8.2%). Herbicidal properties of Thuja essential oils were assessed against three invasive weed species in crops: Sinapis arvensis L., Phalaris paradoxa L. and Lolium rigidum Gaud. The study of herbicidal activity was carried out on the weed germination, seed vigour and seedling growth. Our results showed a strong inhibitory effect on all tested weeds following a dose-dependent manner, property that could be valourised in managing biocontrol of weeds.     

Composition and Antimicrobial Activity of the Essential Oils of Laserpitium latifolium L. and L. ochridanum Micevski (Apiaceae)

The chemical composition and antimicrobial activity of essential oils of Laserpitium latifolium and L. ochridanum were investigated. The essential oils were isolated by steam distillation and characterized by GC‐FID and GC/MS analyses. All essential oils were distinguished by high contents of monoterpenes, and α‐pinene was the most abundant compound in the essential oils of L. latifolium underground parts and fruits (contents of 44.4 and 44.0%, resp.). The fruit essential oil was also rich in sabinene (26.8%). Regarding the L. ochridanum essential oils, the main constituents were limonene in the fruit oil (57.7%) and sabinene in the herb oil (25.9%). The antimicrobial activity of these essential oils as well as that of L. ochridanum underground parts, whose composition was reported previously, was tested by the broth‐microdilution method against four Gram‐positive and three Gram‐negative bacteria and two Candida albicans strains. Except the L. latifolium underground‐parts essential oil, the other investigated oils showed a high antimicrobial potential against Staphylococcus aureus, S. epidermidis, Micrococcus luteus, or Candida albicans (minimal inhibitory concentrations of 13.0–73.0 μg/ml), comparable to or even higher than that of thymol, which was used as reference compound.     

Impact of chemical polymorphism of Thymus pulegioides on some associated plant species under natural and laboratory conditions

Abstract

Allelopathic potential of Thymus pulegioides L. chemical polymorphism was investigated under natural and laboratory conditions. A field analysis of 127 natural habitats hosting chemotypes of T. pulegioides with different ratios of phenolics, geraniol, and ɑ-terpinyl acetate was conducted. Effects of chemotypes, and their main compounds on seed germination and radicle growth of Trifolium pratense L. and Poa pratensis L. were conducted under laboratory conditions. Field analysis showed that Poa species were more plentiful in comparison with Trifolium species, independent of the chemotypical composition of T. pulegioides habitats. Laboratory tests with plant-acceptors showed a stronger inhibitory effect of essential oils on the germination and radicle growth of P. pratensis but in some instances germination was stimulated. Dissimilar effects were observed for the same allelochemical through air and water on the same plant-acceptor. Significantly, different effects of essential oils on radicle growth occurred in T. pratense and P. pratensis: with sensitivity to the phenolic chemotype via air and the ɑ-terpinyl acetate chemotype through water. This demonstrates that chemical polymorphism can expand communication opportunities of T. pulegioides with associated plant species. Combining investigations in natural habitats with laboratory experiments can help understand the effect of chemical polymorphism on plant-plant ecological interactions.     

Essential Oil Compositions and Antibacterial and Antioxidant Activities of Five Lavandula stoechas Cultivars Grown in Thailand

The essential oils of five Lavandula stoechas cultivars grown in Thailand were characterized for their volatile compounds using GC‐FID and GC/MS methods as well as screened for antibacterial and antioxidant activities. Dried aerial parts, including flowers and stems from each cultivar, were subjected to hydrodistillation for 4 h. The essential oil yields were 0.18 %–0.82 % w/w. Of the 95 compounds detected and identified, 1,8‐cineole, fenchone, and camphor were considered the major compounds. Essential oil from each cultivar demonstrated different patterns of antibacterial activity and a variety of antioxidant properties. The highest antibacterial activity, MIC=0.39 mg mL^?1, was observed from the essential oil of L. stoechas ‘major’ (against Klebsiella pneumoniae and Salmonella typhimurium) and the essential oil of L. stoechas ‘white lavender’ (against S. typhimurium). The essential oil of L. stoechas×viridis ‘St. Brelade’ possessed the highest antioxidant capacity, as determined by the DPPH and ABTS assays (IC₅₀ of 67.65 and 89.26 mg mL^?1, respectively). The results indicated that some of these essential oils could be used as key ingredients in lavender oil products in Thailand to increase their therapeutic efficacy, depending on their intended application.     

Variation of the Chemical Composition and Antimicrobial Activity of the Essential Oils of Natural Populations of Tunisian Daucus carota L. (Apiaceae)

The essential oils of Daucus carota L. (Apiaceae) seeds sampled from ten wild populations spread over northern Tunisia were characterized by GC‐FID and GC/MS analyses. In total, 36 compounds were identified in the D. carota seed essential oils, with a predominance of sesquiterpene hydrocarbons in most samples (22.63–89.93% of the total oil composition). The main volatile compounds identified were β‐bisabolene (mean content of 39.33%), sabinene (8.53%), geranyl acetate (7.12%), and elemicin (6.26%). The volatile composition varied significantly across the populations, even for oils of populations harvested in similar areas. The chemometric principal component analysis and the hierarchical clustering identified four groups, each corresponding to a composition‐specific chemotype. The in vitro antimicrobial activity of the isolated essential oils was preliminarily evaluated, using the disk‐diffusion method, against one Gram‐positive (Staphylococcus aureus) and two Gram‐negative bacteria (Escherichia coli and Salmonella typhimurium), as well as against a pathogenic yeast (Candida albicans). All tested essential oils exhibited interesting antibacterial and antifungal activities against the assayed microorganisms.     

Study of antifungal activities of seven essential oils from some Iranian medicinal plants against various postharvest phytopathogenic fungi

The aim of this study was to find the antifungal activities of seven essential oils from some Iranian medicinal plants that have maximum (100%) inhibition effect on the mycelium growth of postharvest phytopathogenic fungi. Among 20 examined species belonging to three families, only 7 species could stop the mycelium growth of phytopathogenic fungi. The selected plants include Trachyspermum ammi, Zataria multiflora Boiss., Satureia hortensis, Caryophillum aromaticus, Menthe piperita, Cuminum cyminum L. and Carum carvi, and fungi include Aspergillus flavus, Botrytis cinerea, Penicillium italicum, Penicillium expansum, Penicillium commune, Rhizopus stolonifer and Rhizopus lyococcus. The results showed that the essential oil of these plants could stop the mycelium growth at 500 ppm, but could not completely inhibit the spore germination, however reduced the spore germination to 80–90%. Among the fungi Rhizopus stolonifer and Rhizopus lyococcus are more resistant to the inhibition effects of essential oils. Among the plants, Cuminum cyminum L. and Carum carvi were slightly weaker than other plants. Also except for Cuminum cyminum L. and Carum carvi, the essential oils of other plants had fungicide effect while these two plants in most cases had fugistatic effect. The results showed that these essential oils can be used as an effective alternative control method.     

Chemical Composition and Antibacterial Activity of Essential Oils from Different Parts of Litsea cubeba

The composition of the essential oils obtained by hydrodistillation of different parts of Litsea cubeba, including roots, stems, leaves, alabastra (flower buds), flowers, and fruits, were investigated by GC (RI) and GC/MS. The antimicrobial activity of the oils was assessed with disc diffusion and microbroth dilution assays. The results showed large variations in the composition among the different oils. The major components in the oils from roots and fruits, from stems, leaves, and alabastra, and from flowers were citral B (neral), β‐phellandrene, and β‐terpinene, respectively. The inhibition zone (DD) and MIC values for the bacterial strains tested, which were all sensitive to the essential oil of L. cubeba, were in the range of 10.1–35.0 mm and 100–1000 μg/ml, respectively. Hence, the oils of the various parts showed moderate activity against the tested bacteria. This investigation showed that the antibacterial activity of L. cubeba was attributed to the essential oils, thus they can be a potential medicinal resource.     

Larvicidal and Nematicidal Activities of the Leaf Essential Oil of Croton regelianus

The chemical composition of the leaf essential oil of Croton regelianus collected from wild plants growing in two different sites at Ceará State (Brazil) was analyzed by GC/MS and GC‐FID. Twenty monoterpenoids, representing more than 96% of the chemical composition of the oils, were identified and quantified. The oils showed similar chemical composition but considerable variation in the levels of each constituent. Ascaridole (33.9–17.0%), p‐cymene (22.3–21.6%), and camphor (13.0–3.1%) were the predominant constituents. The monoterpene ascaridole was isolated and characterized by spectroscopic data. The essential oils and the isolated compounds were tested against Aedes aegypti and Artemia sp. larvae, and the root knot nematode Meloidogyne incognita. The bioassay results show that the essential oil of C. regelianus and ascaridole were moderately active against the M. incognita, but strongly effective against both A. aegypti and Artemia sp. larvae.     

In Vitro Trypanocidal and Antibacterial Activities of Essential Oils from Four Species of the Family Annonaceae

The objective of this study was to evaluate the chemical composition, and the trypanocidal and antibacterial activities of the essential oils from four species of Annonaceae: Bocageopsis multiflora (Mart .) R.E.Fr ., Duguetia quitarensis Benth ., Fusaea longifolia (Aubl. ) Saff ., and Guatteria punctata (Aubl .) R.A.Howard . The chemical composition of the essential oils from the aerial parts yielded 23, 20, 21 and 23 constituents, respectively, which were identified by GC/MS. The trypanocidal activity was evaluated against the amastigote and trypomastigote forms of T. cruzi. The antibacterial activity was evaluated by the microdilution method against enterohemorrhagic Escherichia coli, Pseudomonas aeruginosa, Streptococcus mutans, Streptococcus pyogenes, and methicillin‐resistant Staphylococcus aureus. The results of trypanocidal activity showed that the essential oils of the four species were active at the tested concentrations, with G. punctata essential oil being the most active, with IC₅₀=0.029 μg/mL, and selectivity index (SI)=32, being 34 times more active than the reference drug benznidazole. All EOs showed strong antibacterial activity (minimum inhibitory concentrations of 4.68–37.5 μg/mL) against strains of S. mutans.     

Chemical,Antioxidant, and Antimicrobial Evaluation of Essential Oils and an Anatomical Study of the Aerial Parts from Baccharis Species (Asteraceae)

The aim of this study was to evaluate the chemical, antioxidant, and antimicrobial activity of the essential oils as well as the anatomy of the aerial parts from Baccharis aracatubaensis, Baccharis burchellii, and Baccharis organensis owing to the therapeutic potential of Baccharis. The volatile constituents were analyzed using GC/MS, the antioxidant activity was evaluated by oxygen radical absorbance capacity (ORAC_FL) and DPPH assays, and the antimicrobial activity by a microdilution technique. Of the 56 compounds identified, only seven (β‐caryophyllene, γ‐muurolene, bicyclogermacrene, β‐germacrene, spathulenol, τ‐muurolol, and α‐cadinol) were common in the three specimens studied. Of these, γ‐muurolene was found abundantly in B. aracatubaensis, while bicyclogermacrene was abundant in B. burchellii and B. organensis. The essential oils exhibited antioxidant activity in the ORAC_FL (>500.0 μmol TE g^?1) and DPPH assays. However, they did not exhibit any antimicrobial activity. Secretory ducts and flagelliform glandular trichomes were observed in the anatomical study of all the Baccharis species studied.     

Chemical Composition,Antimicrobial, Nitric Oxide Inhibition and Cytotoxic Activity of Essential Oils from Zanthoxylum acanthopodium DC. Leaves and Stems from Vietnam

This study was aimed to investigate the chemical composition and biological activities of leaf and stem essential oils of Zanthoxylum acanthopodium DC. from Vietnam. Their chemical composition was analyzed by GC/MS. Antimicrobial activities were evaluated by microdilution broth assay. Anti-inflammatory activity was evaluated by the ability to inhibit nitric oxide production in macrophage cells. Cytotoxic activity was evaluated using the sulforhodamine B assay on three human cancer cell lines. Forty-four compounds were identified in the leaf oil, among which dehydroaromadendrane (23.4 %), (E)-carpacin (17.6 %), 2-tridecanone (12.2 %), and 9-methyl-2-decanone (11.8 %) were the most abundant. The stem oil contained fifty-five identified constituents, mainly γ-gurjunene (51.1 %) and butyl acetate (11.8 %). Both oils exhibited inhibitory effects on three bacterial strains, namely S. aureus, E. coli, P. aeruginosa and a fungal strain C. albican, while showed insignificant effects on B. subtilis, L. fermentum, and S. enterica. Both oils showed weak NO production inhibition in LPS-induced RAW264.7 cells, but exhibited potent cytotoxic activity against all three tested cell lines SK-LU-1, MCF-7, and HepG2 with the IC₅₀ values ranging from 16.03±0.77 to 35.60±1.62 μg/mL. This is the first report on the antimicrobial, anti-inflammatory and cytotoxic activities of essential oils from the leaves and stems of Z. acanthopodium.     

In vitro evaluation of antileishmanial activity and toxicity of essential oils of Artemisia absinthium and Echinops kebericho

Potential toxicity, costs, and drug‐resistant pathogens necessitate the development of new antileishmanial agents. Medicinal and aromatic plants constitute a major source of natural organic compounds. In this study, essential oils of Artemisia absinthium L. and Echinops kebericho Mesfin were investigated by GC and GC/MS analyses. Isolated oils were screened for antileishmanial activity against two Leishmania strains (L. aethiopica and L. donovani), and toxicity on the human monocytic leukemia (THP‐1) cell line and red blood cells in vitro. GC/MS Analysis revealed 65 compounds (93.74%) for Artemisia absinthium and 43 compounds (92.85%) for Echinops kebericho oil. The oils contained the oxygenated monoterpene camphor (27.40%) and the sesquiterpene lactone dehydrocostus lactone (41.83%) as major constituents, respectively. Both oils showed activity against promastigote (MIC 0.0097–0.1565 μl/ml) and axenic amastigote forms (EC₅₀ 0.24–42.00 nl/ml) of both leishmania species. Weak hemolytic effect was observed for both oils, showing a slightly decreased selectivity index (SI 0.8–19.2) against the THP‐1 cell line. Among the two oils tested, E. kebericho exerted strong antileishmanial activity that was even higher than that of amphotericin B with significant cytotoxicity. This study, therefore, demonstrated the potential use of both oils as source of novel agents for the treatment of leishmaniasis.     

Repellency of essential oils against Nephotettix cincticeps: Laboratory and glasshouse assays

Four oils from Piper nigrum, Litsea cubeba, Zanthoxylum bungeanum and Curcuma longa were obtained by ethanol extraction. The repellency of these oils and two major compounds (linalool and piperine) was evaluated against female adult and third‐instar nymphs of the rice pest, Nephotettix cincticeps, under laboratory and glasshouse conditions. Paired‐choice and no‐choice assays were used for each treatment, with essential oils evaluated after 24 and 48 hr of exposure and chemical compounds evaluated after 12 and 24 hr of exposure. The potential effects of essential oils on activities of glutathione S tranferase (GST), carboxyl esterase (CarE) and acetyl cholinesterase (AchE) were also evaluated after 48 hr of exposure to leafhoppers. The constituents of the essential oils were determined using GC‐MS. The results showed that the major components in the oils were piperine (34.75%) for P. nigrum, 9,12‐octadecadienoic acid (Z,Z) (18.74%) for L. cubeba, ethanone, 1‐(2‐hydroxy‐4,6‐dimethoxyphenyl) (18.51%) for Z. bungeanum and turmerone (15.89%) for C. longa. In all cases, the essential oils repelled female adults and third‐instar nymphs of N. cincticeps. The repellency of the tested oils and chemicals compounds in the paired‐choice assay was higher than in the no‐choice assay. In all experimental conditions, P. nigrum and C. longa oils were the most and the least potent, respectively. Linalool was the best repellent among the single‐tested compounds under laboratory conditions. In the glasshouse study, the highest repellency was observed in the mixture of linalool and piperine. GST and CarE activities of leafhoppers were significantly enhanced by exposure to the four essentials oils; AchE activity increased significantly only in the P. nigrum and L. cubeba assays. Our results clearly indicate that the tested oils and chemical compounds are promising agents for developing plant‐based pesticides to control N. cincticeps.     

Repellent,Insecticidal and Antimicrobial Activities of Leaf Essential Oils from Three Eucalyptus Species

Developing effective and eco‐friendly antimicrobials and pesticides has become a highly important issue. The repellent, insecticidal and antimicrobial activity of essential oils (EOs) isolated by hydrodistillation from dried leaves of the three Eucalyptus species (E. cloeziana, E. umbellata and E. benthamii) were investigated. During GC/MS analysis, α‐pinene (47.36 %), 1,8‐cineol (38.53 %) and α‐pinene (35.31 %) were identified as major components of E. cloeziana, E. umbellata and E. benthamii, respectively. The EOs from E. cloeziana exhibited the longest effective protection time (465 min, at 50.0 % w/w) for humans among the EOs studied. The effective protection time was 30 min and 300 min at concentrations of 12.5 % (w/w) and 25.0 % (w/w), respectively. Fumigating insecticidal activity of EOs from three Eucalyptus species was tested by airtight fumigation in conical flask, which indicated that essential oils had a highly and rapidly insecticidal activity on Culex pipiens quinquefasciatus. The antimicrobial activity of EOs was evaluated by using disc diffusion and agar dilution methods. There was no significant difference in the antibacterial activity of EOs from E. cloeziana and E. umbellate and they had the same MICs (20 mL/L) on Staphylococcus aureus, Salmonella typhi, Bacillus subtilis and Escherichia coli. E. benthamii had the worst microbial inhibitory effect among the three Eucalyptus essential oils and the MIC value for the test species is 40 mL/L except for Rhodotorula Harrison (10 mL/L).