Fungicidal activity of essential oils of Cinnamomum zeylanicum (L.) and Syzygium aromaticum (L.) Merr et L.M. Perry against crown rot and anthracnose pathogens isolated from banana

AIMS: To develop a post-harvest treatment system against post-harvest fungal pathogens of banana using natural products. METHODS AND RESULTS: Colletotrichum musae was isolated and identified as the causative agent responsible for anthracnose peel blemishes while three fungi, namely Lasiodiplodia theobromae, C. musae and Fusarium proliferatum, were identified as causative agents responsible for crown rot. During the liquid bioassay, cinnamon [Cinnamomum zeylanicum (L.)] leaf, bark and clove [Syzygium aromaticum (L.)] oils were tested against the anthracnose and crown rot pathogens. The test oils were fungistatic and fungicidal against the test pathogens within a range of 0.03-0.11% (v/v). CONCLUSIONS: Cinnamon and clove essential oils could be used as antifungal agents to manage post harvest fungal diseases of banana. SIGNIFICANCE AND IMPACT OF THE STUDY: Cinnamon and clove essential oil could be used as alternative post-harvest treatments on banana. Banana treated with essential oil is chemically safe and acceptable to consumers. Benomyl (Benlate), which is currently used to manage fungal pathogens, can cause adverse health effects and could be replaced with volatile essential oils.     

Chemical composition and antifungal activity of essential oil and various extract of Silene armeria L

The aims of this study were to examine the chemical composition of the essential oil isolated from the floral parts of Silene armeria L. by hydrodistillation, and to test the efficacy of essential oil and various leaf extracts (n-hexane, chloroform, ethyl acetate and methanol) as an antifungal potential. The GC-MS analysis determined that 28 compounds, which represented 89.03% of total oil, were present in the oil containing mainly 1-butene, methylcyclopropane, 2-butene and caryophyllene oxide. The oil (1000ppm/disc) and the leaf extracts (1500ppm/disc) revealed remarkable antifungal effect against Fusarium oxysporum, Fusarium solani, Phytophthora capsici, Colletotrichum capsici, Sclerotinia sclerotiorum, Botrytis cinerea and Rhizoctonia solani, in the growth inhibition range of 39.6-67.6% and 9.3-61.3%, respectively, along with their respective MIC values ranging from 62.5 to 1000mug/ml and 125 to 2000mug/ml. The essential oil had also a strong detrimental effect on spore germination of all the tested plant pathogens along with concentration as well as time-dependent kinetic inhibition of B. cinerea. Thus, the results obtained in this study demonstrate that S. armeria essential oil and various organic extracts possess a wide range spectrum of fungicidal activity and could become an alternative to synthetic fungicides for controlling certain important plant fungal diseases.     

Antibiofilm activity and post antifungal effect of lemongrass oil on clinical Candida dubliniensis isolate

Candidal infections are often difficult to eradicate due to the resistance of biofilms to antifungal agents. This study aimed at determining the effects of lemongrass (Cymbopogon citratus DC) oil against Candida dubliniensis in both planktonic and biofilms form. The results from broth microdilution method revealed that the minimum inhibitory and minimum fungicidal concentration of lemongrass oil on C. dubliniensis were 0.43 and 0.86 mg/ml, respectively. Employing a formazan salt (XTT tetrazolium) reduction assay for biofilm study, the results showed that the average percentage (mean ± SD) inhibition of lemongrass oil (0.43 mg/ml) on biofilm formation was 91.57 ± 1.31%, while it exhibited more than 80% killing activity against C. dubliniensis in biofilm at concentrations of 1.7 mg/ml. In addition, a significant reduction (P = 0.03) of candidal adhesion to acrylic occurred after a 15 min exposure to 1.7 mg/ml of lemongrass oil. Moreover, limited exposure of yeasts to lemongrass oil at subcidal concentration can suppress growth for more than 24 h. Altogether, the results obtained indicate that lemongrass oil possessed antifungal and antibiofilm activities and could modulate candidal colonization. Therefore, the efficacy of lemongrass oil merits further development of this agent for the therapy of oral candidiasis.     

Chemically characterized Cymbopogon martinii (Roxb.) Wats. essential oil for shelf life enhancer of herbal raw materials based on antifungal,antiaflatoxigenic, antioxidant activity,and favorable safety profile

The study reports antifungal and antiaflatoxigenic efficacy of chemically characterized Cymbopogon martinii essential oil (CMEO) against aflatoxigenic Aspergillus flavus causing infestation to stored herbal raw materials. In addition, the antioxidant activity and safety profile of CMEO were also assessed to recommend it as ideal preservative for stored herbal raw materials. The GC–MS of CMEO showed nerol as the major component (79.91%). CMEO inhibited growth and aflatoxin secretion of A. flavus LHPA₉ at 0.5 and 0.4 μl/ml respectively, showing better efficacy over synthetic antimicrobial Propineb 70. It also exhibited broad fungitoxic spectrum against fungi causing postharvest deterioration of herbal raw materials. The TEM analysis of CMEO-treated fungal cells showed disruption of plasma-membrane and deformed cell organelles. The EO also caused inhibition of ergosterol content emphasizing plasma membrane as active site during antimicrobial action. CMEO also exhibited pronounced antioxidant activity (IC₅₀ = 49 μl/ml) better than nerol, the major component of CMEO. The LD₅₀ of CMEO, determined through oral administration on mice, was calculated as 2569.16 mg/kg body weight indicating its favorable safety profile as preservative. CMEO may thus be recommended as postharvest preservative in enhancement of shelf life of herbal raw materials against storage fungi, mycotoxins, and oxidative deterioration.     

Rice weevil response to basil oil fumigation

Basil oil, Ocimum basilicum L., is a volatile plant essential oil that is known to have insecticidal activity against stored product pests such as rice weevil, Sitophilus oryzae (L.). Basil oil was diluted in acetone and applied to a sponge held inside a tea strainer for fumigations in containers with and without rice. Basil oil fumigation (3 ml, 10% concentration) caused high mortality in adult rice weevils when weevils were exposed in air in a sealed 1 L plastic container. However, when basil oil was placed in packaged rice, weevil mortality was low and reproduction was not affected. Effectiveness of plant essential oil fumigation should be conducted under realistic conditions to avoid experimental artifacts and misleading results.     

Antifungal effects of essential oils from oregano and fennel on Sclerotinia sclerotiorum

AIMS: The antifungal effects of essential oils of oregano (Origanum syriacum var. bevanii) and fennel (Foeniculum vulgare) were evaluated against Sclerotinia sclerotiorum. Effects of the essential oils on morphological structures of hyphae and sclerotia were studied under light and scanning electron microscopes (SEM). METHODS AND RESULTS: Inhibitory effects of volatile and contact phases of the essential oils used were determined on hyphae and sclerotia. Both essential oils have a marked antifungal effect against S. sclerotiorum. Soil amendment with essential oils has significant effect on reducing sclerotial viability. Both essential oils significantly inhibited the fungal growth in soil, thereby increasing the number of surviving tomato seedling by 69.8% and 53.3%, respectively. Light and SEM observations on pathogen hyphae and sclerotia revealed considerable morphological alterations in hyphae and sclerotia. CONCLUSIONS: The significant reduction in the mycelial growth and germination of sclerotia would greatly reduce the pathogen inoculum source. This may influence the rate of disease development in soil. SIGNIFICANCE AND IMPACT OF THE STUDY: Considering the reduction in the number of diseased plants in infested soil amended with essential oils, we concluded that oregano and fennel essential oils could be used as possible bio fungicides alternative to synthetic fungicides against phytopathogenic fungi.     

Antifungal activity of volatile compounds generated by essential oils against fungi commonly causing deterioration of bakery products

AIMS: To investigate the volatile fractions of 16 essential oils for activity against the more common fungi causing spoilage of bakery products, Eurotium amstelodami, E. herbariorum, E. repens, E. rubrum, Aspergillus flavus, A. niger and Penicillium corylophilum. METHODS AND RESULTS: The study applied 50 microl of pure essential oils in a sterilized filter paper, were carried out at pH 6 and at different water activity levels (0.80-0.90). First, a wheat flour based agar medium was used, where cinnamon leaf, clove, bay, lemongrass and thyme essential oils where found to totally inhibit all microorganisms tested. These five essential oils were then tested in sponge cake analogues, but the antifungal activity detected was much more limited. CONCLUSION: Five essential oils showed potential antifungal capacity against all species tested, over a wide range of water availability. Their activity, however, seems to be substrate-dependent. More research is needed to make them work in real bakery products, as in the preliminary study limited effectiveness was found. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential of the cinnamon leaf, clove, bay, lemongrass and thyme essential oils against species belonging to Eurotium, Aspergillus and Penicillium genus has been demonstrated.     

Nematicidal Activity of Plant Essential Oils against Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae)

The nematicidal activity and poisoning symptoms of 88 plant essential oils against Bursaphelenchus xylophilus were examined by an immersion bioassay. Results were compared with those of three trunk-injection nematicides: fenitrithion, levamisol hydrochloride, and morantel tartrate. As judged by 24 h LC₅₀ values, cinnamon bark oil (0.12 mg/ml) was the most effective nematicide, followed by coriander herb oil (0.14 mg/ml). Potent nematicidal activity was also observed with lemongrass, oregano, thyme red, and clove bud oils (LC₅₀, 0.57-0.88 mg/ml). Fenitrothion was ineffective (LC₅₀, > 10 mg/ml). In typical poisoning symptoms in B. xylophilus, these essential oils exerted rapid nematicidal action and the nematodes killed usually showed an extended shape, whereas levamisole hydrochloride and morantel tartrate usually exhibited semicircular and coiling shapes, respectively. The essential oils described merit further study as botanical nematicides for the control of pine wilt disease caused by B. xylophilus.     

Substrate-induced lipase gene expression and aflatoxin production in Aspergillus parasiticus and Aspergillus flavus

AIMS: To establish a relationship between lipase gene expression and aflatoxin production by cloning the lipA gene and studying its expression pattern in several aflatoxigenic and nontoxigenic isolates of Aspergillus flavus and A. parasiticus. METHODS AND RESULTS: We have cloned a gene, lipA, that encodes a lipase involved in the breakdown of lipids from aflatoxin-producing A. flavus, A. parasiticus and two nonaflatoxigenic A. flavus isolates, wool-1 and wool-2. The lipA gene was transcribed under diverse media conditions, however, no mature mRNA was detected unless the growth medium was supplemented with 0.5% soya bean or peanut oil or the fungus was grown in lipid-rich medium such as coconut medium. The expression of the lipase gene (mature mRNA) under substrate-induced conditions correlated well with aflatoxin production in aflatoxigenic species A. flavus (SRRC 1007) and A. parasiticus (SRRC 143). CONCLUSIONS: Substrate-induced lipase gene expression might be indirectly related to aflatoxin formation by providing the basic building block 'acetate' for aflatoxin synthesis. No direct relationship between lipid metabolism and aflatoxin production can be ascertained, however, lipase gene expression correlates well with aflatoxin formation. SIGNIFICANCE AND IMPACT OF THE STUDY: Lipid substrate induces and promotes aflatoxin formation. It gives insight into genetic and biochemical aspects of aflatoxin formation.     

Effects of lemongrass oil on the morphological characteristics and peptidoglycan synthesis of Escherichia coli cells

The antibacterial effect of lemongrass oil, obtained from the aerial part of Cymbopogon citratus, on cells of Escherichia coli was investigated by electron microscopy and by measuring cell wall formation. Two strains of E. coli K-12 were used, one of which required diaminopimelic acid in the growth medium for its murein formation. Lemongrass oil was found to elicit morphological changes like filamentation, inhibition of septum formation, spheroplast formation, production of 'blisters', 'bulges' or mesosomes, as well as lysis and development of abnormally shaped cells. The incorporation of radioactively labelled diaminopimelic acid into the cell wall murein of strain W7, was inhibited by lemongrass oil in a dose dependent way. The sequence of changes induced by lemongrass oil on bacterial cell morphology and also its interference with murein synthesis in E. coli cells were interpreted to involve the penicillin binding proteins PBP 2 and PBP 3.     

INVESTIGATIONS ON FUNGICIDES. I. FUNGICIDAL AND SYSTEMIC FUNGICIDAL ACTIVITY IN CERTAIN ARYLOXYALKANECARBOXYLIC ACIDS

Fifty-four aryloxyalkanecarboxylic acids have been examined as systemic fungicides. Of these, four which produced negligible damage in broad-bean seedlings yet conferred systemic fungicidal protection to broad beans against Botrytis fabae and to tomatoes against Alternaria solanixvere studied in detail. The direct fungicidal activity of twenty compounds was assessed against B. fabae and Pythium ultimum. No correlation between fungicidal and systemic fungicidal action toward B. fabae was established. Other possibilities regarding their mode of action as systemic fungicides are discussed. The systemic fungicidal activity of a-phenoxyziobutyric and 2:4:6-trichlorophenoxyacetic acids in beans and of the latter compound in tomato plants was found to depend upon seasonal factors, but for 3-phenoxybutyric and 5-phenoxycaproic acids such variation was not observed. Results obtained in the bean test by two methods of assessment were found to correlate. The potato petiole test (van Raalte) for assessing systemic fungicidal activity was studied and modified. Evidence was obtained that the results might be unreliable owing to toxic effects produced by the compounds on the petiole tissue. Attempts were made to avoid this complication, but when phytotoxicity was eliminated, little fungicidal activity was shown.     

Intercropping and mixed herb distillation for high-quality oil yield using lemon-scented basil (Ocimum africanum Lour.) cv. CIM-Jyoti and lemongrass (Cymbopogon flexuous (Nees ex Steud.) cv. Krishna

Intercropping and sole cropping of lemongrass and lemon-scented basil crops were evaluated to know the utility of lemongrass intercropping with lemon-scented basil oil yield and chemical profiles by utilizing the space available during the initial lag phase to increase the essential oil yield and income of the farmer. The results showed that Intercropping of lemongrass variety Krishna with variety CIM Jyoti of lemon-scented basil recorded significantly higher essential oil yield than different cultivation/cropping of lemongrass and lemon-scented basil. Meanwhile, the essential oil obtained after distillation of lemongrass, lemon-scented basil, and both oil samples are analyzed for chemical composition. A mixed distillation of lemongrass and lemon-scented basil recorded a higher percentage of citral I and citral II than lemongrass and lemon-scented basil. Also, camphor percentage is higher in the mixed sample compared to others. However, caryophyllene, citronellol, and geraniol percent were higher in lemon-scented basil than other essential oil samples. The gross income obtained under intercropping of lemongrass and lemon-scented basil during the initial lag phase was significantly higher than the sole cropping of lemongrass and lemon-scented basil. The co-distillation of lemon-scented basil lemongrass didn't impact odour and altered their essential oil's chemical profile.     

Control of Aspergillus section Flavi growth and aflatoxin accumulation by plant essential oils

Aims:  The antifungal effect of Pimpinella anisum (anise), Pëumus boldus (boldus), Mentha piperita (peppermint), Origanum vulgare (oregano) and Minthosthachys verticillata (peperina) essential oils against Aspergillus section Flavi (two isolates of Aspergillus parasiticus and two isolates of Aspergillus flavus ) was evaluated in maize meal extract agar at 0·982 and 0·955 water activities, at 25°C.
Methods and Results:  The percentage of germination, germ-tube elongation rate, growth rate and aflatoxin B₁ (AFB₁) accumulation at different essential oils concentrations were evaluated. Anise and boldus essential oils were the most inhibitory at 500 mg kg⁻¹ to all growth parameters of the fungus. These essential oils inhibited the percentage of germination, germ-tube elongation rate and fungal growth. AFB₁ accumulation was completely inhibited by anise, boldus and oregano essential oils. Peperina and peppermint essential oils inhibited AFB₁ production by 85–90% in all concentrations assayed.
Conclusions:  Anise and boldus essential oils could be considered as effective fungitoxicans for Aspergillus section flavi .
Significance and Impact of the Study:  Our results suggest that these phytochemical compounds could be used alone or in conjunction with other substances to control the presence of aflatoxigenic fungi in stored maize.     

Citral,a component of lemongrass oil,activates PPARα and γ and suppresses COX-2 expression

Lemongrass is a widely used herb as a food flavoring, as a perfume, and for its analgesic and anti-inflammatory purposes; however, the molecular mechanisms of these effects have not been elucidated. Previously, we identified carvacrol from the essential oil of thyme as a suppressor of cyclooxygenase (COX)-2, a key enzyme for prostaglandin synthesis, and also an activator of peroxisome proliferator-activated receptor (PPAR), a molecular target for “lifestyle-related” diseases. In this study, we evaluated the essential oil of lemongrass using our established assays for COX-2 and PPARs. We found that COX-2 promoter activity was suppressed by lemongrass oil in cell-based transfection assays, and we identified citral as a major component in the suppression of COX-2 expression and as an activator of PPARα and γ. PPARγ-dependent suppression of COX-2 promoter activity was observed in response to citral treatment. In human macrophage-like U937 cells, citral suppressed both LPS-induced COX-2 mRNA and protein expression, dose-dependently. Moreover, citral induced the mRNA expression of the PPARα-responsive carnitine palmitoyltransferase 1 gene and the PPARγ-responsive fatty acid binding protein 4 gene, suggesting that citral activates PPARα and γ, and regulates COX-2 expression. These results are important for understanding the anti-inflammatory and anti-lifestyle-related disease properties of lemongrass.     

阿维菌素与植物精油复配对朱砂叶螨杀螨的增效作用研究

为了得到对朱砂叶螨(Tetranychuscinnabarinus)具有较好杀螨活性的植物精油与阿维菌素复配配方,并为杀螨剂开发应用提供指导,本研究采用喷雾法测定了柠檬草、广藿香、山鸡椒、亚洲薄荷植物精油及阿维菌素对朱砂叶螨的毒力,分别采用共毒因子法和共毒系数法评价了山鸡椒和亚洲薄荷精油对阿维菌素的增效作用和复配最佳配比.结果表明,柠檬草精油和广藿香精油基本无杀螨活性,山鸡椒精油、亚洲薄荷精油处理朱砂叶螨24h后LC50分别为772.801mg/L和1040.187mg/L.阿维菌素与亚洲薄荷1∶272,1∶679复配具有增效作用.阿维菌素与亚洲薄荷1∶400复配时共毒系数最大,可达160.因此,阿维菌素与亚洲薄荷1∶400复配防治朱砂叶螨具有明显增效作用,这为杀螨剂的开发应用研究提供了参考.     

Characterization and anti-Aspergillus flavus impact of nanoparticles synthesized by Penicillium citrinum

This work was conducted to evaluate the ability of grape molding fungus; Penicillium citrinum to synthesize silver nanoparticles (Ag NPs). The potency of biosynthesized Ag NPs was checked against the aflatoxigenic Aspergillus flavus var. columnaris, isolated from sorghum grains. Biosynthesized Ag NPs were characterized and confirmed in different ways. X ray diffraction (XRD), Energy Dispersive Spectroscopy (EDS), Transmission Electron Microscopy (TEM) and optical absorption measurements confirmed the bio-synthesis of Ag NPs. The in vitro antifungal investigation showed that biosynthesized Ag NPs were capable of inhibiting the growth of aflatoxigenic A. flavus var. columnaris. Utilization of plant pathogenic fungi in the Ag NPs biosynthesis as well as the use of bio-Ag NPs to control fungal plant diseases instead of chemicals is promising. Further work is needed to confirm the efficacy of the bio-Ag NPs against different mycotoxigenic fungi and to determine the potent applicable doses.     

Antifungal activity of different plant extracts against Drechslera bicolor causing leaf blight of bell pepper

Aqueous extracts of 48 plants belonging to six different major groups of the plant kingdom, two commercially available botanicals and different fungicides were screened for antifungal activity against Drechslera bicolor causing leaf blight of bell pepper. The test fungi were isolated from bell pepper leaves collected from Udaipur district, Rajasthan, India. Among several botanicals, maximum inhibition of fungal growth was obtained by marigold, lat jeera, lemon grass, mehandi, onion and neem, respectively. Neem oil was superior over Zatropin against the fungus. Vitavax was also found as the best fungicide followed by Quintal and Saaf against the test fungus. The results revealed that these plants could be exploited for ecofriendly management of the diseases caused by the test fungal pathogen and seed biodeterioration during storage.     

Fungal Contamination of Raw Materials of Some Herbal Drugs and Recommendation of <Emphasis Type="Italic">Cinnamomum camphora</Emphasis> Oil as Herbal Fungitoxicant

The paper explores fungal infection and aflatoxin B(1) contamination of six medicinal plant samples viz. Adhatoda vasica Nees, Asparagus racemosus Linn., Evolvulus alsinoides Linn., Glycyrrhiza glabra Linn., Plumbago zeylanica Linn. and Terminalia chebula Retz. A total of 858 fungal isolates were detected from the raw materials. Maximum number of fungal isolates was detected from A. racemosus (228). The genus Aspergillus was found to be the most dominant genus causing infection to most of the raw materials. Among the 32 isolates of A. flavus tested, 13 isolates were found to be toxigenic elaborating aflatoxin B(1). The highest elaboration of aflatoxin B(1) was 394.95 ppb by the isolates of A. flavus from G. glabra. The essential oil of Cinnamomum camphora (L.) Presl showed efficacy in arresting aflatoxin B(1) by the toxigenic strain. The growth of a toxigenic strain of A. flavus decreased progressively with increasing concentration of essential oil from leaves of C. camphora. The oil completely inhibited aflatoxin B(1) production even at 750 ppm. Hence, the oil of C. camphora is recommended as herbal fungitoxicant against the fungal contamination of the raw materials.     

Fungitoxic and Phytotoxic Studies with Essential Oil of Ocimum adscendens

On screening the leaf extracts of some higher plants for their volatile antifungal activity against the test organism Aspergillus flavus, the extract of Ocimum adscendens exhibited the strongest fungitoxicity. The leaves showed maximum, fungitoxicity as compared with other plant parts. The volatile fungitoxic fraction obtained as an essential oil was standardized by various physico-chemical properties. The oil showed its fungicidal nature and broad range of activity at its minimum inhibitory concentration. The oil was thermostable and the toxicity remained unchanged even on autoclaving and on storage for up to 360 days. Moreover, the oil proved more active than some prevalent synthetic fungicides and exhibited no phytotoxic effect onVigna radiata.