Antifungal activity of volatile fractions of essential oils from four aromatic wild plants in israel

Essential oils were extracted fromMajorana syriaca, Satureja thymbra, Micromeria fruticosa, andSalvia triloba, and their volatile fractions were tested for their antifungal activity against the soil-borne pathogensFusarium oxysporum andMacrophomina phaseolina and the foliar pathogensBotrytis cinerea andExserohilum turcicum. Results showed a fungistatic effect of 1, 2.5, and 5l of the various essential oils on fungal mycelium growth. The most significant effect was exerted by essential oils extracted fromM. syriaca, which inhibited the growth ofB. cinerea by 44% and of all the other fungi tested by 100%.Contribution from the Agricultural Research Organization, the Volcani Center, Bet Dagan, Israel. No. 3555-E, 1992 series.     

Phytotoxic and antimicrobial activity of volatile constituents ofArtemisia princeps var.orientalis

The volatile constituents ofArtemisia princeps var.orientalis (wormwood) were investigated for phytotoxic and antimicrobial activities. The germination and radicle elongation of receptor plants were inhibited by volatile substances emitted from wormwood leaf and effects were concentration-dependent. Essential oil of the plant extracted by Karlsruker's apparatus suppressed seed germination and seedling elongation of the receptor plants at a threshold concentration of 4.8l/100 ml.Escherichia coli was not susceptible to the wormwood essential oil, but the growth ofBacillus subtilis, Aspergillus nidulans, Fusarium solani, andPleurotus ostreatus was inhibited severely.     

Allelopathy ofSasa cernua

Sasa (Sasa cernua Makino) is a very serious weed pest. Its allelopathy was studied using lettuce, wheat, timothy, and green amaranth as testing species. Cultured in the rhizosphere soil ofSasa cernua, the seedlings were inhibited by 42–80% compared with the controls cultured in normal soil and vermiculite. The phenolic fraction extracted with 1 M NaOH from the rhizosphere soil ofS. cernua caused significant inhibitions on the seed germination and seedling growth of lettuce, timothy, green amaranth, and barnyard grass.p-Coumaric, ferulic, vanillic, andp-hydroxybenzoic acids andp-hydroxybenzaldehyde were identified as the main allelochemicals in sasa soil by HPLC and [¹H]NMR. Their contents in the rhizosphere soil were 5640, 1060, 860, 810 and 630 μg/100 g soil. The neutral fraction inhibited the seed germination and seedling growth of lettuce in the TLC direct bioassay. Volatile compounds released from sasa leaves also inhibited the growth of lettuce, wheat, timothy, and green amaranth grown under light, and the growth of etiolated seedlings of barley and wheat. These results confirm thatS. cernua produces typical allelopathy through its rhizosphere soil and air space.     

Effect of Essential Oils from <Emphasis Type="Italic">Lippia geminata</Emphasis> and <Emphasis Type="Italic">Cymbopogon jwarancusa</Emphasis> on In vitro Growth and Sporulation of Two Rice Pathogens

Sheath blight and brown spot disease of rice caused by Rhizoctonia solani and Bipolaris oryzae causes significant yield loss in rice production worldwide. The present study was undertaken to examine the effect of two essential oils (EOs) from Lippia geminata and Cymbopogon jwarancusa on in vitro growth and sporulation of these two pathogens. The fungal radial growth was inhibited at very low concentration (25 ppm) of the EOs. Similarly, fungal spore production was also inhibited up to ≥80% at 500 ppm of EOs. However, fungal sporulation was completely retarded at 1,000 ppm of L. geminata EO. Very low oil concentrations (10 ppm) accelerated the radial growth (0–5 mm) and spore germination (3.5–8.5%) of the pathogens. At higher oil concentrations, the mycelial growth and spore productions were completely inhibited. The IC₅₀ value of the EO of C. jwarancusa was 365.45 and 336.74 ppm and for L. geminata, it was 420.16 and 481.47 ppm against B. oryzae and R. solani, respectively. GC–MS analysis of the oils showed 54.36% piperitone and 30.86% α-phellandrene as major compounds in C. jwarancusa whereas 25.9% geranial and 14.6% neral in L. geminata oil. Essential oils from Lippia geminata and Cymbopogon jwarancusa appear to be good candidates for the in vitro control of these two rice pathogens and can be successfully utilized in management strategies of pathogens in appropriate formulation.     

Chemical Composition and Ability of Essential Oils from Six Aromatic Plants to Counteract Lipid Oxidation in Emulsions

Essential oils with antioxidant properties are of increasing interest in West Africa where there are many antioxidant rich plants. The objective of this study was to determine the essential oil extracted from six native plants (Lippia multiflora, Lippia rugosa, Monodora tenuifolia, Ocimum gratissimum, Pimenta racemosa, Cymbopogon citratus) extracted by hydrodistillation from local plants in Benin. These samples were also evaluated for their antioxidant capacity using the conjugated autoxidizable triene (CAT) assay performed in stripped tung oil-in-water emulsion. The essential oil of P. racemosa, containing high amounts of chavicol (10.3 %) and eugenol (54.5 %), showed the strongest antioxidant activity, followed by that from O. gratissimum containing large amounts of thymol (50.2 %). The essential oil extracted from M. tenuifolia exhibited a moderate antioxidant activity. This essential oil is primarily composed of sesquiterpene alcohols such as α-cadinol (20.5 %), its isomer, α-muurolol (14.7 %), and germacrene D-4-ol (16.8 %). Essential oils from L. multiflora, L. rugosa and C. citratus oils showed poor ability to protect tung oil from oxidation. Finally, essential oils containing phenolic compounds and, in a lesser extent, sesquiterpene alcohols, exhibited the highest CAT values indicating that these compounds are the key determinants of the antioxidant activity of these essential oils in oil-in-water emulsions.     

Extraction of Essential Oil from Laurel Leaves by Using Microwaves

Abstract

The effects of microwave power and time in solvent-free microwave extraction (SFME) on the yield and composition of the essential oil obtained from laurel (Laurus nobilis L.) leaves were studied. The extraction was also performed by hydrodistillation as a control. Specific gravities and refractive indices of the essential oils obtained by different methods and at various conditions were also examined. The main constituent of laurel essential oil was 1,8-cineole (630–730 mg/mL). Essential oils obtained by SFME and hydrodistillation were comparable with respect to both yield and composition while the process time was reduced by 55–60% when SFME was used.     

Evaluation of ammonium thiosulfate as a soil urease inhibitor

Interest in use of ammonium thiosulfate (ATS) in conjunction with urea as a fertilizer has been stimulated by recent reports that this compound retards hydrolysis of urea by soil urease and thereby reduces volatilization of urea N as ammonia from soils fertilized with urea. We evaluated ATS as a soil urease inhibitor by studying its effects on urea hydrolysis, seed germination, and early seedling growth in soil. We found that ATS significantly retarded urea hydrolysis only when applied at rates as high as 2,500 or 5,000µg g^–1 soil, whereasN-(n-butyl) thiophosphoric triamide (NBPT) (a patented inhibitor of urea hydrolysis in soil) caused substantial retardation of urea hydrolysis when applied at rates as low as 1µg g^–1 soil. We also found that ATS had an adverse effect on germination of corn or wheat seeds in soil when applied at the rate of 2,500 or 5,000µg g^–1 soil and caused a dramatic reduction of early seedling growth of corn or wheat when applied at the rate of 1,000, 2,500, or 5,000µg g^–1 soil. These findings indicate that ATS has little, if any, potential value for retarding hydrolysis of urea fertilizer in soil.     

Allelopathy in agroecosystems: Wheat phytotoxicity and its possible roles in crop rotation

The germination rates of cotton and wheat seeds were significantly affected by various extracts of wheat mulch and soils collected from the wheat field. This toxicity was even more pronounced against seedling growth. Five allelochemics: ferulic,p-coumaric,p-OH benzoic, syringic, and vanillic acids, were identified from the wheat mulch and its associated soil. Quantitatively, ferulic acid was found at higher concentrations thanp-coumaric acid in the soil. Various concentrations of ferulic andp-coumaric acids were toxic to the growth of radish in a bioassay. The functional aspects of allelochemic transfer from decaying residue to soil and the subsequent microbial degradation within agroecosystems are discussed, particularly as they relate to wheat crop rotation, with wheat and cotton, in Pakistan.     

Antibacterial and Antifungal Activities of the Essential Oils of Two Saltcedar Species from Tunisia

The chemical composition of the volatile constituents from the flowering parts of Suaeda fructicosa and Limonium echioides were analysed by GC-FID and GC-MS. Sixty-five compounds were identified in L. echioides aerial parts. 48 out of 65 were found common to the aerial part of S. fructicosa. Palmitic acid was found as a predominant compound in both tested halophytic oils. Furthermore, the essential oil was tested against six bacteria and four fungi at different concentrations. Both oils, tested at 0.5 and 0.8 mg ml⁻¹, inhibited the visible growth of Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus, Escherichia coli and Salmonella typhimurium, but no antibacterial effect was detected against Pseudomonas aeruginosa. Additionally, both halophytic oils failed to show antifungal activity against all the test fungi when applied at 80, 200 and 500 μg/disc.     

植物精油及化合物对埃及伊蚊幼虫的生物活性

植物精油及化合物对登革热的主要媒介埃及伊蚊幼虫具有杀幼虫活性。从269种植物中提取的361个植物精油中,超过60%具有较高的生物活性(LC_(50)100 mg/L),这些植物主要为桃金娘科、唇形科和芸香科。精油中富含苯丙烷类、倍半萜烯类和单萜烯类物质具有最高的活性。着重介绍了植物精油对埃及伊蚊幼虫的活性、影响精油的活性因素、分子结构与活性相关性及精油及化合物的作用机理。     

Allelopathic activity in wheat-conventional and wheat-no-till soils: Development of soil extract bioassays

The primary objective of this research was to determine if soil extracts could be used directly in bioassays for the detection of allelopathic activity. Here we describe: (1) a way to estimate levels of allelopathic compounds in soil; (2) how pH, solute potential, and/or ion content of extracts may modify the action of allelopathic compounds on germination and radicle and hypocotyl length of crimson clover (Trifolium incarnatum L.) and ivyleaved morning glory (Ipomoea hederacea L. Jacquin.); and (3) how biological activity of soil extracts may be determined. A water-autoclave extraction procedure was chosen over the immediate-water and 5-hr EDTA extraction procedures, because the autoclave procedure was effective in extracting solution and reversibly bound ferulic acid as well as phenolic acids from wheat debris. The resulting soil extracts were used directly in germination bioassays. A mixture of phenolic acids similar to that obtained from wheat-no-till soils did not affect germination of clover or morning glory and radicle and hypocotyl length of morning glory. The mixture did, however, reduce radicle and hypocotyl length of clover. Individual phenolic acids also did not inhibit germination, but did reduce radicle and hypocotyl length of both species. 6-MBOA (6-methoxy-2,3-benzoxazolinone), a conversion product of 2-o-glucosyl-7-methoxy-1,4-benzoxazin-3-one, a hydroxamic acid in living wheat plants, inhibited germination and radicle and hypocotyl length of clover and morning glory. 6-MBOA, however, was not detected in wheat debris, stubble, or soil extracts. Total phenolic acids (FC) in extracts were determined with Folin and Ciocalteu's phenol reagent. Levels of FC in wheat-conventionaltill soil extracts were not related to germination or radicle and hypocotyl length of either species. Levels of FC in wheat-no-till soil extracts were also not related to germination of clover or morning glory, but were inversely related to radicle and hypocotyl length of clover and morning glory. FC values, solute potential, and acidity of wheat-no-till soil extracts appeared to be independent (additive) in action on clover radicle and hypocotyl length. Radicle and hypocotyl length of clover was inversely related to increasing FC and solute potential and directly related to decreasing acidity. Biological activity of extracts was determined best from slopes of radicle and hypocotyl length obtained from bioassays of extract dilutions. Thus, data derived from the water-autoclave extraction procedure, FC analysis, and slope analysis for extract activity in conjunction with data on extract pH and solute potential can be used to estimate allelopathic activity of wheat-no-till soilsThe use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of products named, or criticism of similar ones not mentioned.     

Difference in hydroxamic acid content in roots and root exudates of wheat (Triticum aestivum L.) and rye (Secale cereale L.): Possible role in allelopathy

Hydroxamic acids (Hx) produced by some cereal crops have been associated with allelopathy. However, the release of Hx to the soil by the producing plant-an essential condition for a compound to be involved in allelopathy-has not been shown. GC and HPLC analysis of roots and root exudates of wheat (Triticum aestivum L.) and rye (Secale cereale L.) cultivars, with high Hx levels in their leaves, demonstrated the presence of these compounds in the roots of all cultivars analyzed and in root exudates of rye. Moreover, bioassays employing root exudates collected from wheat and rye seedlings demonstrated that only rye exudates inhibited root growth of wild oats,Avena fatua L., a weed whose root growth is inhibited by Hx. These results suggest that rye could potentially interfere with the growth ofAvena fatua in nature and that this interference could be due to the release of Hx to the soil by way of roots.     

Devil's-claw (Proboscidea louisianica), essential oil and its components

The potential allelopathic activity of devil's-claw [Proboscidea louisianica (Mill.) Thellung] essential oil and a few of the compounds it contains on the elongation of cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) radicles was studied using a Petri dish bioassay. Essential oil was collected by steam distillation using an all-glass-Teflon assembly. Ether extracts of the steam distillates from fresh devil's-claw were inhibitory to cotton and wheat radicle elongation. The following six components of devil's-claw essential oil identified by CGC-MS-DS were inhibitory to cotton and/or wheat at a concentration of 1 mM: vanillin, piperitenone, -cadinene,p-cymen-9-ol, -bisabolol, and phenethyl alcohol.     

BIOFUMIGANT COMPOUNDS RELEASED BY FIELD PENNYCRESS (<Emphasis Type="Italic">Thlaspi arvense</Emphasis>) SEEDMEAL

Defatted field pennycress (Thlaspi arvense L.) seedmeal was found to completely inhibit seedling germination/emergence when added to a sandy loam soil containing wheat (Triticum aestivum L.) and arugula [Eruca vesicaria (L.) Cav. subsp. sativa (Mill.) Thell.] seeds at levels of 1.0% w/w or higher. Covering the pots with Petri dishes containing the soil-seedmeal mixture decreased germination of both species at the lowest application rate (0.5% w/w), suggesting that the some of the phytotoxins were volatile. CH₂Cl₂, MeOH, and water extracts of the wetted seedmeal were bioassayed against wheat and sicklepod (Senna obtusifolia (L.) H. S. Irwin & Barneby) radicle elongation. Only the CH₂Cl₂ extract was strongly inhibitory to both species. Fractionation of the CH₂Cl₂ extract yielded two major phytotoxins, identified by gas chromatography–mass spectrometry and NMR as 2-propen-1-yl (allyl) isothiocyanate (AITC) and allyl thiocyanate (ATC), which constituted 80.9 and 18.8%, respectively, of the active fraction. When seeds of wheat, arugula and sicklepod were exposed to volatilized AITC and ATC, germination of all three species was completely inhibited by both compounds at concentrations of 5 ppm or less. In field studies, where seedmeal was applied at 0.50, 1.25, and 2.50 kg/m² and tarped with black plastic mulch, all of the treatments significantly reduced dry weight of bioassay plants compared to the tarped control, with the highest seedmeal rate decreasing dry matter to less than 10% of the control 30 d after seedmeal application. Field pennycress seedmeal appears to offer excellent potential as a biofumigant for high-value horticultural crops for both conventional and organic growers.Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Fumigant toxicity of essential oils against four major stored-product insects

The fumigant toxicity of 28 essential oils extracted from various spice and herb plants and some of their major constituents were assessed for adult coleopteransRhyzopertha dominica, Oryzaephilus surinamensis, Tribolium castaneum, andSitophilus oryzae. Three groups of active materials were distinguished: (1) The compounds terpinen 4-ol, 1,8-cineole, and the essential oils of three-lobed sage, sage, bay laurel, rosemary, and lavender were most active againstR. dominica; (2) The compounds linalool,-terpineol, and carvacrol and the essential oils of oregano, basil, Syrian marjoram, and thyme were most active againstO. surinamensis; and (3) the compound 1,8-cineole and the essential oils anise and peppermint were active againstT. castaneum.     

Comparative Study of Essential Oils Extracted from Algerian Myrtus communis L. Leaves Using Microwaves and Hydrodistillation

Two different extraction methods were used for a comparative study of Algerian Myrtle leaf essential oils: solvent-free-microwave-extraction (SFME) and conventional hydrodistillation (HD). Essential oils analyzed by GC and GC-MS presented 51 components constituting 97.71 and 97.39% of the total oils, respectively. Solvent-Free-Microwave-Extract Essential oils SFME-EO were richer in oxygenated compounds. Their major compounds were 1,8-cineole, followed by α-pinene as against α-pinene, followed by 1,8-cineole for HD. Their antimicrobial activity was investigated on 12 microorganisms. The antioxidant activities were studied with the 2,2-diphenyl-1-picrylhydrazyl (DPPH^•) radical scavenging method. Generally, both essential oils showed high antimicrobial and weak antioxidant activities. Microstructure analyses were also undertaken on the solid residue of myrtle leaves by Scanning Electronic Microscopy (SEM); it showed that the SFME-cellular structure undergoes significant modifications compared to the conventional HD residual solid. Comparison between hydrodistillation and SFME presented numerous distinctions. Several advantages with SFME were observed: faster kinetics and higher efficiency with similar yields: 0.32% dry basis, in 30 min as against 180 min for HD.     

Phytotoxicity of <Emphasis Type="Italic">Phytolacca americana</Emphasis> Leaf Extracts on the Growth,and Physiological Response of <Emphasis Type="Italic">Cassia mimosoides</Emphasis>

We examined the allelochemical effects of control soil, native soil (treated soil), and leaf extracts of Phytolacca americana (pokeweed) on the germination rate and seedling growth of Cassia mimosoides var. nomame. We also studied the resulting changes in root-tip ultrastructure and peroxidase isozyme biochemistry. P. americana leaf extract inhibited seed germination, seedling growth, and biomass when compared to control and treated soil. Root and shoot growth in treated soil was stimulated relative to control soil, but root growth was inhibited by 50% in the leaf extract treatment. Biomass of C. mimosoides seedlings grown on leaf extract was reduced sevenfold when compared to the control seedlings. The amounts of total phenolic compounds in the leaf extract, treated soil, and control soil were 0.77, 0.14, and 0.03 mg l⁻¹, respectively. The root tips of C. mimsoides treated with leaf extracts of P. americana showed amyloplasts and large central vacuoles with electron-dense deposits inside them when compared to control root tips. The activity of guaiacol peroxidase (GuPOX) in whole plant, roots, and shoots of C. mimosoides increased as leaf extract increased; maximum activity was observed in extract concentrations of 75% and higher. Root GuPOX activity was three times higher than in shoots. Therefore, we conclude that inhibition of C. mimosoides growth is related to the phenolic compounds in the P. americana leaf extract and the ultrastructure changes in root-tip cells and increased GuPOX activity is a response to these allelochemicals.     

Allelopathic and autotoxic effects ofAnastatica hierochuntica L.

Laboratory experiments were undertaken to investigate the autotoxic effects ofAnastatica hierochuntica and possible effects on five other desert plants:Rumex cyprius, Trigonella stellata, Diplotaxis harra, Cleome droserifolia, andFarsetia aegyptia. Seed germination, seedling growth, and cell division of all species tested were inhibited by the shoot aqueous extract ofA. hierochuntica. A gradual increase in the percentage of prophase and decrease in the other mitotic stages as well as the mitotic index were observed with increasing extract concentration. At an extract concentration of 8% the mitotic index was reduced from the control by 55% inC. droserifolia, 54% inT. stellata, 45% inF. aegyptia, 43% inA. hierochuntica, and 35% inR. cyprius. The inhibitory substances are apparently released onto soil by repeated washing of the standing plants by rain and dew interception.     

A growth inhibitory factor from lambsquarters (Chenopodium album)

Aqueous extract of air-dried lambsquarters (Chenopodium album) at 25 mg/ml significantly inhibited germination and growth of radish and wheat seeds. Soybean seed germination was not inhibited; however, hypocotyl growth was significantly reduced. Germination of radish seeds in sand amended with pulverized lambsquarters shoots at 2 and 4 mg/g was reduced 40 and 95%, respectively. Shoot dry weight and plant height were also reduced 30 and 9%, respectively, at 4 mg/g, but not at 2 mg/g concentration. Residues after extraction with water incorporated in sand were not inhibitory, indicating water solubility of the inhibitor(s). Aqueous extract of shoots decomposed for five days lost nearly 40% of its inhibitory effect; 20% of it still persisted in the extract of shoots decomposed for 30 days. The filtrate from ultrafiltration of aqueous extract through a pad of molecular-weight cutoff 1000 inhibited radish seeds germination and growth, indicating that the molecular weight of the inhibitor(s) was less than 1000. Partitioning of the aqueous extract by a series of solvents resulted in isolation of an inhibitor(s) in the butanol fraction. Seven phenolics were identified in this fraction using high-performance liquid chromatography (HPLC). Paper chromatographic analysis of the butanol fraction revealed six bands, of which one band withR _f =0.83 inhibited germination and growth of radish seeds. Chlorogenic acid identified by HPLC appeared to be the principal component of the phytotoxin.     

Phytotoxicity of water-soluble substances from alfalfa and barley soil extracts on four crop species

Problems associated with continuously planting alfalfa (Medicago saliva L.) or seeding to thicken depleted alfalfa stands may be due to autotoxicity, an intraspecific form of allelopathy. A bioassay approach was utilized to characterize the specificity and chemical nature of phytotoxins in extracts of alfalfa soils as compared to fallow soil or soil where a cereal was the previous crop. In germination chamber experiments, water-soluble substances present in methanol extracts of soil cropped to alfalfa or barley (Hordeum vulgare L.) decreased seedling root length of alfalfa L-720, winter wheat (Triticum aestivum L. Nugaines) and radish (Raphanus sativa L. Crimson Giant). Five days after germination, seedling dry weights of alfalfa and radish in alfalfa soil extracts were lower compared to wheat or red clover (Trifolium pralense L. Kenland). Growth of red clover was not significantly reduced by soil extracts from cropped soil. Extracts of crop residue screened from soil cropped to alfalfa or barley significantly reduced seedling root length; extracts of alfalfa residue caused a greater inhibition of seedling dry weight than extracts of barely residue. A phytotoxic, unidentified substance present in extracts of crop residue screened from alfalfa soil, which inhibited seedling root length of alfalfa, was isolated by thin-layer chromatography (TLC). Residues from a soil cropped continuously to alfalfa for 10 years had the greatest phytotoxic activity.