In vivo antifungal activity of the essential oil of Bupleurum gibraltarium against Plasmopara halstedii in sunflower

The antifungal activity of the essential oil of the aerial parts of Bupleurum gibraltarium was evaluated against Plasmopara halstedii. Fungus spores were inoculated in sunflower seedlings, previously treated with several essential oil solutions, and the sporulation percentage was measured after an 11-day treatment. The oil at a concentration of 5.0 mL/L clearly inhibited the fungus sporulation. The contact between fungus sporangia and essential oil was minimized, so it seems that the oil pretreatment could activate the defense response of the sunflower seedlings against the pathogen invasion. The main compounds in the oil were sabinene (31.1%), alpha-pinene (15.6%), and 2,3,4-trimethylbenzaldehyde (10.9%), among a total of 65 components identified.     

Characterization of volatile constituents of Haplopappus greenei and studies on the antifungal activity against phytopathogens

Essential oil of Haplopappus greenei A. Gray was obtained by hydrodistillation of aerial parts, which were subsequently analyzed by gas chromatography and gas chromatography-mass spectrometry. Major components were identified as carvacrol (8.7%), beta-pinene (7.6%), trans-pinocarveol (6.2%), and caryophyllene oxide (5.8%), respectively. In total, 104 components representing 84.9% of the investigated essential oil were characterized. Furthermore, the essential oil was evaluated for antimalarial, antimicrobial, and antifungal activities. However, only antifungal activity was observed against the strawberry anthracnose-causing fungal plant pathogens Colletotrichum acutatum, Colletotrichum fragariae, and Colletotrichum gloeosporioides using the direct overlay bioautography assay. Major essential oil components were also evaluated for antifungal activity; the carvacrol standard demonstrated nonselective activity against the three Colletotrichum species and the other compounds were inactive.     

Essential oil constituents and in vitro antimicrobial activity of Decalepis hamiltonii roots against foodborne pathogens

Hydrodistillation of Decalepis hamiltonii roots yielded an essential oil (0.33% v/w) that contained 2-hydroxy-4-methoxybenzaldehyde (37.45%), 2-hydroxybenzaldehyde (31.01%), 4-O-methylresorcylaldehyde (9.12%), benzyl alcohol (3.16%), and alpha-atlantone (2.06%) as major constituents, with aromatic aldehydes constituting the main fraction of this root's essential oil. The oil was tested for its antimicrobial activity against foodborne pathogens responsible for food spoilage and human pathologies using standard antimicrobial assays. It exhibited strong antimicrobial activity against Bacillus cereus, Bacillus megaterium, Candida albicans, Escherichia coli, Micrococcus luteus, Micrococcus roseus, and Staphylococcus aureus at a concentration range of 1:0 with inhibitory activities of 27, 23, 16, 19, 22, 19, and 23 mm, respectively, which are comparable to those of the standards. The roots of D. hamiltonii, therefore, may be considered as an inexpensive source of an essential oil rich in antimicrobial compounds against foodborne pathogens.     

Cyclopenta[b]benzofurans from Aglaia species with pronounced antifungal activity against rice blast fungus (Pyricularia grisea)

Eight flavaglines, six cyclopenta[b]benzofurans, a cyclopenta[bc]benzopyran, and a benzo[b]oxepine, together with an aromatic butyrolactone were isolated from Aglaia odorata, A. elaeagnoidea, and A. edulis (Meliaceae) and tested against the three plant pathogens Pyricularia grisea, Fusarium avenaceum, and Alternaria citri for antifungal properties. Using the microdilution technique linked with digital image analysis of germ tubes, the benzofurans displayed strong activity, whereas the benzopyran, benzoxepine, and butyrolactone were inactive at the highest concentration tested. P. grisea, responsible for rice blast disease, was the most susceptible fungus against all benzofurans, with rocaglaol as the most active derivative. Based on EC(50), EC(90), and MIC values, the antifungal activity of rocaglaol was clearly higher than of the reference compounds, blasticidin S and Benlate.     

Larvicidal activity of lignans identified in Phryma leptostachya Var. asiatica roots against three mosquito species

The insecticidal activity of phytochemicals isolated from the roots of Phryma leptostachya var. asiatica against third instar larvae of Culex pipiens pallens, Aedes aegypti, and Ocheratatos togoi was examined. The two constituents of P. leptostachya var. asiatica roots were identified as the leptostachyol acetate (I) and 8'-acetoxy-2,2',6-trimethoxy-3,4,4',5'-dimethylenedioxyphenyl-7,7'-dioxabicyclo[3.3.0]octane (II) by spectroscopic analysis. Compound I was lethal to C. pipiens pallens, A. aegypti, and O. togoi at 10 ppm. Compound II showed weak or no insecticidal activity against three mosquito species at 10 ppm. The LC(50) values of I against C. pipiens pallens, A. aegypti, and O. togoi were 0.41, 2.1, and 2.3 ppm, respectively. Naturally occurring P. leptostachya var. asiatica root-derived compounds merit further study as potential mosquito larval control agents or lead compounds.     

Activity of antifungal proteins against mold in sorghum caryopses in the field

Sorghums were stressed with pathogenic fungi and sprinkling to determine relationships between changes in chitinase and sormatin in caryopses and grain mold resistance. Panicles of 10 cultivars differing in mold resistance and accumulation of antifungal proteins (AFPs) were inoculated at anthesis with Fusarium moniliforme and Curvularia lunata spores. Panicles were sampled at 30 and 50 days after anthesis, and caryopses were evaluated for chitinase and sormatin using western blots. Sprinkling panicles (to mimic rainfall) decreased sormatin and chitinase in most cultivars. Inoculation decreased AFPs in susceptible cultivars, but resistant cultivars maintained or increased AFPs in caryopses. Grain mold resistance corresponded to induction of AFP synthesis in response to sprinkling, fungal stress, and/or adverse field conditions. Sormatin and chitinase appear to be an active part of the defense mechanism of the caryopsis against grain mold.     

Chromatographic separation and in vitro activity of sorgoleone congeners from the roots of sorghum bicolor

Sorgoleone, 2-hydroxy-5-methoxy-3-[(8'Z,11'Z)-8',11',14'-pentadecatriene]-p-benzoquinone (1), and its corresponding hydroquinone are the major components of the root exudate of Sorghum bicolor. The name sorgoleone includes minor analogues differing in the length or degree of unsaturation of the 3-alkyl side chain. These compounds are known to be phytotoxic, probably through inhibition of photosystem II (PSII) driven oxygen evolution, as previously demonstrated for 1. Isolation of these sorgoleone congeners was achieved by C(8) column chromatography and argentation thin-layer chromatography, and the purified compounds were structurally characterized. The abilities of the minor sorgoleones to inhibit PSII were similar to that of the major compound, suggesting that all of these sorgoleone congeners contribute to the overall allelopathy of sorghum.     

Feeding deterrents from Aconitum episcopale roots against the red flour beetle, Tribolium castaneum

The screening for insecticidal principles from several Chinese medicinal herbs showed that the ethanol extract of Aconitum episcopale roots possessed significant feeding deterrence against the red flour beetle, Tribolium castaneum . From the ethanol extract, six feeding deterrents were isolated by bioassay-guided fractionation. The compounds were identified as chasmanine, crassicauline A, karacoline, sachaconitine, talatisamine, and yunaconitine from their spectroscopic data. Chasmanine, talatisamine, karacoline, and sachaconitine exhibited feeding deterrent activity against T. castaneum adults, with EC(50) values of 297.0, 342.8, 395.3, and 427.8 ppm, respectively. Yunaconitine and crassicauline A also possessed feeding deterrent activity against T. castaneum adults, with EC(50) values of 653.4 and 1134.5 ppm, respectively.     

Separation of tonoplast vesicles enriched in atpase and pyrophosphatase activity from maize roots

Continuous sucrose gradient (15–35%) centrifugation of maize (Zea mays L.) root microsomal membranes yielded two well‐separated fractions of tonoplast vesicles located between 19–21% (Peak I) and 25–26% sucrose (Peak II). Marker enzyme analyses indicated that both fractions were essentially free from plasma membrane, mitochondria and Golgi contaminations. The adenosine triphosphate (ATP) supported proton transport activity was found in both Peak I and Peak II with a 70 to 30% distribution. The pyrophosphatase (PP_;) supported proton transport activity was found only in Peak II. Both hydrolytic activities assumed a bell shape pH dependency with pH optimum at 6.5–7.5 and at 6.5–8.5 for ATPase and PP_; ase, respectively. The K_m of the ATPase and PP_iase, at their respective optimal pH, was found to be 1.2 mM and 0.02 mM, respectively. Both ATPase and PPjase activities were strongly inhibited by N.N'‐dicyclohexylcarbodiimide (DCCD) and diethylstilbestrol (DES) but not by molybdate. Peak I contained nitrate‐sensitive and vanadate‐insensitive ATP hydrolysis activity. In addition to catalyzing the nitrate and vanadate‐insensitive hydrolysis of PP; Peak II also contained some minor ATP hydrolysis activity that was sensitive to vanadate and nitrate. The results indicate that H⁺‐ATPases and H⁺‐PP_fase occur different populations of tonoplast vesicles from corn roots.     

Nematicidal and antifungal activities of annonaceous acetogenins from Annona squamosa against various plant pathogens

The methanol extract of Annona squamosa seeds was highly active against two phytoparasitic nematodes, Bursaphelenchus xylophilus and Meloidogyne incognita. It efficiently suppressed plant diseases, caused by Phytophthora infestans and Puccinia recondita. Ten annonaceous acetogenins (AAs) were isolated, and their chemical structures were identified by mass and nuclear magnetic resonance spectral data. Out of 10 substances, eight displayed strong in vitro nematicidal activity against B. xylophilus with LD(50) values ranging 0.006 to 0.048 μg/mL. Squamocin-G showed potent nematicidal activity against M. incognita. Squamocin, squamocin-G, and squamostatin-A also displayed potent in vitro and in vivo antifungal activities against P. infestans causing tomato late blight. In addition, squamostatin-A effectively controlled the development of wheat leaf rust caused by P. recondita. Our findings suggested that A. squamosa seeds and its bioactive AAs can be an alternative resource of a promising botanical nematicide and fungicide to control various plant diseases.     

Synthesis and antifungal activity of novel bisdithiocarbamate derivatives of carbohydrates against Fusarium oxysporum f. sp. lini

Novel carbamic esters possessing a carbohydrate moiety derived from glycerol or D-glucose with two N,N-diethyldithiocarbamoyl groups and a series of bisdithiocarbamic esters having a ketone or an alkyl ester have been synthesized. The in vitro activity of these new compounds was evaluated against Fusarium oxysporum f. sp. lini. Some of the compounds [bis[1,3-S-(N,N-diethyldithiocarbamoyl)]-1, 3-dideoxyglycerol) and diethyl N,N'-(1,3-dideoxyglycer-1, 3-diyl)bis(dithiocarbamate)] were more active for inhibiting vegetative mycelium growth than, respectively, the commercial N, N-diethyldithiocarbamic acid sodium salt and Maneb. The structure activity of these new compounds is discussed.     

Composition and antifungal activity on soil-borne pathogens of the essential oil of Salvia sclarea from Greece

The hydrodistilled essential oils of the aerial parts of wild-growing Salvia sclarea originated from two localities in Greece were analyzed by GC-MS. Sixty-six compounds, representing 93.26-98.19% of the oils, were identified. Linalyl acetate (19.75-31.05%), linalool (18.46-30.43%), geranyl acetate (4.45-12.1%), and alpha-terpineol (5.08-7.56%) were the main components. The antifungal activity of the oil of one locality and of the main components, linalyl acetate and linalool, was evaluated in vitro against three soil-borne pathogens.     

Inhibitory activity against tobacco mosaic virus (TMV) replication of pinoresinol and syringaresinol lignans and their glycosides from the root of Rhus javanica var. roxburghiana

Four new diepoxylignan glycosides, pinoresinol-4'-O-[6' '-O-(E)-feruloyl]-beta-D-glucopyranoside (1), pinoresinol-4'-O-[4' ',6' '-O-(E)-diferuloyl]-beta-D-glucopyranoside (2), pinoresinol-4'-O-[3' ',6' '-O-(E)-diferuloyl]-beta-D-glucopyranoside (3), and syringaresinol- 4'-O-[4' ',6' '-O-(E)-diferuloyl]-beta-D-glucopyranoside (4), together with three known compounds, pinoresinol (5), syringaresinol (6), and pinoresinol-4'-O-beta-D-glucopyranoside (7), were isolated from the n-butanol extract of Rhus javanica var. roxburghiana, and their structures were established using various spectroscopic techniques. Three glycosides (2-4) of the lignans showed moderate inhibition of multiplication of the tobacco mosaic virus.     

Nitrogenase activity on the roots of tropical forage grasses

Nitrogen fixation in the rhizospheres of field grown tropical forage grasses was studied by the acetylene reduction method. Values varied considerably between sites but indicate the possible economic importance of several of the species studied. Maximal nitrogenase activity measured (nmoles C₂H₄g^?1 dry roots h^?1) was 754 for Pennisetum purpureum, 750 for Brachiaria mutica, 341 for Digitaria decumbens, 299 for Panicum maximum, 283 for Paspalum notatum, 269 for Cynodon dactylon, 41 for Melinis minutiflora and 29 for Hyparrhenia rufa. Nitrogenase activity varied considerably with season and was maximal during active vegetative growth of two of the grasses. Significant differences between Paspalum notatum ecotypes and cultivars. in Azotohacter paspali occurrence and nitrogen fixation, indicate the possibility of plant breeding to enhance nitrogen fixation in grass rhizospherc associations. Other research lines of agronomic importance are fertilizer effects. In intact soil plant cores with the Paspalum system 10 parts/10⁶ NH_4⁺J-N inhibited nitrogenase activity within 2 h and 10 parts/10⁶ NO^?₃-N within 4 h. but after 1 week these effects were negligible. In the field, nitrogenase activity on roots of P. purpureum and D. decumbens, assayed 2 weeks after top dressings of 20 kg N ha^?1 as NH₄NO₃. was not affected even after eight such dressings.     

Insecticidal and antifungal activity of a protein from Pouteria torta seeds with lectin-like properties

This paper describes the purification and characterization of a novel protein from the seeds of Pouteria torta (family Sapotaceae). The protein was purified by a combination of gel filtration, ion-exchange, and reverse phase chromatographies. SDS-PAGE of the purified protein resulted in a single protein band of 14 kDa in the presence and absence of DTT. The lectin-like activity of pouterin was best inhibited by glycoproteins such as fetuin, asialofetuin, heparin, orosomucoid, and ovoalbumin. Pouterin inhibited the growth of the fungi Fusarium oxysporum and Colletotrichum musae and of the yeast Saccharomyces cerevisiae. The incorporation of pouterin into an artificial diet (final concentration = 0.12%, w/w) caused 50% mortality in larvae of the insect Callosobruchus maculatus, whereas 0.08% pouterin produced an ED50.     

Assessment of the availability of ions to plant roots from the determination of their chemical activity in nutrient solutions

In soilless culture, the chemical composition of the nutrient solutions is usually expressed in terms of ion concentrations which do not reflect their actual availability to plant roots : even in aqueous media, the ions supplied as salts can give rise to complexes ; furthermore, other kinds of ion interactions can be involved.

The VEGACT model, developed from thermodynamic concepts used in geochemistry, affords a more reliable assessment of the energy level of the ions. Using a particular example, at equal concentrations, the roots are shown to take up potassium or nitrate ions more readily than calcium or phosphate ions. This model also affords the prediction of the possible occurrence of phosphate precipitation within nutrient solutions of a given composition.     

Phytoalexins from the Vitaceae: biosynthesis, phytoalexin gene expression in transgenic plants, antifungal activity, and metabolism

Resistance of plants to infection by phytopathogenic microorganisms is the result of multiple defense reactions comprising both constitutive and inducible barriers. In grapevine, the most frequently observed and best characterized defense mechanisms are the accumulation of phytoalexins and the synthesis of PR-proteins. Particular attention has been given here to stilbene phytoalexins produced by Vitaceae, specifically, their pathway of biosynthesis (including stilbene phytoalexin gene transfer experiments to other plants) and their biological activity together with fungal metabolism.     

Resistance to powdery mildew in populations of barley landraces from Morocco

Forty-eight populations of barley landraces collected from Morocco were screened for resistance to powdery mildew and a number of different resistance genes were detected. Landraces originated from the collection of the International Center for Agricultural Research in the Dry Areas – ICARDA, Aleppo, Syria. Twenty populations of tested landraces (about 42%) showed resistance reactions and 46 single plant lines were selected. Fourteen of these lines were tested in the seedling stage with 17 and another 32 lines with 23 differential isolates of powdery mildew, respectively. The isolates were chosen according to their virulence spectra observed on the Pallas isolines differential set. Five lines originating from five populations of landraces showed resistance to all prevalent in Europe powdery mildew virulence genes. Thirty-five lines (76%) showed resistance reaction type 2. The distribution of reaction type scores indicated that about 81% of all reaction types observed were classified as powdery mildew resistance (scores 0, 1 and 2). In forty-one lines (89%) the presence of unknown genes alone or in combination with a specific one was detected. Four different resistance alleles (Mlat, Mla6, Mla14 and Mla22) were postulated to be present in the tested lines alone or in combination. Among specific resistance alleles the most common was allele Mlat (resistance Atlas). This allele was postulated to be present in twenty-three (50%) tested lines. The use of new identified sources of resistance to powdery mildew in barley breeding is discussed.     

Bioactivity-guided fractionation for the butyrylcholinesterase inhibitory activity of furanocoumarins from Angelica archangelica L. roots and fruits

Isolation and identification of the inhibitors of butyrylcholinesterase (BChE), obtained from the extracts of roots and fruits of Angelica archangelica L., are reported. Our results confirmed the weak inhibitory effect of Angelica roots on acetylcholinesterase activity. BChE inhibition was much more pronounced at a concentration of 100 μg/mL for hexane extracts and attained a higher rate than 50%. The TLC bioautography guided fractionation and spectroscopic analysis led to the isolation and identification of imperatorin from the fruit's hexane extract and of heraclenol-2'-O-angelate from the root's hexane extract. Both compounds showed significant BChE inhibition activity with IC(50) = 14.4 ± 3.2 μM and IC(50) = 7.5 ± 1.8 μM, respectively. Only C8-substituted and C5-unsubstituted furanocoumarins were active, which could supply information about the initial structures of specific BChE inhibitors.     

Isolation and antifungal activity of 4-phenyl-3-butenoic acid from Streptomyces koyangensis strain VK-A60

An antifungal compound was isolated from the culture broth of Streptomyces koyangensis strain VK-A60 using various chromatographic procedures. On the basis of the high-resolution EI-mass and 1H and 13C NMR data, the compound was identified as 4-phenyl-3-butenoic acid. Colletotrichum orbiculare, Magnaporthe grisea, and Pythium ultimum were most sensitive to 4-phenyl-3-butenoic acid. Strong inhibitory effects of 4-phenyl-3-butenoic acid also were found against Pectobacterium carotovorum subsp. carotovorum and Ralstonia solanacearum. 4-Phenyl-3-butenoic acid effectively suppressed the development of M. grisea on rice leaves at the concentration of more than 10 microg/mL, and the protective activity was in general similar to that of the commercial fungicide tricyclazole. Treatment with 100 microg/mL of 4-phenyl-3-butenoic acid also effectively inhibited the anthracnose development on cucumber plants, although its in vivo efficacy was somewhat less effective than that of the commercial fungicide chlorothalonil.