Seasonal variation in antifungal,antibacterial and acetylcholinesterase activity in seven South African seaweeds

Seven seaweeds were collected from the intertidal zone at Rocky Bay on the east coast of South Africa. The species were Caulerpa racemosa var. laetevirens, Codium capitatum, Halimeda cuneata, Ulva fasciata, Amphiroa bowerbankii, Amphiroa ephedraea and Dictyota humifusa. Six bimonthly collections were made within a few days of the new moon to correspond with spring tide. Methanol extracts were tested for antifungal, antibacterial and acetylcholinesterase (AChE) inhibitory activity. No seasonal variation was observed in antifungal activity, with D. humifusa extracts being the most active. The seaweed extracts inhibited the growth of the Gram-positive bacteria, with Bacillus subtilis being more susceptible than Staphylococcus aureus. Dictyota humifusa was the only seaweed able to inhibit the Gram-negative Escherichia coli. Seasonal variation in antibacterial activity was observed, with the extracts generally having no activity in summer and having antibacterial activity in late winter (July collection) and early spring (September and November collections). Dictyota humifusa was the most effective seaweed species, having antibacterial activity throughout the year. All the extracts tested had AChE inhibitory activity, with no seasonal variation in the levels of activity. Dictyota humifusa extracts were the most effective at inhibiting AChE activity.     

Antifungal activity of essential oils and their synergy with fluconazole against drug-resistant strains of Aspergillus fumigatus and Trichophyton rubrum

The aim of this study was to screen certain plant essential oils and active compounds for antifungal activity and their in vitro interaction with fluconazole against drug-resistant pathogenic fungi. The methods employed in this work included disc diffusion, broth macrodilution, time kill methods and checkerboard microtiter tests. Oil compositions were evaluated by gas chromatography-mass spectrometry (GC-MS) analysis. Transmission electron microscopy was used to assess the effect of essential oils on cellular structures of test fungi. Test fungal strains exhibited resistance to at least two drugs (fluconazole and itraconazole). Among the 21 essential oils or active compounds tested, ten showed promising antifungal activity. GC-MS analysis revealed the presence of major active compounds in the essential oils used. Cinnamaldehyde showed the most promising antifungal activity and killing potency against Aspergillus fumigatus MTCC2550 and Trichophyton rubrum IOA-9. Cinnamaldehyde showed strongest synergy with fluconazole against A. fumigatus and T. rubrum by reducing the minimum inhibitory concentration of fluconazole up to 8-fold. Zones of lysis of the cell wall and cell membrane appeared to be where cinnamaldehyde acted on fungi. This study highlights the broad spectrum antifungal activity of essential oils and active compounds and their synergy with fluconazole against drug-resistant fungi.     

Molecular characterization of fungal endophytes from Calotropis procera plants in Taif region (Saudi Arabia) and their antifungal activities

Fungal endophytes were isolated from the leaves of Calotropis procera (Apocynaceae) collected from Taif region (Saudi Arabia). Thirty-three different taxa were recovered. The overall foliar colonization rate was 35.1%. A total of 161 isolates were obtained and identified into 33 distinct operational taxonomic units based on the sequencing of the internal transcribed spacer regions of the rRNA gene. The most prevalent fungi were Aspergillus flavus, Chaetomium globosum, Cochliobolus lunatus, Fusarium dimerum, F. oxysporum, and Penicillium chrysogenum. A total of 161 isolates were tested for antifungal activities against four plant pathogenic fungi (Alternaria alternata, Fusarium oxysporum, Botrytis cinerea, and Pythium ultimum), of which 33 isolates showed antifungal activity against at least one plant pathogenic fungi. Four isolates of Chaetomium globosum and three isolates of Myrothecium verrucaria showed the strongest antifungal activity. This study reported the occurrence of a much wider spectrum of fungi, when compared with previous work. Also, it confirmed the variation of different isolates from the same species in terms of antifungal activity.     

Herbal remedies for the management of seed-borne fungal pathogens by an edible plant Decalepis hamiltonii (Wight & Arn)

Abstract

Antifungal activity-guided assay of solvent extracts of Decalepis hamiltonii (Wight & Arn) (Asclepiadaceae) against important phytopathogenic fungi, known to cause diseases in sorghum, maize and paddy proved to be highly significant. Among the five solvent extracts tested, Petroleum ether extract showed highly significant antifungal activity. Phytochemical analysis revealed that the antifungal active principle is a phenolic compound. TLC separation of the phenolic fraction using chloroform as an eluting solvent revealed the presence of seven bands but the antifungal activity was observed only in band five with R_f value 0.77. The antifungal active compound is identified as 2-hydroxy-4-methoxybenzaldehyde based on Nuclear Magnetic Resonance (NMR) and mass spectral analysis. The Minimal inhibitory concentration (MIC) varied between 200 μg ml^?1 and 700 μg ml^?1 depending on the fungal species. Seed treatment of the active principle significantly increased seed germination and seed vigour with a corresponding decrease in seed mycoflora. The antifungal active compound was effective against all the 24 fungal species tested suggesting broad-spectrum antifungal activity. Comparative evaluation of the active principle with the synthetic fungicides revealed that the antifungal activity of the active principle obtained from the plant is better than that of synthetic fungicide. This plant being an edible one can be exploited in the management of seed-borne pathogenic fungi and the prevention of biodeterioration of grains and mycotoxin elaboration during storage.     

黄花倒水莲内生真菌生物活性评价及HNLF-44菌株鉴定

为充分开发黄花倒水莲(Polygala fallax)的内生真菌资源，获得具有抗植物病原真菌、抗氧化活性的内生真菌，该文以黄花倒水莲内生真菌为研究对象，使用平板对峙法检测内生真菌对6种植物病原真菌的抑菌活性，测定内生真菌发酵液的DPPH清除自由基能力和总还原能力，评价内生真菌的抗氧化活性，并对具有强抑菌活性和抗氧化活性的菌株进行形态和ITS鉴定。结果表明：(1)黄花倒水莲内生真菌中有2株内生真菌对香蕉专化尖孢镰刀菌、柑橘树脂病菌、叶点霉菌、香蕉具条叶斑病菌、茄病镰刀菌、三七根腐病菌具有明显的抑菌活性，抑菌率在50.3%～91.4%之间，其中HNLF-5对柑橘树脂病菌的抑菌率为73.2%,HNLF-44对香蕉专化尖孢镰刀菌抑菌率为91.4%。(2)内生真菌发酵液具有良好的抗氧化活性，DPPH清除率均在80%以上，总还原能力吸光值范围为0.279 2～0.748 8。(3)HNLF-44菌株为链格孢属真菌。该研究表明，药用植物黄花倒水莲内生真菌具有较好的生物活性，为后续从黄花倒水莲内生真菌中挖掘潜在新型抑菌活性和抗氧化活性物质奠定了基础。     

A non-polyene antifungal antibiotic fromStreptomyces albidoflavus PU 23

In all 312 actinomycete strains were isolated from water and soil samples from different regions. All these isolates were purified and screened for their antifungal activity against pathogenic fungi. Out of these, 22% of the isolates exhibited activity against fungi. One promising strain,Streptomyces albidoflavus PU 23 with strong antifungal activity against pathogenic fungi was selected for further studies. Antibiotic was extracted and purified from the isolate.Aspergillus spp. was most sensitive to the antibiotic followed by other molds and yeasts. The antibiotic was stable at different temperatures and pH tested and there was no significant loss of the antifungal activity after treatment with various detergents and enzymes. Synergistic effect was observed when the antibiotic was used in combination with hamycin. The antibiotic was fairly stable for a period of 12 months at 4°C. The mode of action of the antibiotic seems to be by binding to the ergosterol present in the fungal cell membrane resulting in the leakage of intracellular material and eventually death of the cell. The structure of the antibiotic was determined by elemental analysis and by ultraviolet (UV), Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and liquid chromatography mass spectra (LCMS). The antibiotic was found to be a straight chain polyhydroxy, polyether, non-proteinic compound with a single double bond, indicating a nonpolyene antifungal antibiotic     

Effect of Cultivation Time on Production of Antifungal Metabolite(s) by Streptomyces hygroscopicus in Laboratory‐Scale Bioreactor

Biological control agents offer one of the best alternatives to reduce the use of pesticides . Fungi from the genera Alternaria, Colletotrichum and Fusarium are listed among the most important storage pathogens of apple fruits. During storage, transport and marketing, pathogenic fungi can cause significant losses of apple fruits. This investigation studied the potential of Streptomyces hygroscopicus as a biocontrol agent against pathogenic fungi obtained from apple fruit samples expressing rot symptoms. Production of antifungal metabolites by S. hygroscopicus was carried out in 3‐l bench‐scale bioreactor (Biostat^® Aplus, Sartorius AG, Germany) during 7 days. Fermentation was carried out at 27°C with aeration rate of 0.5 vvm and agitation rate of 200 rpm. The aim was to analyse bioprocess parameters of batch biofungicide production in medium containing glucose as a carbon source and to examine at which stage of bioprocess production of antifungal metabolite(s) against six phytopathogenic fungi occurs. In vitro antifungal activity of the produced metabolites against six fungi of the genera Colletotrichum, Fusarium and Alternaria grown on potato dextrose agar were determined every 24 h using wells technique. Antifungal activity of cell‐free culture filtrate and filtrate treated with high temperature were tested. The filtrate treated with high temperature did not show any antifungal activity suggesting that active components are thermo unstable. Stationary phase of growth occurred between the third and fourth day of cultivation when production of secondary metabolites begins. Obtained results showed that maximal antifungal activity is achieved on fifth and sixth day of S. hygroscopicus cultivation under defined conditions (inhibition zone diameter higher than 30 mm for all test fungi).     

Antifungal activity of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> 355 against wood-surface contaminant fungi

A strain of Bacillus subtilis was examined for antifungal activity against phytopathogenic and wood-surface contaminant fungi. The bacterium was grown in five culture media with different incubation times in order to study cell development, sporulation, and the production of metabolites with antifungal activity. The anti-sapstain and anti-mould activity of the bacterium grown in yeast extract glucose broth (YGB) medium in wood was also evaluated. In YGB, the bacterium inhibited the growth of several fungi and displayed a broader spectrum of activity than in the other media tested. A relationship between bacterial spore production and the formation of metabolites with antifungal activity was detected. YGB medium displayed effective control in wood block tests. YGB medium was extracted with solvents of increasing polarity and the dry residues were applied to silicagel plates, resolved with the appropriate solvent and sprayed with different solutions, detecting the presence, of amines, and higher alcohols. The bioautographic method revealed the presence of at least two active compounds against the blue-stain fungus Cladosporium cucumerinum.     

Isolation,characterisation and antifungal activity of marine actinobacteria from Goa and Kerala,the west coast of India

In total, 53 marine actinobacteria were isolated from the soils of six different locations in Goa and Kerala, on the west coast of India. All the isolates were screened for their antifungal properties against some phytopathogenic fungi by dual culture experiments. Among the 53 actinobacterial isolates, five isolates inhibited the growth of phytopathogens, namely Colletotrichum falcatum, Thielaviopsis paradoxa and Fusarium semitectum. But none of them were effective against Aspergillus niger, Aspergillus candidus and Aspergillus flavus. The antifungal activity of the actinobacteria was tested by food poisoning techniques, using four different concentrations (0.5%, 1.0%, 1.5% and 2.0%) of cell-free culture filtrates, which showed promising activity (almost 100% inhibition) against three pathogenic and one non-pathogenic fungi at 2% extract concentration. A comparison of the antifungal activity of the actinobacteria was also made with three commercial fungicides, namely hexaconazole, thiophanate methyl and propiconazole. The identity of the antagonistic actinobacteria was confirmed based on the morphological, cultural, biochemical, chemo-taxonomical and physiological characteristics. Among 5 antagonistic isolates, three antagonistic isolates were assigned to the genus Streptomyces, Nocardiopsis (1) and Saccharopolyspora (1).     

Potential of phosphate solubilising Pseudomonas as biofungicide

Beneficial effects of phosphate solublising Pseudomonas isolates were studied. Out of 30 cultures of bacteria and fungi, 25 cultures solubilised 8–70% P on solid and 9–73 μg ml^?1 in liquid medium. These were tested for antifungal activity against Aspergillus niger, Sclerotium rolfsii, Rhizoctonia solani, Fusarium oxysporum and Pythium aphanidermatum. The cultures of Pf-1, Pf-6, Pf-8, Pf-11, T-9 and T-10 did not inhibit any of the fungi tested, whereas Pf-9 was inhibitory to all. On the basis of P-solubilisation and antifungal activity Pf-9 and T-4 were finally selected for subsequent studies and were identified as Pseudomonas spp.     

Antifungal Activity of 2,4-Dihydroxyacylophenones and Related Compounds

The antifungal activity of 2,4-dihydroxyacylophenones and related compounds against Trichophyton spp and other fungi were investigated to determine their structure-activity relationships.

The activity of these compounds was found to be closely related to the length of the acyl and alkyl substituents attached to the 1,3-dihydroxybenzene moiety In addition, differences in activity were observed depending on the position of the alkyl substituents and on the number of substituents attached to the 1,3-dihydroxybenzene moiety. Some compounds tested showed potent antifungal activity against Trichophyton spp. and other fungi that was more active than amphotericin B.     

The Phenolic Contents and Antimicrobial Activities of Some Marine Algae from the Mediterranean Sea (Algeria)

In this study, three marine algae collected from western coast of algerian mediteranean sea (Ulva lactuca, Dictyota dichotoma, and Corallina elongata) were tested using the agar-well diffusion method for their production of antibacterial and antifungal agents on various organisms that cause diseases of humans and plants (Eschirichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Salmonella sp, Candida albicans, and Penicillium sp.). The total phenol content and antimicrobial activity were determined using different crude seaweeds extracts (methanol, diethylether, and chloroform). The results show that the chloroform extracts of (Ulva lactuca and Corallina elongata) had the highest activity against E. coli and Salmonella sp. The methanol extract obtained from (Ulva lactuca, Dictyota dichotoma, and Corallina elongata) showed antifungal activity for Candida albicans. The results of the study revealed that the seaweeds from Algeria appear to have immense potential as a source of antibacterial and antifungal compounds; they can be used in treating diseases caused by these organisms.     

Antifungal activity and mode of action of silver nano-particles on Candida albicans

In this study, the antifungal effects of silver nano-particles (nano-Ag) and their mode of action were investigated. Nano-Ag showed antifungal effects on fungi tested with low hemolytic effects against human erythrocytes. To elucidate the antifungal mode of action of nano-Ag, flow cytometry analysis, a glucose-release test, transmission electron microscopy (TEM) and the change in membrane dynamics using 1,6-diphenyl-1,3,5-hexatriene (DPH), as a plasma membrane probe, were performed with Candida albicans. The results suggest nano-Ag may exert an antifungal activity by disrupting the structure of the cell membrane and inhibiting the normal budding process due to the destruction of the membrane integrity. The present study indicates nano-Ag has considerable antifungal activity, deserving further investigation for clinical applications. K.-J. Kim and W. S. Sung contributed equally to this work and should be considered co-first authors.     

Isolation and characterization of a new antifungal metabolite ofTrichoderma reesei

A mycelial extract ofTrichoderma reesei (P-12) was separated into four fractions by high performance liquid chromatography (HPLC). Out of these, two were found to exhibit antifungal activity when tested against plant pathogenic fungi. The level of antifungal compounds was higher in media containing glucose as the carbon source as compared to one containing cellulose. The synthesis of these antifungal compounds started after 3 days of inoculation at 30°C and continued upto 8 days. No further increase was recorded beyond this period.     

Effect of the antifungal activity of oxygenated aromatic essential oil compounds on the white-rot Trametes versicolor and the brown-rot Coniophora puteana

Essential oils and their constituents have a long history of applications as antimicrobial agents, but their use as wood preservatives has not yet been reported. In this study, 22 essential oil phenols, phenol ethers, and aromatic aldehydes have been tested for their antifungal activity against the wood-decaying fungi Trametes versicolor and Coniophora puteana. Minimal inhibitory concentrations of the selected compounds added to potato dextrose agar (PDA) in defined concentrations were determined by a screening test with the agar dilution method. A significant difference in the tolerance of the tested fungi towards the selected compounds was discovered and attributed to the differences in their metabolic characteristics. The influence of the chemical structure of the tested essential oil compounds on their antifungal activity is also discussed.     

Antifungal Activities of N-Arylbenzenesulfonamides against Phytopathogens and Control Efficacy on Wheat Leaf Rust and Cabbage Club Root Diseases

A set of N-arylbenzenesulfonamides with various substituents at the arylamine and benzenesulfonyl positions were prepared, and their antifungal properties were measured in vitro against such plant pathogenic fungi as Pythium ultimum, Phytophthora capsici, Rhizoctonia solani, and Botrytis cinerea. Compounds 3, 4, 8, 9, 10, 14, 16, 18, 20, 21, 24 and 27 had antifungal activity over a broad spectrum of the phytopathogenic fungi tested, where 50% of inhibition (ED₅₀) was in the range of 3-15 μg/ml. Based on the in vitro activity, six derivatives (3, 4, 10, 18, 21 and 27) were selected and tested further for their fungicidal efficacy in vivo. The fungicidal efficacy of 10, 21 and 27 had a disease control value of over 85% at 50 μg/ml against wheat leaf rust, while that of 4 was selective against cabbage club root disease.     

Synthesis,Antifungal Activity,and Molecular Simulation Study of L–Carvone-Derived 1,3,4-Oxadiazole-Thioether Compounds

To discover potent antifungal molecules with new and distinctive structures, 20 novel L-carvone-derived 1,3,4-oxadiazole-thioether compounds 5 a – 5 t were synthesized through multi-step reaction of L-carvone, and their structures were confirmed by FT-IR, ¹H-NMR, ¹³C-NMR, and HR-MS. The antifungal activities of compounds 5 a – 5 t were preliminarily tested by in vitro method, and the results indicated that all of the title compounds displayed certain antifungal activities against the eight tested plant fungi, especially for P. piricola. Among them, compound 5 i (R=p-F) with the most significant antifungal activity deserved further study for discovering and developing novel natural product-based antifungal agents. Moreover, two molecular simulation technologies were employed for the investigation of their structure–activity relationships (SARs). Firstly, a reasonable and effective 3D-QSAR model was established by the comparative molecular field (CoMFA) method, and the relationship of the substituents linked with the benzene rings and the inhibitory activities of the title compounds against P. piricola was elucidated. Then, the binding mode of compound 5 i (R=p-F) and its potential biological target (CYP51) was simulated by molecular docking, and it was found that compound 5 i could readily bind with CYP51 in the active site, and the ligand-receptor interactions involved three hydrogen bonds and several hydrophobic effects.     

Antifungal Activity of Volatile Compounds Produced by an Edible Mushroom Hypsizygus marmoreus against Phytopathogenic Fungi

Volatile compounds with antifungal activity produced by edible mushrooms have potential as biological control agents to combat fungal diseases and reduce fungicide use in agriculture. Here we investigated the antifungal activity of volatile compounds produced by the edible mushroom Hypsizygus marmoreus (TUFC 11906) against eight phytopathogenic fungi. The results showed that volatile compounds from the mycelia and culture filtrates (CFs) of H. marmoreus had antifungal activity against some phytopathogenic fungi. Among them, the mycelial growth and conidial germination of Alternaria brassicicola were significantly inhibited by 60 and 100%, respectively. Moreover, the volatile compounds from CFs inhibited the lesion formation of A. brassicicola on detached cabbage leaves by 94%. The volatile compounds had higher antifungal activity against A. brassicicola than other fungi. With the removal of the volatile compounds from conidia of A. brassicicola, the conidia began to germinate, which indicates fungistatic activity of the compounds. The volatile compounds were isolated from the CFs of H. marmoreus, and the major volatile compound with antifungal activity was estimated to be 2‐methylpropanoic acid 2,2‐dimethyl‐1‐(2‐hydroxy‐1‐methylethyl)propyl ester. As the volatile compound produced by H. marmoreus is a product of an edible mushroom and has fungistatic activity against some phytopathogenic fungi, especially A. brassicicola, it may be possible to use the compounds as a novel safe agent for protecting crops in the field and during storage.