The antifungal activity of extracts of Osmundea pinnatifida, an edible seaweed, indicates its usage as a safe environmental fungicide or as a food additive preventing post-harvest fungal food contamination

Discovery of novel acrylopimaric acid triazole derivatives as promising antifungal agents

BACKGROUND

To further develop potential natural fungicides, two series of new acrylopimaric acid triazole derivatives were synthesized, and their antifungal activities were tested and evaluated.

RESULTS

In vitro antifungal activity results indicated that compound 5m exhibited significant inhibitory activity against Rhizoctonia solani with an half maximal effective concentration (EC50) value of 1.528 mg/L. Its antifungal effect was comparable to that of the commercially available fungicide fluconazole, epoxiconazole and propiconazole (EC50 values of 1.441, 0.815 and 1.173 mg/L). Subsequently, in vivo studies were conducted on compound 5m, which revealed its significant protective and curative effects against R. solani. In addition, physiological and biochemical studies showed that compound 5m could disrupt the morphology and ultrastructure of R. solani mycelium, increase cell membrane permeability, inhibit ergosterol synthesis, and enhance the activity of defense enzymes in rice plants. Three-dimensional quantitative structure-activity relationship (3D-QSAR) studies revealed that the molecular structure significantly influenced the binding of compound 5m to the receptor, thereby enhancing its antifungal activity.

CONCLUSION

Compound 5m exhibits excellent antifungal activity against R. solani, making it a promising candidate fungicide for the prevention and control of R. solani. © 2024 Society of Chemical Industry.

Controlling Argas arboreus and A. persicus (Acari: Argasidae) by Adiantum capillus-veneris L. extracts with phytochemical analysis

Argas species are parasites associated mostly with birds. Their infestations of the host may cause blood loss, resulting in anemia and finally death. Egypt loses millions of tons annually from birds because of these parasites. In addition, they can transmit pathogens to animals and humans. The acaricidal effects of the ethanolic and methanolic extracts of Adiantum capillus-veneris at different concentrations (1-4%) against semi-fed adults of Argas arboreus and A. persicus were investigated during 30 days after treatments. Mobility and mortality, acaricide efficacy, and the concentration that kills 50% of specimens (LC50) were estimated. The percentage of dead adults of both Argas species appeared during 6 days considerably until 30 days was significantly increased after treatment of either ethanol or methanol extracts of Adiantum at 1-4%, versus control groups. Ethanolic extracts (100% mortality) were more effective than methanolic ones (90% mortality) for both Argas species. Argas arboreus (80% efficacy and 5.9% LC50) was more resistant than A. persicus (100% efficacy and 4.1% LC50). Generally, males were more resistant than females. The chemical profile (by gas chromatography-mass spectrometry analysis) for the ethanolic extract of Ad. capillus-veneris at 4% (the most effective extract) was provided for the first time, which showed that the major group was sugars and sugar alcohols, and the main components were thymol-ß-d-glucopyranoside, D-(-)-Tagatofuranose, D-Arabinose, D-Galactose, D-(-)-Fructofuranose and Anthracene, 1-methyl. The efficiency of all these components was discussed. Based on the findings, bioactive compounds present in Ad. capillus-veneris have the potential to be applied as substitutes for synthetic acaricides and a biological control agent in the management of A. arboreus and A. persicus ticks.

The Brown Alga Bifurcaria bifurcata Presents an Anthelmintic Activity on All Developmental Stages of the Parasitic Nematode Heligmosomoides polygyrus bakeri

The current control of gastrointestinal (GI) parasitic nematodes mainly relies on the widespread use of anthelmintics, which has inevitably led to resistance. Therefore, there is an urgent need to find new sources of antiparasitic compounds. Macroalgae represent a rich source of active molecules and are widely described as having medicinal properties. In the present study, we investigated the potential anthelmintic activity of aqueous extracts from three species of algae (Bifurcaria bifurcata, Grateloupia turuturu and Osmundea pinnatifida) on the murine parasite Heligmosomoides polygyrus bakeri. Using a set of complementary in vitro tests, including larval development assays, egg hatching tests and nematicidal activity assays on larvae and adults, we report the nematicidal activity of aqueous extracts of B. bifurcata. In addition, aqueous extract fractionation using liquid/liquid partitioning with a solvent of increasing polarity was performed in order to identify the groups of active molecules underlying the anthelmintic activity. Non-polar extracts (heptane, ethyl acetate) demonstrated high anthelmintic potential, highlighting the role of non-polar metabolites such as terpenes. Here, we highlight the strong anthelmintic potential of the brown alga B. bifurcata on a mouse model of GI parasites, thus confirming the strong interest in algae as natural alternatives for the control of parasitic nematodes.

Anti-Fungal Activity of Moutan cortex Extracts against Rice Sheath Blight (Rhizoctonia solani) and Its Action on the Pathogen's Cell Membrane

Rice sheath blight (RSB) caused by Rhizoctonia solani is one of the most destructive diseases of rice (Oryza sativa). Although chemical fungicides are the most important control methods, their long-term unreasonable application has brought about problems such as environmental pollution, food risks, and non-target poisoning. Therefore, considering the extraction of fungistatic substances from plants may be an alternative in the future. In this study, we found that the Moutan cortex ethanol extract has excellent antifungal activity against R. solani, with a 100% inhibition rate at 1000 μg/mL, which aroused our great exploration interest. In-depth exploration found that the antifungal active ingredients of M. cortex were mainly concentrated in the petroleum ether extract of the M. cortex ethanol extract, which still maintained a 100% inhibition rate with 250 μg/mL, and its effective medium concentration (EC₅₀) was 145.33 μg/mL against R. solani. Through the measurement of extracellular relative conductivity and OD₂₆₀, the petroleum ether extract induced leakage of intracellular electrolytes and nucleic acids, indicating that the cell membrane was ruined. Therefore, we preliminarily determined that the cell membrane may be the target of the petroleum ether extract. Moreover, we found that petroleum ether extract reduced the content of ergosterol, a component of the cell membrane, which may be one of the reasons for the cell membrane destruction. Furthermore, the increase of MDA content would lead to membrane lipid peroxidation, further aggravating membrane damage, resulting in increased membrane permeability. Also, the destruction of the cell membrane was observed by the phenomenon of the mycelium being transparent and broken. In conclusion, this is the first report of the M. cortex petroleum ether extract exhibiting excellent antifungal activity against R. solani. The effect of the M. cortex petroleum ether extract on R. solani may be on the cell membrane, inducing the disorder of intracellular substances and metabolism, which may be one of the antifungal mechanisms against R. solani.

Bioprocessing of Two Crop Residues for Animal Feeding into a High-Yield Lovastatin Feed Supplement

Simple Summary

Lovastatin is a fungal secondary metabolite that can mitigate rumen methane production. This work aimed at evaluating the lovastatin production by solid-state fermentation from selected crop residues and A. terreus strains, considering the post-fermented residues as feed supplements for ruminants. Fermented oat straw by A. terreus CDBB H-194 exhibited the highest lovastatin yield (23.8 mg/g DM fed). GC–MS analysis identified only a couple of compounds from the residues fermented by CDBB H-194 (1,3-dipalmitin trimethylsilyl ether in the fermented oat straw) and stearic acid hydrazide in the fermented wheat bran) that could negatively affect ruminal bacteria and fungi.

Abstract

This work aimed to evaluate the lovastatin (Lv) production by solid-state fermentation (SSF) from selected crop residues, considering the post-fermented residues as feed supplements for ruminants. The SSF was performed with two substrates (wheat bran and oat straw) and two A. terreus strains (CDBB H-194 and CDBB H-1976). The Lv yield, proximate analysis, and organic compounds by GC–MS in the post-fermented residues were assessed. The combination of the CDBB H-194 strain with oat straw at 16 d of incubation time showed the highest Lv yield (23.8 mg/g DM fed) and the corresponding degradation efficiency of hemicellulose + cellulose was low to moderate (24.1%). The other three treatments showed final Lv concentrations in decreasing order of 9.1, 6.8, and 5.67 mg/g DM fed for the oat straw + CDBB H-1976, wheat bran + CDBB H-194, and wheat bran + CDBB H-1976, respectively. An analysis of variance of the 2² factorial experiment of Lv showed a strong significant interaction between the strain and substrate factors. The kinetic of Lv production adequately fitted a zero-order model in the four treatments. GC–MS analysis identified only a couple of compounds from the residues fermented by A. terreus CDBB H-194 (1,3-dipalmitin trimethylsilyl ether in the fermented oat straw and stearic acid hydrazide in the fermented wheat bran) that could negatively affect ruminal bacteria and fungi. Solid-state fermentation of oat straw with CDBB H-194 deserves further investigation due to its high yield of Lv; low dietary proportions of this post-fermented oat straw could be used as an Lv-carrier supplement for rumen methane mitigation.

Marine Macroalgae, a Source of Natural Inhibitors of Fungal Phytopathogens

Fungal phytopathogens are a growing problem all over the world; their propagation causes significant crop losses, affecting the quality of fruits and vegetables, diminishing the availability of food, leading to the loss of billions of euros every year. To control fungal diseases, the use of synthetic chemical fungicides is widely applied; these substances are, however, environmentally damaging. Marine algae, one of the richest marine sources of compounds possessing a wide range of bioactivities, present an eco-friendly alternative in the search for diverse compounds with industrial applications. The synthesis of such bioactive compounds has been recognized as part of microalgal responsiveness to stress conditions, resulting in the production of polyphenols, polysaccharides, lipophilic compounds, and terpenoids, including halogenated compounds, already described as antimicrobial agents. Furthermore, many studies, in vitro or in planta, have demonstrated the inhibitory activity of these compounds with respect to fungal phytopathogens. This review aims to gather the maximum of information addressing macroalgae extracts with potential inhibition against fungal phytopathogens, including the best inhibitory results, while presenting some already reported mechanisms of action.

Marine algae as efficacious bioresources housing antimicrobial compounds for preserving foods - A review

Certain synthetic chemicals used in global food industries eliminate pathogenic food microbes and prevent spoilage. Nevertheless, their toxicity precludes human consumption. This phenomenon has made scientific fraternity to look for alternative antimicrobial compounds from natural resources. In recent times, marine algae have been illustrated to be potent and rich sources of antimicrobial agents as chemical replacements for applications in food. Identifying novel antimicrobial agents from natural resources have become a worldwide research with immense significance. Marine algae are now considered as one of the most inexhaustible and unexposed sources of antimicrobial agents due to their abundance in seawaters and renewability. This review elaborated on marine algal antimicrobial agents against foodborne pathogens, mode of action and cumulated the prospective use of algal compounds in active food packaging as a natural food preservative. Due to poor solubility, unpleasant odor and ineffectiveness of plant derived antimicrobial agents against Gram-negative bacteria, researchers opted for marine algae, an ideal candidate to be used as natural food preservatives. This article elaborates and summarizes the efficient bioactive molecules in marine algae and their possible application in food preservation to extend shelf life of foods without causing any toxicity. In conclusion, marine algae have potential antimicrobial property against food pathogens and have more advantages than other natural sources of antimicrobial agents.

Protective Effects of Fucoxanthin on High Glucose- and 4-Hydroxynonenal (4-HNE)-Induced Injury in Human Retinal Pigment Epithelial Cells

The incidence of diabetes mellitus is increasing due to the eating and living habits of modern people. As the disease progresses, the long-term effects of diabetes can cause microvascular disease, causing dysfunction in different parts of the body, which, in turn, leads to different complications, such as diabetic neuropathy, diabetic nephropathy, and diabetic retinopathy (DR). DR is the main cause of vision loss and blindness in diabetic patients. Persistent hyperglycemia may cause damage to the retina, induce the accumulation of inflammatory factors, and destroy the blood–retinal barrier function. Fucoxanthin (Fx) is a marine carotenoid extracted from seaweed. It accounts for more than 10% of the total carotenoids in nature. Fx is mainly found in brown algae and has strong antioxidant properties, due to its unique biologically active structure. This carotenoid also has the effects of reducing lipid peroxidation, reducing DNA damage, and preventing cardiovascular diseases as well as anti-inflammatory and anti-tumor effects. However, there is no relevant research on the protective effect of Fx in DR. Therefore, in this study, we explore the protective effect of Fx on the retina. Human retinal epithelial cells (ARPE-19) are used to investigate the protective effect of Fx on high glucose stress- (glucose 75 mM) and high lipid peroxidation stress (4-hydroxynonenal, 4-HNE (30 μM))-induced DR. The cell viability test shows that Fx recovered the cell damage, and Western blotting shows that Fx reduced the inflammation response and maintained the integrity of the blood–retinal barrier by reducing its apoptosis and cell adhesion factor protein expression. Using an antioxidant enzyme assay kit, we find that the protective effect of Fx may be related to the strong antioxidant properties of Fx, which increases catalase and reduces oxidative stress to produce a protective effect on the retina.

Marine Bioactive Compounds against Aspergillus fumigatus: Challenges and Future Prospects

With the mortality rate of invasive aspergillosis caused by Aspergillus fumigatus reaching almost 100% among some groups of patients, and with the rapidly increasing resistance of A. fumigatus to available antifungal drugs, new antifungal agents have never been more desirable than now. Numerous bioactive compounds were isolated and characterized from marine resources. However, only a few exhibited a potent activity against A. fumigatus when compared to the multitude that did against some other pathogens. Here, we review the marine bioactive compounds that display a bioactivity against A. fumigatus. The challenges hampering the discovery of antifungal agents from this rich habitat are also critically analyzed. Further, we propose strategies that could speed up an efficient discovery and broaden the dimensions of screening in order to obtain promising in vivo antifungal agents with new modes of action.