Marine Macroalgae, a Source of Natural Inhibitors of Fungal Phytopathogens

Algae and Cyanobacteria Fatty Acids and Bioactive Metabolites: Natural Antifungal Alternative Against Fusarium sp

Fungal diseases caused by Fusarium spp. significantly threaten food security and sustainable agriculture. One of the traditional strategies for eradicating Fusarium spp. incidents is the use of chemical and synthetic fungicides. The excessive use of these products generates environmental damage and has negative effects on crop yield. It puts plants in stressful conditions, kills the natural soil microbiome, and makes phytopathogenic fungi resistant. Finally, it also causes health problems in farmers. This drives the search for and selection of natural alternatives, such as bio-fungicides. Among natural products, algae and cyanobacteria are promising sources of antifungal bio-compounds. These organisms can synthesize different bioactive molecules, such as fatty acids, phenolic acids, and some volatile organic compounds with antifungal activity, which can damage the fungal cell membrane that surrounds the hyphae and spores, either by solubilization or by making them porous and disrupted. Research in this area is still developing, but significant progress has been made in the identification of the compounds with potential for controlling this important pathogen. Therefore, this review focuses on the knowledge about the mechanisms of action of the fatty acids from macroalgae, microalgae, and cyanobacteria as principal biomolecules with antifungal activity, as well as on the benefits and challenges of applying these natural metabolites against Fusarium spp. to achieve sustainable agriculture.

Antifungal Properties of Sargassum cinereum and Padina boergesenii Extracts Against Fungi Associated with Strawberry Fruits Concerning Mycotoxin Production

Strawberries are susceptible to decay and destruction while being harvested and stored. This study had the following objectives: (1) the documentation of fungi and mycotoxin production associated with infected strawberry fruits; (2) the evaluation of the primary phytochemicals of Sargassum cinereum and Padina boergesenii by gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared (FT-IR) analysis to identify the active chemical composition of the seaweed extracts; and (3) the assessment of the antifungal activity of five extracts from brown seaweeds both in vitro and in vivo against fungal infections on fresh fruit under post-harvest conditions. The most common fungi were Aspergillus niger 14.36%, Botrytis cinerea 38.29%, and Mucor irregularis 16.88%. Padina boergesenii acetone extract had the highest in vitro antifungal activity. The methanol extracts of both S. cinereum and P. boergesenii were effective against the pathogenicity and aggressiveness (in vivo) on post-harvest strawberry fruits. B. cinerea could produce botrydial and dihydrobotrydial toxins with concentrations of 8.14 µg/mL and 4.26 µg/mL, respectively. A. niger could produce ochratoxin A with a concentration of 10.05 µg/mL. The present study demonstrates that the extracts of macroalgae S. cinereum and P. boergesenii contain secondary metabolites and antioxidants, indicating their potential utilization in antifungal applications.

Exploring marine compounds as potential biocontrol agents against powdery mildew for agricultural sustainability: a computer-based approach

Powdery mildew is a pervasive fungal disease causing significant economic losses globally. Continuous use of synthetic fungicides has led to environmental concerns and resistant fungal strains. This study explores marine-derived cephalostatins from the South African Natural Compounds Database as novel fungicidal agents for managing powdery mildew. Using molecular docking techniques, we investigated the interaction between selected cephalostatins and critical proteins involved in powdery mildew pathogenesis. Compounds were selected based on drug-likeness and bioactivity, adhering to Lipinski's Rule of Five. Molecular interactions, binding affinities, and stability were analysed using AutoDock Vina, PyMOL, and Discovery Studio. Cephalostatin 17 exhibited the highest binding affinity (-10.4 kcal/mol), indicating strong potential for inhibiting fungal growth through significant hydrogen bonding and hydrophobic interactions. The study's primary limitation is the reliance on computational predictions, necessitating experimental validation. Cephalostatin 17 stands out as a promising candidate for sustainable agricultural practices.

Potential Activity of Arthrospira platensis as Antioxidant, Cytotoxic and Antifungal against Some Skin Diseases: Topical Cream Application

This research evaluated the antifungal effectiveness of Arthrospira platensis ethanol, methanol, ethyl acetate and acetone extracts against the tested pathogenic fungi (Candida albicans, Trichophyton rubrum and Malassezia furfur). Antioxidant and cytotoxicity effectiveness of A. platensis extracts against four distinct cell lines were also assessed. Methanol extract of A. platensis exhibited the highest inhibition zones against Candida albicans as measured by the well diffusion method. A transmission electron micrograph of the treated group of Candida cells with A. platensis methanolic extract showed mild lysis and vacuolation of the cytoplasmic organelles. In vivo, after induced infection of mice by C. albicans and treatment with A. platensis methanolic extract cream, the skin layer emerged with the removal of Candida spherical plastopores. The extract of A. platensis recorded the highest antioxidant activity using the DPPH (2, 2- diphenyl-1-picrylhydrazyl) scavenging method (IC50 28 mg/mL). A cytotoxicity test using a MTT assay showed that the A. platensis extract had strong cytotoxic activity against the HepG2 cell line (IC50 20.56 ± 1.7 μg/mL) and moderate cytotoxic activity against MCF7 and the Hela cell (IC50 27.99 ± 2.1 μg/mL). Gas Chromatography/Mass Spectroscopy (GC/MS) results revealed that the effective activity of A. platensis extract could be linked to a synergistic impact between their prominent composition as alkaloids, phytol, fatty acids hydrocarbons, phenolics and phthalates. A. platensis extract contains active metabolites that constitute a promising source of antifungal, antioxidant and anti-proliferative compounds for the pharmaceutical drug industry.

Seaweed Extracts to Control Postharvest Phytopathogenic Fungi in Rocha Pear

Fungal infections cause losses amounting to between 20 and 25% of the fruit industry's total outcome, with an escalating impact on agriculture in the last decades. As seaweeds have long demonstrated relevant antimicrobial properties against a wide variety of microorganisms, extracts from Asparagopsis armata, Codium sp., Fucus vesiculosus, and Sargassum muticum were used to find sustainable, ecofriendly, and safe solutions against Rocha pear postharvest fungal infections. Alternaria alternata, Botrytis cinerea, Fusarium oxysporum, and Penicillium expansum mycelial growth and spore germination inhibition activities were tested in vitro with five different extracts of each seaweed (n-hexane, ethyl acetate, aqueous, ethanolic, and hydroethanolic). An in vivo assay was then performed using the aqueous extracts against B. cinerea and F. oxysporum in Rocha pear. The n-hexane, ethyl acetate, and ethanolic extracts from A. armata showed the best in vitro inhibitory activity against B. cinerea, F. oxysporum, and P. expansum, and promising in vivo results against B. cinerea using S. muticum aqueous extract were also found. The present work highlights the contribution of seaweeds to tackle agricultural problems, namely postharvest phytopathogenic fungal diseases, contributing to a greener and more sustainable bioeconomy from the sea to the farm.