Investigating the Efficiency of Hydroxycinnamic Acids to Inhibit the Production of Enniatins by Fusarium avenaceum and Modulate the Expression of Enniatins Biosynthetic Genes

C apsicum fruits as functional ingredients with antimicrobial activity: an emphasis on mechanisms of action

Capsicum spp. fruits (CFs) are a basic ingredient in the diet and have been used as active ingredients in the pharmaceutical, cosmetic, and food products, due to their antioxidant, anti-inflammatory, antiseptic, and antimicrobial properties. The antimicrobial activity is the most studied property due to its effectiveness against pathogenic species, however, few studies have focused on the mechanisms of action involved. Therefore, this review discusses the effects generated by the CFs compounds on the viability and metabolism of microorganisms, highlighting the mechanisms by which these compounds exert their antimicrobial effects. The information provided shows that CFs are mainly source of capsaicinoids and phenolic compounds responsible for the inhibition of bacteria, yeasts, and fungi, through an increase in the permeabilization of the membrane and cell wall. Also, these compounds show an antiviral effect associated with the inactivation of virus binding proteins, preventing their replication and infection. Despite this, there is still a lack of information about the mechanisms that regulate the interactions between CFs compounds and food-important-microorganisms. Therefore, future research should focus on new antimicrobial compounds from CFs for their subsequent use against novel infectious agents, mainly virus of importance in health such as SARS-CoV-2.

Computational Strategy for Minimizing Mycotoxins in Cereal Crops: Assessment of the Biological Activity of Compounds Resulting from Virtual Screening

Cereal crops are frequently affected by toxigenic Fusarium species, among which the most common and worrying in Europe are Fusarium graminearum and Fusarium culmorum. These species are the causal agents of grain contamination with type B trichothecene (TCTB) mycotoxins. To help reduce the use of synthetic fungicides while guaranteeing low mycotoxin levels, there is an urgent need to develop new, efficient and environmentally-friendly plant protection solutions. Previously, F. graminearum proteins that could serve as putative targets to block the fungal spread and toxin production were identified and a virtual screening undertaken. Here, two selected compounds, M1 and M2, predicted, respectively, as the top compounds acting on the trichodiene synthase, a key enzyme of TCTB biosynthesis, and the 24-sterol-C-methyltransferase, a protein involved in ergosterol biosynthesis, were submitted for biological tests. Corroborating in silico predictions, M1 was shown to significantly inhibit TCTB yield by a panel of strains. Results were less obvious with M2 that induced only a slight reduction in fungal biomass. To go further, seven M1 analogs were assessed, which allowed evidencing of the physicochemical properties crucial for the anti-mycotoxin activity. Altogether, our results provide the first evidence of the promising potential of computational approaches to discover new anti-mycotoxin solutions

Bioprospecting Phenols as Inhibitors of Trichothecene-Producing Fusarium: Sustainable Approaches to the Management of Wheat Pathogens

Fusarium spp. are ubiquitous fungi able to cause Fusarium head blight and Fusarium foot and root rot on wheat. Among relevant pathogenic species, Fusarium graminearum and Fusarium culmorum cause significant yield and quality loss and result in contamination of the grain with mycotoxins, mainly type B trichothecenes, which are a major health concern for humans and animals. Phenolic compounds of natural origin are being increasingly explored as fungicides on those pathogens. This review summarizes recent research activities related to the antifungal and anti-mycotoxigenic activity of natural phenolic compounds against Fusarium, including studies into the mechanisms of action of major exogenous phenolic inhibitors, their structure-activity interaction, and the combined effect of these compounds with other natural products or with conventional fungicides in mycotoxin modulation. The role of high-throughput analysis tools to decipher key signaling molecules able to modulate the production of mycotoxins and the development of sustainable formulations enhancing potential inhibitors' efficacy are also discussed.

Ammoides pusilla Essential Oil: A Potent Inhibitor of the Growth of Fusarium avenaceum and Its Enniatin Production

Enniatins are mycotoxins produced by Fusarium species contaminating cereals and various agricultural commodities. The co-occurrence of these mycotoxins in large quantities with other mycotoxins such as trichothecenes and the possible synergies in toxicity could lead to serious food safety problems. Using the agar dilution method, Ammoides pusilla was selected among eight Tunisian plants for the antifungal potential of its essential oil (EO) on Fusarium avenaceum mycelial growth and its production of enniatins. Two EO batches were produced and analyzed by GC/MS-MS. Their activities were measured using both contact assays and fumigant tests (estimated IC50 were 0.1 µL·mL⁻¹ and 7.6 µL·L⁻¹, respectively). The A. pusilla EOs and their volatiles inhibited the germination of spores and the mycelial growth, showing a fungistatic but not fungicidal activity. The accumulation of enniatins was also significantly reduced (estimated IC50 were 0.05 µL·mL⁻¹ for the contact assays and 4.2 µL·L⁻¹ for the fumigation assays). The most active batch of EO was richer in thymol, the main volatile compound found. Thymol used as fumigant showed a potent fungistatic activity but not a significant antimycotoxigenic activity. Overall, our data demonstrated the bioactivity of A. pusilla EO and its high potential to control F. avenaceum and its enniatins production in agricultural commodities.

Screening of Wood/Forest and Vine By-Products as Sources of New Drugs for Sustainable Strategies to Control Fusarium graminearum and the Production of Mycotoxins

Fusarium graminearum is a fungal pathogen that can colonize small-grain cereals and maize and secrete type B trichothecene (TCTB) mycotoxins. The development of environmental-friendly strategies guaranteeing the safety of food and feed is a key challenge facing agriculture today. One of these strategies lies on the promising capacity of products issued from natural sources to counteract crop pests. In this work, the in vitro efficiency of sixteen extracts obtained from eight natural sources using subcritical water extraction at two temperatures was assessed against fungal growth and TCTB production by F. graminearum. Maritime pine sawdust extract was shown to be extremely efficient, leading to a significant inhibition of up to 89% of the fungal growth and up to 65% reduction of the mycotoxin production by F. graminearum. Liquid chromatography/mass spectrometry analysis of this active extract revealed the presence of three families of phenolics with a predominance of methylated compounds and suggested that the abundance of methylated structures, and therefore of hydrophobic compounds, could be a primary factor underpinning the activity of the maritime pine sawdust extract. Altogether, our data support that wood/forest by-products could be promising sources of bioactive compounds for controlling F. graminearum and its production of mycotoxins.