Antifungal properties and mechanisms of three volatile aldehydes(octanal,nonanal and decanal)on Aspergillus flavus

The harmof Aspergillus flavus(A.flavus)and aflatoxin is a severe food safety problemworldwide,which causes huge economic losses every year.Therefore,it is urgent to control the growth of A.flavus and the biosynthesis of aflatoxin.Plant-derived natural compounds are superior to synthetic fungicide in inhibiting the growth of A.flavus benefiting from their high safety to the environment,humans and stock,and low cost.This study aimed to evaluate the antifungal effects and potential antifungal mechanisms of three plant-derived compounds(octanal,nonanal and decanal)against A.flavus.We determined the minimum inhibitory concentrations(MICs)and action mechanism of the three volatile aldehydes on A.flavus and also performed calcofluor white(CW)staining for visualizing the distribution of septa.Cell respiration metabolism and the pathogenicity on maize kernels were also carried out to evaluate the efficacy of the three volatile aldehydes on the growth of A.flavus.The results showed that the three volatile aldehydes could inhibit the germination of spores and mycelial growth of A.flavus,the MICs on spores and mycelia were:octanal(1.0 and 0.5μL/mL),nonanal(0.5 and 2.0μL/mL),and decanal(1 and 5μL/mL).The three volatile aldehydes could strongly damage the integrity of both the cell wall and the cell membrane of A.flavus.Meanwhile,they could decrease the content of total lipid and inhibit respiration metabolism of A.flavus cell.Results of in vitro antifungal test showed that all the three volatile aldehydes could effectively prevent the growth of A.flavus on maize kernels.The study revealed that octanal,nonanal and decanal could effectively inhibit the growth of A.flavus both in culture medium and on maize kernels to different extent.The results confirmed that the plant-derived compounds could be developed into promising antifungal agents applied in the preservation of grains.This study provides a theoretical basis for the research and application of potential antifungal agents.

Vanillin and its derivatives,potential promising antifungal agents,inhibit Aspergillus flavus spores via destroying the integrity of cell membrane rather than cell wall

To study the structure-antifungal activity of vanillin against Aspergillus flavus(A.flavus),the susceptibilities of A.flavus to vanillin and its isomers(o-vanillin,2-hydroxy-4-methoxybenzaldehyde(HMB),2-hydroxy-5-methoxybenzaldehyde)and the possible antifungal mechanisms have been investigated.All the four volatile aldehydes could inhibit the germination of spores,and the minimum inhibitory concentrations(MICs)of them were in this order:vanillin(200μg/mL),o-vanillin(100μg/mL),2-hydroxy-5-methoxybenzaldehyde(100μg/mL),HMB(70μg/mL).The minimum fungicidal concentrations(MFCs)of them were in this order:vanillin(240μg/mL),o-vanillin(160μg/mL),HMB(140μg/mL),2-hydroxy-5-methoxybenzaldehyde(140μg/mL).Spore size was arrested at 0 h with the treatment of the four volatile aldehydes.Effects of the four volatile aldehydes on the cell wall and cell membrane integrity of A flavus were observed by calcofluor white(CW)staining and propidium iodide(PI)staining.The results showed that HMB exerted the strongest antifungal and fungicidal effects on the growth of A.flavus.The four volatile aldehydes had little influence on cell wall integrity after 3-hour treatment,however,they could strongly damage the cell membrane integrity.All the four volatile aldehydes could effectively prevent the growth of A.flavus on peanut seeds.The antifungal mechanisms of the four volatile aldehydes provide theoretical foundations for their development of new antifungal agents.

Synergistic antifungal mechanism of effective components from essential oil against Penicillium roqueforti

Essential oil(EO)has significant antifungal activity.However,there is limited information on the mechanism of the synergistic antifungal effect of the effective components of EO against fungi.In the present study,molecular electrostatic potential and molecular docking were used for the first time to investigate the synergistic antifungal mechanism of eugenol and citral small molecule(C_(EC))against Penicillium roqueforti.The results showed that the C_(EC)treatment made the activity ofβ-(1,3)-glucan synthase(GS)and chitin synthase(CS)decreas by 20.2%and 11.1%,respectively,and the contents of which decreased by 85.0%and 27.9%,respectively compared with the control group.Molecular docking revealed that C EC small molecules could bind to GS and CS through different amino acid residues,inhibiting their activity and synthesis.The C EC can combine with tryptophan,tyrosine,and phenylalanine in the cell membrane,causing damage to the cell membrane.The binding sites between small molecules and amino acids were mainly around the OH group.In addition,C EC affected the energy metabolism system and inhibited the glycolysis pathway.Simultaneously,C EC treatment reduced the ergosterol content in the cell membrane by 58.2%compared with the control group.Finally,changes in𝛽-galactosidase,metal ion leakage,and relative conductivity confirmed the destruction of the cell membrane,which resulted in the leakage of cell contents.The above results showed that C EC can kill P.roqueforti by inhibiting energy metabolism and destroying the integrity of the cell membrane.

Complex coacervation microcapsules by tannic acid crosslinking prolong the antifungal activity of cinnamaldehyde against Aspergillus brasiliensis

The antifungal activity and encapsulation properties of cinnamaldehyde-loaded microcapsules by tannic acid were investigated.The results showed that cinnamaldehyde exhibited a high in vitro antifungal effect against Aspergillus brasiliensis through altering the morphology of the hyphae,and its inhibition zone diameter(IZD)exceeded 15 mm with a minimum inhibitory concentration of 1.0 mg/mL.Cinnamaldehyde-loaded microcapsules crosslinked with tannic acid have a high encapsulation efficiency(92.53±5.20%)and antifungal activity(37.82±0.63 mm),and the retention rate was 2.5 times of that of unencapsulated cinnamaldehyde after 30-d storage at 37℃.Furthermore,the antifungal stability was enhanced(IZD 25.37 mm)after 60-d storage at 37℃ as compared with that of cinnamaldehyde(IZD 22.07 mm).The results of cell membrane integrity and the extracellular protein content also indicated that the microencapsulation could effectively protect cinnamaldehyde,delay the decrease of antifungal effect and improve its long-term antifungal activity against A.brasiliensis by increasing the retention rate of cinnamaldehyde after storage.

Effect of cinnamaldehyde on Rhizopus stolonifer and on the conservation of sweet potato

Objectives:Rhizopus stolonifer,which causes soft rot of sweet potato,has resulted in substantial loss of economy postharvest.Materials and Methods:The antifungal effect and mechanism of cinnamaldehyde(CIN)against R.stolonifer were explored by biochemical analysis and RNA-sequencing in this research,and the edible quality of CIN-treated sweet potato was evaluated.Results:The results showed that CIN inhibited the growth of R.stolonifer and reduced the incidence of soft rot in sweet potato at a minimum inhibitory concentration of 1000μL/L.The damage of the cell walls of R.stolonifer by CIN was associated with the upregulation of CHT1.Cytosolic leakage and malondialdehyde content increased following CIN-treatment,which was correlated with increased reactive oxygen species levels and decreased catalase activity.Upregulation of ERG genes and oxidative stress-related genes following CIN treatment was associated with impaired cell membrane integrity.The mitochondrial structure of R.stolonifer was damaged by CIN treatment resulting in decreased respiration rates and ATP production,which was correlated with lower expression levels of IDH1,COX4,and QCR7.Conclusions:Our research suggests that the inhibition of CIN on R.stolonifer was related to the disruption of its normal gene expression network,and CIN maintained the nutritional and edible quality of sweet potato.This study provides valuable insights into the antifungal mechanism of CIN on R.stolonifer and the maintenance of root quality,which contributes to the effcient use of CIN for controlling soft rot in sweet potato.

Insight into the antifungal mechanism of Neosartorya fischeri antifungal protein

Small, cysteine-rich, highly stable antifungal proteins secreted by filamentous Ascomycetes have great po- tential for the development of novel antifungal strate- gies. However, their practical application is still limited due to their not fully clarified mode of action. The aim of this work was to provide a deep insight into the anti-fungal mechanism of Neosartorya fischeri antifungal protein （NFAP）, a novel representative of this protein group. Within a short exposure time to NFAP, reduced cellular metabolism, apoptosis induction, changes in the actin distribution and chitin deposition at the hyphal tip were observed in NFAP-sensitive Aspergillus nidulans. NFAP did show neither a direct membrane disrupting- effect nor uptake by endocytosis. Investigation of A. nidulans signalling mutants revealed that NFAP acti- vates the cAMP/protein kinase A pathway via G-protein signalling which leads to apoptosis and inhibition of polar growth. In contrast, NFAP does not have any in- fluence on the cell wall integrity pathway, but an un- known cell wall integrity pathway-independent mitogen activated protein kinase A-activated target is assumed to be involved in the cell death induction. Taken to- gether, it was concluded that NFAP shows similarities, but also differences in its mode of antifungal action compared to two most investigated NFAP-related pro-teins from Aspergillus giganteus and Penicillium chrysogenum.

Structure-Activity Relationship, Cytotoxicity and Mode of Action of 2-Ester-substituted 1,5-Benzothiazepines as Potent Antifungal Agents

Our studies examined the structural features responsible for the antifungal activity of 2-ethoxycarbonyl-1,5- benzothiazepine （7a）. Three series of 1,5-benzothiazepine derivatives were synthesized and screened for their antifungal activity. The results suggested that the ethoxycarbonyl group at the 2 position and the imine moiety on the seven-membered ring are essential for activity. The most potent of the synthesized analogues （7a, 7b） were further studied by evaluating their cytotoxicity and mode of action （for 7a）. The results showed that compounds 7a and 7b were relatively safe for BV2 cells, but compound 7a interfered with Cryptococcus neoformans cell wall integrity by increasing the chitinase activity. Therefore, compound 7a was considered safe as an antifungal agent for animal cells.

Integrative cytology and proteome alterations unravel the multitarget effect of a novel alkaloid antofine against Penicillium italicum

Penicillium italicum is the causal agent of citrus blue mold,which is a major threat to the global citrus fruit industry.Antofine,a natural phenanthroindolizidine alkaloid,is water-soluble and exhibits a broad range of biological activities.However,whether it can inhibit P italicum growth and the potential inhibitory mechanism remains to be elucidated.This study aimed to investigate the antifungal mechanism of antofine against P italicum using scanning electron microscopy,transmission electron microscopy(TEM),propidium iodide staining,and tandem mass tag-labeled quantitative proteomic analysis.Antofine was found to exhibit its preeminent antifungal activity against P italicum with a minimum inhibitory concentration of 1.56 mg/L and a minimum fungicidal concentration of 6.25 mg/L.The challenge test revealed that antofine inhibited the development of citrus blue mold during a 6-d P italicum-infected period.Antofine acted on its potential multitargets to inhibit P italicum growth by synergistically activating oxidative stress through accumulating excess reactive oxygen species,impairing membrane integrity.inducing membrane lipid peroxidation,and disrupting mitochondrial function,thereby disrupting the membrane system and reducing cell via-bility.Moreover,antofine treatment downregulated most differentially expressed proteins involved in carbon metabolism,pyruvate metabolism,and the tricarboxylic acid cycle(TCA)in P italicum mycelia,which may explain the mitochondrial decomposition observed by TEM and the de-clines in ATP levels as well as the activities of TCA-related enzymes.These results indicate that antofine treatment inhibited P italicum growth by targeting the cell membrane and mitochondria.