Special Issue "Microbial and Plant Phytotoxins"

A special issue of Toxins (ISSN 2072-6651). This special issue belongs to the section "Plant Toxins".

Deadline for manuscript submissions: closed (15 August 2021).

Special Issue Editors

Dr. Marco Masi
E-Mail Website1 Website2
Guest Editor
Department of Chemical Sciences, University of Naples “Federico II”, Complesso Universitario Monte S. Angelo, Via Cintia 4, 80126 Napoli, Italy
Interests: organic chemistry; bioactive natural substances; natural product isolation and characterization; spectroscopy; ecology; biological control
Prof. Dr. Antonio Evidente
E-Mail Website1 Website2
Guest Editor
Department of Chemical Sciences, University of Naples “Federico II”, Complesso Universitario Monte S. Angelo, Via Cintia 4, 80126 Napoli, Italy
Interests: bioactive natural substances; spectroscopy; natural product isolation and characterization; organic chemistry; ecology; biological control; biopolymer for formulation of natural products
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Special Issue Information

Dear Colleagues,

Phytotoxins are generally considered secondary metabolites produced by phytopathogenic fungi and/or bacteria that play an important role in the disease induction on the host plant. They are frequently produced as a mixture of low molecular weight metabolites belonging to several class of natural compounds. The toxins are produced in vivo but also in vitro, and frequently, the latter reproduce similar symptoms to those observed in vivo. Microbial phytotoxins are able to cause serious diseases to agrarian, ornamental, and forest plants with consequently heavy economic losses in food quality and production and environmental heritage. Pasture and greenhouses are also affected by this problem. Rarely, the phytotoxins are host-specific but frequently possess different biological activities with potential application in different fields such as agriculture and medicine. When microbial phytotoxins are produced by microbes that are pathogenic for weeds, including parasitic plants, they represent an important tool to develop biohebicides. This strategy represents a green-friendly alternative to the massive use of chemicals, which are one of the main causes of environmental pollution and risk for human and animal health. Allelopathic plants also produce phytotoxic metabolites that can be used in different fields. In particular, in agriculture, they could be used to find new potential bioherbicides to combat weeds, including parasitic plants, through seed inhibition or stimulation and suppression of radical growth.

Thus, this Special Issue of Toxins will report articles describing both microbial and plant phytotoxins, focusing on their biological properties and their potential practical application in different fields.

Dr. Marco Masi
Prof. Dr. Antonio Evidente
Guest Editors

Manuscript Submission Information

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Keywords

  • phytotoxins
  • fungi and bacteria
  • plants
  • secondary metabolites
  • biological activity

Published Papers (6 papers)

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Research

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Article
Using Azadirachtin to Transform Spodoptera frugiperda from Pest to Natural Enemy
Toxins 2021, 13(8), 541; https://0-doi-org.brum.beds.ac.uk/10.3390/toxins13080541 - 03 Aug 2021
Viewed by 718
Abstract
Spodoptera frugiperda and Rhopalosiphum maidis, as main pests, seriously harm the safety of maize. At present, chemical pesticides are mainly used to control these pests. However, due to residue and resistance problems, more green, environmentally benign, simple preventive control technology is needed. [...] Read more.
Spodoptera frugiperda and Rhopalosiphum maidis, as main pests, seriously harm the safety of maize. At present, chemical pesticides are mainly used to control these pests. However, due to residue and resistance problems, more green, environmentally benign, simple preventive control technology is needed. In this study, we reported the reason for the antifeedant activity of azadirachtin on S. frugiperda and proposed that S. frugiperda treated with azadirachtin would turn from pest into natural enemy. S. frugiperda showed an obvious antifeeding phenomenon to maize leaf treated with various azadirachtin concentrations (0.5~20 mg/L). It was found that maize leaf treated with 1 mg/L of azadirachtin has a stimulating effect on the antenna and sensillum basiconicum of S. frugiperda, and azadirachtin can affect the feeding behavior of S. frugiperda. Additionally, after treating maize leaves or maize leaves + R. maidis with 1 mg/L of azadirachtin, the predatory behavior of S. frugiperda changed from a preference for eating maize leaves to R. maidis. Moreover, the molting of R. maidis can promote the change of this predatory behavior. Our results, for the first time, propose that the combined control technology of azadirachtin insecticide and biological control could turn S. frugiperda from pest into natural enemy, which can effectively eliminate R. maidis and protect maize. This combined control technology provides a new way for pest management and has good ecological, environmental, and economic benefits. Full article
(This article belongs to the Special Issue Microbial and Plant Phytotoxins)
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Article
Activity of Some Plant and Fungal Metabolites towards Aedes albopictus (Diptera, Culicidae)
Toxins 2021, 13(4), 285; https://0-doi-org.brum.beds.ac.uk/10.3390/toxins13040285 - 18 Apr 2021
Viewed by 555
Abstract
Aedes albopictus (Skuse) is a widespread mosquito, a vector of important human arboviruses, including Chikungunya, Dengue and Zika. It is an extremely difficult species to control even for the onset of resistances to chemicals insecticides, therefore ecofriendly products are urgently needed. In this [...] Read more.
Aedes albopictus (Skuse) is a widespread mosquito, a vector of important human arboviruses, including Chikungunya, Dengue and Zika. It is an extremely difficult species to control even for the onset of resistances to chemicals insecticides, therefore ecofriendly products are urgently needed. In this study, the activity of Amaryllidaceae alkaloids and some of their semisynthetic derivatives, of 2-methoxy-1,4-naphthoquinone and two analogues, of cyclopaldic acid and epi-epoformin on the survival and development of Ae. albopictus larvae was evaluated. First-instar larval exposure for 24 and 48 h to cyclopaldic acid, resulted in mortality mean per-centage of 82.4 and 96.9 respectively; 1,2-O,O-diacetyllycorine 48h post-treatment caused 84.7% mortality. Larval and pupal duration were proved to decrease significantly when larvae were exposed to cyclopaldic acid, 1,2-O,O-diacetyllycorine and N-methyllycorine iodide. The mean number of third-instar larvae surviving to 2-methyl-1,4-naphthoquinone, 2-hydroxy-1,4-naphthoquinone and 2-methoxy-1,4-naphthoquinone was significantly lower than the number of correspondent control larvae over the time. This study indicated that 1,2-O,O’-diacetyllycorine, N-methyllycorine iodide, cyclopaldic acid and 1,4-naphthoquinone structural derivatives have good potential for developing bioinsecticides for mosquito control programs. The obtained results are of general interest due to the global importance of the seri-ous human diseases such a vector is able to spread. Full article
(This article belongs to the Special Issue Microbial and Plant Phytotoxins)
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Article
Anti-Biofilm Activity of the Fungal Phytotoxin Sphaeropsidin A against Clinical Isolates of Antibiotic-Resistant Bacteria
Toxins 2020, 12(7), 444; https://0-doi-org.brum.beds.ac.uk/10.3390/toxins12070444 - 08 Jul 2020
Cited by 8 | Viewed by 986
Abstract
Many pathogens involved in human infection have rapidly increased their antibiotic resistance, reducing the effectiveness of therapies in recent decades. Most of them can form biofilms and effective drugs are not available to treat these formations. Natural products could represent an efficient solution [...] Read more.
Many pathogens involved in human infection have rapidly increased their antibiotic resistance, reducing the effectiveness of therapies in recent decades. Most of them can form biofilms and effective drugs are not available to treat these formations. Natural products could represent an efficient solution in discovering and developing new drugs to overcome antimicrobial resistance and treat biofilm-related infections. In this study, 20 secondary metabolites produced by pathogenic fungi of forest plants and belonging to diverse classes of naturally occurring compounds were evaluated for the first time against clinical isolates of antibiotic-resistant Gram-negative and Gram-positive bacteria. epi-Epoformin, sphaeropsidone, and sphaeropsidin A showed antimicrobial activity on all test strains. In particular, sphaeropsidin A was effective at low concentrations with Minimum Inhibitory Concentration (MIC) values ranging from 6.25 μg/mL to 12.5 μg/mL against all reference and clinical test strains. Furthermore, sphaeropsidin A at sub-inhibitory concentrations decreased methicillin-resistant S. aureus (MRSA) and P. aeruginosa biofilm formation, as quantified by crystal violet staining. Interestingly, mixtures of sphaeropsidin A and epi-epoformin have shown antimicrobial synergistic effects with a concomitant reduction of cytotoxicity against human immortalized keratinocytes. Our data show that sphaeropsidin A and epi-epoformin possess promising antimicrobial properties. Full article
(This article belongs to the Special Issue Microbial and Plant Phytotoxins)
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Article
Toxicity of Carlina Oxide—A Natural Polyacetylene from the Carlina acaulis Roots—In Vitro and in Vivo Study
Toxins 2020, 12(4), 239; https://0-doi-org.brum.beds.ac.uk/10.3390/toxins12040239 - 09 Apr 2020
Cited by 3 | Viewed by 993
Abstract
There are several reports indicating that the roots of the Carlina acaulis L. used to be commonly applied as a treatment measure in skin diseases and as an antiparasitic agent, starting from antiquity to the 19th century; however, nowadays, it has lost its [...] Read more.
There are several reports indicating that the roots of the Carlina acaulis L. used to be commonly applied as a treatment measure in skin diseases and as an antiparasitic agent, starting from antiquity to the 19th century; however, nowadays, it has lost its importance. Currently, numerous studies are being conducted assessing the possibility of reintroducing C. acaulis-derived extracts to phytotherapy. Determining the safety profile of the main constituents of the plant material is crucial for achieving this goal. Here, we aimed to determine the toxicity profile of carlina oxide, one of the most abundant components of the C. acaulis root extract. We obtained the carlina oxide by distillation of C. acaulis roots in the Deryng apparatus. The purity of the standard was evaluated using GC-MS, and the identity was confirmed by IR, Raman, and NMR spectroscopy. In vitro cytotoxicity was assessed using a panel of human cell lines of skin origin, including BJ normal fibroblasts and UACC-903, UACC-647, and C32 melanoma cells. This was accompanied by an in vivo zebrafish acute toxicity test (ZFET). In vitro studies showed a toxic effect of carlina oxide, as demonstrated by an induction of apoptosis and necrosis in both normal and melanoma cells. Decreased expression of AKT kinase and extracellular signal-regulated kinase 1/2 (ERK1/2) was noted in the UACC-647 melanoma cell line. It was also observed that carlina oxide modified the expression of programmed cell death-ligand 1 (PD-L1) in tested cell lines. Carlina oxide exhibited high in vivo toxicity, with LC50 = 10.13 µg/mL upon the 96 h of exposure in the ZFET test. Here, we demonstrate that carlina oxide displays toxic effects to cells in culture and to living organisms. The data indicate that C. acaulis-based extracts considered for therapeutic use should be completely deprived of carlina oxide. Full article
(This article belongs to the Special Issue Microbial and Plant Phytotoxins)
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Article
Phytotoxic Metabolites Isolated from Neufusicoccum batangarum, the Causal Agent of the Scabby Canker of Cactus Pear (Opuntia ficus-indica L.)
Toxins 2020, 12(2), 126; https://0-doi-org.brum.beds.ac.uk/10.3390/toxins12020126 - 18 Feb 2020
Cited by 10 | Viewed by 1110
Abstract
Six phytotoxins were obtained from the culture filtrates of the ascomycete Neofusicoccum batangarum, the causal agent of the scabby canker of cactus pear (Opuntia ficus-indica L.) in minor Sicily islands. The phytotoxins were identified as (−)-(R)-mellein (1); [...] Read more.
Six phytotoxins were obtained from the culture filtrates of the ascomycete Neofusicoccum batangarum, the causal agent of the scabby canker of cactus pear (Opuntia ficus-indica L.) in minor Sicily islands. The phytotoxins were identified as (−)-(R)-mellein (1); (±)-botryoisocoumarin A (2); (−)-(3R,4R)- and (−)-(3R,4S)-4-hydroxymellein (3 and 4); (−)-terpestacin (5); and (+)-3,4-dihydro-4,5,8-trihydroxy-3-methylisocoumarin, which we named (+)-neoisocoumarin (6). This identification was done by comparing their spectral and optical data with those already reported in literature. The absolute configuration (3R,4S) to (+)-neoisocoumarin (6) was determined using the advanced Mosher method. All six metabolites were shown to have phytotoxicity on the host (cactus pear) and non-host (tomato) plants, and the most active compounds were (±)-botryoisocoumarin A (2), (−)-terpestacin (5), and (+)-neoisocoumarin (6). Full article
(This article belongs to the Special Issue Microbial and Plant Phytotoxins)
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Review

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Review
Fungal Bioactive Anthraquinones and Analogues
Toxins 2020, 12(11), 714; https://0-doi-org.brum.beds.ac.uk/10.3390/toxins12110714 - 12 Nov 2020
Cited by 4 | Viewed by 768
Abstract
This review, covering the literature from 1966 to the present (2020), describes naturally occurring fungal bioactive anthraquinones and analogues biosynthesized by the acetate route and concerning several different functionalized carbon skeletons. Hydrocarbons, lipids, sterols, esters, fatty acids, derivatives of amino acids, and aromatic [...] Read more.
This review, covering the literature from 1966 to the present (2020), describes naturally occurring fungal bioactive anthraquinones and analogues biosynthesized by the acetate route and concerning several different functionalized carbon skeletons. Hydrocarbons, lipids, sterols, esters, fatty acids, derivatives of amino acids, and aromatic compounds are metabolites belonging to other different classes of natural compounds and are generated by the same biosynthetic route. All of them are produced by plant, microorganisms, and marine organisms. The biological activities of anthraquinones and analogues comprise phytotoxic, antibacterial, antiviral, anticancer, antitumor, algicide, antifungal, enzyme inhibiting, immunostimulant, antiplatelet aggregation, cytotoxic, and antiplasmodium activities. The review also covers some practical industrial applications of anthraquinones. Full article
(This article belongs to the Special Issue Microbial and Plant Phytotoxins)
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