Structural Diversity and Biological Activities of Fungal Cyclic Peptides, Excluding Cyclodipeptides

Micro-scale screening of genetically modified Fusarium fujikuroi strain extends the apicidin family

Apicidins are a class of naturally occurring cyclic tetrapeptides produced by few strains within the Fusarium genus. These secondary metabolites have gained significant attention due to their antiprotozoal activity through HDAC inhibition, thereby highlighting their potential for the treatment of malaria. Predominantly, apicidins have been isolated from Fusarium semitectum, offering a deep insight into the biosynthetic pathway responsible for their formation. A similar biosynthetic gene cluster has also been identified in the rice pathogenic fungus F. fujikuroi, leading the discovery of three additional apicidins through genetic manipulation. Routine mass spectrometric screening of these compound-producing strains revealed another metabolite structurally related to previously studied apicidins. By optimizing culture conditions and developing an effective isolation method, we obtained a highly pure substance, whose chemical structure was fully elucidated using NMR and HRMS fragmentation. Further studies were conducted to determine cytotoxicity, antimalarial activity, and HDAC inhibitory activity of this new secondary metabolite alongside the previously known apicidins. This work not only expands the apicidin class with a new member but also provides extensive insights and comparative analysis of apicidin-like substances produced by F. fujikuroi.

The Immunosuppressive Properties of Cyclo-[D-Pro-Pro-β3-HoPhe-Phe-] Tetrapeptide Selected from Stereochemical Variants of Cyclo-[Pro-Pro-β3-HoPhe-Phe-] Peptide

The anti-inflammatory, antiviral, and anti-cancer properties, as well as the mechanism of action of cyclo-[Pro-Pro-β3-HoPhe-Phe-] tetrapeptide (denoted as 4B8M), were recently described. The aim of this work was to synthesize and evaluate the immunosuppressive actions of the stereochemical variants of 4B8M by sequential substitution of L-amino acids by D-amino acids (a series of peptides denoted as P01-P07) using parent 4B8M as a reference compound. In addition, diverse available bioinformatics tools using machine learning and artificial intelligence were tested to find the bio-pharmacokinetic and polypharmacological attributes of analyzed stereomers. All peptides were non-toxic to human peripheral blood mononuclear cells (PBMCs) and only cyclo-[D-Pro-Pro-β3-HoPhe-Phe-] peptide (P03) was capable of inhibiting mitogen-induced PBMC proliferation. The peptides inhibited the lipopolysaccharide (LPS)-induced production of tumor necrosis factor-alpha (TNF-α) to various degrees, with P04 (cyclo-[Pro-Pro-D-β3-HoPhe-Phe-]) and P03 being the most potent. For further in vivo studies, P03 was selected because it had the combined properties of inhibiting cell proliferation and TNF-α production. P03 demonstrated a comparable ability to 4B8M in the inhibition of auricle edema and lymph node cell number and in the normalization of a distorted blood cell composition in contact sensitivity to the oxazolone mouse model. In the mouse model of carrageenan-induced inflammation of the air pouch, P03 exhibited a similar inhibition of the cell number in the air pouches as 4B8M, but its inhibitory effects on the percentage of neutrophils and eosinophils in the air pouches and blood, as well as on mastocyte degranulation in the air pouches, were stronger in comparison to 4B8M. Lastly, in a mouse model of dextran sulfate-induced colitis, similar effects to 4B8M regarding thymocyte number restoration and normalization of the blood cell pictures by P03 were observed. In summary, depending on either experimental findings or in silico predictions, P03 demonstrated comparable, or even better, anti-inflammatory and bio-pharmacokinetic properties to 4B8M and may be considered as a potential therapeutic. The possibility of P00 and P03 identification by circular dichroism measurements was tested by quantum-chemical calculations.

Metabolic and Lipid Biomarkers for Pathogenic Algae, Fungi, Cyanobacteria, Mycobacteria, Gram-Positive Bacteria, and Gram-Negative Bacteria

The utilization of metabolomics and lipidomics analytical platforms in the study of pathogenic microbes is slowly expanding. These research approaches will significantly contribute to the establishment of microbial metabolite and lipid databases of significant value to all researchers in microbiology. In this review, we present a high-level overview of some examples of biomarkers that can be used to detect the presence of microbes, monitor the expansion/decline of a microbe population, and add to our understanding of microbe biofilms and pathogenicity. In addition, increased knowledge of the metabolic functions of pathogenic microbes can contribute to our understanding of microbes that are utilized in diverse industrial applications. Our review focuses on lipids, secondary metabolites, and non-ribosomal peptides that can be monitored using electrospray ionization high-resolution mass spectrometry (ESI-HRMS).

Metabolite profiles of Paragliomastix luzulae (formerly named as Acremonium striatisporum) KMM 4401 and its co-cultures with Penicillium hispanicum KMM 4689

The marine holothurian-derived fungal strain KMM 4401 has been identified as Paragliomastix luzulae using 28S rDNA, ITS regions and the partial TEF1 gene sequences. The metabolite profile of the fungal culture was studied by UPLC-MS technique. The strain KMM 4401 is a source of various virescenoside-type isopimarane glycosides suggested as chemotaxonomic feature for this fungal species. Also Px. luzulae KMM 4401 was proposed as possible source of new bioactive secondary metabolites especially antimicrobials. Moreover, the co-cultures of Px. luzulae KMM 4401 with another marine fungus Penicillium hispanicum KMM 4689 inoculated simultaneously or after two weeks were investigated by same way. It was shown, that P. hispanicum KMM 4689 suppressed the production of most of Px. luzulae KMM 4401 metabolites. On the other hand, the co-cultivation of P. hispanicum KMM 4689 and Px. luzulae KMM 4401 resulted in increasing of production of main deoxyisoaustamide alkaloids of P. hispanicum KMM 4689 on 50-190%.

New Cyclic Pentapeptides from the Mangrove-Derived Aspergillus fumigatus GXIMD 03099

Four new cyclic pentapeptides, avellanins D-G (1-4), together with four known compounds (5-8), were isolated from a mangrove-derived Aspergillus fumigatus GXIMD 03099 fungus from Acanthus ilicifolius L. Their structures were elucidated by analysis of HRESIMS, NMR, and ESI-MS/MS data. Their absolute configurations were determined by X-ray diffraction analysis and Marfey's method. Compounds 1-8 were screened for insecticidal and antibacterial activities. Compound 2 showed insecticidal activity against newly hatched larvae of Culex quinquefasciatus with an LC50 value of 86.6 µM; compound 4 had weak activity against Vibrio harveyi with an MIC value of 5.85 µM.

Targeting Fks1 proteins for novel antifungal drug discovery

Fungal infections are a major threat to human health. The limited availability of antifungal drugs, the emergence of drug resistance, and a growing susceptible population highlight the critical need for novel antifungal agents. The enzymes involved in fungal cell wall synthesis offer potential targets for antifungal drug development. Recent studies have enhanced our focus on the enzyme Fks1, which synthesizes β-1,3-glucan, a critical component of the cell wall. These studies provide a deeper understanding of Fks1's function in cell wall biosynthesis, pathogenicity, structural biology, evolutionary conservation across fungi, and interaction with current antifungal drugs. Here, we discuss the role of Fks1 in the survival and adaptation of fungi, guided by insights from evolutionary and structural analyses. Furthermore, we delve into the dynamics of Fks1 modulation with novel antifungal strategies and assess its potential as an antifungal drug target.

Biocompatible strategies for peptide macrocyclisation

Peptides are increasingly important drug candidates, offering numerous advantages over conventional small molecules. However, they face significant challenges related to stability, cellular uptake and overall bioavailability. While individual modifications may not address all these challenges, macrocyclisation stands out as a single modification capable of enhancing affinity, selectivity, proteolytic stability and membrane permeability. The recent successes of in situ peptide modifications during screening in combination with genetically encoded peptide libraries have increased the demand for peptide macrocyclisation reactions that can occur under biocompatible conditions. In this perspective, we aim to distinguish biocompatible conditions from those well-known examples that are fully bioorthogonal. We introduce key strategies for biocompatible peptide macrocyclisation and contextualise them within contemporary screening methods, providing an overview of available transformations.

Comparative metabolomic study of fungal foliar endophytes and their long-lived host Astrocaryum sciophilum: a model for exploring the chemodiversity of host-microbe interactions

Introduction

In contrast to the dynamics observed in plant/pathogen interactions, endophytic fungi have the capacity to establish enduring associations within their hosts, leading to the development of a mutually beneficial relationship that relies on specialized chemical interactions. Research indicates that the presence of endophytic fungi has the ability to significantly modify the chemical makeup of the host organism. Our hypothesis proposes the existence of a reciprocal exchange of chemical signals between plants and fungi, facilitated by specialized chemical processes that could potentially manifest within the tissues of the host. This research aimed to precisely quantify the portion of the cumulative fungal endophytic community's metabolome detectable within host leaves, and tentatively evaluate its relevance to the host-endophyte interplay. The understory palm Astrocaryum sciophilum (Miq.) Pulle was used as a interesting host plant because of its notable resilience and prolonged life cycle, in a tropical ecosystem.

Method

Using advanced metabolome characterization, including UHPLC-HRMS/MS and molecular networking, the study explored enriched metabolomes of both host leaves and 15 endophytic fungi. The intention was to capture a metabolomic "snapshot" of both host and endophytic community, to achieve a thorough and detailed analysis.

Results and discussion

This approach yielded an extended MS-based molecular network, integrating diverse metadata for identifying host- and endophyte-derived metabolites. The exploration of such data (>24000 features in positive ionization mode) enabled effective metabolome comparison, yielding insights into cultivable endophyte chemodiversity and occurrence of common metabolites between the holobiont and its fungal communities. Surprisingly, a minor subset of features overlapped between host leaf and fungal samples despite significant plant metabolome enrichment. This indicated that fungal metabolic signatures produced in vitro remain sparingly detectable in the leaf. Several classes of primary metabolites were possibly shared. Specific fungal metabolites and/or compounds of their chemical classes were only occasionally discernible in the leaf, highlighting endophytes partial contribution to the overall holobiont metabolome. To our knowledge, the metabolomic study of a plant host and its microbiome has rarely been performed in such a comprehensive manner. The general analytical strategy proposed in this paper seems well-adapted for any study in the field of microbial- or microbiome-related MS and can be applied to most host-microbe interactions.

From microbes to molecules: a review of microbial-driven antioxidant peptide generation

Oxidative stress, arising from excess reactive oxygen species (ROS) or insufficient antioxidant defenses, can damage cellular components, such as lipids, proteins, and nucleic acids, resulting in cellular dysfunction. The relationship between oxidative stress and various health disorders has prompted investigations into potent antioxidants that counteract ROS's detrimental impacts. In this context, antioxidant peptides, composed of two to twenty amino acids, have emerged as a unique group of antioxidants and have found applications in food, nutraceuticals, and pharmaceuticals. Antioxidant peptides are sourced from natural ingredients, mainly proteins derived from foods like milk, eggs, meat, fish, and plants. These peptides can be freed from their precursor proteins through enzymatic hydrolysis, fermentation, or gastrointestinal digestion. Previously published studies focused on the origin and production methods of antioxidant peptides, describing their structure-activity relationship and the mechanisms of food-derived antioxidant peptides. Yet, the role of microorganisms hasn't been sufficiently explored, even though the production of antioxidant peptides frequently employs a variety of microorganisms, such as bacteria, fungi, and yeasts, which are recognized for producing specific proteases. This review aims to provide a comprehensive overview of microorganisms and their proteases participating in enzymatic hydrolysis and microbial fermentation to produce antioxidant peptides. This review also covers endogenous peptides originating from microorganisms. The information obtained from this review might guide the discovery of novel organisms adept at generating antioxidant peptides.

Cyclic Peptides in Pipeline: What Future for These Great Molecules?

Cyclic peptides are molecules that are already used as drugs in therapies approved for various pharmacological activities, for example, as antibiotics, antifungals, anticancer, and immunosuppressants. Interest in these molecules has been growing due to the improved pharmacokinetic and pharmacodynamic properties of the cyclic structure over linear peptides and by the evolution of chemical synthesis, computational, and in vitro methods. To date, 53 cyclic peptides have been approved by different regulatory authorities, and many others are in clinical trials for a wide diversity of conditions. In this review, the potential of cyclic peptides is presented, and general aspects of their synthesis and development are discussed. Furthermore, an overview of already approved cyclic peptides is also given, and the cyclic peptides in clinical trials are summarized.

Filamentous fungi for sustainable vegan food production systems within a circular economy: Present status and future prospects

Filamentous fungi serve as potential candidates in the production of different value-added products. In the context of food, there are several advantages of using filamentous fungi for food. Among the main advantages is that the fungal biomass used food not only meets basic nutritional requirements but that it is also rich in protein, low in fat, and free of cholesterol. This speaks to the potential of filamentous fungi in the production of food that can substitute animal-derived protein sources such as meat. Moreover, life-cycle analyses and techno-economic analyses reveal that fungal proteins perform better than animal-derived proteins in terms of land use efficiency as well as global warming. The present article provides an overview of the potential of filamentous fungi as a source of food and food supplements. The commercialization potential as well as social, legal and safety issues of fungi-based food products are discussed.

Absolute Stereochemistry Determination of Bioactive Marine-Derived Cyclopeptides by Liquid Chromatography Methods: An Update Review (2018-2022)

Cyclopeptides are considered as one of the most important classes of compounds derived from marine sources, due to their structural diversity and a myriad of their biological and pharmacological activities. Since marine-derived cyclopeptides consist of different amino acids, many of which are non-proteinogenic, they possess various stereogenic centers. In this respect, the structure elucidation of new molecular scaffolds obtained from natural sources, including marine-derived cyclopeptides, can become a very challenging task. The determination of the absolute configurations of the amino acid residues is accomplished, in most cases, by performing acidic hydrolysis, followed by analyses by liquid chromatography (LC). In a continuation with the authors' previous publication, and to analyze the current trends, the present review covers recently published works (from January 2018 to November 2022) regarding new cyclopeptides from marine organisms, with a special focus on their biological/pharmacological activities and the absolute stereochemical assignment of the amino acid residues. Ninety-one unreported marine-derived cyclopeptides were identified during this period, most of which displayed anticancer or antimicrobial activities. Marfey's method, which involves LC, was found to be the most frequently used for this purpose.

A comprehensive review of microorganism-derived cyclic peptides: Bioactive functions and food safety applications

Cyclic peptides possess advanced structural characteristics of stability and play a vital role in medical treatment and agriculture. However, the biological functions of microorganism-derived cyclic peptides (MDCPs) and their applications in food industry were relatively absent. MDCPs are derived from extensive fermented food or soil. In this review, the synthesis approaches and structural characteristics are overviewed, while the interrelationship between bioactivities and functions is emphasized. This review summarizes the bioactivities of MDCPs from in vitro to in vivo, including antimicrobial activities, immune regulation, and antiviral cell activation. Their multiple functions as well as applications during food product processing, packaging, and storage are also comprehensively reviewed. Remarkably, some potential risks and cytotoxicity of MDCPs are also critically discussed. Moreover, future applications of MDCPs in the development of novel food additives and bioengineering materials are organized. Based on this review of native MDCPs, it is noteworthy that expected improvements of synthetic cyclic peptides in bioactive properties present potential valuable applications in future food, including artificial meat.

Efficient production of a cyclic dipeptide (cyclo-TA) using heterologous expression system of filamentous fungus Aspergillus oryzae

Background

Cyclic dipeptides are an important class of natural products owing to their structural diversity and biological activities. In fungi, the cyclo-ring system is formed through the condensation of two α-amino acids via non-ribosomal peptide synthetase (NRPS). However, there are few investigations on the functional identification of this enzyme. Additionally, information on how to increase the production of cyclic dipeptide molecules is relatively scarce.

Results

We isolated the Eurotium cristatum NWAFU-1 fungus from Jing-Wei Fu brick tea, whose fermentation metabolites contain echinulin-related cyclic dipeptide molecules. We cloned the cirC gene, encoding an NRPS, from E. Cristatum NWAFU-1 and transferred it into the heterologous host Aspergillus oryzae. This transformant produced a novel metabolite possessing an l-tryptophan-l-alanine cyclic dipeptide backbone (Cyclo-TA). Based on the results of heterologous expression and microsomal catalysis, CriC is the first NRPS characterized in fungi that catalyzes the formation of a cyclic dipeptide from l-tryptophan and l-alanine. After substrate feeding, the final yield reached 34 mg/L. In this study, we have characterized a novel NRPS and developed a new method for cyclic dipeptide production.

Conclusions

In this study we successfully expressed the E. Cristatum NWAFU-1 criC gene in A. oryzae to efficiently produce cyclic dipeptide compounds. Our findings indicate that the A. oryzae heterologous expression system constitutes an efficient method for the biosynthesis of fungal Cyclic dipeptides.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01872-8.

Antiviral Activity of a Cyclic Pro-Pro-β3-HoPhe-Phe Tetrapeptide against HSV-1 and HAdV-5

The core of Cyclolinopeptide A (CLA, cyclo(LIILVPPFF)), responsible for its high immunosuppressive activity, contains a Pro-Pro-Phe-Phe sequence. A newly synthesized cyclic tetrapeptide, cyclo(Pro-Pro-β3-HoPhe-Phe) (denoted as 4B8M) bearing the active sequence of CLA, was recently shown to exhibit a wide array of anti-inflammatory properties in mouse models. In this investigation, we demonstrate that the peptide significantly inhibits the replication of human adenovirus C serotype 5 (HAdV-5) and Herpes simplex virus type-1 (HSV-1) in epithelial lung cell line A-549, applying Cidofovir and Acyclovir as reference drugs. Based on a previously established mechanism of its action, we propose that the peptide may inhibit virus replication by the induction of PGE2 acting via EP2/EP4 receptors in epithelial cells. In summary, we reveal a new, antiviral property of this anti-inflammatory peptide.

Out for a RiPP: challenges and advances in genome mining of ribosomal peptides from fungi

Covering up to June 2021Ribosomally synthesized and post-translationally modified peptides (RiPPs) from fungi are an underexplored class of natural products, despite their propensity for diverse bioactivities and unique structural features. Surveys of fungal genomes for biosynthetic gene clusters encoding RiPPs have been limited in their scope due to our incomplete understanding of fungal RiPP biosynthesis. Through recent discoveries, along with earlier research, a clearer picture has been emerging of the biosynthetic principles that underpin fungal RiPP pathways. In this Highlight, we trace the approaches that have been used for discovering currently known fungal RiPPs and show that all of them can be assigned to one of three distinct families based on hallmarks of their biosynthesis, which are in turn imprinted on their corresponding gene clusters. We hope that our systematic exposition of fungal RiPP structural and gene cluster features will facilitate more comprehensive approaches to genome mining efforts in the future.

Metabolomic Profiles of the Creeping Wood Sorrel Oxalis corniculata in Radioactively Contaminated Fields in Fukushima: Dose-Dependent Changes in Key Metabolites

The biological impacts of the Fukushima nuclear accident, in 2011, on wildlife have been studied in many organisms, including the pale grass blue butterfly and its host plant, the creeping wood sorrel Oxalis corniculata. Here, we performed an LC–MS-based metabolomic analysis on leaves of this plant collected in 2018 from radioactively contaminated and control localities in Fukushima, Miyagi, and Niigata prefectures, Japan. Using 7967 peaks detected by LC–MS analysis, clustering analyses showed that nine Fukushima samples and one Miyagi sample were clustered together, irrespective of radiation dose, while two Fukushima (Iitate) and two Niigata samples were not in this cluster. However, 93 peaks were significantly different (FDR < 0.05) among the three dose-dependent groups based on background, low, and high radiation dose rates. Among them, seven upregulated and 15 downregulated peaks had single annotations, and their peak intensity values were positively and negatively correlated with ground radiation dose rates, respectively. Upregulated peaks were annotated as kudinoside D (saponin), andrachcinidine (alkaloid), pyridoxal phosphate (stress-related activated vitamin B6), and four microbe-related bioactive compounds, including antibiotics. Additionally, two peaks were singularly annotated and significantly upregulated (K₁R₁H₁; peptide) or downregulated (DHAP(10:0); decanoyl dihydroxyacetone phosphate) most at the low dose rates. Therefore, this plant likely responded to radioactive pollution in Fukushima by upregulating and downregulating key metabolites. Furthermore, plant-associated endophytic microbes may also have responded to pollution, suggesting their contributions to the stress response of the plant.

Mutation of a prenyltransferase results in accumulation of subglutinols and destruxins and enhanced virulence in the insect pathogen, Metarhizium anisopliae

The insect pathogenic fungus, Metarhizium anisopliae is a commercialized microbial agent used in biological control efforts targeting a diverse range of agricultural and other insect pests. The second step in the synthesis of a group of M. anisopliae α-pyrone diterpenoids (termed subglutinols) involves the activity of a prenyltransferase family geranylgeranyl diphosphate synthase (product of the subD/MaGGPPS5 gene). Here, we show that targeted gene disruption of MaGGPPS5 results in earlier conidial germination and faster greater vegetative growth compared to the wild type (WT) parent and complemented strains. In addition, insect bioassays revealed that the ΔMaGGPPS5 mutant strain displayed significantly increased virulence, with a ~50% decrease in the mean lethal time (LT₅₀ , from 6 to 3 days) to kill (50% of) target insects, and an ~15-40-fold decrease in the mean lethal dose (LC₅₀ ). Metabolite profiling indicated increased accumulation in the ΔMaGGPPS5 mutant of select subglutinols (A, B and C) and destruxins (A, A2, B and B2), the latter a set of fungal secondary metabolites that act as insect toxins, with a concomitant loss of production of subglutinol 'analogue 45'. These data suggest that the increased virulence phenotype seen for the ΔMaGGPPS5 strain can, at least in part, be attributed to a combination of faster growth and increased insect toxin production, linking the production of two different secondary metabolite pathways, and represent a novel approach for the screening of isolates with enhanced virulence via modulation of terpenoid secondary metabolite biosynthesis.

Cyclosporin Structure and Permeability: From A to Z and Beyond

Cyclosporins are natural or synthetic undecapeptides with a wide range of actual and potential pharmaceutical applications. Several members of the cyclosporin compound family have remarkably high passive membrane permeabilities that are not well-described by simple structural metrics. Here we review experimental studies of cyclosporin structure and permeability, including cyclosporin-metal complexes. We also discuss models for the conformation-dependent permeability of cyclosporins and similar compounds. Finally, we identify current knowledge gaps in the literature and provide recommendations regarding future avenues of exploration.

Genome Mining and Molecular Networking-Based Metabolomics of the Marine Facultative Aspergillus sp. MEXU 27854

The marine-facultative Aspergillus sp. MEXU 27854, isolated from the Caleta Bay in Acapulco, Guerrero, Mexico, has provided an interesting diversity of secondary metabolites, including a series of rare dioxomorpholines, peptides, and butyrolactones. Here, we report on the genomic data, which consists of 11 contigs (N50~3.95 Mb) with a ~30.75 Mb total length of assembly. Genome annotation resulted in the prediction of 10,822 putative genes. Functional annotation was accomplished by BLAST searching protein sequences with different public databases. Of the predicted genes, 75% were assigned gene ontology terms. From the 67 BGCs identified, ~60% belong to the NRPS and NRPS-like classes. Putative BGCs for the dioxomorpholines and other metabolites were predicted by extensive genome mining. In addition, metabolomic molecular networking analysis allowed the annotation of all isolated compounds and revealed the biosynthetic potential of this fungus. This work represents the first report of whole-genome sequencing and annotation from a marine-facultative fungal strain isolated from Mexico.

Antiamoeboid activity of squamins C-F, cyclooctapeptides from Annona globifora

Free-living amoebae of Acanthamoeba spp. are causative agents of human infections such as granulomatous amoebic encephalitis (GAE) and Acanthamoeba keratitis (AK). The exploration of innovative chemical entities from natural sources that induce intrinsic apoptotic pathway or a Programmed Cell Death (PCD) in Acanthamoeba protozoa is essential to develop new therapeutic strategies. In this work, the antiamoeboid activity of squamins C-F (1-4), four cyclooctapeptides isolated from Annona globiflora was tested in vitro against Acanthamoeba castellanii Neff, A. polyphaga, A. quina, and A. griffini, and a structure-activity relationship was also established. The most sensitive strain against all tested cyclooctapeptides was A. castellanii Neff being the R conformers of the S-oxo-methionine residue, squamins D (2) and F (4), the most active against the trophozoite stage. It is remarkable that all four peptides showed no cytotoxic effects against murine macrophages cell line J774A.1. The analysis of the mode of action of squamins C-F against A. castellanii indicate that these cyclopeptides induced the mechanisms of programmed cell death (PCD). All peptides trigger mitochondrial damages, significant inhibition of ATP production compared to the negative control, chromatin condensation and slight damages in membrane that affects its permeability despite it conserves integrity at the IC₉₀ for 24 h. An increase in reactive oxygen species (ROS) was observed in all cases.

Computational exploration of natural peptides targeting ACE2

Interaction between the SARS-COV-2 (2019 novel coronavirus) spike protein and ACE2 receptors expressed on cellular surfaces initialises viral attachment and consequent infection. Blocking this interaction shows promise for blocking or ameliorating the virus' pathological effects on the body. By contrast to work focusing on the coronavirus, which has significant potential diversity through possible accumulation of mutations during transmission, targeting the conserved ACE2 protein expressed on human cells offers an attractive alternative route to developing pharmacological prophylactics against viral invasion. In this study, we screened a virtual database of natural peptides in silico, with ACE2 as the target, and performed structural analyses of the interface region in the SARS-COV-2 RBD/ACE2 complex. These analyses have identified 15 potentially effective compounds. Analyses of ACE2/polypeptide interactions suggest that these peptides can block viral invasion of cells by stably binding in the ACE2 active site pocket. Molecular simulation results for Complestatin and Valinomycin indicate that they may share this mechanism. The discovery of this probable binding mechanism provides a frame of reference for further optimization, and design of high affinity ACE2 inhibitors that could serve as leads for production of drugs with preventive and therapeutic effects against SARS-COV-2.Communicated by Ramaswamy H. Sarma.

In Vitro Selection of Macrocyclic d/l-Hybrid Peptides against Human EGFR

d/l-Hybrid peptides are an attractive class of molecular modality because they are able to exhibit high proteolytic stability and unique structural diversity which cannot be accessed by those consisting of only proteinogenic l-amino acids. Despite such an expectation, it has not been possible to devise de novo d/l-hybrid peptides capable of disrupting the function of a protein target(s) due to the lack of an effective method that reliably constructs a highly diverse library and screens active species. Here we report for the first time construction of a library consisting of 10¹² members of macrocyclic d/l-hybrid peptides containing five kinds of d-amino acids and performance of the RaPID selection against human EGFR as a showcase to uncover PPI (protein-protein interaction) inhibitors.

Phytotoxic Secondary Metabolites from Fungi

Fungal phytotoxic secondary metabolites are poisonous substances to plants produced by fungi through naturally occurring biochemical reactions. These metabolites exhibit a high level of diversity in their properties, such as structures, phytotoxic activities, and modes of toxicity. They are mainly isolated from phytopathogenic fungal species in the genera of Alternaria, Botrytis, Colletotrichum, Fusarium, Helminthosporium, and Phoma. Phytotoxins are either host specific or non-host specific phytotoxins. Up to now, at least 545 fungal phytotoxic secondary metabolites, including 207 polyketides, 46 phenols and phenolic acids, 135 terpenoids, 146 nitrogen-containing metabolites, and 11 others, have been reported. Among them, aromatic polyketides and sesquiterpenoids are the main phytotoxic compounds. This review summarizes their chemical structures, sources, and phytotoxic activities. We also discuss their phytotoxic mechanisms and structure-activity relationships to lay the foundation for the future development and application of these promising metabolites as herbicides.

Converting peptides into drugs targeting intracellular protein-protein interactions

Peptides are gaining increasing attention as therapeutics to target intracellular protein-protein interactions that are involved in disease progression. In this review, we discuss how peptides that are able to bind and inhibit a therapeutic target can be translated into drug leads. We discuss the advantages of using peptides as therapeutics to target intracellular protein-protein interactions, chemical strategies to generate macrocyclic peptides that are resistant to proteolytic enzymes, high-throughput screening approaches to identify peptides that have high affinity for therapeutic targets, strategies that permit these peptides to cross cell membranes and so reach intracellular targets, and the importance of investigating their mode-of-action in guiding the development of novel therapeutics.

Dynamics of Chemical Diversity during Co-Cultures: An Integrative Time-Scale Metabolomics Study of Fungal Endophytes Cophinforma mamane and Fusarium solani

A rapid and efficient metabolomic study of Cophinforma mamane and Fusarium solani co-cultivation in time-series based analysis was developed to study metabolome variations during their fungal interactions. The fungal metabolomes were studied through the integration of four metabolomic tools: MS-DIAL, a chromatographic deconvolution of liquid-chromatography-mass spectrometry (LC/MS); MS-FINDER, a structure-elucidation program with a wide range metabolome database; GNPS, an effective method to organize MS/MS fragmentation spectra, and MetaboAnalyst, a comprehensive web application for metabolomic data analysis and interpretation. Co-cultures of C. mamane and F. solani induced different patterns of metabolite production over 10 days of incubation and induced production of five de novo compounds not occurring in monocultures. These results emphasize that co-culture in time-frame analysis is an interesting method to unravel hidden metabolome in the investigation of fungal chemodiversity.

Temperature Replica Exchange Molecular Dynamics Simulations of Cyclic Peptide Conformation

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Identification and dereplication of endophytic Colletotrichum strains by MALDI TOF mass spectrometry and molecular networking

The chemical diversity of biologically active fungal strains from 42 Colletotrichum, isolated from leaves of the tropical palm species Astrocaryum sciophilum collected in pristine forests of French Guiana, was investigated. The collection was first classified based on protein fingerprints acquired by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) correlated with cytotoxicity. Liquid chromatography coupled to high-resolution tandem mass spectrometry (LC-HRMS/MS) data from ethyl acetate extracts were acquired and processed to generate a massive molecular network (MN) using the MetGem software. From five Colletotrichum strains producing cytotoxic specialized metabolites, we predicted the occurrence of peptide and cytochalasin analogues in four of them by MN, including a similar ion clusters in the MN algorithm provided by MetGem software. Chemoinformatics predictions were fully confirmed after isolation of three pentacyclopeptides (cyclo(Phe-Leu-Leu-Leu-Val), cyclo(Phe-Leu-Leu-Leu-Leu) and cyclo(Phe-Leu-Leu-Leu-Ile)) and two cytochalasins (cytochalasin C and cytochalasin D) exhibiting cytotoxicity at the micromolar concentration. Finally, the chemical study of the last active cytotoxic strain BSNB-0583 led to the isolation of four colletamides bearing an identical decadienamide chain.

Metabolites from Clonostachys Fungi and Their Biological Activities

Clonostachys (teleomorph: Bionectria) fungi are well known to produce a variety of secondary metabolites with various biological activities to show their pharmaceutical and agrochemical applications. Up to now, at least 229 secondary metabolites, mainly including 84 nitrogen-containing metabolites, 85 polyketides, 40 terpenoids, and 20 other metabolites, have been reported. Many of these compounds exhibit biological activities, such as cytotoxic, antimicrobial, antileishmanial, antimalarial activities. This mini-review aims to summarize the diversity of the secondary metabolites as well as their occurrences in Clonostachys fungi and biological activities.

Victorin, the host-selective cyclic peptide toxin from the oat pathogen Cochliobolus victoriae, is ribosomally encoded

The necrotrophic fungal pathogen Cochliobolus victoriae produces victorin, a host-selective toxin (HST) essential for pathogenicity to certain oat cultivars with resistance against crown rust. Victorin is a mixture of highly modified heterodetic cyclic hexapeptides, previously assumed to be synthesized by a nonribosomal peptide synthetase. Herein, we demonstrate that victorin is a member of the ribosomally synthesized and posttranslationally modified peptide (RiPP) family of natural products. Analysis of a newly generated long-read assembly of the C. victoriae genome revealed three copies of precursor peptide genes (vicA1-3) with variable numbers of "GLKLAF" core peptide repeats corresponding to the victorin peptide backbone. vicA1-3 are located in repeat-rich gene-sparse regions of the genome and are loosely clustered with putative victorin biosynthetic genes, which are supported by the discovery of compact gene clusters harboring corresponding homologs in two distantly related plant-associated Sordariomycete fungi. Deletion of at least one copy of vicA resulted in strongly diminished victorin production. Deletion of a gene encoding a DUF3328 protein (VicYb) abolished the production altogether, supporting its predicted role in oxidative cyclization of the core peptide. In addition, we uncovered a copper amine oxidase (CAO) encoded by vicK, in which its deletion led to the accumulation of new glycine-containing victorin derivatives. The role of VicK in oxidative deamination of the N-terminal glycyl moiety of the hexapeptides to the active glyoxylate forms was confirmed in vitro. This study finally unraveled the genetic and molecular bases for biosynthesis of one of the first discovered HSTs and expanded our understanding of underexplored fungal RiPPs.

The Structural Diversity of Marine Microbial Secondary Metabolites Based on Co-Culture Strategy: 2009-2019

Marine microorganisms have drawn great attention as novel bioactive natural product sources, particularly in the drug discovery area. Using different strategies, marine microbes have the ability to produce a wide variety of molecules. One of these strategies is the co-culturing of marine microbes; if two or more microorganisms are aseptically cultured together in a solid or liquid medium in a certain environment, their competition or synergetic relationship can activate the silent biosynthetic genes to produce cryptic natural products which do not exist in monocultures of the partner microbes. In recent years, the co-cultivation strategy of marine microbes has made more novel natural products with various biological activities. This review focuses on the significant and excellent examples covering sources, types, structures and bioactivities of secondary metabolites based on co-cultures of marine-derived microorganisms from 2009 to 2019. A detailed discussion on future prospects and current challenges in the field of co-culture is also provided on behalf of the authors’ own views of development tendencies.

New Cytotoxic Cerebrosides from the Red Sea Cucumber Holothuria spinifera Supported by In-Silico Studies

Bioactivity-guided fractionation of a methanolic extract of the Red Sea cucumber Holothuria spinifera and LC-HRESIMS-assisted dereplication resulted in the isolation of four compounds, three new cerebrosides, spiniferosides A (1), B (2), and C (3), and cholesterol sulfate (4). The chemical structures of the isolated compounds were established on the basis of their 1D NMR and HRMS spectral data. Metabolic profiling of the H. spinifera extract indicated the presence of diverse secondary metabolites, mostly hydroxy fatty acids, diterpenes, triterpenes, and cerebrosides. The isolated compounds were tested for their in vitro cytotoxicities against the breast adenocarcinoma MCF-7 cell line. Compounds 1, 2, 3, and 4 displayed promising cytotoxic activities against MCF-7 cells, with IC50 values of 13.83, 8.13, 8.27, and 35.56 µM, respectively, compared to that of the standard drug doxorubicin (IC50 8.64 µM). Additionally, docking studies were performed for compounds 1, 2, 3, and 4 to elucidate their binding interactions with the active site of the SET protein, an inhibitor of protein phosphatase 2A (PP2A), which could explain their cytotoxic activity. This study highlights the important role of these metabolites in the defense mechanism of the sea cucumber against fouling organisms and the potential uses of these active molecules in the design of new anticancer agents.

Effect of a dianthin G analogue in the differentiation of rat bone marrow mesenchymal stem cells into cardiomyocytes

Loss of cardiomyocytes due to myocardial infarction results in ventricular remodeling which includes non-contractile scar formation, which can lead to heart failure. Stem cell therapy aims to replace the scar tissue with the functional myocardium. Mesenchymal stem cells (MSCs) are undifferentiated cells capable of self-renewal as well as differentiation into multiple lineages. MSCs can be differentiated into cardiomyocytes by treating them with small molecules and peptides. Here, we report for the first time, the role of a cyclic peptide, an analogue of dianthin G, [Glu²]-dianthin G (1) in the in vitro cardiac differentiation of rat bone marrow MSCs. In this study, [Glu²]-dianthin G (1) was synthesized using solid-phase total synthesis and characterized by NMR spectroscopy. MSCs were treated with two different concentrations (0.025 and 0.05 mM) of the peptide separately for 72 h and then incubated for 15 days to allow the cells to differentiate into cardiomyocytes. Treated cells were analyzed for the expression of cardiac-specific genes and proteins. Results showed significant upregulation of cardiac-specific genes GATA4, cardiac troponin T (cTnT), cardiac troponin I (cTnI), cardiac myosin heavy chain, and connexin 43 in the treated MSCs compared to the untreated control. For cardiac-specific proteins, GATA4, cTnT, and Nkx2.5 were analyzed in the treated cells and were shown to have significant upregulation as compared to the untreated control. In conclusion, this study has demonstrated the cardiac differentiation potential of [Glu²]-dianthin G (1)-treated rat bone marrow MSCs in vitro both at the gene and at the protein levels. Transplantation of pre-differentiated MSCs into the infarcted myocardium may result in the efficient regeneration of cardiac cells and restoration of normal cardiac function.

Newly reported alkaloids produced by marine-derived Penicillium species (covering 2014-2018)

Alkaloids, especially heterocyclic alkaloids, have received remarkable attention due to their intriguing structures and potential pharmacological activities. The marine fungi residing in extreme environmental conditions are among the richest sources of these basic nitrogen-containing compounds. Fungal species belonging to the genus Penicillium have been studied worldwide for their biosynthetic potential for generating bioactive alkaloids. This paper offers a systematic review of the newly reported alkaloids produced by marine-derived Penicillium species over the past five years (covering the literature from the beginning of 2014 through the end of 2018) and describes the structural diversity, biological activities, and plausible biosynthetic pathway of the reported compounds. A total of 106 alkaloids and 81 references are included in this review, which is expected to be beneficial for drug development and biosynthesis in the near future.

Nidulantes of Aspergillus (Formerly Emericella): A Treasure Trove of Chemical Diversity and Biological Activities

The genus Emericella (Ascomycota) includes more than thirty species with worldwide distribution across many ecosystems. It is considered a rich source of diverse metabolites. The published classes of natural compounds that are discussed here are organized according to the following biosynthetic pathways: polyketides (azaphilones, cyclopentenone pigments, dicyanides, furan derivatives, phenolic ethers, and xanthones and anthraquinones); shikimate derivatives (bicoumarins); mevalonate derivatives (meroterpenes, sesquiterpenes, sesterterpenes and steroids) and amino acids derivatives (alkaloids (indole-derivatives, isoindolones, and piperazine) and peptides (depsipeptides)). These metabolites produce the wide array of biological effects associated with Emericella, including antioxidant, antiproliferative, antimalarial, antiviral, antibacterial, antioxidant, antihypertensive, anti-inflammatory, antifungal and kinase inhibitors. Careful and extensive study of the diversity and distribution of metabolites produced by the genus Emericella (either marine or terrestrial) revealed that, no matter the source of the fungus, the composition of the culture medium effectively controls the metabolites produced. The topic of this review is the diversity of metabolites that have been identified from Emericella, along with the contextual information on either their biological or geographic sources. This review presents 236 natural compounds, which were reported from marine and terrestrial Emericella. Amongst the reported compounds, only 70.2% were biologically assayed for their effects, including antimicrobial or cytotoxicity. This implies the need for substantial investigation of alternative activities. This review includes a full discussion of compound structures and disease management, based on materials published from 1982 through December 2019.

Do Epichloë Endophytes and Their Grass Symbiosis Only Produce Toxic Alkaloids to Insects and Livestock?

Epichloë endophytes in forage grasses have attracted widespread attention and interest of chemistry researchers as a result of the various unique chemical structures and interesting biological activities of their secondary metabolites. This review describes the diversity of unique chemical structures of taxa from Epichloë endophytes and grass infected with Epichloë endophytes and demonstrates their reported biological activities. Until now, nearly 160 secondary metabolites (alkaloids, peptides, indole derivatives, pyrimidines, sesquiterpenoids, flavonoids, phenol and phenolic acid derivatives, aliphatic metabolites, sterols, amines and amides, and others) have been reported from Epichloë endophytes and grass infected with Epichloë endophytes. Among these, non-alkaloids account for half of the population of total metabolites, indicating that they also play an important role in Epichloë endophytes and grass infected with Epichloë endophytes. Also, a diverse array of secondary metabolites isolated from Epichloë endophytes and symbionts is a rich source for developing new pesticides and drugs. Bioassays disclose that, in addition to toxic alkaloids, the other metabolites isolated from Epichloë endophytes and symbionts have notable biological activities, such as antifungal, anti-insect, and phytotoxic activities. Accordingly, the biological functions of non-alkaloids should not be neglected in the future investigation of Epichloë endophytes and symbionts.

Recent Discovery of Heterocyclic Alkaloids from Marine-Derived Aspergillus Species

Nitrogen heterocycles have drawn considerable attention due to of their significant biological activities. The marine fungi residing in extreme environments are among the richest sources of these basic nitrogen-containing secondary metabolites. As one of the most well-known universal groups of filamentous fungi, marine-derived Aspergillus species produce a large number of structurally unique heterocyclic alkaloids. This review attempts to provide a comprehensive summary of the structural diversity and biological activities of heterocyclic alkaloids that are produced by marine-derived Aspergillus species. Herein, a total of 130 such structures that were reported from the beginning of 2014 through the end of 2018 are included, and 75 references are cited in this review, which will benefit future drug development and innovation.

Mariannamides A and B, new cyclic octapeptides isolated from Mariannaea elegans NBRC102301

Two new cyclic octapeptides, mariannamides A (1) and B (2), have been isolated from Mariannaea elegans NBRC102301, a Pinus densiflora-derived filamentous fungus. Their structures were elucidated to be cyclo-(l-Leu¹-l-Pro¹-l-Pro²-l-Leu²-l-Ile¹-l-Pro³-l-Val¹-l-Ile²) and cyclo-(l-Leu¹-l-Pro¹-l-Pro²-l-Leu²-l-Ile¹-l-Pro³-l-Val¹-l-Val²) based on spectroscopic data and Marfey's method. Mariannamide A (1) promoted mRNA expression of sirtuin 1 (SIRT1) in C2C12 cells, a mouse skeletal muscle myoblast cell line, and showed the antimicrobial activity against Escherichia coli and Cryptococcus neoformans.

New Peptides from The Marine-Derived Fungi Aspergillus allahabadii and Aspergillus ochraceopetaliformis

Four new peptides were isolated from the culture broths of the marine-derived fungi Aspergillus allahabadii and A. ochraceopetaliformis. Based on the results of chemical and spectroscopic analyses, two compounds (1 and 2) from A. allahabadii were determined to be cyclopentapeptides, while those from A. ochraceopetaliformis were a structurally-related cyclodepsihexapeptide (3) and its linear analog (4). In addition to the presence of a D-amino acid residue, the almost reversed sequence of peptides in 3 and 4, relative to those of the 1 and 2, is notable. These new compounds exhibited moderate inhibition against the enzyme sortase A as well as a weak inhibition against isocitrate lyase (2).

Metabolic Profiling of Water-Soluble Compounds from the Extracts of Dark Septate Endophytic Fungi (DSE) Isolated from Scots Pine (Pinus sylvestris L.) Seedlings Using UPLC-Orbitrap-MS

Endophytes are microorganisms living inside plant hosts and are known to be beneficial for the host plant vitality. In this study, we isolated three endophytic fungus species from the roots of Scots pine seedlings growing on Finnish drained peatland setting. The isolated fungi belonged to dark septate endophytes (DSE). The metabolic profiles of the hot water extracts of the fungi were investigated using Ultrahigh Performance Liquid Chromatography with Diode Array Detection and Electron Spray Ionization source Mass Spectrometry with Orbitrap analyzer (UPLC-DAD-ESI-MS-Orbitrap). Out of 318 metabolites, we were able to identify 220, of which a majority was amino acids and peptides. Additionally, opine amino acids, amino acid quinones, Amadori compounds, cholines, nucleobases, nucleosides, nucleotides, siderophores, sugars, sugar alcohols and disaccharides were found, as well as other previously reported metabolites from plants or endophytes. Some differences of the metabolic profiles, regarding the amount and identity of the found metabolites, were observed even though the fungi were isolated from the same host. Many of the discovered metabolites have been described possessing biological activities and properties, which may make a favorable contribution to the host plant nutrient availability or abiotic and biotic stress tolerance.

Non-lipopeptide fungi-derived peptide antibiotics developed since 2000

The 2,5-diketopiperazines (DKPs) are the smallest cyclopeptides and their basic structure includes a six-membered piperazine nucleus. Typical peptides lack a special functional group in the oligopeptide nucleus. Both are produced by at least 35 representative genera of fungi, and possess huge potential as pharmaceutical drugs and biocontrol agents. To date, only cyclosporin A has been developed into a commercial product. This review summarises 186 fungi-derived compounds reported since 2000. Antibiotic (antibacterial, antifungal, synergistic antifungal, antiviral, antimycobacterial, antimalarial, antileishmanial, insecticidal, antitrypanosomal, nematicidal and antimicroalgal) activities are discussed for 107 of them, including 66 DKPs (14 epipolythiodioxopiperazines, 20 polysulphide bridge-free thiodiketopiperazines, and 32 sulphur-free prenylated indole DKPs), 15 highly N-methylated, and 26 non-highly N-methylated typical peptides. Structure-activity relationships, mechanisms of action, and research methods are covered in detail. Additionally, biosynthases of tardioxopiperazines and neoechinulins are highlighted. These compounds have attracted considerable interest within the pharmaceutical and agrochemical industries.

Fungi-derived lipopeptide antibiotics developed since 2000

Lipopeptide antibiotics have linear or cyclic structures with one or more hydrocarbon tails linked to the N-terminus of a short oligopeptide that may be chemically modified and/or contain unusual amino acid residues in their structures. They possess huge potential as pharmaceutical drugs and biocontrol agents, and ˜30 representative genera of fungi are known to produce them. Some chemically synthesised derivatives have already been developed into commercial products or subjected to clinical trials, including cilofungin, caspofungin, micafungin, anidulafungin, rezafungin, emodepside, fusafungine and destruxins. This review summarizes 200 fungi-derived compounds reported since 2000, including 95 cyclic depsipeptides, 67 peptaibiotics (including 35 peptaibols, eight lipoaminopeptides, and five lipopeptaibols), and 38 non-depsipeptide and non-peptaibiotic lipopeptides. Their sources, structural sequences, antibiotic activities (e.g. antibacterial, antifungal, antiviral, antimycobacterial, antimycoplasmal, antimalarial, antileishmanial, insecticidal, antitrypanosomal and nematicidal), structure-activity relationships, mechanisms of action, and specific relevance are discussed. These compounds have attracted considerable interest within the pharmaceutical and agrochemical industries.

Sclerin, a New Cytotoxic Cyclononapeptide from Annona scleroderma

A new cytotoxic cyclononapeptide, sclerin, cyclo(–Dab¹–Ser²–Tyr³–Gly⁴–Thr⁵–Val⁶–Ala⁷– Ile⁸–Pro⁹–) (1), was isolated from the methanol extract of the seeds of Annona scleroderma, together with the known metabolite, cyclosenegalin A, cyclo(–Pro¹–Gly²–Leu³–Ser⁴–Ala⁵–Val⁶–Thr⁷–) (2). The planar structures for the two compounds were established by comprehensive analysis of NMR and ESI-HRMS data, and the absolute stereochemistry was stablished by Marfey’s method. Compound 1 showed moderate cytotoxic activity against the human prostate carcinoma cell line DU-145 at µM concentration.

Thiodiketopiperazines with two spirocyclic centers extracted from Botryosphaeria mamane, an endophytic fungus isolated from Bixa orellana L

Three thiodiketopiperazines, botryosulfuranols A-C (1-3) were isolated from the endophytic fungus Botryosphaeria mamane. The three compounds present sulfur atoms on α- and β-positions of phenylalanine derived residues and unprecedented two spirocyclic centers at C-4 and C-2'. Their planar structures were determined by spectroscopic analysis and absolute configurations were achieved by X-ray diffraction analysis and ECD and NMR chemical shifts calculations. Botryosulfuranol A (1) was the most cytotoxic compound against four cancer cell lines (HT-29, HepG2, Caco-2, HeLa) and two healthy cell lines (IEC6, Vero) highlighting the importance of an electrophilic center for cell growth inhibition.

Insecticidal Activities of Chloramphenicol Derivatives Isolated from a Marine Alga-Derived Endophytic Fungus, Acremonium vitellinum, against the Cotton Bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

A great deal of attention has been focused on the secondary metabolites produced by marine endophytic fungi, which can be better alternatives to chemicals, such as biopesticides, for control of polyphagous pests. On the basis of its novel biocontrol attributes, chemical investigation of a marine alga-derived endophytic fungus, Acremonium vitellinum, resulted in the isolation of three chloramphenicol derivatives (compounds 1–3). Their chemical structures were elucidated by detailed analysis of their nuclear magnetic resonance spectra, high-resolution electrospray ionization mass spectrometry, and by comparison with the data available in the literature. In this paper, compound 2 was firstly reported as the natural origin of these fungal secondary metabolites. The insecticidal activities of compounds 1–3 against the cotton bollworm, Helicoverpa armigera, were evaluated. The natural compound 2 presented considerable activity against H. armigera, with an LC₅₀ value of 0.56 ± 0.03 mg/mL (compared to matrine with an LC₅₀ value of 0.24 ± 0.01 mg/mL). Transcriptome sequencing was used to evaluate the molecular mechanism of the insecticidal activities. The results presented in this study should be useful for developing compound 2 as a novel, ecofriendly and safe biopesticide.