Purification of andibenin and a chromanone analogue from rhizospheric Aspergillus flavus and soil-borne Penicillium notatum exhibiting cytotoxic and antibacterial properties

The discovery of bioactive compounds from fungal natural sources holds immense potential for the development of novel therapeutics. The present study investigates the extracts of soil-borne Penicillium notatum and rhizosphere-inhabiting Aspergillus flavus for their antibacterial, antifungal, and cytotoxic potential. Additionally, two compounds were purified using chromatographic and spectroscopic techniques. The results demonstrated that the ethyl acetate fraction of A. flavus exhibited prominent cytotoxic activity against Artemia salina, whereas the ethyl acetate fraction of P. notatum displayed promising antibacterial potential. At dose concentrations of 10, 100, and 1000 µg mL-1, the ethyl acetate fraction of A. flavus showed mortality percentages of 7.6%, 66.4%, and 90%, respectively. The ethyl acetate fraction of P. notatum extract exhibited significant antibacterial activity, forming inhibition zones measuring 41, 38, 34, 34, and 30 mm against B. subtilis, S. flexneri, E. coli, K. pneumoniae, and S. aureus, respectively, at 1000 µg mL-1. At this concentration, inhibition zones of 28, 27, and 15 mm were recorded for P. vulgaris, S. typhi, and X. oryzae. Using bioassay-guided approach, one compound each was purified from the fungal extracts. The initial purification involved mass spectroscopic analysis, followed by structural elucidation using 500 MHz nuclear magnetic resonance (NMR) spectroscopy. Compound 1, derived from A. flavus, was identified as ethyl 2-hydroxy-5,6-dimethyl-4-oxocyclohex-2-ene-1-carboxylate, with a mass of 212, whereas compound 2, isolated from P. notatum, was identified as 3-amino-2-(cyclopenta-2,4-dien-1-ylamino)-8-methoxy-4H-chromen-4-one, with an exact mass of 270. Based on bioassay results, compound 1 was subjected to brine shrimp lethality assay and compound 2 was tested for its antibacterial potential. Compound 1 exhibited 30% lethality against brine shrimp larvae at a concentration of 100 µg mL-1, whereas at 1000 µg mL-1 the mortality increased to 70%. Compound 2 displayed notable antibacterial potential, forming inhibition zones of 30, 24, 19, and 12 mm against S. aureus, E. coli, B. subtilis, and S. flexneri, respectively. In comparison, the standard antibiotic tetracycline produced inhibition zones of 18, 18, 15, and 10 mm against the respective bacterial strains at the same concentration.

Novel Bioactive Natural Products from Marine-Derived Penicillium Fungi: A Review (2021-2023)

Marine-derived Penicillium fungi are productive sources of structurally unique and diverse bioactive secondary metabolites, representing a hot topic in natural product research. This review describes structural diversity, bioactivities and statistical research of 452 new natural products from marine-derived Penicillium fungi covering 2021 to 2023. Sediments are the main sources of marine-derived Penicillium fungi for producing nearly 56% new natural products. Polyketides, alkaloids, and terpenoids displayed diverse biological activities and are the major contributors to antibacterial activity, cytotoxicity, anti-inflammatory and enzyme inhibitory capacities. Polyketides had higher proportions of new bioactive compounds in new compounds than other chemical classes. The characteristics of studies in recent years are presented.

Secondary metabolites isolated from Penicillium christenseniae SD.84 and their antimicrobial resistance effects

A pair of new quinolone alkaloid enantiomers, (Ra)-(-)-viridicatol (1) and (Sa)-(+)-viridicatol (4), and seven known compounds, namely, 2, 3 and 5-9, were isolated from Penicillium christenseniae SD.84. The structures of 1 and 4 were determined using NMR and HRESIMS data. Theoretical calculations through CD and ECD confirmed 1 and 4 as a pair of enantiomers. The MIC values of 4 against Staphylococcus aureus and methicillin-resistant S. aureus were 12.4 and 24.7 μM, respectively, compound 1 had no inhibitory activity. Antimicrobial assays of 2, 3, and 5-7 showed a moderate activity against S. aureus and methicillin-resistant S. aureus. This study demonstrated the remarkable potential of Penicillium sp. to produce new drug-resistant leading compounds, thereby advancing the mining for new sources of antimicrobial agents.

Penicillium molds impact the transcriptome and evolution of the cheese bacterium Staphylococcus equorum

The observation that Penicillium molds can inhibit the growth of Staphylococcus was a catalyst for the antibiotic revolution. Considerable attention has been paid to purified Penicillium metabolites that inhibit bacteria, but little is known about how Penicillium species impact the ecology and evolution of bacteria in multispecies microbial communities. Here, we investigated how four different species of Penicillium can impact global transcription and evolution of a widespread Staphylococcus species (S. equorum) using the cheese rind model microbiome. Through RNA sequencing, we identified a core transcriptional response of S. equorum against all five tested Penicillium strains, including upregulation of thiamine biosynthesis, fatty acid degradation, and amino acid metabolism as well as downregulation of genes involved in the transport of siderophores. In a 12-week evolution experiment where we co-cultured S. equorum with the same Penicillium strains, we observed surprisingly few non-synonymous mutations across S. equorum populations evolved with the Penicillium species. A mutation in a putative DHH family phosphoesterase gene only occurred in populations evolved without Penicillium and decreased the fitness of S. equorum when co-cultured with an antagonistic Penicillium strain. Our results highlight the potential for conserved mechanisms of Staphylococcus-Penicillium interactions and demonstrate how fungal biotic environments may constrain the evolution of bacterial species.IMPORTANCEFungi and bacteria are commonly found co-occurring both in natural and synthetic microbiomes, but our understanding of fungal-bacterial interactions is limited to a handful of species. Conserved mechanisms of interactions and evolutionary consequences of fungal-bacterial interactions are largely unknown. Our RNA sequencing and experimental evolution data with Penicillium species and the bacterium S. equorum demonstrate that divergent fungal species can elicit conserved transcriptional and genomic responses in co-occurring bacteria. Penicillium molds are integral to the discovery of novel antibiotics and production of certain foods. By understanding how Penicillium species affect bacteria, our work can further efforts to design and manage Penicillium-dominated microbial communities in industry and food production.

Discovery, Antitumor Activity, and Fermentation Optimization of Roquefortines from Penicillium sp. OUCMDZ-1435

Meleagrin and oxaline, which belong to the roquefortine alkaloids with a unique dihydroindole spiroamide framework, have significant bioactivities, especially tumor cell inhibitory activity. In order to discover the requefortine alkaloids, Penicillium sp. OUCMDZ-1435 was fished and identified from marine fungi using molecular probe technology. Meleagrin (1) and oxaline (2) were isolated from it. In addition, we first reported that compounds 1 and 2 could effectively inhibit the proliferation and metastasis of the human HepG2 cell and induce HepG2 cell apoptosis and cell cycle arrest in the G2/M phase. Additionally, the fermentation of Meleagrin (1) was optimized to increase its yield to 335 mg/L. These results provided bioactive inspiration and fungus resources for roquefortine alkaloid development.

Marketed Quinoa (Chenopodium quinoa Willd.) Seeds: A Mycotoxin-Free Matrix Contaminated by Mycotoxigenic Fungi

A total of 25 marketed quinoa seed samples different for origin, farming system and packaging were analyzed for the presence of mycotoxigenic fungi (by isolation both on Potato Dextrose Agar and with the deep-freezing blotter method) and relative contamination by mycotoxins (by LC-MS/MS analysis). Fungal microorganisms, but not mycotoxins, were detected in all the samples, and 25 isolates representative of the mycobiota were obtained. Morphological and molecular characterization and, for some isolates, the in vitro mycotoxigenic profile, allowed the identification of 19 fungal species within five different genera: Alternaria, Aspergillus, Penicillium, Cladosporium and Fusarium. Among the identified species, Alternaria abundans, A. chartarum, A. arborescens, Cladosporium allicinum, C. parasubtilissimum, C. pseudocladosporioides, C. uwebraunianum, Aspergillus jensenii, A. tubingensis, Penicillium dipodomyis, P. verrucosum and P. citreosulfuratum were first reported on quinoa, and Alternaria infectoria and Fusarium oxysporum were first reported on quinoa seeds. The geographical origin, farming system and packaging were showed to affect the amount and type of the isolated fungal species, highlighting that the level of fungal presence and their related secondary metabolites is conditioned by different steps of the quinoa supply chain. However, despite the presence of mycotoxigenic fungi, the marketed quinoa seeds analyzed resulted in being free from mycotoxins.

Biosensor approach for electrochemical quantitative assessment and qualitative characterization of the effect of fusaric acid on a culture-receptor

Fusaric acid (FA) is a secondary fungal metabolite, which is widespread on corn and corn-based feed and food; FA has non-specific toxicity. Biosensor method is an express and easy-to-use method for quantitative and qualitative assessment of FA effect. Search for cultures has been performed for the formation of laboratory models of FA biosensor with the Clark-type oxygen electrode as transducer: respiration intensity of chosen cultures changed in the presence of FA. Resting cells of Fusarium oxysporum f. sp. vasinfectum and Bacillus subtilis were used as receptors of the amperometric biosensor for FA determination in aqueous solution. To enhance the sensitivity of detection, induction by substrate was performed for Bacillus subtilis. Response-concentration linear dependencies were obtained in a range of 0.5-500 FA mg/L. Biosensor models were applied to characterize influence of FA on microbial cells and investigate some features of FA transport. The dependences of the cells' response to FA on FA concentration were obtained; the kinetic parameters S_0.5 and V_max were determined for each culture. Inhibition-threshold FA (S^it) concentrations were similar for both studied cultures. At concentrations lower than S^it, the process of simple diffusion governed FA transport into cells and caused the cells' response to FA for non-induced culture.

Natural products in the predatory defence of the filamentous fungal pathogen Aspergillus fumigatus

The kingdom of fungi comprises a large and highly diverse group of organisms that thrive in diverse natural environments. One factor to successfully confront challenges in their natural habitats is the capability to synthesize defensive secondary metabolites. The genetic potential for the production of secondary metabolites in fungi is high and numerous potential secondary metabolite gene clusters have been identified in sequenced fungal genomes. Their production may well be regulated by specific ecological conditions, such as the presence of microbial competitors, symbionts or predators. Here we exemplarily summarize our current knowledge on identified secondary metabolites of the pathogenic fungus Aspergillus fumigatus and their defensive function against (microbial) predators.

Adsorption Mechanism of Patulin from Apple Juice by Inactivated Lactic Acid Bacteria Isolated from Kefir Grains

In the food industry, microbiological safety is a major concern. Mycotoxin patulin represents a potential health hazard, as it is heat-resistant and may develop at any stage during the food chain, especially in apple-based products, leading to severe effects on human health, poor quality products, and profit reductions. The target of the study was to identify and characterize an excellent adsorbent to remove patulin from apple juice efficiently and to assess its adsorption mechanism. To prevent juice fermentation and/or contamination, autoclaving was involved to inactivate bacteria before the adsorption process. The HPLC (high-performance liquid chromatography) outcome proved that all isolated strains from kefir grains could reduce patulin from apple juice. A high removal of 93% was found for juice having a 4.6 pH, 15° Brix, and patulin concentration of 100 μg/L by Lactobacillus kefiranofacien, named JKSP109, which was morphologically the smoothest and biggest of all isolates in terms of cell wall volume and surface area characterized by SEM (Scanning electron microscopy) and TEM (transmission electron microscopy). C=O, OH, C–H, and N–O were the main functional groups engaged in patulin adsorption indicated by FTIR (Fourier transform–infrared). E-nose (electronic nose) was performed to evaluate the aroma quality of the juices. PCA (Principal component analysis) results showed that no significant changes occurred between control and treated juice.

Genome-wide characterization of peptidyl-prolyl cis-trans isomerases in Penicillium and their regulation by salt stress in a halotolerant P. oxalicum

Peptidyl-prolyl cis-trans isomerases (PPIases) are the only class of enzymes capable of cis-trans isomerization of the prolyl peptide bond. The PPIases, comprising of different families viz., cyclophilins, FK506-binding proteins (FKBPs), parvulins and protein phosphatase 2A phosphatase activators (PTPAs), play essential roles in different cellular processes. Though PPIase gene families have been characterized in different organisms, information regarding these proteins is lacking in Penicillium species, which are commercially an important fungi group. In this study, we carried out genome-wide analysis of PPIases in different Penicillium spp. and investigated their regulation by salt stress in a halotolerant strain of Penicillium oxalicum. These analyses revealed that the number of genes encoding cyclophilins, FKBPs, parvulins and PTPAs in Penicillium spp. varies between 7-11, 2-5, 1-2, and 1-2, respectively. The halotolerant P. oxalicum depicted significant enhancement in the mycelial PPIase activity in the presence of 15% NaCl, thus, highlighting the role of these enzymes in salt stress adaptation. The stress-induced increase in PPIase activity at 4 and 10 DAI in P. oxalicum was associated with higher expression of PoxCYP18. Characterization of PPIases in Penicillium spp. will provide an important database for understanding their cellular functions and might facilitate their applications in industrial processes through biotechnological interventions.

Penicimeroterpenoids A-C, Meroterpenoids with Rearrangement Skeletons from the Marine-Derived Fungus Penicillium sp. SCSIO 41512

Three novel andrastin-type meroterpenoids, penicimeroterpenoids A-C (1-3), possessing two unprecedented skeletons consisting of fused 6/5/6/6/7 and 6/5/6/6/4 polycyclic systems, were obtained from the marine-derived fungus Penicillium sp. SCSIO 41512. Their structures were determined by spectroscopic methods, and the absolute configurations were further determined by single-crystal X-ray diffraction analysis for 1 and quantum chemical calculations of ECD spectra for 2 and 3, respectively. A plausible biosynthetic pathway for 1-3 was proposed.

Aspergillus, Penicillium and Cladosporium species associated with dried date fruits collected in the Perugia (Umbria, Central Italy) market

A total of 20 dried date samples, chosen as representative among those available on the Perugia (Umbria, Central Italy) market, were analyzed for the possible occurrence of fungal species and related contamination by fungal secondary metabolites. Twenty-six isolates, representative of the total mycobiota, were obtained and morphologically identified as belonging to the genera Aspergillus, Penicillium and Cladosporium. Inside each genus, molecular characterization (by partial sequencing of ITS region and/or β-tubulin and calmodulin regions for Aspergillus and Penicillium isolates or actin region for Cladosporium isolates) and in vitro mycotoxigenic profile characterization (by LC-MS/MS analysis) showed the presence of the following species: A. flavus, A. tubingensis, P. brevicompactum, P. chrysogenum, P. crustosum, P. glabrum, P. solitum, P. venetum, C. cladosporioides, C. limoniforme and C. halotolerans, with A. tubingensis as the prevalent species and P. crustosum, P. solitum, P. venetum and C. limoniforme first reported here on dates. Date packaging and format showed an effect on the incidence of isolated fungi, with the lowest incidence recovered from whole dates and in hermetic bag packaging. These findings can be useful both for dried dates producers and consumers, guiding them towards choices of packaging and format with a lower risk of mycotoxigenic species presence. However, no fungal metabolites were detected in the dried date samples analyzed, which were therefore regarded as safe for human consumption, underlining the absence of correspondence between fungal isolation and mycotoxin contaminations.

Thiodiketopiperazines Produced by Penicillium crustosum and Their Activities to Promote Gastrointestinal Motility

Three new thiodiketopiperazines (1–3), along with two known analogues (4 and 5), were isolated from the fermentation broth of Penicillium crustosum. Their structures were elucidated through extensive spectroscopic analysis and the absolute configurations of new compounds were determined by Mosher ester analysis and calculated ECD spectra. Compound 4 and 5 have the activity to promote the gastrointestinal motility of zebrafish via acting on the cholinergic nervous system.

An endophytic Fungi of Ginkgo biloba L. produces antimicrobial metabolites as potential inhibitors of FtsZ of Staphylococcus aureus

A total of 58 fungal isolates, belonging to 24 genera, were obtained from the leaves, stems and roots of Ginkgo biloba L.. Among them, one endophytic fungal strain, Penicillium cataractum SYPF 7131, displayed the strongest antibacterial activity. Four new compounds (1-4) were isolated from the strain fermentation broth together with four known compounds (5-8). These structures were determined on the basis of 1D and 2D NMR and [Rh₂(OCOCF₃)₄]-induced electronic circular dichroism (ECD) spectroscopic analyses. All the isolated compounds were screened for their in vitro antimicrobial activities. Compound 3 and 4 showed moderate inhibitory activity against Staphylococcus aureus. Compound 7 exhibited significant inhibitory activity against S. aureus with MIC value of 10 μg/mL. Further, the in silico molecular docking studies of the active compounds was used to explore the binding interactions with the active site of filamentous temperature-sensitive protein Z (FtsZ) from Staphylococcus aureus. The docking results revealed that compounds 3, 4 and 7 showed high binding energies, strong H-bond interactions and hydrophobic interactions with FtsZ from S. aureus validating the observed antimicrobial activity. Based on antimicrobial activities and docking studies, compounds 3, 4 and 7 were identified as promising antimicrobial lead molecules.

Insights into Penicillium brasilianum Secondary Metabolism and Its Biotechnological Potential

Over the past few years Penicillium brasilianum has been isolated from many different environmental sources as soil isolates, plant endophytes and onion pathogen. All investigated strains share a great ability to produce bioactive secondary metabolites. Different authors have investigated this great capability and here we summarize the metabolic potential and the biological activities related to P. brasilianum’s metabolites with diverse structures. They include secondary metabolites of an alkaloid nature, i.e., 2,5-diketopiperazines, cyclodepsipeptides, meroterpenoids and polyketides. Penicillium brasilianum is also described as a great source of enzymes with biotechnological application potential, which is also highlighted in this review. Additionally, this review will focus on several aspects of Penicillium brasilianum and interesting genomic insights.

Chemical diversity from the Tibetan Plateau fungi Penicillium kongii and P. brasilianum

Two new secondary metabolites, kongiilines A and B (1, 7), and two asperphenamate derivatives, asperphenamates B and C (5–6), together with 16 known compounds (2–4, 8–20), were isolated from Tibetan Plateau fungi Penicillium kongii and Penicillium brasilianum. This is the first report on asperphenamates B and C as naturally occurring compounds, and that aspterric acid is isolated from P. brasilianum for the first time. Their structures were elucidated by different spectroscopic techniques including high-resolution electrospray ionisation mass spectrum, 1D nuclear magnetic resonance (NMR), and 2D NMR as well as electronic circular dichroism. Compounds 4, 5, and 10 exhibited cytotoxicity activities against human colon carcinoma HCT116 cell line with IC₅₀ values of 88.16, 77.68, and 36.92 μM, respectively. Fungi from Tibetan Plateau represent important and rich resources for the investigation of new chemicals.

Anti-inflammatory effects of secondary metabolites isolated from the marine-derived fungal strain Penicillium sp. SF-5629

After the chemical investigation of the ethyl acetate extract of the marine-derived fungal strain Penicillium sp. SF-5629, the isolation and structural elucidation of eight secondary metabolites, including (3R,4S)-6,8-dihydroxy-3,4,7-trimethylisocoumarin (1), (3S,4S)-sclerotinin A (2), penicitrinone A (3), citrinin H1 (4), emodin (5), ω-hydroxyemodin (6), 8-hydroxy-6-methyl-9-oxo-9H-xanthene-1-carboxylate (7), and 3,8-dihydroxy-6-methyl-9-oxo-9H-xanthene-1-carboxylate (8) were carried out. Evaluation of the anti-inflammatory activity of these metabolites showed that 4 inhibited nitric oxide and prostaglandin E2 production in lipopolysaccharide-stimulated BV2 microglia, with IC₅₀ values of 8.1 ± 1.9 and 8.0 ± 2.8 μM, respectively. The inhibitory function of 4 was confirmed based on decreases in inducible nitric oxide synthesis and cyclooxygenase-2 gene expression. In addition, 4 was found to suppress the phosphorylation of inhibitor kappa B-α, interrupt the nuclear translocation of nuclear factor kappa B, and decrease the activation of p38 mitogen-activated protein kinase.

Biosynthetic pathways of ergot alkaloids

Ergot alkaloids are nitrogen-containing natural products belonging to indole alkaloids. The best known producers are fungi of the phylum Ascomycota, e.g., Claviceps, Epichloë, Penicillium and Aspergillus species. According to their structures, ergot alkaloids can be divided into three groups: clavines, lysergic acid amides and peptides (ergopeptines). All of them share the first biosynthetic steps, which lead to the formation of the tetracyclic ergoline ring system (except the simplest, tricyclic compound: chanoclavine). Different modifications on the ergoline ring by specific enzymes result in an abundance of bioactive natural products, which are used as pharmaceutical drugs or precursors thereof. From the 1950s through to recent years, most of the biosynthetic pathways have been elucidated. Gene clusters from several ergot alkaloid producers have been identified by genome mining and the functions of many of those genes have been demonstrated by knock-out experiments or biochemical investigations of the overproduced enzymes.

Secondary metabolites from Penicillium corylophilum isolated from damp buildings

Indoor exposure to the spores and mycelial fragments of fungi that grow on damp building materials can result in increased non-atopic asthma and upper respiratory disease. The mechanism appears to involve exposure to low doses of fungal metabolites. Penicillium corylophilum is surprisingly common in damp buildings in USA, Canada and western Europe. We examined isolates of P. corylophilum geographically distributed across Canada in the first comprehensive study of secondary metabolites of this fungus. The sesquiterpene phomenone, the meroterpenoids citreohybridonol and andrastin A, koninginin A, E and G, three new alpha pyrones and four new isochromans were identified from extracts of culture filtrates. This is the first report of koninginins, meroterpenoids and alpha pyrones from P. corylophilum. These secondary metabolite data support the removal of P. corylophilum from Penicillium section Citrina and suggest that further taxonomic studies are required on this species.