Cladosporine A, a new indole diterpenoid alkaloid with antimicrobial activities from Cladosporium sp

A new illudane sesquiterpene from the edible fungus Pholiota nameko

Fungi have different genetic expression abilities and biosynthetic pathways under different cultivation conditions, which can produce various secondary metabolites. The "one strain many compounds" strategy is used to activate silent biosynthetic genes of fungi to produce various compounds, which is an effective method. In order to discover various new compounds in the edible fungus Pholiota nameko, a fermentation strategy involving precursor feeding and enzyme inhibitor addition has been employed. A new illudane sesquiterpene (1), along with one known indole diterpenoid alkaloid, cladosporine A (2) were isolated from the extracts of liquid culture of P. nameko. The new compound was identified by combination of 1D and 2D NMR, MS, optical rotation, and ECD calculations. We conducted experiments on the cytotoxicity of all isolated compounds on three cancer cell lines, but we did not observe any significant cytotoxicity (IC50 > 40 μM).

The Genus Cladosporium: A Prospective Producer of Natural Products

Cladosporium, a genus of ascomycete fungi in the Dematiaceae family, is primarily recognized as a widespread environmental saprotrophic fungus or plant endophyte. Further research has shown that the genus is distributed in various environments, particularly in marine ecosystems, such as coral reefs, mangroves and the polar region. Cladosporium, especially the marine-derived Cladosporium, is a highly resourceful group of fungi whose natural products have garnered attention due to their diverse chemical structures and biological activities, as well as their potential as sources of novel leads to compounds for drug production. This review covers the sources, distribution, bioactivities, biosynthesis and structural characteristics of compounds isolated from Cladosporium in the period between January 2000 and December 2022, and conducts a comparative analysis of the Cladosporium isolated compounds derived from marine and terrestrial sources. Our results reveal that 34% of Cladosporium-derived natural products are reported for the first time. And 71.79% of the first reported compounds were isolated from marine-derived Cladosporium. Cladosporium-derived compounds exhibit diverse skeletal chemical structures, concentrating in the categories of polyketides (48.47%), alkaloids (19.21%), steroids and terpenoids (17.03%). Over half of the natural products isolated from Cladosporium have been found to have various biological activities, including cytotoxic, antibacterial, antiviral, antifungal and enzyme-inhibitory activities. These findings testify to the tremendous potential of Cladosporium, especially the marine-derived Cladosporium, to yield novel bioactive natural products, providing a structural foundation for the development of new drugs.

Indole Diterpene Derivatives from the Aspergillus flavus GZWMJZ-288, an Endophytic Fungus from Garcinia multiflora

A new indole diterpene, 26-dihydroxyaflavininyl acetate (1), along with five known analogs (2-6) were isolated from the liquid fermentation of Aspergillus flavus GZWMJZ-288, an endophyte from Garcinia multiflora. The structures of these compounds were identified through NMR, MS, chemical reaction, and X-ray diffraction experiments. Enzyme inhibition activity screening found that compounds 1, 4, and 6 have a good binding affinity with NPC1L1, among which compound 6 exhibited a stronger binding ability than ezetimibe at a concentration of 10 µM. Moreover, compound 5 showed inhibitory activity against α-glucosidase with an IC50 value of 29.22 ± 0.83 µM, which is 13 times stronger than that of acarbose. The results suggest that these aflavinine analogs may serve as lead compounds for the development of drugs targeting NPC1L1 and α-glucosidase. The binding modes of the bioactive compounds with NPC1L1 and α-glucosidase were also performed through in silico docking studies.

A new indole alkaloid from Cladosporium sp. SCSIO41205

A new indole compound, N-hydroxy-N-(2-(1-hydroxy-2-methoxy-1H-indol-3-yl)ethyl acetamide (1), together with four known compounds, N-(2-(1H-indol-3-yl)ethylacetamide (2), N-acetylamicoumacin C (3), N-(2-phenylethyl)acetamide (4), and (2 R,3S)-1-(4-hydroxyphenyl)butane-2,3-diol (5) were isolated from Cladosporium sp. SCSIO41205. Their structures were established by detailed analysis of the NMR and HR-ESI-MS data.

Cladamide: a new ceramide from the endophytic fungus Cladosporium cladosporioides

A new ceramide, named cladamide (1), in addition to cinnamic acid (2), para-coumaric acid (3), stigmasterol-3-O-β-D-glucoside (4), and uracil (5), was isolated from the white beans culture of Cladosporium cladosporioides, a marine-derived endohpytic fungus isolated from the leaves of the mangrove, Avicennia marina (Forssk.) Vierh. Structure elucidation of compound 1 was established on the basis of extensive 1D and 2D NMR spectroscopic techniques in combination with HR-ESI-MS. The ability of the isolated compounds to inhibit acetylcholine esterase was evaluated. Compound 3 showed the highest acetylcholine esterase inhibitory activity (IC₅₀ = 0.057 ± 0.003 µM), followed by compound 4 (IC₅₀ = 0.068 ± 0.003 µM) and compound 1 (IC₅₀ = 0.099 ± 0.005 µM) compared to donepezil, the positive control, (IC₅₀ = 0.044 ± 0.002 µM). Compounds 2 and 5 showed lower activity (IC₅₀ = 0.182 ± 0.009 and 0.236 ± 0.012 µM, respectively). The results were further validated by molecular docking study.

The chemical structures and biological activities of indole diterpenoids

Indole diterpenoids (IDTs) are an essential class of structurally diverse fungal secondary metabolites, that generally appear to be restricted to a limited number of fungi, such as Penicillium, Aspergillus, Claviceps, and Epichloe species, etc. These compounds share a typical core structure consisting of a cyclic diterpene skeleton of geranylgeranyl diphosphate (GGPP) and an indole ring moiety derived from indole-3-glycerol phosphate (IGP). 3-geranylgeranylindole (3-GGI) is the common precursor of all IDTs. On this basis, it is modified by cyclization, oxidation, and prenylation to generate a large class of compounds with complex structures. These compounds exhibit antibacterial, anti-insect, and ion channel inhibitory activities. We summarized 204 compounds of IDTs discovered from various fungi over the past 50 years, these compounds were reclassified, and their biological activities were summarized. This review will help to understand the structural diversity of IDTs and provide help for their physiological activities.

The Biosynthesis Related Enzyme, Structure Diversity and Bioactivity Abundance of Indole-Diterpenes: A Review

Indole diterpenes are a large class of secondary metabolites produced by fungi, possessing a cyclic diterpenoid backbone and an indole moiety. Novel structures and important biological activity have made indole diterpenes one of the focuses of synthetic chemists. Although the discovery, identification, structural diversity, biological activity and especially structure–activity relationship of indole diterpenes have been reported in some papers in recent years, they are absent of a systematic and comprehensive analysis, and there is no elucidation of enzymes related to this kind of natural product. Therefore, it is necessary to summarize the relevant reports to provide new perspectives for the following research. In this review, for the first time, the function of related synthases and the structure–activity relationship of indole diterpenes are expounded, and the recent research advances of them are emphasized.

Aspulvins A-H, Aspulvinone Analogues with SARS-CoV-2 Mpro Inhibitory and Anti-inflammatory Activities from an Endophytic Cladosporium sp

Eight new aspulvinone analogues, aspulvins A-H (1-8) and aspulvinones D, M, O, and R (9-12), were isolated from cultures of the endophytic fungus Cladosporium sp. 7951. Detailed spectroscopic analyses were conducted to determine the structures of the new compounds. All isolates displayed different degrees of inhibitory activity against the severe acute respiratory syndrome coronavirus 2 main protease (SARS-CoV-2 Mpro) at 10 μM. Notably, compounds 9, 10, and 12 showed potential SARS-CoV-2 Mpro inhibition with IC50 values of 10.3 ± 0.6, 9.4 ± 0.6, and 7.7 ± 0.6 μM, respectively. For all compounds except 3 and 4, the anti-inflammatory activity occurred by inhibiting the release of lactate dehydrogenase (LDH) with IC50 values ranging from 0.7 to 7.4 μM. Compound 10 showed the most potent anti-inflammatory activity by inhibiting Casp-1 cleavage, IL-1β maturation, NLRP3 inflammasome activation, and pyroptosis. The findings reveal that the aspulvinone analogues 9, 10, and 12 could be promising candidates for coronavirus disease 2019 (COVID-19) treatment as they inhibit SARS-CoV-2 infection and reduce inflammatory reactions caused by SARS-CoV-2.

Antimicrobial Diterpenes: Recent Development From Natural Sources

Antimicrobial resistance has been posing an alarming threat to the treatment of infectious diseases over the years. Ineffectiveness of the currently available synthetic and semisynthetic antibiotics has led the researchers to discover new molecules with potent antimicrobial activities. To overcome the emerging antimicrobial resistance, new antimicrobial compounds from natural sources might be appropriate. Secondary metabolites from natural sources could be prospective candidates in the development of new antimicrobial agents with high efficacy and less side effects. Among the natural secondary metabolites, diterpenoids are of crucial importance because of their broad spectrum of antimicrobial activity, which has put it in the center of research interest in recent years. The present work is aimed at reviewing recent literature regarding different classes of natural diterpenes and diterpenoids with significant antibacterial, antifungal, antiviral, and antiprotozoal activities along with their reported structure–activity relationships. This review has been carried out with a focus on relevant literature published in the last 5 years following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 229 diterpenoids from various sources like plants, marine species, and fungi are summarized in this systematic review, including their chemical structures, classification, and significant antimicrobial activities together with their reported mechanism of action and structure–activity relationships. The outcomes herein would provide researchers with new insights to find new credible leads and to work on their synthetic and semisynthetic derivatives to develop new antimicrobial agents.

The chemistry and biology of fungal meroterpenoids (2009-2019)

Fungal meroterpenoids are secondary metabolites from mixed terpene-biosynthetic origins. Their intriguing chemical structural diversification and complexity, potential bioactivities, and pharmacological significance make them attractive targets in natural product chemistry, organic synthesis, and biosynthesis. This review provides a systematic overview of the isolation, chemical structural features, biological activities, and fungal biodiversity of 1585 novel meroterpenoids from 79 genera terrestrial and marine-derived fungi including macrofungi, Basidiomycetes, in 441 research papers in 2009-2019. Based on the nonterpenoid starting moiety in their biosynthesis pathway, meroterpenoids were classified into four categories (polyketide-terpenoid, indole-, shikimate-, and miscellaneous-) with polyketide-terpenoids (mainly tetraketide-) and shikimate-terpenoids as the primary source. Basidiomycota produced 37.5% of meroterpenoids, mostly shikimate-terpenoids. The genera of Ganoderma, Penicillium, Aspergillus, and Stachybotrys are the four dominant producers. Moreover, about 56% of meroterpenoids display various pronounced bioactivities, including cytotoxicity, enzyme inhibition, antibacterial, anti-inflammatory, antiviral, antifungal activities. It's exciting that several meroterpenoids including antroquinonol and 4-acetyl antroquinonol B were developed into phase II clinically used drugs. We assume that the chemical diversity and therapeutic potential of these fungal meroterpenoids will provide biologists and medicinal chemists with a large promising sustainable treasure-trove for drug discovery.

The Genus Cladosporium: A Rich Source of Diverse and Bioactive Natural Compounds

Fungi are renowned as one of the most fruitful sources of chemodiversity and for their ubiquitous occurrence. Among the many taxonomic groupings considered for the implications deriving from their biosynthetic aptitudes, the genus Cladosporium stands out as one of the most common in indoor environments. A better understanding of the impact of these fungi on human health and activities is clearly based on the improvement of our knowledge of the structural aspects and biological properties of their secondary metabolites, which are reviewed in the present paper.

Two new diterpenoids from Penicillium chrysogenum MT-12, an endophytic fungus isolated from Huperzia serrata

Two new diterpenoids, penicichrysogene A (1) and penicichrysogene B (2), were isolated from the solid substrate fermentation cultures of Penicillium chrysogenum MT-12, an endophytic fungus isolated from the medicinal plant of Huperzia serrata. Their structures were elucidated on the basis of extensive spectroscopic and spectrometric data (1D and 2D NMR, UV, IR, and HRESIMS). The absolute configurations of 1 and 2 were assigned on the basis of experimental and calculated electronic circular dichroism spectra. Compound 1 exhibited inhibitory activity on ATP release of thrombin-activated platelets with IC₅₀ = 42.7 ± 3.5 μM.

Recent progress of antibacterial natural products: Future antibiotics candidates

The discovery of novel antibacterial molecules plays a key role in solving the current antibiotic crisis issue. Natural products have long been an important source of drug discovery. Herein, we reviewed 256 natural products from 11 structural classes in the period of 2016-01/2020, which were selected by SciFinder with new compounds or new structures and MICs lower than 10 μg/mL or 10 μM as criterions. This review will provide some effective antibacterial lead compounds for medicinal chemists, which will promote the antibiotics research based on natural products to the next level.

Effect of introducing amino acids into phenazine-1-carboxylic acid on phloem mobility

To develop new phenazine carboxylic acid derivatives with better phloem mobility, five novel 7-amino acid substituted phenazine-1-carboxylic acids were synthesised by introducing amino acids into PCA at the 7-position. The phloem mobility experiments in Ricinus communis seedlings showed that retaining the carboxyl group of PCA and conjugating amino acids to its phenazine ring can also endow PCA with phloem mobility. Comparing our previous research, we found the amino acids substituted at 7-position on phenazine ring of PCA could clearly enhance the phloem mobility of PCA than that of amino acids conjugated with carboxyl group. Especially, the phloem transport concentration of the compound 7-L-isoleucine substituted PCA (7d) was 21 times higher than PCA-L-isoleucine conjugate (8d). These data suggest that the introduction of amino acids at different structural sites on the phenazine ring could effectively enhance the phloem mobility of PCA and it is worth a further study.