Isolation of a novel paxilline analog pyrapaxilline from fungus that inhibits LPS-induced NO production

Peniditerpenoids A and B: Oxidized Indole Diterpenoids with Osteoclast Differentiation Inhibitory Activity from a Mangrove-Sediment-Derived Penicillium sp

An unprecedented di-seco-indole diterpenoid, peniditerpenoid A (1), and a rare N-oxide-containing indole diterpenoid derivative, peniditerpenoid B (2), together with three known ones (3-5), were obtained from the mangrove-sediment-derived fungus Penicillium sp. SCSIO 41411. Their structures were determined by the analysis of spectroscopic data, quantum chemical calculations, and X-ray diffraction analyses. Peniditerpenoid A (1) inhibited lipopolysaccharide-induced NF-κB with an IC50 value of 11 μM and further effectively prevented RANKL-induced osteoclast differentiation in bone marrow macrophages. In vitro studies demonstrated that 1 exerted significant inhibition of NF-κB activation in the classical pathway by preventing TAK1 activation, IκBα phosphorylation, and p65 translocation. Furthermore, 1 effectively reduced the level of NFATc1 activation, resulting in the attenuation of osteoclast differentiation. Our findings suggest that 1 holds promise as an inhibitor with significant potential for the treatment of diseases related to osteoporosis.

Indole Diterpenes from Mangrove Sediment-Derived Fungus Penicillium sp. UJNMF0740 Protect PC12 Cells against 6-OHDA-Induced Neurotoxicity via Regulating the PI3K/Akt Pathway

In our chemical investigation into Penicillium sp. UJNMF0740 derived from mangrove sediment, fourteen indole diterpene analogs, including four new ones, are purified by multiple chromatographic separation methods, with their structures being elucidated by the analyses of NMR, HR-ESIMS, and ECD data. The antibacterial and neuroprotective effects of these isolates were examined, and only compounds 6 and 9 exhibited weak antibacterial activity, while compounds 5, 8, and 10 showed protective effects against the injury of PC12 cells induced by 6-hydroxydopamine (6-OHDA). Additionally, compound 5 could suppress the apoptosis and production of reactive oxygen species (ROS) in 6-OHDA-stimulated PC12 cells as well as trigger the phosphorylation of PI3K and Akt. Taken together, our work enriches the structural diversity of indole diterpenes and hints that compounds of this skeleton can repress the 6-OHDA-induced apoptosis of PC12 cells via regulating the PI3K/Akt signaling pathway, which provides evidence for the future utilization of this fascinating class of molecules as potential neuroprotective agents.

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.

Secondary Metabolites of Endophytes Associated with the Zingiberaceae Family and Their Pharmacological Activities

Zingiberaceae is commonly known as the ginger family and has been extensively studied in the last decades for its pharmacological purposes. The study of ginger includes microorganisms known as endophytes, which raise interest for the research community because they can produce a wide range of secondary metabolites. This review discusses the secondary metabolites of endophytes from the Zingiberaceae family and their pharmacological activities. We detail the group of secondary metabolites, updated for its absolute structures, source and part origins, and, especially, pharmacological divided properties. Zingiberaceae endophytes have 106 volatile compounds and 52 isolated constituents, including 17 polyketides, five nonribosomal peptides, five aromatic compounds, three alkaloids, and 21 terpene-alkaloids. They have antimicrobial, anticancer, antioxidant, and anti-inflammatory activities. Secondary metabolites from plant endophytes of the Zingiberaceae family have the potential to be therapeutic drugs in the future. Research on endophytic bacteria or fungi has been little performed. Therefore, this study supports a new drug discovery from Zingiberaceae endophytes and compares them for future drug development.

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.

Anti-Diabetic Indole-Terpenoids From Penicillium sp. HFF16 Isolated From the Rhizosphere Soil of Cynanchum bungei Decne

Finding novel anti-diabetic compounds with effective suppression activities against hepatic glucagon response is urgently required for the development of new drugs against diabetes. Fungi are well known for their ability to produce new bioactive secondary metabolites. As part of our ongoing research, five new indole-terpenoids (1–5), named encindolenes D-H, were isolated from the fungus Penicillium sp. HFF16 from the rhizosphere soil of Cynanchum bungei Decne. The structures of the compounds were elucidated by spectroscopic data and ECD analysis. In the anti-diabetic activity assay, compounds 1–5 could inhibit the hepatic glucose production with EC50 values of 17.6, 30.1, 21.3, 9.6, and 9.9 μM, respectively, and decrease the cAMP contents in glucagon-induced HepG2 cells.

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.

Inhibition of cellular inflammatory mediator production and amelioration of learning deficit in flies by deep sea Aspergillus-derived cyclopenin

In the course of screening lipopolysaccharide (LPS)-induced nitric oxide (NO) production inhibitors, two related benzodiazepine derivatives, cyclopenol and cyclopenin, were isolated from the extract of a deep marine-derived fungal strain, Aspergillus sp. SCSIOW2. Cyclopenol and cyclopenin inhibited the LPS-induced formation of NO and secretion of IL-6 in RAW264.7 cells at nontoxic concentrations. In terms of the mechanism underlying these effects, cyclopenol and cyclopenin were found to inhibit the upstream signal of NF-κB activation. These compounds also inhibited the expression of IL-1β, IL-6, and inducible nitric oxide synthase (iNOS) in mouse microglia cells, macrophages in the brain. In relation to the cause of Alzheimer's disease, amyloid-β-peptide is known to induce inflammation in the brain. Therefore, the present study investigated the ameliorative effects of these inhibitors on an in vivo Alzheimer's model using flies. Learning deficits were induced by the overexpression of amyloid-β42 in flies, and cyclopenin but not cyclopenol was found to rescue learning impairment. Therefore, novel anti-inflammatory activities of cyclopenin were identified, which may be useful as a candidate of anti-inflammatory agents for neurodegenerative diseases.

Indole-Diterpenoids with Protein Tyrosine Phosphatase Inhibitory Activities from the Marine-Derived Fungus Penicillium sp. KFD28

Five new indole-terpenoids named penerpenes E-I (1-5), along with seven known ones (6-12), were isolated from the marine-derived fungus Penicillium sp. KFD28 from a bivalve mollusk, Meretrix lusoria. The structures of the new compounds were elucidated from spectroscopic data and ECD spectroscopic analyses. Compound 1 was assigned as an indole-diterpenoid with a unique 6/5/5/6/6/5/5 heptacyclic ring system. Compound 2 represents an indole-diterpenoid with a new carbon skeleton derived from paxilline by the loss of three carbons (C-23/24/25). Compound 3 contains an additional oxygen atom between C-21 and C-22 compared to paxilline to form an unusual 6/5/5/6/6/7 hexacyclic ring system bearing a 1,3-dioxepane ring, which is rarely encountered in natural products. Compounds 1, 2, 4, and 6 showed inhibitory activities against protein tyrosine phosphatase 1B (PTP1B) with IC₅₀ values of 14, 27, 23, and 13 μM, respectively.

Indole Diterpenoids from an Endophytic Penicillium sp

A chemical investigation of the endophyte Penicillium sp. (strain ZO-R1-1), isolated from roots of the medicinal plant Zingiber officinale, yielded nine new indole diterpenoids (1-9), together with 13 known congeners (10-22). The structures of the new compounds were elucidated by 1D and 2D NMR analysis in combination with HRESIMS data. The absolute configuration of the new natural products 1, 3, and 7 was determined using the TDDFT-ECD approach and confirmed for 1 by single-crystal X-ray determination through anomalous dispersion. The isolated compounds were tested for cytotoxicity against L5178Y, A2780, J82, and HEK-293 cell lines. Compound 1 was the most active metabolite toward L5178Y cells, with an IC₅₀ value of 3.6 μM, and an IC₅₀ against A2780 cells of 8.7 μM. Interestingly, 1 features a new type of indole diterpenoid scaffold with a rare 6/5/6/6/6/6/5 heterocyclic system bearing an aromatic ring C, which is suggested to be important for the cytotoxic activity of this natural product against L5278Y and A2780 cells.

Tremorgenic Mycotoxins: Structure Diversity and Biological Activity

Indole-diterpenes are an important class of chemical compounds which can be unique to different fungal species. The highly complex lolitrem compounds are confined to Epichloë species, whilst penitrem production is confined to Penicillium spp. and Aspergillus spp. These fungal species are often present in association with pasture grasses, and the indole-diterpenes produced may cause toxicity in grazing animals. In this review, we highlight the unique structural variations of indole-diterpenes that are characterised into subgroups, including paspaline, paxilline, shearinines, paspalitrems, terpendoles, penitrems, lolitrems, janthitrems, and sulpinines. A detailed description of the unique biological activities has been documented where even structurally related compounds have displayed unique biological activities. Indole-diterpene production has been reported in two classes of ascomycete fungi, namely Eurotiomycetes (e.g., Aspergillus and Penicillium) and Sordariomycetes (e.g., Claviceps and Epichloë). These compounds all have a common structural core comprised of a cyclic diterpene skeleton derived from geranylgeranyl diphosphate (GGPP) and an indole moiety derived from tryptophan. Structure diversity is generated from the enzymatic conversion of different sites on the basic indole-diterpene structure. This review highlights the wide-ranging biological versatility presented by the indole-diterpene group of compounds and their role in an agricultural and pharmaceutical setting.