Purpurolide A, 5/5/5 Spirocyclic Sesquiterpene Lactone in Nature from the Endophytic Fungus Penicillium purpurogenum

A new resorcylic acid lactone from the endophytic fungus Chaetosphaeronema sp

A new 14-membered resorcylic acid lactone (RAL14), chaetolactone A (1), along with three known ones (2-4), was obtained from the fermentation of the soil-derived fungus Chaetosphaeronema sp. SSJZ001. Their structures were established based on extensive spectroscopic data analyses (UV, IR, HRESIMS, 1D, and 2D NMR),13C NMR chemical shifts calculations coupled with the DP4+ probability method, theoretical calculations of ECD spectra, as well as X-ray diffraction analysis. All compounds were evaluated for their cytotoxic effects against A549, HO-8910, and MCF-7 cell lines.

Bergamotenes: A comprehensive compile of their natural occurrence, biosynthesis, toxicity, therapeutic merits and agricultural applications

Sesquiterpenoids constitute the largest subgroup of terpenoids that have numerous applications in pharmaceutical, flavor, and fragrance industries as well as biofuels. Bergamotenes, a type of bicyclic sesquiterpenes, are found in plants, insects, and fungi with α-trans-bergamotene as the most abundant compound. Bergamotenes and their related structures (Bergamotane sesquiterpenoids) have been shown to possess diverse biological activities such as antioxidant, anti-inflammatory, immunosuppressive, cytotoxic, antimicrobial, antidiabetic, and insecticidal effects. However, studies on their biotechnological potential are still limited. This review compiles the characteristics of bergamotenes and their related structures in terms of occurrence, biosynthesis pathways, and biological activities. It further discusses their functionalities and potential applications in pharmaceutical, nutraceuticals, cosmeceuticals, and pest management sectors. This review also opens novel perspectives in identifying and harnessing bergamotenes for pharmaceutical and agricultural purposes.

New Hydroxylactones and Chloro-Hydroxylactones Obtained by Biotransformation of Bicyclic Halolactones and Their Antibacterial Activity

The aim of this study was to obtain new halolactones with a gem-dimethyl group in the cyclohexane ring (at the C-3 or C-5 carbon) and a methyl group in the lactone ring and then subject them to biotransformations using filamentous fungi. Halolactones in the form of mixtures of two diasteroisomers were subjected to screening biotransformations, which showed that only compounds with a gem-dimethyl group located at the C-5 carbon were transformed. Strains from the genus Fusarium carried out hydrolytic dehalogenation, while strains from the genus Absidia carried out hydroxylation of the C-7 carbon. Both substrates and biotransformation products were then tested for antimicrobial activity against multidrug-resistant strains of both bacteria and yeast-like fungi. The highest antifungal activity against C. dubliniensis and C. albicans strains was obtained for compound 5b, while antimicrobial activity against S. aureus MRSA was obtained for compound 4a.

Purpurolide C-based microneedle promotes macrophage-mediated diabetic wound healing via inhibiting TLR4-MD2 dimerization and MYD88 phosphorylation

Delayed wound healing in diabetes is a global challenge, and the development of related drugs is a clinical problem to be solved. In this study, purpurolide C (PC), a small-molecule secondary metabolite of the endophytic fungus Penicillium purpurogenum, was found to promote diabetic wound healing. To investigate the key regulation targets of PC, in vitro RNA-seq, molecular docking calculations, TLR4-MD2 dimerization SDS-PAGE detection, and surface plasmon resonance (SPR) were performed, indicating that PC inhibited inflammatory macrophage activation by inhibiting both TLR4-MD2 dimerization and MYD88 phosphorylation. Tlr4 knockout in vivo attenuated the promotion effect of PC on wound healing. Furthermore, a delivery system consisting of macrophage liposome and GelMA-based microneedle patches combined with PC (PC@MLIP MN) was developed, which overcame the poor water solubility and weak skin permeability of PC, so that successfully punctured the skin and delivered PC to local tissues, and accurately regulated macrophage polarization in diabetic wound management. Overall, PC is an anti-inflammatory small molecule compound with a well-defined structure and dual-target regulation, and the PC@MLIP MN is a promising novel biomaterial for the management of diabetic wound.

Fungal Bergamotane Sesquiterpenoids-Potential Metabolites: Sources, Bioactivities, and Biosynthesis

The marine environment represents the largest ecosystem on the Earth's surface. Marine-derived fungi are of remarkable importance as they are a promising pool of diverse classes of bioactive metabolites. Bergamotane sesquiterpenoids are an uncommon class of terpenoids. They possess diverse biological properties, such as plant growth regulation, phototoxic, antimicrobial, anti-HIV, cytotoxic, pancreatic lipase inhibition, antidiabetic, anti-inflammatory, and immunosuppressive traits. The current work compiles the reported bergamotane sesquiterpenoids from fungal sources in the period ranging from 1958 to June 2022. A total of 97 compounds from various fungal species were included. Among these metabolites, 38 compounds were derived from fungi isolated from different marine sources. Furthermore, the biological activities, structural characterization, and biosynthesis of the compounds are also discussed. The summary in this work provides a detailed overview of the reported knowledge of fungal bergamotane sesquiterpenoids. Moreover, this in-depth and complete review could provide new insights for developing and discovering new valuable pharmaceutical agents from these natural metabolites.

Penicipurate A, a new polyketide derivative from the endophytic fungus Penicillium purpurogenum

A new polyketide derivative containing a 3-hydroxydecanoic acid ester moiety, penicipurate A (1), was purified from the solid cultures of the fungus Penicillium purpurogenum, a fungal strain endophytic in the leaves of Edgeworthia chrysantha. The structure of 1 was established by spectroscopic methods, including UV, IR, HRESIMS, 1D, and 2D NMR and ¹³C NMR chemical shifts calculations coupled with DP4+ analysis, as well as the chemical degradation method. Compound 1 showed moderate inhibitory activity against pancreatic lipase (PL) with an IC₅₀ value of 9.61 ± 1.42 µM.

Two New Nor-seco-Isodhilarane-Type Meroterpenoids from the Endophytic Fungus Penicillium purpurogenum

Two new nor-seco isodhilarane meroterpenoids (NSIMs), purpurogenolides F (1) and G (2), along with three known meroterpenoid analogs (3-5), were isolated from the cultures of an endophytic fungus, Penicillium purpurogenum. Structures and absolute configurations of the new NSIMs were determined based on extensive spectroscopic data analyses, including HR-ESI-MS, UV, IR, NMR chemical shift calculations together with DP4+ probability analysis, as well as ECD calculations. All the isolated meroterpenoids were assessed for their anti-inflammatory activities, and compound 4 exhibited moderate inhibitory activity against the nitric oxide (NO) production in lipopolysaccharide (LPS) induced RAW 264.7 cells with an IC₅₀ value of 20.85±2.31 μM.

Unusual (2R,6R)-bicyclo[3.1.1]heptane ring construction in fungal α-trans-bergamotene biosynthesis

Bergamotenes are bicyclo[3.1.1]heptane sesquiterpenes found abundantly in plants and fungi. Known bergamotene derivatives all possess (2S,6S)-bergamotene backbone. In this study, two (+)-α-trans-bergamotene derivatives (1 and 2) with unusual (2R,6R) configuration were isolated and elucidated from marine fungus Nectria sp. HLS206. The first (+)-α-trans-bergamotene synthase NsBERS was characterized using genome mining and heterologous expression-based strategies. Based on homology search, we characterized another (+)-α-trans-bergamotene synthase LsBERS from Lachnellula suecica and an (+)-α-bisabolol synthase BcBOS from Botrytis cinerea. We proposed that the cyclization mechanism of (+)-α-trans-bergamotene involved endo-anti cyclization of left-handed helix farnesyl pyrophosphate by (6R)-bisabolyl cation, which was supported by molecular docking. The biosynthesis-based volatiles (3-6) produced by heterologous fungal expression systems elicited significant electroantennographic responses of Helicoverpa armigera and Spodoptera frugiperda, respectively, suggesting their potential in biocontrol of these pests. This work enriches diversity of sesquiterpenoids and fungal sesquiterpene synthases, providing insight into the enzymatic mechanism of formation of enantiomeric sesquiterpenes.

Endophytic Fungal Terpenoids: Natural Role and Bioactivities

Endophytic fungi are a highly diverse group of fungi that intermittently colonize all plants without causing symptoms of the disease. They sense and respond to physiological and environmental changes of their host plant and microbiome. The inter-organism interactions are largely driven by chemical networks mediated by specialized metabolites. The balance of these complex interactions leads to healthy and strong host plants. Endophytic strains have particular machinery to produce a plethora of secondary metabolites with a variety of bioactivities and unknown functions in an ecological niche. Terpenoids play a key role in endophytism and represent an important source of bioactive molecules for human health and agriculture. In this review, we describe the role of endophytic fungi in plant health, fungal terpenoids in multiple interactions, and bioactive fungal terpenoids recently reported from endophytes, mainly from plants used in traditional medicine, as well as from algae and mangroves. Additionally, we highlight endophytic fungi as producers of important chemotherapeutic terpenoids, initially discovered in plants. Despite advances in understanding endophytism, we still have much to learn in this field. The study of the role, the evolution of interactions of endophytic fungi and their terpenoids provide an opportunity for better applications in human health and agriculture.

Seco and Nor-seco Isodhilarane-Type Meroterpenoids from Penicillium purpurogenum and the Configuration Revisions of Related Compounds

Seco and nor-seco isodhilarane-type meroterpenoids (SIMs and NSIMs) are mainly found in Penicillium fungi and have been characterized by highly congested polycyclic skeletons and a broad range of bioactivities. However, the literature reports inconsistent configuration assignments for some SIMs and NSIMs, due to their complex polycyclic systems and multichiral centers. Herein, we described eight SIMs and NSIMs isolated from the EtOAc extract of Penicillium purpurogenum, which led to the configuration revisions of purpurogenolide C (1a), berkeleyacetal B (2a), chrysogenolide F (3a), and berkeleyacetal C (4a) as compounds 1-4, respectively. Furthermore, extensive re-evaluation of the experimental and computational ¹³C NMR chemical shifts of the reported 39 SIMs and NSIMs provided an empirical approach for determining the C-9 relative configuration, according to the ¹³C NMR chemical shifts of C-9, which contributed to the configuration revisions of another three SIMs (5a and 6a) and NSIMs (7a), denoted as compounds 5-7, respectively. Biological assays indicated that compound 3 exhibited cytotoxic activity against HepG2 and A549 cell lines with IC₅₀ values of 5.58 and 6.80 μM, respectively. Compounds 2-4, 8, 9, and 32 showed moderate hepatoprotective activity at 10 μM in the APAP-induced HepG2 cell injury model.

Immunosuppressive Sesquiterpenoids from the Edible Mushroom Craterellus odoratus

The aim of this work was to comprehensively understand the chemical constituents of the edible mushroom Craterellus ordoratus and their bioactivity. A chemical investigation on this mushroom led to the isolation of 23 sesquiterpenoids including eighteen previously undescribed bergamotane sesquiterpenes, craterodoratins A–R (1–18), and one new victoxinine derivative, craterodoratin S (19). The new structures were elucidated by detailed interpretation of spectrometric data, theoretical nuclear magnetic resonance (NMR) and electronic circular dichroism (ECD) calculations, and single-crystal X-ray crystallographic analysis. Compounds 1 and 2 possess a ring-rearranged carbon skeleton. Compounds 3, 10, 12–15, 19, 20 and 23 exhibit potent inhibitory activity against the lipopolysaccharide (LPS)-induced proliferation of B lymphocyte cells with the IC₅₀ values ranging from 0.67 to 22.68 μM. Compounds 17 and 20 inhibit the concanavalin A (ConA)-induced proliferation of T lymphocyte cell with IC₅₀ values of 31.50 and 0.98 μM, respectively. It is suggested that C. ordoratus is a good source for bergamotane sesquiterpenoids, and their immunosuppressive activity was reported for the first time. This research is conducive to the further development and utilization of C. ordoratus.

Sesquiterpenoids Specially Produced by Fungi: Structures, Biological Activities, Chemical and Biosynthesis (2015-2020)

Fungi are widely distributed in the terrestrial environment, freshwater, and marine habitat. Only approximately 100,000 of these have been classified although there are about 5.1 million characteristic fungi all over the world. These eukaryotic microbes produce specialized metabolites and participate in a variety of ecological functions, such as quorum detection, chemical defense, allelopathy, and maintenance of symbiosis. Fungi therefore remain an important resource for the screening and discovery of biologically active natural products. Sesquiterpenoids are arguably the richest natural products from plants and micro-organisms. The rearrangement of the 15 high-ductility carbons gave rise to a large number of different skeletons. At the same time, abundant structural variations lead to a diversification of biological activity. This review examines the isolation, structural determination, bioactivities, and synthesis of sesquiterpenoids that were specially produced by fungi over the past five years (2015-2020).

Flow Chemistry-Enabled Divergent and Enantioselective Total Syntheses of Massarinolin A, Purpurolides B, D, E, 2,3-Deoxypurpurolide C, and Structural Revision of Massarinolin A

Massarinolin A and purpurolides are bioactive bergamotane sesquiterpenes condensed with a variety of synthetically challenging ring systems: a bicyclo[3.1.1]heptane, an oxaspiro[3.4]octane, and a dioxaspiro[4.4]nonane (oxaspirolactone). Herein, we report the first enantioselective total syntheses of massarinolin A, purpurolides B, D, E, and 2,3-deoxypurpurolide C. Our synthesis and computational analysis also led to a structural revision of massarinolin A. The divergent approach features an enantioselective organocatalyzed Diels-Alder reaction to install the first stereogenic center in high ee, a scalable flow photochemical Wolff rearrangement to build the key bicyclo[3.1.1]heptane, a furan oxidative cyclization to form the oxaspirolactone, a late-stage allylic C-H oxidation, and a Myers' NBSH-promoted sigmatropic elimination to install the exo methylene group of massarinolin A.

Z, Cubilla-Rios L. Structurally Uncommon Secondary Metabolites Derived from Endophytic Fungi

Among microorganisms, endophytic fungi are the least studied, but they have attracted attention due to their high biological diversity and ability to produce novel and bioactive secondary metabolites to protect their host plant against biotic and abiotic stress. These compounds belong to different structural classes, such as alkaloids, peptides, terpenoids, polyketides, and steroids, which could present significant biological activities that are useful for pharmacological or medical applications. Recent reviews on endophytic fungi have mainly focused on the production of novel bioactive compounds. Here, we focus on compounds produced by endophytic fungi, reported with uncommon bioactive structures, establishing the neighbor net and diversity of endophytic fungi. The review includes compounds published from January 2015 to December 2020 that were catalogued as unprecedented, rare, uncommon, or possessing novel structural skeletons from more than 39 different genera, with Aspergillus and Penicillium being the most mentioned. They were reported as displaying cytotoxic, antitumor, antimicrobial, antiviral, or anti-inflammatory activity. The solid culture, using rice as a carbon source, was the most common medium utilized in the fermentation process when this type of compound was isolated.

A critical review on the use of DP4+ in the structural elucidation of natural products: the good, the bad and the ugly. A practical guide

Covering: 2015 up to the end of 2020Even in the golden age of NMR, the number of natural products being incorrectly assigned is becoming larger every day. The use of quantum NMR calculations coupled with sophisticated data analysis provides ideal complementary tools to facilitate the elucidation process in challenging cases. Among the current computational methodologies to perform this task, the DP4+ probability is a popular and widely used method. This updated version of Goodman's DP4 synergistically combines NMR calculations at higher levels of theory with the Bayesian analysis of both scaled and unscaled data. Since its publication in late 2015, the use of DP4+ to solve controversial natural products has substantially grown, with several predictions being confirmed by total synthesis. To date, the structures of more than 200 natural products were determined with the aid of DP4+. However, all that glitters is not gold. Besides its intrinsic limitations, on many occasions it has been improperly used with potentially important consequences on the quality of the assignment. Herein we present a critical revision on how the scientific community has been using DP4+, exploring the strengths of the method and how to obtain optimal results from it. We also analyze the weaknesses of DP4+, and the paths to by-pass them to maximize the confidence in the structural elucidation.

Gelstriamine A, a Triamino Monoterpene Indole Alkaloid with a Caged 6/5/7/6/6/5 Scaffold and Analgesic Alkaloids from Gelsemium elegans Stems

A novel triamino monoterpene indole alkaloid with an unprecedented skeleton, gelstriamine A (1), four new monoterpene indole alkaloids (2-5), and 12 known analogues (6-17) were isolated from Gelsemium elegans. The structures of 1-5 were established using extensive spectroscopic techniques, NMR calculations with iJ/dJ-DP4 and 2D C-H COSY ANNs analysis, ECD calculations, chemical methods, and single crystal X-ray diffraction analysis. Gelstriamine A (1) possesses an unprecedented 6/5/7/6/6/5 heterohexacyclic scaffold bearing a unique hexahydrooxazolo[4,5-b]pyridin-2(3H)-one motif, and a plausible biosynthetic pathway was proposed. All the isolated alkaloids 1-17 showed discernible analgesic activities in an acetic acid-induced writhing test in mice, and N-desmethoxyhumantenine N₄-oxide (3) exhibited more potent analgesic activities than those of morphine at doses of 0.04 and 0.2 mg/kg.

Paeonone A, a novel nonanortriterpenoid from the roots of Paeonia lactiflora

Paeonone A (1), a unique nonanortriterpenoid, and a new octanortriterpenoid, paeonone B (2), were isolated from the roots of Paeonia lactiflora, together with a known analogue, palbinone (3). Paeonone A (1) is the first example of naturally occurring nonanortriterpenoid with a diketo acid group. Extensive NMR and HRESIMS experiments were applied to identify the structures of 1 and 2, and their absolute configurations were solved by single-crystal X-ray diffraction and ECD data. Biological properties of 1-3 were explored against pancreatic lipase and cancer cell lines.

Biological Activities of Some New Secondary Metabolites Isolated from Endophytic Fungi: A Review Study

Secondary metabolites isolated from plant endophytic fungi have been getting more and more attention. Some secondary metabolites exhibit high biological activities, hence, they have potential to be used for promising lead compounds in drug discovery. In this review, a total of 134 journal articles (from 2017 to 2019) were reviewed and the chemical structures of 449 new metabolites, including polyketides, terpenoids, steroids and so on, were summarized. Besides, various biological activities and structure-activity relationship of some compounds were aslo described.

Progress on Terpenoids With Biological Activities Produced by Plant Endophytic Fungi in China Between 2017 and 2019

Plant endophytic fungi are an important part of plant microecosystems and a natural resource for human survival and development. Various bioactive natural products produced by plant endophytic fungi show promising prospects in biopharmacy, agricultural production, and industrial fermentation. Terpenoids, the most numerous and structurally diverse natural products from endophytic fungi, possess a broad range of biological activities and huge potential for drug development. It is critically significant for ecological and economic benefits to develop their activities. This paper utilized literature analysis to summarize 200 terpenoids with biological activities that are derived from plant endophytic fungi in China between 2017 and 2019. Among them, sesquiterpenoids were the most important kind of terpenoids, and Trichoderma and Aspergillus species were main terpenoid-producing plant endophytic fungi. Furthermore, these terpenoids displayed multifarious biological activities, including antimicrobial, antipathogenic, and anti-inflammatory activities, as well as cytotoxicity, antitumor agents, and enzyme inhibition.

Endophytic Penicillium species and their agricultural, biotechnological, and pharmaceutical applications

Penicillium genus constituted by over 200 species is one of the largest and fascinating groups of fungi, particularly well established as a source of antibiotics. Endophytic Penicillium has been reported to colonize their ecological niches and protect their host plant against multiples stresses by exhibiting diverse biological functions that can be exploited for countless applications including agricultural, biotechnological, and pharmaceutical. Over the past 2 decades, endophytic Penicillium species have been investigated beyond their antibiotic potential and numerous applications have been reported. We comprehensively summarized in this review available data (2000-2019) regarding bioactive compounds isolated from endophytic Penicillium species as well as the application of these fungi in multiple agricultural and biotechnological processes. This review has shown that a very large number (131) of endophytes from this genus have been investigated so far and more than 280 compounds exhibiting antimicrobial, anticancer, antiviral, antioxidants, anti-inflammatory, antiparasitics, immunosuppressants, antidiabetic, anti-obesity, antifibrotic, neuroprotective effects, and insecticidal and biocontrol activities have been reported. Moreover, several endophytic Penicillium spp. have been characterized as biocatalysts, plant growth promoters, phytoremediators, and enzyme producers. We hope that this review summarizes the status of research on this genus and will stimulate further investigations.

Three new polyketides from the endophytic fungus Penicillium purpurogenum

Three new polyketides including two benzophenone derivatives, penibenzones A and B (1 and 2), and a new phthalide derivative, penibenzone C (3), along with six known compounds, were isolated from the solid-substrate cultures of the endophytic fungus Penicillium purpurogenum IMM003. Their structures were elucidated on the basis of spectroscopic data (UV, IR, HRESIMS, 1D and 2D NMR). All compounds were evaluated for inhibitory activity against pancreatic lipase, but none of them displayed activity.[Formula: see text].

Flavipesides A-C, PKS-NRPS Hybrids as Pancreatic Lipase Inhibitors from a Marine Sponge Symbiotic Fungus Aspergillus flavipes 164013

Three unusual chlorinated PKS-NRPS hybrid metabolites, flavipesides A-C (1-3), were isolated from a strain of marine sponge symbiotic fungus Aspergillus flavipes 164013. Their structures were determined by spectroscopic data analysis, and absolute configurations were assigned by single-crystal X-ray diffraction with ECD spectral analysis. Flavipesides A-C showed potent pancreatic lipase (PL) inhibitory activity with IC₅₀ values of 0.07-0.23 μM.

Spirodesertols A and B, two highly modified spirocyclic diterpenoids with an unprecedented 6-isopropyl-3H-spiro[benzofuran-2,1′-cyclohexane] motif from Salvia deserta

Two highly modified spirocyclic diterpenoids with an unprecedented 6-isopropyl-3H-spiro[benzofuran-2,1′-cyclohexane] motif and four new icetexane diterpenoids were isolated from Salvia deserta. 1 showed more potent cytotoxicity than cis-platin.

Survey of natural products reported by Asian research groups in 2018

The new natural products reported in 2018 in peer-reviewed articles in journals with good reputations were reviewed and analyzed. The advances made by Asian research groups in the field of natural products chemistry in 2018 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on their structural classification.

Spirocyclic Motifs in Natural Products

Spirocyclic motifs are emerging privileged structures for drug discovery. They are also omnipresent in the natural products domain. However, until today, no attempt to analyze the structural diversity of various spirocyclic motifs occurring in natural products and their relative populations with unique compounds reported in the literature has been undertaken. This review aims to fill that void and analyze the diversity of structurally unique natural products containing spirocyclic moieties of various sizes.

Hot off the press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as vlasoulamine A from Vladimiria souliei.

Cytotoxic metabolites from the endophytic fungus Chaetomium globosum 7951

The following compounds were isolated from acetate extracts of Chaetomium globosum 7951 solid cultures: demethylchaetocochin C (1) and chaetoperazine A (3), two new epipolythiodioxopiperazine (ETP) alkaloids, a novel pyridine benzamide, 4-formyl-N-(3′-hydroxypyridin-2′-yl) benzamide (6), and three known ETP derivatives (2, 4, and 5). The structures of these compounds were determined using extensive spectroscopic data analysis. Compounds 1–3, and 6, inhibited the growth of MCF-7, MDA-MB-231, H460 and HCT-8 cells with an IC₅₀ of 4.5 to 65.0 μM.

Demethylchaetocochin C and chaetoperazine A, two new epipolythiodioxopiperazine alkaloids, and three known analogs were isolated from Chaetomium globosum 7951. Demethylchaetocochin C significantly inhibits human lung cancer cell growth.