Meroterpenoids produced by fungi: Occurrence, structural diversity, biological activities, and their molecular targets

Four new meroterpenoid derivatives with cytotoxicity from the mangrove-derived fungus Penicillium sp. HLLG-122

Four new meroterpenoids, including two seco isodhilarane-type meroterpenoids peniciacetals J-K (1 and 2), two austins-type meroterpenoids peniciacetals L-M (3 and 4), along with five known analogues (5-9) were isolated from the mangrove-derived fungus Penicillium sp. HLLG-122 based on the OSMAC approach. The structures, including absolute configurations of new compounds were elucidated by HRESIMS, 1D, 2D NMR spectroscopic data, X-ray diffraction analysis, and quantum chemical electronic circular dichroism (ECD) calculation. Peniciacetal J (1) was characterized with a unique 6/7/6/5/6/5 hexacyclic systems with a furan ring moiety. Compound 3 showed weak cytotoxicity against HepG2 and MCF-7 cell lines with IC50 values of 38.9 and 34.1 μM, respectively. Compound 8 showed moderate cytotoxicity against HepG2 and MCF-7 cell lines with IC50 values of 10.7 and 13.3 μM, respectively. Compound 9 exhibited good cytotoxicity against HepG2 cell line with the IC50 value of 4.8 μM.

Racemic Meroterpenoid with a 6/6/4/6/6/10/3 Skeleton via [2 + 2] and [4 + 2] Coupling of Sesquiterpenoid and Pyrone Units

Hypbeaone A (1), a pair of racemic meroterpenoids featuring a 6/6/4/6/6/10/3 heptacyclic core, along with its biogenic precursor, hypermonone A (2), were isolated from Hypericum beanii. Compound 1 represented the first trimeric meroterpenoid that should be biosynthesized through intermolecular [2 + 2] and [4 + 2] cycloadditions of two pyrones and one sesquiterpenoid unit. Its structure was unequivocally determined by spectroscopic analysis and X-ray crystallography. Both compounds (±)-1 and 2 exhibited potential α-glucosidase inhibitory activities.

Geranyl hydroquinone alleviates rheumatoid arthritis-associated pain by suppressing neutrophil accumulation, N1 polarization and ROS production in mice

Pain hypersensitivity is a hallmark of rheumatoid arthritis (RA); however, the underlying mechanisms and effective therapies remain largely undefined. Emerging studies suggest that neutrophils play a significant role in the pathology of RA, yet their involvement in RA-associated pain is still unclear. The present study investigates whether neutrophil activity contributes to pain pathogenesis in RA. Our flow cytometry analysis reveals that the accumulation and N1 polarization (indicated by the ratio of CD45+CD66b+CD95+ subset) of neutrophils occur in synovial fluid samples from RA patients, positively correlating with pain scores. In the collagen-induced rheumatoid arthritis (CIA) model, mice demonstrate neutrophil accumulation, N1 polarization (indicated by the ratio of CD45+Ly-6G+CD95+ subset), and reactive oxygen species (ROS) production in affected paw tissues. Geranyl hydroquinone (GHQ), a natural meroterpenoid with antioxidative properties, reverses N1 polarization and ROS production in synovial neutrophils from RA patients in vitro. Moreover, a 10-day oral administration of GHQ alleviates pain hypersensitivity and reduces neutrophil accumulation, N1 polarization, and ROS production in CIA mice. Notably, GHQ treatment reverses TNF-α-evoked ROS production in neutrophils in vitro through downregulating gene expression associated with the ROS pathway. Further, liquid chromatography-tandem mass spectrometry and biochemical analyses indicate that GHQ binds to microsomal glutathione S-transferase 3 (MGST3) in neutrophils. In vitro and in vivo evidence demonstrates that the RA-specific analgesic and antioxidative effects of GHQ require MGST3. Lastly, GHQ administration exhibits superior therapeutic effects compared to methotrexate, a first-line disease-modifying antirheumatic drug, in CIA mice. Collectively, our findings indicate that neutrophil accumulation, N1 polarization and ROS production contribute to RA-associated pain, suggesting that targeting these pathways, such as with GHQ, could be a viable strategy for RA treatment.

Natural Products as Novel Therapeutic Agents for Triple-Negative Breast Cancer: Current Evidence, Mechanisms, Challenges, and Opportunities

Breast cancer (BC) tops the list of causes for female fatalities globally, with the elusive triple-negative breast cancer (TNBC) constituting 10-20% of all cases. Current clinical strategies for combating TNBC encompass a multifaceted approach, including surgical intervention, radiation therapy, chemotherapy, and advanced targeted drugs and immunotherapies. While these modalities have catalyzed significant advancements in TNBC management, lingering limitations continue to pose formidable challenges. There is an acute need for novel therapeutics in the realm of TNBC treatment. Natural products (NPs) have emerged as a rich reservoir for pharmaceutical innovation, owing to their extraordinary range of structures and physicochemical properties. Scholars have reported diverse evidence of NPs' efficacy against TNBC. This review aims to comprehensively explore the bioactive constituents, specifics and commonalities of chemical structure, and pharmacological mechanisms of NPs, specifically examining their multifaceted roles in impeding TNBC. NPs, which have recently garnered significant interest, are intriguing in terms of their capacity to combat TNBC through multifaceted mechanisms, including the suppression of tumor cell proliferation, the induction of apoptosis, and the inhibition of tumor metastasis. These natural agents primarily encompass a range of compounds, including terpenoids, glycosides, phenolic compounds, and alkaloids. An in-depth exploration has unveiled their involvement in key signaling pathways, including the transforming growth factor-beta (TGF-β), vascular endothelial growth factor A (VEGFA), phosphoinositide 3-kinase/protein kinase B (PI3K/AKT), Wingless/Int-1 (Wnt) /β-catenin, and mitogen-activated protein kinase (MAPK) pathways. Meanwhile, this review also looks at the challenges and opportunities that arise from harnessing natural compounds to influence TNBC, while outlining the prospective trajectory for future research in the field of NPs.

Mining of Meroterpenoids with Anti-inflammatory Activity from the Mangrove Endophytic Fungus Talaromyces sp. JNQQJ-4 by Genome Analysis and Molecular Network Strategy

Talaromeroterpenoids A-G (1-7), seven new 3,5-dimethylorsellinic-acid-derived meroterpenoids, and two known analogues (8 and 9) were isolated from the mangrove endophytic fungus Talaromyces sp. JNQQJ-4 by genome analysis and a molecular networking strategy. Their structures and absolute configurations were established by nuclear magnetic resonance data, high-resolution electrospray ionization mass spectrometry, and X-ray diffraction. Compound 1 possesses an unprecedented rearrangement 7/6/6/6/5/5 hexacyclic skeleton based on a 2,8,18,21-tetraoxa-hexacyclo-[12.5.2.13,12.01,16.04,10.016,22]docosane core. In bioassays, compound 2 exhibited promising anti-inflammatory activity by suppressing the expression of pro-inflammatory factors and inactivating the NF-κB signaling pathway.

Total Synthesis of DMOA-Derived Meroterpenoids: Achieving Selectivity in the Synthesis of (+)-Berkeleyacetal D and (+)-Peniciacetal I

The synthesis of complex natural products requires efficient control over chemoselectivity, stereoselectivity, and regioselectivity. Berkeleyacetals, a subfamily of 3,5-dimethylorsellinic acid (DMOA)-derived meroterpenoids, pose substantial synthetic challenges due to their densely functionalized and highly oxidized architectures, which have constrained synthetic efforts. Here, we present the first total synthesis of this class of DMOA-derived meroterpenoids, specifically (+)-berkeleyacetal D and (+)-peniciacetal I. Our approach features a chemoselective deprotonation followed by an intramolecular single-electron transfer (SET) from an enolate to an alkyl bromide, enabling the construction of the 2,3-dihydrofuran ring in berkeleyacetal D. Additional selective transformations include an endo-selective intramolecular Diels-Alder reaction, chemoselective methylations and semihydrogenation of [3]dendralene, and a solvent-controlled diastereoselective epoxidation. Beyond providing a synthetic route to these densely congested natural products, our study offers mechanistic insights into achieving selectivity in the assembly of architecturally demanding molecules.

Modifications of Prenyl Side Chains in Natural Product Biosynthesis

In recent years, there has been a growing interest in understanding the enzymatic machinery responsible for the modifications of prenyl side chains and elucidating their roles in natural product biosynthesis. This interest stems from the pivotal role such modifications play in shaping the structural and functional diversity of natural products, as well as from their potential applications to synthetic biology and drug discovery. In addition to contributing to the diversity and complexity of natural products, unique modifications of prenyl side chains are represented by several novel biosynthetic mechanisms. Representative unique examples of epoxidation, dehydrogenation, oxidation of methyl groups to carboxyl groups, unusual C-C bond cleavage and oxidative cyclization are summarized and discussed. By revealing the intriguing chemistry and enzymology behind these transformations, this comprehensive and comparative review will guide future efforts in the discovery, characterization and application of modifications of prenyl side chains in natural product biosynthesis.

Biosynthesis and Assembly Logic of Fungal Hybrid Terpenoid Natural Products

In recent decades, fungi have emerged as significant sources of diverse hybrid terpenoid natural products, and their biosynthetic pathways are increasingly unveiled. This review mainly focuses on elucidating the various strategies underlying the biosynthesis and assembly logic of these compounds. These pathways combine terpenoid moieties with diverse building blocks including polyketides, nonribosomal peptides, amino acids, p-hydroxybenzoic acid, saccharides, and adenine, resulting in the formation of plenty of hybrid terpenoid natural products via C-O, C-C, or C-N bond linkages. Subsequent tailoring steps, such as oxidation, cyclization, and rearrangement, further enhance the biological diversity and structural complexity of these hybrid terpenoid natural products. Understanding these biosynthetic mechanisms holds promise for the discovery of novel hybrid terpenoid natural products from fungi, which will promote the development of potential drug candidates in the future.

DMOA-derived polycyclic meroterpenoids with antiviral activities from the deep-sea-derived fungus Penicillium pancosmium A6A

Two undescribed 3,5-dimethylorsellinic acid (DMOA) derived meroterpenoids, namely pancosterpenoids A (1) and B (2), were discovered from the EtOAc extract of the deep-sea sediment-derived fungus Penicillium pancosmium A6A. The gross structures were established by detailed analysis of the spectroscopic data (NMR and HRESIMS spectra), while their absolute configurations were resolved by comparing the experimental and calculated ECD data as well as X-ray single crystal diffraction analysis. Pancosterpenoid A (1) was the first representative of DMOA-derived meroterpenoids possessing a 6/6/6/5/5 pentacyclic system, while pancosterpenoid B (2) belongs to a class of rare 13-nor-citreohybridone meroterpenoids. Two metabolites were evaluated the antiviral effects against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) trVLP pseudovirus. As a result, compounds 1 and 2 showed moderately inhibitory activities with IC50 values of 22.37 and 18.12 μM, respectively.

Facile constructed meroterpenoids with novel hexadecahydroacephenanthrylene carbon skeleton using the biotransformation and chemical synthesis method

Bioaspermeroterpenoid A (1), the first meroterpenoid with an unprecedented hexadecahydroacephenanthrylene carbon skeleton, together with two analogues bioaspermeroterpenoids B and C (2 and 3) were co-isolated from the biotransformation extract of aspermeroterpene C by the fungus Penicillium herquei GZU-31-6. On the other hand, bioaspermeroterpenoid Aa (1a) featuring the same hexadecahydroacephenanthrylene carbon skeleton was synthesized from the precursor aspermeroterpene C by the nucleophilic addition reaction in the presence of CH3ONa. Furthermore, bioaspermeroterpenoids A and C showed good inhibitory activities against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 cells with IC50 values of 26.08 and 7.50 µM, respectively, compared to the positive control (Indomethacin, IC50 24.1 µM). Especially, bioaspermeroterpenoids A and C also significantly suppressed the protein expression of iNOS and COX-2 at the concentration of 12.5 μM.

Unified enantiospecific synthesis of drimane meroterpenoids enabled by enzyme catalysis and transition metal catalysis

Merging the advantages of biocatalysis and chemocatalysis in retrosynthetic analysis can significantly improve the efficiency and selectivity of natural product synthesis. Here, we describe a unified approach for the synthesis of drimane meroterpenoids by combining heterologous biosynthesis, enzymatic hydroxylation, and transition metal catalysis. In phase one, drimenol was produced by engineering a biosynthetic pathway in Escherichia coli. Cytochrome P450BM3 from Bacillus megaterium was engineered to catalyze the C-3 hydroxylation of drimenol. By means of nickel-catalyzed reductive coupling, six drimane meroterpenoids (+)-hongoquercins A and B, (+)-ent-chromazonarol, 8-epi-puupehenol, (-)-pelorol, and (-)-mycoleptodiscin A were synthesized in a concise and enantiospecific manner. This strategy offers facile access to the congeners of the drimane meroterpenoid family and lays the foundation for activity optimization.

Target Discovery of Dhilirane-Type Meroterpenoids by Biosynthesis Guidance and Tailoring Enzyme Catalysis

Dhilirane-type meroterpenoids (DMs) featuring a 6/6/6/5/5 ring system represent a rare group of fungal meroterpenoids. To date, merely 11 DMs have been isolated or derived, leaving their chemical diversity predominantly unexplored. Herein, we leverage an understanding of biosynthesis to develop a workflow for discovery of DMs by genome mining, metabolite analysis, and tailoring enzyme catalysis. Twenty-three new DMs, including seven unprecedented scaffolds, were consequently identified. An α-ketoglutarate (α-KG)-dependent oxygenase DhiD was found to catalyze the stereodivergent ring contraction of dhilirolide D to form the dhilirane skeleton; while the cytochrome P450 DhiH reshaped the structural diversity by establishing diverse C-C bonds and oxidation. Crystallographic and mutagenesis experiments provide a molecular basis for the DhiD reaction and its stereodivergent products. Notably, DhiD exhibits substrate-controlled catalytic versatility in the chemical expansion of DMs through ring contraction, hydroxylation, dehydrogenation, epoxidation, isomerization, epimerization, and α-ketol cleavage. Bioassay results demonstrated that the obtained meroterpenoids exhibited anti-inflammatory and insecticidal activities. Our work provides insight into nature's arsenal for DM biosynthesis and the functional versatility of α-KG-dependent oxygenase and P450, which can be applied for target discovery and diversification of DM-type natural products.

Genome-wide identification and expression analysis of the OSC gene family in Platycodon grandiflorus

Platycodon grandiflorus stands as one of the most extensively utilized traditional Chinese medicinal herbs, with triterpenoids and their derivatives serving as its primary medicinal components. Oxido squalene cyclase (OSC), serving as a crucial enzyme in the triterpenoid synthesis pathway, has the capability to enzymatically generate significant quantities of sterols and triterpenoid intermediates. While the OSC gene family has been identified in numerous species, bioinformatics research on this family remains scant. Presently, the specific members of this gene family in Platycodon grandiflorus have yet to be definitively determined. In this study, we successfully identified a total of 15 PgOSC genes within the genome of Platycodon grandiflorus by conducting homology comparisons. These genes were discovered to be unevenly distributed across the five chromosomes of the species, organized in the form of gene clusters. Subsequently, we conducted a thorough analysis of the OSC gene family's evolutionary relationship by constructing a phylogenetic tree. Other characteristics of PgOSC family members, including gene structure, conserved motifs, protein three-dimensional structure, subcellular localization, and cis-acting elements were thoroughly characterized. Furthermore, We analyzed the expression of PgOSC gene in different tissues of Platycodon grandiflorus by qRT-PCR, and found that the expression of PgOSC genes in root was higher than that in stem and leaf. Upon comparing the effects of salt, heat, and drought treatments, we observed a significant induction of PgOSC gene expression in Platycodon grandiflorus specifically under salt stress conditions. In summary, this study comprehensively identified and analyzed the OSC gene family, aiming to provide basic biological information for exploring the members of PgOSC gene family.

Macrophorins H and L, two new HMG-conjugate macrophorins from rihzospheric Penicillium sp. NX-05-G-3

Macrophorins H (4) and L (5), two rare HMG-conjugate macrophorins along with three known macrophorins (1-3), three DMOA-derived meroterpenoids (6-8) and two ergosterol derivates (9-10) were isolated from sterilized rice medium cultured Penicillium sp. NX-05-G-3. Their structures were elucidated by 1D and 2D NMR. The cytotoxicities of all compounds were evaluated, and compounds 1 and 2 showed extensive cytotoxicity against human cancer cell lines Hela, SCC15, MDA-MB-453 and A549, with IC50 values ranging from 17.6 to 32.8 µM.

Anti-neuroinflammatory andrastin-type meroterpenoids from the marine-derived fungus Penicillium chrysogenum HNNU w0032

A new andrastin-type meroterpenoid penimerodione A (1), and three known analogues (2-4), were isolated from the culture of a marine-derived fungus Penicillium chrysogenum HNNU w0032 by the guidance of MS/MS-based molecular networking. The planar structure of 1 was established by extensive NMR spectroscopic and HRESIMS analyses, and the absolute configuration was elucidated by a single-crystal X-ray diffraction. Compound 1 showed significant inhibitory effect on NO production in LPS-stimulated BV-2 macrophages with an IC50 value of 5.9 ± 0.3 μM. The Western blot result revealed that compound 1 exerted an anti-neuroinflammatory effect via the MAPK signalling pathway.

Biosynthesis of fungal terpenoids

Covering: up to August 2023Terpenoids, which are widely distributed in animals, plants, and microorganisms, are a large group of natural products with diverse structures and various biological activities. They have made great contributions to human health as therapeutic agents, such as the anti-cancer drug paclitaxel and anti-malarial agent artemisinin. Accordingly, the biosynthesis of this important class of natural products has been extensively studied, which generally involves two major steps: hydrocarbon skeleton construction by terpenoid cyclases and skeleton modification by tailoring enzymes. Additionally, fungi (Ascomycota and Basidiomycota) serve as an important source for the discovery of terpenoids. With the rapid development of sequencing technology and bioinformatics approaches, genome mining has emerged as one of the most effective strategies to discover novel terpenoids from fungi. To date, numerous terpenoid cyclases, including typical class I and class II terpenoid cyclases as well as emerging UbiA-type terpenoid cyclases, have been identified, together with a variety of tailoring enzymes, including cytochrome P450 enzymes, flavin-dependent monooxygenases, and acyltransferases. In this review, our aim is to comprehensively present all fungal terpenoid cyclases identified up to August 2023, with a focus on newly discovered terpenoid cyclases, especially the emerging UbiA-type terpenoid cyclases, and their related tailoring enzymes from 2015 to August 2023.

Naturally Occurring Norsteroids and Their Design and Pharmaceutical Application

The main focus of this review is to introduce readers to the fascinating class of lipid molecules known as norsteroids, exploring their distribution across various biotopes and their biological activities. The review provides an in-depth analysis of various modified steroids, including A, B, C, and D-norsteroids, each characterized by distinct structural alterations. These modifications, which range from the removal of specific methyl groups to changes in the steroid core, result in unique molecular architectures that significantly impact their biological activity and therapeutic potential. The discussion on A, B, C, and D-norsteroids sheds light on their unique configurations and how these structural modifications influence their pharmacological properties. The review also presents examples from natural sources that produce a diverse array of steroids with distinct structures, including the aforementioned A, B, C, and D-nor variants. These compounds are sourced from marine organisms like sponges, soft corals, and starfish, as well as terrestrial entities such as plants, fungi, and bacteria. The exploration of these steroids encompasses their biosynthesis, ecological significance, and potential medical applications, highlighting a crucial area of interest in pharmacology and natural product chemistry. The review emphasizes the importance of researching these steroids for drug development, particularly in addressing diseases where conventional medications are inadequate or for conditions lacking sufficient therapeutic options. Examples of norsteroid synthesis are provided to illustrate the practical applications of this research.

Insights into Ganoderma fungi meroterpenoids opening a new era of racemic natural products in mushrooms

Ganoderma meroterpenoids (GMs) containing 688 structures to date were discovered to have multiple remarkable biological activities. 65.6% of meroterpenoids featuring stereogenic centers from Ganoderma species are racemates. Further, GMs from different Ganoderma species seem to have their own characteristics. In this review, a comprehensive summarization of GMs since 2000 is presented, including GM structures, structure corrections, biological activities, physicochemical properties, total synthesis, and proposed biosynthetic pathways. Additionally, we especially discuss the racemic nature, species-related structural distribution, and structure-activity relationship of GMs, which will provide a likely in-house database and shed light on future studies on GMs.

HPPO-Derived Meroterpenoids from the Marine-Derived Fungus Penicillium sp. SCSIO 41691

Seven new 4-hydroxy-6-phenyl-2H-pyran-2-one (HPPO) derived meroterpenoids, 1-methyl-12a,12b-epoxyarisugacin M (1), 1-methyl-4a,12b-epoxyarisugacin M (2), 2,3-dihydroxy-3,4a-epoxy-12a-dehydroxyisoterreulactone A (3), 2-hydroxy-12a-dehydroxyisoterreulactone A (4), 3'-demethoxyterritrems B' (5), 4a-hydroxyarisugacin P (6), and 1-epi-arisugacin H (7), together with two known analogues (8 and 9), were isolated from the marine-derived fungal strain Penicillium sp. SCSIO 41691. Their structures were elucidated by spectroscopic methods, and the absolute configurations of compounds 1 and 3 were determined by single-crystal X-ray diffraction. Among them, 1 and 2 had a unique methyl migration in the basic meroterpenoid skeleton with a 12a,12b-epoxy or 4a,12b-epoxy group, and 3 was a highly oxygenated HPPO-derived meroterpenoid featuring a rare 6/5/6/6/6/6 hexacyclic system with a 3,4a-epoxy group. Biologically, 5 exhibited inhibitory activity against lipopolysaccharide-induced nitric oxide production in RAW 264.7 cells with an IC50 value of 21 μM, more potent than the positive control indomethacin.

Lipid-Lowering Meroterpenoids Penihemeroterpenoids A-F from Penicillium herquei GZU-31-6 via Targeting the AMPK/ACC/SREBP-1c Signaling Pathway

Penihemeroterpenoids A-C, the first meroterpenoids with an unprecedented 6/5/6/5/5/6/5 heptacyclic ring system, together with precursors penihemeroterpenoids D-F, were co-isolated from the fungus Penicillium herquei GZU-31-6. Among them, penihemeroterpenoids C-F exhibited lipid-lowering effects comparable to those of the positive control simvastatin by the activation of the AMPK/ACC/SREBP-1c signaling pathway, downregulated the mRNA levels of lipid synthesis genes FAS and PNPLA3, and increased the level of mRNA expression of the lipid export gene MTTP.

Two Cytochrome P450 Enzymes Form the Tricyclic Nested Skeleton of Meroterpenoids by Sequential Oxidative Reactions

Meroterpenoid clavilactones feature a unique benzo-fused ten-membered carbocyclic ring unit with an α,β-epoxy-γ-lactone moiety, forming an intriguing 10/5/3 tricyclic nested skeleton. These compounds are good inhibitors of the tyrosine kinase, attracting a lot of chemical synthesis studies. However, the natural enzymes involved in the formation of the 10/5/3 tricyclic nested skeleton remain unexplored. Here, we identified a gene cluster responsible for the biosynthesis of clavilactone A in the basidiomycetous fungus Clitocybe clavipes. We showed that a key cytochrome P450 monooxygenase ClaR catalyzes the diradical coupling reaction between the intramolecular hydroquinone and allyl moieties to form the benzo-fused ten-membered carbocyclic ring unit, followed by the P450 ClaT that exquisitely and stereoselectively assembles the α,β-epoxy-γ-lactone moiety in clavilactone biosynthesis. ClaR unprecedentedly acts as a macrocyclase to catalyze the oxidative cyclization of the isopentenyl to the nonterpenoid moieties to form the benzo-fused macrocycle, and a multifunctional P450 ClaT catalyzes a ten-electron oxidation to accomplish the biosynthesis of the 10/5/3 tricyclic nested skeleton in clavilactones. Our findings establish the foundation for the efficient production of clavilactones using synthetic biology approaches and provide the mechanistic insights into the macrocycle formation in the biosynthesis of fungal meroterpenoids.

Production of non-natural 5-methylorsellinate-derived meroterpenoids in Aspergillus oryzae

Fungal meroterpenoids are diverse structurally intriguing molecules with various biological properties. One large group within this compound class is derived from the aromatic precursor 3,5-dimethylorsellinic acid (DMOA). In this study, we constructed engineered metabolic pathways in the fungus Aspergillus oryzae to expand the molecular diversity of meroterpenoids. We employed the 5-methylorsellinic acid (5-MOA) synthase FncE and three additional biosynthetic enzymes for the formation of (6R,10'R)-epoxyfarnesyl-5-MOA methyl ester, which served as a non-native substrate for four terpene cyclases from DMOA-derived meroterpenoid pathways. As a result, we successfully generated six unnatural 5-MOA-derived meroterpenoid species, demonstrating the effectiveness of our approach in the generation of structural analogues of meroterpenoids.

Novel 6/7/6 ring system diterpenoids and cytochalasins from the fungus Eutypella scoparia GZU-4-19Y and their anti-inflammatory activity

Two new compounds eutyditerpenoid A (1) and seco-phenochalasin B (5), together with seven known compounds diaporthein A (2), aspergillon A (3), phenochalasin B (4), cytochalasins Z24 and Z25 (6 and 7), scoparasins A and B (8 and 9) were isolated from marine-derived Eutypella scoparia GZU-4-19Y. Among them, eutyditerpenoid A (1) with a rare 6/7/6 ring system possesing an anhydride moiety was the first example in the pimarane-type diterpenoids. Their structures were determined based on spectroscopic methods and the electronic circular dichroism (ECD) calculations. In the bioassays, all of the isolates were evaluated for their inhibitory activity against NO production induced by lipopolysaccharide in RAW 264.7 cells. Compounds 3 and 7 showed potent NO inhibition activity with IC50 values of 2.1 and 17.1 μM respectively, and the former also significantly suppressed the protein expression of iNOS and COX-2 at the concentration of 2.5 μM.

Meroterpenoids from the marine-derived fungus Aspergillus terreus GZU-31-1 exerts anti-liver fibrosis effects by targeting the Nrf2 signaling in vitro

Six undescribed meroterpenoids aspertermeroterpenes A-F and four known analogues were isolated from the marine-derived fungus Aspergillus terreus GZU-31-1. Their structures were elucidated based on spectroscopic methods and electronic circular dichroism calculations. All meroterpenoids possessed the unique acetyl group at C-11, and also aspertermeroterpene A featured the rare C-14 decarboxylated in DMOA meroterpenoids. In the bioassays, aspermeroterpene B exhibited a potent inhibitory effect on the activation of hepatic stellate cells at the concentration of 5 μM via targeting the Nrf2 signaling. This is the first time reported that aspermeroterpene B as a previously undescribed carbon skeleton of meroterpenoid possessed anti-liver fibrosis effect.

Terpenoid balance in Aspergillus nidulans unveiled by heterologous squalene synthase expression

Filamentous fungi produce numerous uncharacterized natural products (NPs) that are often challenging to characterize because of cryptic expression in laboratory conditions. Previously, we have successfully isolated novel NPs by expressing fungal artificial chromosomes (FACs) from a variety of fungal species into Aspergillus nidulans. Here, we demonstrate a twist to FAC utility wherein heterologous expression of a Pseudogymnoascus destructans FAC in A. nidulans altered endogenous terpene biosynthetic pathways. In contrast to wild type, the FAC transformant produced increased levels of squalene and aspernidine type compounds, including three new nidulenes (1- 2, and 5), and lost nearly all ability to synthesize the major A. nidulans characteristic terpene, austinol. Deletion of a squalene synthase gene in the FAC restored wild-type chemical profiles. The altered squalene to farnesyl pyrophosphate ratio leading to synthesis of nidulenes and aspernidines at the expense of farnesyl pyrophosphate-derived austinols provides unexpected insight into routes of terpene synthesis in fungi.

Exploring the in vivo anti-cancer potential of Neosetophomone B in leukemic cells using a zebrafish xenograft model

Neosetophomone B (NSP-B) is a unique meroterpenoid fungal secondary metabolite that has previously demonstrated promising anti-cancer properties against various cancer cell lines in vitro. However, its in vivo anti-cancer potential remaines unexplored. To fill this gap in our knowledge, we tested NSP-B's in vivo anti-cancer activity using a zebrafish model, an organism that has gained significant traction in biomedical research due to its genetic similarities with humans and its transparent nature, allowing real-time tumor growth observation. For our experiments, we employed the K562-injected zebrafish xenograft model. Upon treating these zebrafish with NSP-B, we observed a marked reduction in the size and number of tumor xenografts. Delving deeper, our analyses indicated that NSP-B curtailed tumor growth and proliferation of leukemic grafted xenograft within the zebrafish. These results show that NSP-B possesses potent in vivo anti-cancer properties, making it a potential novel therapeutic agent for addressing hematological malignancies.

Neosetophomone B induces apoptosis in multiple myeloma cells via targeting of AKT/SKP2 signaling pathway

Multiple myeloma (MM) is a hematologic malignancy associated with malignant plasma cell proliferation in the bone marrow. Despite the available treatments, drug resistance and adverse side effects pose significant challenges, underscoring the need for alternative therapeutic strategies. Natural products, like the fungal metabolite neosetophomone B (NSP-B), have emerged as potential therapeutic agents due to their bioactive properties. Our study investigated NSP-B's antitumor effects on MM cell lines (U266 and RPMI8226) and the involved molecular mechanisms. NSP-B demonstrated significant growth inhibition and apoptotic induction, triggered by reduced AKT activation and downregulation of the inhibitors of apoptotic proteins and S-phase kinase protein. This was accompanied by an upregulation of p21Kip1 and p27Cip1 and an elevated Bax/BCL2 ratio, culminating in caspase-dependent apoptosis. Interestingly, NSP-B also enhanced the cytotoxicity of bortezomib (BTZ), an existing MM treatment. Overall, our findings demonstrated that NSP-B induces caspase-dependent apoptosis, increases cell damage, and suppresses MM cell proliferation while improving the cytotoxic impact of BTZ. These findings suggest that NSP-B can be used alone or in combination with other medicines to treat MM, highlighting its importance as a promising phytoconstituent in cancer therapy.

Cyclohexenoneterpenes A-J: Cytotoxic meroterpenoids from mangrove-associated fungus Penicillium sp. N-5

Ten previously undescribed meroterpenoids, cyclohexenoneterpenes A-J (1-7, 18-20), together with 10 known analogues (8-17) were isolated from the mangrove-associated fungus Penicillium sp. N-5. Their structures were elucidated on the basis of extensive spectroscopic and mass spectrometric data. The absolute configurations of the undescribed compounds were assigned by electronic circular dichroism calculations, the modified Mosher's method, NMR calculations and DP4+ analysis. In the bioassay, compounds 10, 11, 15, and 20 exhibited cytotoxicities against SNB-19, MDA-MB-231, MDA-MB-435 and HCT-116 cell lines with IC50 values ranging from 1.4 to 19.1 μM.

Terpenoid balance in Aspergillus nidulans unveiled by heterologous squalene synthase expression

Filamentous fungi produce numerous uncharacterized natural products (NPs) that are often challenging to characterize due to cryptic expression in laboratory conditions. Previously, we have successfully isolated novel NPs by expressing fungal artificial chromosomes (FACs) from a variety of fungal species into Aspergillus nidulans. Here, we demonstrate a new twist to FAC utility wherein heterologous expression of a Pseudogymnoascus destructans FAC in A. nidulans altered endogenous terpene biosynthetic pathways. In contrast to wildtype, the FAC transformant produced increased levels of squalene and aspernidine type compounds, including three new nidulenes (1-2, 5), and lost nearly all ability to synthesize the major A. nidulans characteristic terpene, austinol. Deletion of a squalene synthase gene in the FAC restored wildtype chemical profiles. The altered squalene to farnesyl pyrophosphate ratio leading to synthesis of nidulenes and aspernidines at the expense of farnesyl pyrophosphate derived austinols provides unexpected insight into routes of terpene synthesis in fungi.

Functional analysis of a fungal P450 enzyme

Fungal cytochrome P450s participate in various physiological reactions, including the synthesis of internal cellular components, metabolic detoxification of xenobiotic compounds, and oxidative modification of natural products. Although functional analysis reports of fungal P450s continue to grow, there are still some difficulties as compared to prokaryotic P450s, because most of these fungal enzymes are transmembrane proteins. In this chapter, we will describe the methods for heterologous expression, in vivo analysis, enzyme preparation, and in vitro enzyme assays of the fungal P450 enzyme Trt6 and isomerase Trt14, which play important roles in the divergence of the biosynthetic pathway of terretonins, as a model for the functional analysis of fungal P450 enzymes.

Identification of new bisabosqual-type meroterpenoids reveals non-enzymatic conversion of bisabosquals into seco-bisabosquals

Bisabosqual-type meroterpenoids are fungi-derived polyketide-terpenoid hybrids bearing a 2,3,3a,3a1,9,9a-hexahydro-1H-benzofuro[4,3,2-cde]chromene skeleton (6/6/6/5 ring system) or its seco-C-ring structure, and exhibit diverse bioactivities. Their unique structural architecture and impressive biological activities have led to considerable interest in discovering new analogues. However, to date, only nine analogues have been identified. Herein, we reported the isolation and identification of six new bisabosqual-type meroterpenoids stachybisbins C-H (1-6), together with one known compound bisabosqual C (7), from Stachybotrys bisbyi PYH05-7. Intriguingly, we found that 7, which contains the intact tetracyclic skeleton, can be non-enzymatically converted into its seco derivative stachybisbin I (8), unveiling the biosynthetic relationship between bisabosquals and seco-bisabosquals. Moreover, based on CRISPR/Cas9-mediated gene disruption, we revealed that the three-gene cluster responsible for the formation of LL-Z1272β is associated with the biosynthesis of bisabosqual-type meroterpenoids, and then proposed a plausible route to 1-8.

The Outstanding Chemodiversity of Marine-Derived Talaromyces

Fungi in the genus Talaromyces occur in every environment in both terrestrial and marine contexts, where they have been quite frequently found in association with plants and animals. The relationships of symbiotic fungi with their hosts are often mediated by bioactive secondary metabolites, and Talaromyces species represent a prolific source of these compounds. This review highlights the biosynthetic potential of marine-derived Talaromyces strains, using accounts from the literature published since 2016. Over 500 secondary metabolites were extracted from axenic cultures of these isolates and about 45% of them were identified as new products, representing a various assortment of chemical classes such as alkaloids, meroterpenoids, isocoumarins, anthraquinones, xanthones, phenalenones, benzofurans, azaphilones, and other polyketides. This impressive chemodiversity and the broad range of biological properties that have been disclosed in preliminary assays qualify these fungi as a valuable source of products to be exploited for manifold biotechnological applications.

Seven new meroterpenoids from the fungus Penicillium sclerotiorum GZU-XW03-2

Seven previously undescribed meroterpenoids, peniscmeroterpenoids H - N (1-7), were isolated from the marine-derived fungus Penicillium sclerotiorum GZU-XW03-2. Their structures were established by the spectroscopic methods and the electronic circular dichroism (ECD) calculations. Peniscmeroterpenoid H was a 6/6/6/5/6 rearranged pentacyclic meroterpenoid, featuring a unique 2-oxaspiro[5.5] undeca-4,7-dien-3-one motif. Peniscmeroterpenoids I and J (2 and 3) owned rare 6(D)/5(E) fused rings were not common in natural products, and compound 2 was the second example of a berkeleyone analogue stripped of the methyl ester fragment. Peniscmeroterpenoid K (4) was the first case where the C-24 was oxidized. In bioassay, compound 5 showed moderate anti-inflammatory activity.

New meroterpenoids from a soil-derived fungus Penicillium sp. SSW03M2 GY and their anti-virulence activity

Two new berkeley meroterpenoids (1 and 2), along with seven known compounds (3‒9) were isolated from a fungus, Penicillium sp. SSW03M2 GY derived from a sediment at Seosan bay, South Korea. Chemical structures of the isolated compounds were elucidated on the basis of 1D, 2D NMR, HRESIMS, and optical rotation. All the isolated compounds, 1 showed anti-virulence activity by significantly inhibiting α-toxin (Hla) secreted by methicillin-resistant Staphylococcus aureus without its growth inhibition.

Late-stage cascade of oxidation reactions during the biosynthesis of oxalicine B in Penicillium oxalicum

Oxalicine B (1) is an α-pyrone meroterpenoid with a unique bispirocyclic ring system derived from Penicillium oxalicum. The biosynthetic pathway of 15-deoxyoxalicine B (4) was preliminarily reported in Penicillium canescens, however, the genetic base and biochemical characterization of tailoring reactions for oxalicine B (1) has remained enigmatic. In this study, we characterized three oxygenases from the metabolic pathway of oxalicine B (1), including a cytochrome P450 hydroxylase OxaL, a hydroxylating Fe(II)/α-KG-dependent dioxygenase OxaK, and a multifunctional cytochrome P450 OxaB. Intriguingly, OxaK can catalyze various multicyclic intermediates or shunt products of oxalicines with impressive substrate promiscuity. OxaB was further proven via biochemical assays to have the ability to convert 15-hydroxdecaturin A (3) to 1 with a spiro-lactone core skeleton through oxidative rearrangement. We also solved the mystery of OxaL that controls C-15 hydroxylation. Chemical investigation of the wild-type strain and deletants enabled us to identify 10 metabolites including three new compounds, and the isolated compounds displayed potent anti-influenza A virus bioactivities exhibiting IC₅₀ values in the range of 4.0-19.9 μmol/L. Our studies have allowed us to propose a late-stage biosynthetic pathway for oxalicine B (1) and create downstream derivatizations of oxalicines by employing enzymatic strategies.

Meroterpenoids from the fungus Penicillium sclerotiorum GZU-XW03-2 and their anti-inflammatory activity

Seven undescribed meroterpenoids, peniscmeroterpenoids A - G, were isolated from the marine-derived fungus Penicillium sclerotiorum GZU-XW03-2. Their structures were established by the spectroscopic methods and the electronic circular dichroism (ECD) calculations. Peniscmeroterpenoid A possessed an unprecedented and highly oxidized 6/7/6/5/5 pentacyclic system, featuring a unique tetrahydrofuro [2,3-b]furan-2(3H)-one motif. Peniscmeroterpenoids B - E owned rare 6(D)/5(E) fused rings were not common in natural products, and peniscmeroterpenoid E is the first example of a berkeleyone analogue stripped of the methyl ester fragment. In bioassays, peniscmeroterpenoids A and D inhibited the production of nitric oxide (NO) in RAW264.7 cells with IC₅₀ values of 26.60 ± 1.15 and 8.79 ± 1.22 μM. Moreover, peniscmeroterpenoid D significantly suppressed the production of pro-inflammatory mediators (COX-2, IL-1β and IL-6) and the protein expression of the enzyme iNOS.

Novel geranylhydroquinone derived meroterpenoids from the fungus Clitocybe clavipes and their cytotoxic activity

Three novel geranylhydroquinone derived meroterpenoids, named clavilactones J and K (1-2) and clavipol C (3), were isolated from the basidiomycete Clitocybe clavipes. Their structures were unambiguously identified by extensive spectroscopic data analysis, and the electronic circular dichroism (ECD) calculation, Gauge-Including Atomic Orbitals (GIAO) NMR calculations and Mo₂(OAc)₄-induced electronic circular dichroism experiments were used to establish their absolute configurations. Compound 1, with two epoxy groups located at the 10-membered carbocycle, is uncommon in the reported meroterpenoids from C. clavipes. All the obtained compounds (1-3) were tested for their cytotoxic activity against human tumor cell line HGC-27 by using the MTT assay. All the compounds exhibited moderate cytotoxic activities against HGC-27 cell with IC₅₀ values ranging from 33.5 to 56.6 μM.

FIP-nha, a fungal immunomodulatory protein from Nectria haematococca, induces apoptosis and autophagy in human gastric cancer cells via blocking the EGFR-mediated STAT3/Akt signaling pathway

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FIP-nha, a new FIP discovered beyond Basidiomycota, has been demonstrated a broad spectrum of antitumor activity and cell selectivity against human cancers.

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FIP-nha inhibited the growth, induced apoptosis and autophagy of gastric cancer cells through competitively binding to EGFR with EGF to blocking the EGFR-mediated STAT3/Akt pathway.

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FIP-nha may be a potential chemotherapy drug that targeted EGFR to treat human gastric cancer.

FIP-nha, a fungal immunomodulatory protein from Nectria haematococca, has been demonstrated a broad spectrum of antitumor activity and cell selectivity against human cancers in our previous study. However, the effect and mechanism of FIP-nha on gastric cancer remains unclear. In this study, we systematically observed the cytotoxicity, biological effect, regulatory mechanism and interaction target of FIP-nha on human gastric cancer cell lines, AGS and SGC7901. Our results demonstrated that FIP-nha inhibited the growth of AGS and SGC7901 cells in a dose-dependent manner and exerted proapoptotic effects on both cells as confirmed by flow cytometry, DAPI staining and western blot analysis. Additionally, the exposure of AGS and SGC7901 to FIP-nha induced autophagy as indicated by western blot analysis, GFP-LC3 and mCherry-GFP-LC3 transfection and acridine orange staining. Furthermore, we found that FIP-nha decreased the phosphorylation of EGFR, STAT3 and Akt and inhibited activation effect of ligand factor EGF to EGFR and its downstream signal molecule STAT3 and Akt. Finally, we proved that FIP-nha located on the surface of gastric cancer cells and bound directly to the transmembrane protein of EGFR by immunoprecipitation, cellular localization, molecular docking, microscale thermophoresis assay. The above findings indicated that FIP-nha inhibited the growth of gastric cancer and induced apoptosis and autophagy through competitively binding to EGFR with EGF to blocking the EGFR-mediated STAT3/Akt pathway. In summary, our study provided novel insights regarding the activity of FIP-nha against gastric cancer and contributed to the clinical application of FIP-nha as a potential chemotherapy drugs that targeted EGFR for human gastric cancer.

Scopariusicides D-M, ent-clerodane-based isomeric meroditerpenoids with a cyclobutane-fused γ/δ-lactone core from Isodon scoparius

Scopariusicides D-M (1-10), ten new ent-clerodane-based meroditerpenoids with a cyclobutane-fused γ/δ-lactone core, were isolated from Isodon scoparius. Their structures were determined by comprehensive analysis of spectroscopic data, single-crystal X-ray diffraction, chemical transformation, and TDDFT ECD calculation. A plausible biosynthetic pathway of 1-10 was proposed in which the asymmetrical cyclobutane ring was formed via a crossed "head-to-tail" intermolecular [2 + 2] cycloaddition in anti/syn facial approaches between an ent-clerodane lactone and a cis-4-hydroxycinnamic acid. Bioactivity evaluation manifested that 5 exhibited significant neuroprotective effect against corticosterone-induced injury in PC12 cells, while 6 and 7 exhibited moderate immunosuppressive activity against human T cell proliferation stimulated by anti-CD3/anti-CD28 mAb.

Cephaloliverols A and B, two sterol-hybrid meroterpenoids from Cephalotaxus oliveri

Cephaloliverols A (1) and B (2), two meroterpenoids based on a sterol and an abietane diterpene possessing a dioxane ring, were isolated from the twigs and leaves of Cephalotaxus oliveri. Their structures were established by spectroscopic analysis and quantum chemical calculation. 1 and 2 represent the first sterol-hybrid meroditerpenoids. The two compounds and their precursors decreased NO production in a dose-dependent manner in LPS-stimulated RAW 264.7 macrophages.

Osteoclastogenesis inhibitory phenolic derivatives produced by the Beibu Gulf coral-associated fungus Acremonium sclerotigenum GXIMD 02501

Three new chlorinated orsellinic aldehyde derivatives, orsaldechlorins A - C (1-3) and a naturally new brominated orsellinic acid (7), along with ten known biosynthetically related phenolic (4-6, 8-13) and cyclohexanone (14) derivatives, were identified from the Beibu Gulf coral-derived fungus Acremonium sclerotigenum GXIMD 02501. Their structures were determined by spectroscopic data interpretation and comparison with those reported in the literature. Several of them showed inhibition of lipopolysaccharide (LPS)-induced NF-κB activation in RAW 264.7 macrophages at 20 μM. Moreover, the two new potent inhibitors (1 and 2) suppressed RANKL-induced osteoclast differentiation without cytotoxicity in bone marrow macrophages cells (BMMs). Our findings reveal that the phenolic compounds could be potential candidates for the prevention and treatment of osteolytic bone diseases.

Anticancer activity of Neosetophomone B by targeting AKT/SKP2/MTH1 axis in leukemic cells

Neosetophomone B (NSP-B), a meroterpenoid fungal secondary metabolite, was investigated for its anticancer potential in leukemic cell lines (K562 and U937). NSP-B treatment of leukemic cells suppressed cell viability by triggering apoptotic cell death. Apoptosis induced by NSP-B is triggered by mitochondrial signaling and caspase activation. Additionally, NSP-B treatment of leukemic cells causes AKT's inactivation accompanied by downregulation of SKP2 oncogene and MTH1 with a concomitant increase of p21Cip1and p27Kip1. Furthermore, NSP-B causes suppression of antiapoptotic proteins, including cIAP1, cIAP2, XIAP, survivin and BCl-XL. Overall, NSP-B reduces cell viability by mitochondrial and caspase-dependent apoptosis. The inhibition of AKT and SKP2 axis could be a promising therapeutic target for leukemia treatment.

Biosynthesis of Fungal Natural Products Involving Two Separate Pathway Crosstalk

Fungal natural products (NPs) usually possess complicated structures, exhibit satisfactory bioactivities, and are an outstanding source of drug leads, such as the cholesterol-lowering drug lovastatin and the immunosuppressive drug mycophenolic acid. The fungal NPs biosynthetic genes are always arranged within one single biosynthetic gene cluster (BGC). However, a rare but fascinating phenomenon that a crosstalk between two separate BGCs is indispensable to some fungal dimeric NPs biosynthesis has attracted increasing attention. The hybridization of two separate BGCs not only increases the structural complexity and chemical diversity of fungal NPs, but also expands the scope of bioactivities. More importantly, the underlying mechanism for this hybridization process is poorly understood and needs further exploration, especially the determination of BGCs for each building block construction and the identification of enzyme(s) catalyzing the two biosynthetic precursors coupling processes such as Diels–Alder cycloaddition and Michael addition. In this review, we summarized the fungal NPs produced by functional crosstalk of two discrete BGCs, and highlighted their biosynthetic processes, which might shed new light on genome mining for fungal NPs with unprecedented frameworks, and provide valuable insights into the investigation of mysterious biosynthetic mechanisms of fungal dimeric NPs which are constructed by collaboration of two separate BGCs.

A Fungal Promiscuous UbiA Prenyltransferase Expands the Structural Diversity of Chrodrimanin-Type Meroterpenoids

Prenyltransferases play important roles in the diversification of natural products and the improvement of biological activities. A UbiA-type prenyltransferase CdnC with substrate promiscuity was identified as the pivotal builder of the noncanonical chrodrimanin skeletons, which carry a benzo-cyclohexanone structure as the nonterpene part. In vitro and heterologous expression studies with CdnC led to the production of a series of novel chrodrimanin-like structures. The discovery of CdnC offers a referable strategy for the biosynthesis and structural diversification of farnesyl-derived meroterpenoids.

Diterpenes Specially Produced by Fungi: Structures, Biological Activities, and Biosynthesis (2010–2020)

Fungi have traditionally been a very rewarding source of biologically active natural products, while diterpenoids from fungi, such as the cyathane-type diterpenoids from Cyathus and Hericium sp., the fusicoccane-type diterpenoids from Fusicoccum and Alternaria sp., the guanacastane-type diterpenoids from Coprinus and Cercospora sp., and the harziene-type diterpenoids from Trichoderma sp., often represent unique carbon skeletons as well as diverse biological functions. The abundances of novel skeletons, biological activities, and biosynthetic pathways present new opportunities for drug discovery, genome mining, and enzymology. In addition, diterpenoids peculiar to fungi also reveal the possibility of differing biological evolution, although they have similar biosynthetic pathways. In this review, we provide an overview about the structures, biological activities, evolution, organic synthesis, and biosynthesis of diterpenoids that have been specially produced by fungi from 2010 to 2020. We hope this review provides timely illumination and beneficial guidance for future research works of scholars who are interested in this area.

Talaromynoids A-I, Highly Oxygenated Meroterpenoids from the Marine-Derived Fungus Talaromyces purpureogenus SCSIO 41517 and Their Lipid Accumulation Inhibitory Activities

Nine new highly oxygenated 3,5-dimethylorsellinic acid-derived meroterpenoids, talaromynoids A-I (1-9), were isolated from the marine-derived fungus Talaromyces purpureogenus SCSIO 41517. Their structures including absolute configurations were elucidated by HRMS, NMR, single-crystal X-ray diffraction analysis, and electronic circular dichroism calculations. Compounds 1 and 7-9 possessed unprecedented 5/7/6/5/6/6, 6/7/6/6/6/5, 6/7/6/5/6/5/4, and 7/6/5/6/5/4 polycyclic systems, respectively. Biologically, compound 5 showed selective inhibitory activity against phosphatase CDC25B with an IC₅₀ value of 13 μM. Moreover, 7-9 and 12 exhibited the activity of reducing triglyceride in 3T3-L1 adipocytes in a dosage-dependent manner.

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.