Polyketide butenolide, diphenyl ether, and benzophenone derivatives from the fungus Aspergillus flavipes PJ03-11

Naturally Occurring Asterric Acid Analogs: Chemistry and Biology

Asterric acid and its analogs belong to diphenyl ethers (DPEs) with multiple substitutions on A/B aromatic rings. This member of DPEs originates from the polyketide pathway and displays a wide range of biological effects. Though the structures of asterric acid analogs are not complex, there were only more than 50 asterric acid analogs found in nature from 1960 to 2023. In this review, the structures, bioactivities, and biosynthesis of asterric acid analogs are summarized. More importantly, the empirical rule about the shielding effect of B-ring on H-6 is suggested, and this provides a convenient and useful way to analyze the NMR spectral data of asterric acid analogs, based on which the chemical shift values of the A-ring in some asterric acid analogs are revised.

Terricoxanthones A-E, unprecedented dihydropyran-containing dimeric xanthones from the endophytic fungus Neurospora terricola HDF-Br-2 associated with the vulnerable conifer Pseudotsuga gaussenii

An investigation on the secondary metabolites from a rice culture broth of the endophytic fungus Neurospora terricola HDF-Br-2 derived from the vulnerable conifer Pseudotsuga gaussenii led to the isolation and characterization of 34 structurally diverse polyketides (1-34). Seven of them are previously undescribed, including five unprecedented dihydropyran-containing (terricoxanthones A-E, 1-5, resp.) and one rare tetrahydrofuran-containing (terricoxanthone F, 6) dimeric xanthones. The structures were elucidated by spectroscopic methods and single-crystal X-ray diffraction analyses. Terricoxanthones each were obtained as a racemic mixture. Their plausible biosynthetic relationships were briefly proposed. Compounds 6, aspergillusone A (8), and alatinone (27) displayed considerable inhibition against Candida albicans with MIC values of 8-16 μg/mL. 4-Hydroxyvertixanthone (12) and 27 exhibited significant inhibitory activities against Staphylococcus aureus, with MIC values of 4-8 μg/mL. Furthermore, compounds 8 and 27 could disrupt biofilm of S. aureus and C. albicans at 128 μg/mL. The findings not only extend the skeletons of xanthone dimers and contribute to the diversity of metabolites of endophytes associated with the endangered Chinese conifer P. gaussenii, but could further reveal the important role of protecting plant species diversity in support of chemical diversity and potential sources of new therapeutics.

Aspercitrininone A, novel antibacterial polyketide featuring unusual spiral skeleton from Aspergillus cristatus

Aspercitrininone A (1), a novel polyketide featuring an unprecedented tetracyclic 6/6/6/5 spiral skeleton, was obtained from the rice fermentation cultures of the fungus Aspergillus cristatus together with five known compounds (2-6). Their structures were determined by HRESIMS data, 1D and 2D NMR spectroscopic analysis, and electronic circular dichroism (ECD) calculations. Aspercitrininone A was revealed as a new type of C/D cycle spiral structure and an unusual addition product of o-quinoid form citrinin with 2-methylterrefuranone. Compounds 1, 4, and 5 exhibited potent antibacterial activities with minimal inhibitory concentration (MIC) values from 13.2 to 67.3 μg/mL against four strains of human pathogenic bacteria in vitro.

Shielding Effects of Aromatic (Indole) Ring for Structural Analysis

This review provides a critical analysis of shielding effects induced by an aromatic (indole) ring of small molecules mainly including three members of naturally occurring secondary metabolites asterric acid analogs, diketopiperazines (DKPs) possessing an aromatic or an indole ring, and rubrolides. Empirical rules about the shielding effects induced by an aromatic (indole) ring are classified, based on which some 1H NMR chemical shift values in the A-ring and structures of asterric acid analogs are revised, and the relative configurations of some DKPs possessing an indole ring are also assigned or revised. The empirical rules could provide an efficient and convenient method for NMR data analysis and configuration determination for the three members of small molecules mentioned above.

Benzophenones-natural metabolites with great Hopes in drug discovery: structures, occurrence, bioactivities, and biosynthesis

Fungi have protruded with enormous development in the repository of drug discovery, making them some of the most attractive sources for the synthesis of bio-significant and structural novel metabolites. Benzophenones are structurally unique metabolites with phenol/carbonyl/phenol frameworks, that are separated from microbial and plant sources. They have drawn considerable interest from researchers due to their versatile building blocks and diversified bio-activities. The current work aimed to highlight the reported data on fungal benzophenones, including their structures, occurrence, and bioactivities in the period from 1963 to April 2023. Overall, 147 benzophenones derived from fungal source were listed in this work. Structure activity relationships of the benzophenones derivatives have been discussed. Also, in this review, a brief insight into their biosynthetic routes was presented. This work could shed light on the future research of benzophenones.

Hypoglycaemic Molecules for the Management of Diabetes Mellitus from Marine Sources

Diabetes mellitus (DM) is a chronic metabolic disorder recognized as a major health problem globally. A defective insulin activity contributes to the prevalence and expansion of DM. Treatment of DM is often hampered by limited options of conventional therapies and adverse effects associated with existing procedures. This has led to a spike in the exploration for potential therapeutic agents from various natural resources for clinical applications. The marine environment is a huge store of unexplored diversity of chemicals produced by a multitude of organisms. To date, marine microorganisms, microalgae, macroalgae, corals, sponges, and fishes have been evaluated for their anti-diabetic properties. The structural diversity of bioactive metabolites discovered has shown promising hypoglycaemic potential through in vitro and in vivo screenings via various mechanisms of action, such as PTP1B, α-glucosidase, α-amylase, β-glucosidase, and aldose reductase inhibition as well as PPAR alpha/gamma dual agonists activities. On the other hand, hypoglycaemic effect is also shown to be exerted through the balance of antioxidants and free radicals. This review highlights marine-derived chemicals with hypoglycaemic effects and their respective mechanisms of action in the management of DM in humans.

Metabolomic Analysis of Extracellular Vesicles from the Cereal Fungal Pathogen Fusarium graminearum

Fusarium graminearum (F. graminearum) is a filamentous fungus that infects cereals such as corn, wheat, and barley, with serious impact on yield as well as quality when the grain is contaminated with mycotoxins. Despite the huge impact of F. graminearum on food security and mammalian health, the mechanisms used by F. graminearum to export virulence factors during infection are not fully understood and may involve non-classical secretory pathways. Extracellular vesicles (EVs) are lipid-bound compartments produced by cells of all kingdoms that transport several classes of macromolecules and are implicated in cell-cell communication. EVs produced by human fungal pathogens carry cargo that facilitate infection, leading us to ask whether plant fungal pathogens also deliver molecules that increase virulence via EVs. We examined the metabolome of the EVs produced by F. graminearum to determine whether they carry small molecules that could modulate plant-pathogen interactions. We discovered that EVs from F. graminearum were produced in liquid medium-containing inducers of trichothecene production, but in lower quantities compared to other media. Nanoparticle tracking analysis and cryo-electron microscopy revealed that the EVs were morphologically similar to EVs from other organisms; hence, the EVs were metabolically profiled using LC-ESI-MS/MS. This analysis revealed that EVs carry 2,4-dihydroxybenzophenone (BP-1) and metabolites that have been suggested by others to have a role in host-pathogen interactions. BP-1 reduced the growth of F. graminearum in an in vitro assay, suggesting that F. graminearum might use EVs to limit metabolite self-toxicity.

Aspergetherins A-D, New Chlorinated Biphenyls with anti-MRSA Activity from the Marine Sponge Symbiotic Fungus Aspergillus terreus 164018

Aspergetherins A-D (1-4), four new chlorinated biphenyls, were isolated from the rice fermentation of a marine sponge symbiotic fungus Aspergillus terreus 164018, along with seven known biphenyl derivatives (5-11). The structures of four new compounds were determined by a comprehensive analysis of the spectroscopic data, including HR-ESI-MS and 2D NMR data. All 11 isolates were evaluated for their anti-bacterial activity against two strains of methicillin-resistant Staphylococcus aureus (MRSA). Among them, compounds 1, 3, 8 and 10 showed anti-MRSA activity with MIC values of 1.0-128 μg/mL. Preliminary structure-activity relationship analysis unveiled that both chlorinated substitution and esterification of 2-carboxylic acid could impact the antibacterial activity of biphenyls.

Polyketides as Secondary Metabolites from the Genus Aspergillus

Polyketides are an important class of structurally diverse natural products derived from a precursor molecule consisting of a chain of alternating ketone and methylene groups. These compounds have attracted the worldwide attention of pharmaceutical researchers since they are endowed with a wide array of biological properties. As one of the most common filamentous fungi in nature, Aspergillus spp. is well known as an excellent producer of polyketide compounds with therapeutic potential. By extensive literature search and data analysis, this review comprehensively summarizes Aspergillus-derived polyketides for the first time, regarding their occurrences, chemical structures and bioactivities as well as biosynthetic logics.

Molecular Networking and Cultivation Profiling Reveals Diverse Natural Product Classes from an Australian Soil-Derived Fungus Aspergillus sp. CMB-MRF324

This study showcases the application of an integrated workflow of molecular networking chemical profiling (GNPS), together with miniaturized microbioreactor cultivation profiling (MATRIX) to successfully detect, dereplicate, prioritize, optimize the production, isolate, characterize, and identify a diverse selection of new chemically labile natural products from the Queensland sheep pasture soil-derived fungus Aspergillus sp. CMB-MRF324. More specifically, we report the new tryptamine enamino tripeptide aspergillamides E-F (7-8), dihydroquinoline-2-one aflaquinolones H-I (11-12), and prenylated phenylbutyrolactone aspulvinone Y (14), along with an array of known co-metabolites, including asterriquinones SU5228 (9) and CT5 (10), terrecyclic acid A (13), and aspulvinones N-CR (15), B (16), D (17), and H (18). Structure elucidation was achieved by a combination of detailed spectroscopic and chemical analysis, biosynthetic considerations, and in the case of 11, an X-ray crystallographic analysis.

Bioactive pulvinones from a marine algicolous fungus Aspergillus terreus NTU243

Marine fungi are regarded as an under-explored source of structurally interesting and bioactive natural products with the potential to provide attractive lead compounds for drug discovery. In this study, several fungal strains were isolated from marine algae collected from the northeastern coast of Taiwan. In the preliminary antimicrobial screening against bacteria and fungi, the ethyl acetate extract of the fermented products of Aspergillus terreus NTU243 derived from a green alga Ulva lactuca was found to exhibit significant antimicrobial activities. Therefore, bioassay-guided separations of the active principle from liquid and solid fermented products of A. terreus NTU243 were undertaken, which resulted in the isolation and purification of 16 compounds. Their structures were elucidated by spectroscopic analysis to be four previously undescribed aspulvinones S-V as well as twelve known compounds. All the isolates were assessed for anti-inflammatory activity by measuring the amount of nitric oxide (NO) production in lipopolysaccharide (LPS)-induced BV-2 cells, and aspulvinone V, butyrolactone I, and (+)-terrein inhibited 45.0%, 34.5%, and 49.2% of NO production, respectively, at 10 μM concentration. Additionally, zymography showed that the conditioned medium of THP-1 cells post-LPS challenged significantly enhanced matrix metalloproteinase (MMP)-9-mediated gelatinolysis, and pretreatment with aspulvinones U and V significantly attenuated MMP-9-mediated gelatinolysis by 56.0% and 67.8%, separately.

γ-Aromatic Butenolides of Microbial Source - A Review of Their Structures, Biological Activities and Biosynthesis

γ-Aromatic butenolides (γ-AB) are an important type of structures found in many bioactive microbial secondary metabolites (SMs). γ-AB refer to a group of natural products (NPs) containing five-membered (unsaturated) lactones with 3-phenyl and 4-benzyl substituents. Their wide-range biological activities have inspired pharmaceutical chemists to explore its biosynthesis mechanisms and design strategies to construct the γ-AB skeleton. Recently, there are a great deal of interesting research progress on the structures, biological activities and biosynthesis of γ-AB. This review will focus on these aspects and summarize the important achievements of γ-AB from 1975 to 2021.

Isolation and acetylcholinesterase inhibitory activity of asterric acid derivatives produced by Talaromyces aurantiacus FL15, an endophytic fungus from Huperzia serrata

Alzheimer's disease (AD) is a neurodegenerative disease and the fourth leading cause of death after cardiovascular disease, tumors, and stroke. Acetylcholinesterase (AChE) inhibitors, which are based on cholinergic damage, remain the mainstream drugs to alleviate AD-related symptoms. This study aimed to explore novel AChE inhibitors produced by the endophytic fungus FL15 from Huperzia serrata. The fungus was identified as Talaromyces aurantiacus FL15 according to its morphological characteristics and ITS, 18S rDNA, and 28S rDNA sequence analysis. Subsequently, seven natural metabolites were isolated from strain FL15, and identified as asterric acid (1), methyl asterrate (2), ethyl asterrate (3), emodin (4), physcion (5), chrysophanol (6), and sulochrin (7). Compounds 1-3, which possess a diphenyl ether structure, exhibited highly selective and moderate AChE inhibitory activities with IC₅₀ values of 66.7, 23.3, and 20.1 μM, respectively. The molecular docking analysis showed that compounds 1-3 interacted with the active catalytic site and peripheral anionic site of AChE, and the esterification substitution groups at position 8 of asterric acid may contribute to its bioactivity. The asterric acid derivatives showed highly selective and moderate AChE inhibitory activities, probably via interaction with the peripheral anionic site and catalytic site of AChE. To the best of our knowledge, this study was the first report of the AChE inhibitory activity of asterric acid derivatives, which opens new perspectives for the design of more effective derivatives that could serve as a drug carrier for new chemotherapeutic agents to treat AD.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-022-03125-2.

7-Hydroxy questin, a new anthraquinone from a wetland fungus Aspergillus flavipes PJ03-11

One new anthraquinone, questinlin (1), four known anthraquinones (2-5), together with three known benzophenone derivatives (6-8) were isolated from a wetland fungus Aspergillus flavipes PJ03-11. Their structures were elucidated on the basis of detailed spectroscopic analysis, including 1D, 2D NMR (HMQC, HMBC), mass spectrometry, and optical rotation and IR spectra. In addition, the cytotoxic activities against three human cancer cell lines (HepG2, Caco-2 and A549) were evaluated. In this article, Aspergillus flavipes PJ03-11, a wetland soil fungus isolated from Honghaitan, Panjin city, Liaoning province, was used to study the secondary metabolites through one strain many compounds (OSMAC) methods. By changing the culture medium and adding the substance stimulating the metabolism of the strain into the fermentation medium, the peak type and amount of ethyl acetate extract in the fermentation medium were studied by HPLC. Finally, 2 mM MgCl₂ was added into the rice solid medium for the expansion fermentation.

Aspulvinones Suppress Postprandial Hyperglycemia as Potent α-Glucosidase Inhibitors From Aspergillus terreus ASM-1

Chemical investigation of Aspergillus terreus ASM-1 fermentation resulted in the isolation of three new prenylated aspulvinones V–X (1–3), together with the previously reported analogs, aspulvinone H (4), J-CR (5), and R (6). Their structures were elucidated by various spectroscopic methods including HRESIMS and NMR, and the absolute configurations of 2 and 3 were determined by ECD comparison. Compounds 1–6 were evaluated for α-glucosidase inhibitory effects with acarbose as positive control. As a result, compounds 1 and 4 exhibited potent α-glucosidase inhibitory activities with IC₅₀ values of 2.2 and 4.6 µM in mixed-type manners. The thermodynamic constants recognized the interaction between inhibitors and α-glucosidase was hydrophobic force-driven spontaneous exothermic reaction. The CD spectra also indicate that the compounds 1 and 4 changed the enzyme conformation. Furthermore, compound 4 significantly suppressed the increases in postprandial blood glucose levels in the C57BL/6J mice.

Prenylated phenylbutyrolactones from cultures of a marine sponge-associated fungus Aspergillus flavipes KUFA1152

Four undescribed prenylated phenylbutyrolactones, aspulvinones R, S, T and U, were isolated together with the previously reported aspulvinones A, B', H and 4-hydroxy-3,5-bis(3-methylbut-2-en-1-yl)benzaldehyde, from cultures of the marine sponge-derived fungus Aspergillus flavipes KUFA1152. The structures of the undescribed compounds were established on the basis of extensive analysis of 1D and 2D NMR and HRMS spectra. In the case of aspulvinone T, the absolute configuration of its stereogenic carbon was established by comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. The structure of the previously reported compounds were elucidated by 1D and 2D NMR analysis as well as comparison of their ¹H or/and ¹³C NMR data with those reported in the literature. Aspulvinones B', H, R, S, T and a mixture of aspulvinones A and U exhibited antibacterial activity against reference strains and multidrug-resistant isolates from the environment as well as capacity to inhibit biofilm formation in the reference strains. However, none of the tested compounds showed potential synergy with clinically relevant antibiotics on multidrug-resistant isolates.

17-Hydroxybrevianamide N and Its N1-Methyl Derivative, Quinazolinones from a Soft-Coral-Derived Aspergillus sp. Fungus: 13S Enantiomers as the True Natural Products

Under the guidance of MS/MS-based molecular networking and HPLC-UV, two new alkaloid racemates, (±)-17-hydroxybrevianamide N (1) and (±)-N1-methyl-17-hydroxybrevianamide N (2), featuring a rare o-hydroxyphenylalanine residue and an imide subunit, were isolated from a soft-coral-derived Aspergillus sp. fungus. The true natural products (+)-1 and (+)-2 were further monitored and obtained from the freshly prepared EtOAc extracts, while (-)-1 and (-)-2 are artifacts generated during extraction and purification processes. Simultaneously, the structures including absolute configurations of (+)-13S-1, (-)-13R-1, (+)-13S-2, and (-)-13R-2 were elucidated on the basis of comprehensive spectroscopic analysis, ECD calculations, and X-ray diffraction data. Interestingly, basic solution promotes the racemization of (+)-1 and (-)-1, whereas acidic solution suppresses the transformation. The current research was concerned with the true natural products and their artifacts, providing critical insight into the isolation and identification of natural products.

New butyrolactone derivatives from the endophytic Fungus Talaromyces sp. CPCC 400783 of Reynoutria japonica Houtt

Six new butyrolactone derivatives (1, 2a/2b, 3a/3b and 4), together with another two known derivatives (5 and 6) were isolated from the endophytic fungus Talaromyces sp. CPCC 400783. Their structures were established by a combination of spectroscopic analysis, including NMR and HRESIMS. The absolute configurations were elucidated by ECD experiments. Subsequently, compound 1, 3b, 4 and 5 exhibited good inhibitory effect against influenza A/WSN/33 (H1N1) virus with IC₅₀ values of 21.93 ± 1.51, 21.54 ± 3.75, 18.36 ± 2.15 and 23.80 ± 3.05 μM respectively.

Expedient Discovery for Novel Antifungal Leads Targeting Succinate Dehydrogenase: Pyrazole-4-formylhydrazide Derivatives Bearing a Diphenyl Ether Fragment

The pyrazole-4-carboxamide scaffold containing a flexible amide chain has emerged as the molecular skeleton of highly efficient agricultural fungicides targeting succinate dehydrogenase (SDH). Based on the above vital structural features of succinate dehydrogenase inhibitors (SDHI), three types of novel pyrazole-4-formylhydrazine derivatives bearing a diphenyl ether moiety were rationally conceived under the guidance of a virtual docking comparison between bioactive molecules and SDH. Consistent with the virtual verification results of a molecular docking comparison, the in vitro antifungal bioassays indicated that the skeleton structure of title compounds should be optimized as an N'-(4-phenoxyphenyl)-1H-pyrazole-4-carbohydrazide scaffold. Strikingly, N'-(4-phenoxyphenyl)-1H-pyrazole-4-carbohydrazide derivatives 11o against Rhizoctonia solani, 11m against Fusarium graminearum, and 11g against Botrytis cinerea exhibited excellent antifungal effects, with corresponding EC₅₀ values of 0.14, 0.27, and 0.52 μg/mL, which were obviously better than carbendazim against R. solani (0.34 μg/mL) and F. graminearum (0.57 μg/mL) as well as penthiopyrad against B. cinerea (0.83 μg/mL). The relative studies on an in vivo bioassay against R. solani, bioactive evaluation against SDH, and molecular docking were further explored to ascertain the practical value of compound 11o as a potential fungicide targeting SDH. The present work provided a non-negligible complement for the structural optimization of antifungal leads targeting SDH.

Goodyschle A, a new butenolide with significant BchE inhibitory activity from Goodyera schlechtendaliana

Goodyschle A (1), a new butenolide, was isolated from the whole grass of Goodyera schlechtendaliana, an orchidaceous edible medicinal plant. The structure of the new compound was elucidated by 1 D and 2 D NMR experiments in addition to HRESIMS analyses. Compound 1 was evaluated for its bioactivities including cytotoxic activity against human gastric cancer (SGC-7901) and human hepatocellular carcinoma (HepG2) cell lines, inhibitory activity on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), and DPPH radical scavenging activity. As a result, compound 1 showed potent BChE inhibitory activity (IC₅₀ value = 6.88 ± 1.63 μM), moderate DPPH radical scavenging activity (IC₅₀ value = 16.25 ± 0.21 μM), and slight AChE inhibitory and cytotoxic activities. These findings suggest that compound 1 is worthy for further investigations in terms of its selective BChE inhibitory activity.

Butyrolactone-I, an efficient α-glucosidase inhibitor, improves type 2 diabetes with potent TNF-α-lowering properties through modulating gut microbiota in db/db mice

The aim of this study was to evaluate the effects of butyrolactone-I (A6) on type 2 diabetes (T2D) in db/db mice because A6 was found to inhibit α-glucosidase activities and TNF-α release, which were associated with improving T2D. Male db/db mice were divided into 6 groups and given an equivalent volume of olive oil, acarbose, or different doses of A6 for 4 wk (n = 8/group). In this study, 11 butenolide derivatives were screened for their α-glucosidase and TNF-α suppressive activity in vitro. A6, an efficient α-glucosidase inhibitor, exerts hypoglycemic and multiple activities in reducing weight, improving glucose tolerance and insulin resistance, increasing short-chain fatty acid (SCFA) levels, activating SCFA-induced increases in glucagon-like peptide 1 and peroxisome proliferator-activated receptor-γ expression, enhancing intestinal mucosal barrier function and mitigating endoxemia in db/db mice. These effects may result from mediation of gut microbiota by A6. Meanwhile, A6, with potent TNF-α-lowering properties, was demonstrated to have multiple salutary effects with excellent structural stability and long-term safety in vivo. A6, an effective α-glucosidase inhibitor with high security and stability, exerted potent antidiabetic effects in vivo. Furthermore, the modulation of gut microbiota of A6 was demonstrated to be one of the mechanisms contributing to anti-inflammation properties and improving endoxemia. Our work confirms that the compound A6 is a prospective drug candidate for T2D.-Wu, W., Liu, L., Zhu, H., Sun, Y., Wu, Y., Liao, H., Gui, Y., Li, L., Liu, L., Sun, F., Lin, H. Butyrolactone-I, an efficient α-glucosidase inhibitor, improves type 2 diabetes with potent TNF-α-lowering properties through modulating gut microbiota in db/db mice.

2-Methyl-versiquinazoline C, a new fumiquinazoline-type alkaloid from the fungus Aspergillus flavipes PJ03-11

A new fumiquinazoline-type alkaloid 2-methyl-versiquinazoline C (1), together with six known compounds (2-7), was isolated from Aspergillus flavipes PJ03-11 using OSMAC method. Their structures were elucidated on the basis of extensive spectroscopic analysis, and the absolute configuration of compound 1 was determined by the experimental and calculated ECD data. In addition, the cytotoxic activities against three human cancer cell lines (HL-60, THP-1, and PC-3) were evaluated.

Two new secondary metabolites from the mangrove endophytic fungus Pleosporales sp. SK7

Two new compounds, an abscisic acid-type sesquiterpene (1), and one asterric acid derivative (2), together with three known compounds (3-5) were isolated from mangrove endophytic fungus Pleosporales sp. SK7. The structures of these metabolites were determined by NMR, X-ray crystal diffraction, CD and HR-ESI-MS. All compounds were tested for their antibacterial, antioxidant and cytotoxic activities, among these compounds, 5 showed cytotoxicity against MDA-MB-435 cell with an IC₅₀ of 25.96 ± 0.32 μM.

Anti-Hyperuricemic Effect of 2-Hydroxy-4-methoxy-benzophenone-5-sulfonic Acid in Hyperuricemic Mice through XOD

Conventionally, benzophenone-type molecules are beneficial for alleviating the UV exposure of humans. More importantly, various compounds with this skeleton have demonstrated various biological activities. In this paper, we report the anti-hyperuricemic effect of the benzophenone compound 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (HMS). Preliminarily, its molecular docking score and xanthine oxidase (XOD) inhibition suggested a good anti-hyperuricemic effect. Then, its anti-hyperuricemic effect, primary mechanisms and general toxicity were examined on a hyperuricemic mouse model which was established using potassium oxonate and hypoxanthine together. HMS demonstrated a remarkable anti- hyperuricemic effect which was near to that of the control drugs, showing promising perspective. General toxicity was assessed and it showed no negative effects on body weight growth and kidney function. Moreover, anti-inflammatory action was observed for HMS via spleen and thymus changes. Its anti-hyperuricemic mechanisms may be ascribed to its inhibition of XOD and its up-regulation of organic anion transporter 1 (OAT1) and down-regulation of glucose transporter 9 (GLUT9).

Asperidines A-C, pyrrolidine and piperidine derivatives from the soil-derived fungus Aspergillus sclerotiorum PSU-RSPG178

One new pyrrolidine derivative, asperidine A (1), and two new piperidine derivatives, asperidines B (2) and C (3), were isolated from the soil-derived fungus Aspergillus sclerotiorum PSU-RSPG178 together with two known alkaloids. Compound 3 possessed an unprecedented 7-oxa-1-azabicyclo[3.2.1]octane skeleton with four chiral centers. Their structures were determined by spectroscopic evidence. The absolute configurations of compounds 2 and 3 were established using Mosher's method and further confirmed for compound 3 by X-ray crystallographic data. Compound 2 dose-dependently inhibited the CFTR-mediated chloride secretion in T84 cells with an IC₅₀ value of 0.96 μM whereas 3 displayed the same activity with the IC₅₀ value of 58.62 μM. Compounds 2 and 3 also significantly reduced intracellular ROS under both normal and H₂O₂-treated conditions compared with their respective controls in a dose-dependent manner without cytotoxic effect on Caco-2 cells. In addition, compound 3 was inactive against noncancerous Vero cells whereas compound 2 was considered to be inactive with the IC₅₀ value of >10 μM.

Sporulosol, a New Ketal from the Fungus Paraconiothyrium sporulosum

Sporulosol (1), a new ketal, together with four known compounds, has been isolated from the liquid fermentation cultures of a wetland-soil-derived fungus, Paraconiothyrium sporulosum. Its structure was elucidated primarily by NMR experiments, and was further confirmed by X-ray crystallography. Sporulosol was obtained as a racemic mixture and the resolved two enantiomers racemized immediately after chiral separation. Sporulosol appears to be the first ketal derived from a 6H-benzo[c]chromen-6-one and a benzofuranone unit. The compound showed modest cytotoxicity toward the human tumor cell line T24, with an IC₅₀ value of 18.2 µM.

Natural Products Research in China From 2015 to 2016

This review covers the literature published by chemists from China during the 2015-2016 on natural products (NPs), with 1,985 citations referring to 6,944 new compounds isolated from marine or terrestrial microorganisms, plants, and animals. The emphasis is on 730 new compounds with a novel skeleton or/and significant bioactivity, together with their source organism and country of origin.

Functionalization of diazotetronic acid and application in a stereoselective modular synthesis of pulvinone, aspulvinones A–E, G, Q and their analogues

Diastereoselective aldol condensation of diazotetronic acid and a subsequent arene C–H insertion provides an efficient route to the aspulvinone motif.

New butenolide derivatives from the marine sponge-derived fungus Aspergillus terreus

Two new butenolide derivatives (±)-asperteretal D ((±)-1) and asperteretal E (2) containing rare 2-benzyl-3-phenyl substituted lactone core, together with nine known analogues (3-11) were obtained from a fungus Aspergillus terreus derived from the marine sponge Phakellia fusca. All the structures were elucidated on the basis of extensive NMR spectroscopic data. The chiral chromatography analyses allowed the separation of the (±)-asperteretal D, of which the absolute configurations were determined by comparing the experimental to calculated electronic circular dichroic (ECD) spectra. Compounds (±)-1, 2-5, and 7 exhibited potent inhibitory activities against α-glucosidase with IC₅₀ values ranging from 8.65 to 20.3 µM (positive control acarbose with an IC₅₀ value of 320 µM). In addition, derivatives 5-8 also showed moderate antioxidant activities.

Metabolites from the Plant Endophytic Fungus Aspergillus sp. CPCC 400735 and Their Anti-HIV Activities

Thirty-three metabolites including five phenalenone derivatives (1-5), seven cytochalasins (6-12), thirteen butenolides (13-25), and eight phenyl derivatives (26-33) were isolated from Aspergillus sp. CPCC 400735 cultured on rice. The structures of all compounds were elucidated by NMR, MS, and CD experiments, of which 1-5 (asperphenalenones A-E), 6 (aspochalasin R), and 13 (aspulvinone R) were identified as new compounds. Specifically, asperphenalenones A-E (1-5) represent an unusual structure composed of a linear diterpene derivative linked to a phenalenone derivative via a C-C bond. Compounds 1, 4, 10, and 26 exhibited anti-HIV activity with IC₅₀ values of 4.5, 2.4, 9.2, and 6.6 μM, respectively (lamivudine 0.1 μM; efavirenz, 0.4 × 10^-3 μM).

Isolation and structure elucidation of a new compound from the fungus Aspergillus flavipes PJ03-11

A new diphenyl ether 3-methylpentyl-2, 4-dichloroasterrate (2), along with a known diphenyl ether butyl 2, 4-dichloroasterrate (1) were isolated from the metabolites of a wetland fungus Aspergillus flavipes. PJ03-11. The structures of 1 and 2 were determined by extensive NMR and HR-ESI-MS experiments. Compounds 1 and 2 showed weak cytotoxic activity, but both of them showed no antimicrobial activity.

γ-Butyrolactones from Aspergillus Species: Structures, Biosynthesis, and Biological Activities

Recently, numerous metabolites possessing uncommon structures and potent bioactivity have been isolated from strains of fungi collected from diverse environments. The genus Aspergillus is known as a rich source of γ-butyrolactones. These are a group of fungal secondary metabolites, consisting of a five-membered lactone bearing two aromatic rings, which shows a great variety of biological activities. This review summarizes the research on the biosynthesis, source, and biological activities of the naturally occurring γ-butyrolactones that have been isolated from Aspergillus species published over the last decades. More than 75 compounds are described and 65 references are cited.

α-Glucosidase Inhibitors from the Marine-Derived Fungus Aspergillus flavipes HN4-13

Three new butenolide derivatives, flavipesolides A-C (1-3), along with 13 known compounds (4-13, aspulvinone Q, monochlorosulochrin, and dihydrogeodin), were isolated from the marine-derived Aspergillus flavipes HN4-13 from a Lianyungang coastal sediment sample. The structures were elucidated by spectroscopic evidence. Compounds 4-6 and 9 were noncompetitive α-glucosidase inhibitors with K_i/IC₅₀ values of 0.43/34, 2.1/37, 0.79/19, and 2.8/90 μM, respectively. Compounds 1-3, 8, 10, and 13 are mixed α-glucosidase inhibitors with K_i/IC₅₀ values of (2.5, 19)/44, (3.4, 14)/57, (9.2, 4.7)/95, (6.3, 5.5)/55, (1.4, 0.60)/9.9, and (2.5, 7.2)/33 μM, respectively (IC₅₀ 101 μM for acarbose and 79 μM for 1-deoxynojirimycin).

Benzophenones from Mango Leaves Exhibit α-Glucosidase and NO Inhibitory Activities

Mango (Mangifera indica L.) is a succulent tropical fruit. Bioactive phytochemical investigation has been carried out to the leaves of mango. Three new benzophenone glycosides, along with 14 known compounds, were purified and identified. The novel benzophenones were elucidated to be 2,4,4',6-tetrahydroxy-3'-methoxybenzophenone-3-C-β-d-glucopyranoside (1), 4,4',6-trihydroxybenzophenone-2-O-α-l-arabinofuranoside (7), and 4',6-dihydroxy-4-methoxybenzophenone-2-O-(2″),3-C-(1″)-1″-desoxy-α-l-fructofuranoside (11). The α-glucosidase inhibitory, NO production inhibitory, and antioxidant activities were assessed for the purified benzophenones and triterpenoids. Some benzophenones showed moderate α-glucosidase and NO inhibitory activities. The IC₅₀ value of the α-glucosidase inhibitory of isolated compounds 1, 13, and 14 were 284.93 ± 20.29, 239.60 ± 25.00, and 297.37 ± 8.12 μM, respectively. Most compounds showed moderate effects to reduce the NO content in 50 and 100 μM. The above results of bioactivity powerfully demonstrated the phytochemicals from mango, especially benzophenones, probably partially rational for its antidiabetes and anti-inflammatory.