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Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products Chemistry".

Deadline for manuscript submissions: closed (30 December 2020) | Viewed by 31648

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Dr. Vincenzo Piccialli

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Department of Chemical Sciences, University of Naples Federico II, Via Cinthia 4, 80126 Naples, Italy
Interests: organic and medicinal chemistry; organic synthesis; catalytic oxidative processes; marine natural products; nucleosides chemistry
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Prof. Dr. Wenhan Lin

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State Key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing 100191, China
Interests: bioactive metabolites derived from marine organisms (sponges and corals); marine mangrove plants and their associated microorganisms
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

Prof. Dr. Peter Proksch is an eminent chemist of marine natural product chemistry. Throughout his career, he devoted over 20 years of his life to researching and teaching at the Heinrich Heine University in Düsseldorf, and his research interests cover marine chemical ecology, bioactive natural compounds with unique structures derived from marine macro- and micro-organisms, OSMAC and co-culture of marine-derived fungi to activate the silent biosynthetic pathways, and the mode of actions of bioactive compounds. He engaged in the field of bioactive marine natural substances, which have potential for pharmaceutical and agriculture applications. At the early stage of his research career, he focused on marine invertebrates such as sponges and corals, which are regarded to be unique sources of chemical entities with potential bioactivities that could lead to potential new drug candidates and serve as a powerful chemical defense against a multitude of natural enemies and competitors. His research group is very productive, working on numerous bioactive compounds from benthic organisms inhabiting different ocean locations. Representative works include his discovery of sponge-derived brominated isoxazoline alkaloids and amide dienon that enzymatically converted from aeroplysinin-1 in the wounded sponge showing pronounced antibiotic activity against many Gram-positive and Gram-negative marine bacteria; brominated bastadins protecting sponges from overgrowth by fouling organisms such as barnacles and mollusks; and dibromohemibastadin (DBHB) preventing fouling by barnacles or mussels through inhibition of a phenoloxidase in the marine environment. In the last few decades prior to his retirement, he explored marine-derived fungi as sources of bioactive natural products due to the fact that many bioactive compounds isolated from sponges or other marine invertebrates are in fact of microbial origins and live within multicellular hosts, and he uncovered diverse fungi-derived new natural products with potent bioactivities, such as fungus-derived chlorflavonin as a new antibacterial agent and new inhibitor of tuberculosis pathogen and multiresistant strains with a new mode of action, phomoxanthone A provoking apoptosis in various tumor cell lines including platin-resistant cells, atropisomeric dihydroanthracenones as the inhibitors of multiresistant Staphylococcus aureus, and embellicine A as a novel NF-κB inhibitor. Further, he focused on the effect of microbial cross-talk on natural product accumulation and developed a microbial co-cultivation methodology to induce cryptic natural products and on the enhancement of constitutive present metabolites compared to axenic cultures. Prof. Proksch supervised more than 80 international doctoral students and published more than 600 peer-review original publications, review articles, and book chapters.

Prof. Dr. Peter Proksch was born in Leipzig in 1953, and studied biology in Cologne, where he received his doctorate, Master, and Bachelor in 1975–1980. After a research stay for two years (1980–1982) as a postdoctoral fellow at the University of California in Irvine (USA), he got a position as an assistant professor habilitated in the field of biology and pharmaceutical biology at the University of Cologne and at the Technical University of Braunschweig in 1982–1989. He was employed as an associate professor for pharmaceutical biology at the University of Würzburg (1990–1999), and then he was promoted as a full professor and a head of the Institute for Pharmaceutical Biology and Biotechnology at Heinrich Heine University Düsseldorf (Germany) until his retirement. Prof. Peter Proksch extended broad international collaborations to help scientists, especially in Asian countries including China, Indonesia, Vietnam, India, and Nigeria. Based on his excellent contribution in the marine natural product science and the international cooperation, he was given the National Friendship Award of the PRC (China) in 2016, the Qilu Friendship Award of Shandong Province (China) in 2014, the Coconut Island Commemorative Award (China) in 2017, an Honorary Doctorate from the University of Abuja (Nigeria) in 2017, a Commemorative Medal of the Vietnamese Academy of Sciences (Vietnam) in 2008, and the First Prize Inventor Award (North-Rhine Westfalia, Germany) in 2008. He has also received an Honorary Professorship of the Three Gorges University (China) (2015) and the Chinese Academy of Tropical Agricultural Science (2016),

Molecules is very pleased to host a Special Issue in honor of Prof. Peter Proksch for his excellent research contribution, and we invite scientists to submit original contributions to “Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career”.

Prof. Dr. Vincenzo Piccialli
Prof. Dr. Wenhan Lin
Guest Editors

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Published Papers (11 papers)

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Research

14 pages, 1781 KiB

Open AccessArticle

Anti-Inflammatory, Antiallergic, and COVID-19 Main Protease (M^pro) Inhibitory Activities of Butenolides from a Marine-Derived Fungus Aspergillus terreus

by Ibrahim Seyda Uras, Sherif S. Ebada, Michal Korinek, Amgad Albohy, Basma S. Abdulrazik, Yi-Hsuan Wang, Bing-Hung Chen, Jim-Tong Horng, Wenhan Lin, Tsong-Long Hwang and Belma Konuklugil

Molecules 2021, 26(11), 3354; https://doi.org/10.3390/molecules26113354 - 02 Jun 2021

Cited by 12 | Viewed by 3374

Abstract

In December 2020, the U.K. authorities reported to the World Health Organization (WHO) that a new COVID-19 variant, considered to be a variant under investigation from December 2020 (VUI-202012/01), was identified through viral genomic sequencing. Although several other mutants were previously reported, VUI-202012/01 proved to be about 70% more transmissible. Hence, the usefulness and effectiveness of the newly U.S. Food and Drug Administration (FDA)-approved COVID-19 vaccines against these new variants are doubtfully questioned. As a result of these unexpected mutants from COVID-19 and due to lack of time, much research interest is directed toward assessing secondary metabolites as potential candidates for developing lead pharmaceuticals. In this study, a marine-derived fungus Aspergillus terreus was investigated, affording two butenolide derivatives, butyrolactones I (1) and III (2), a meroterpenoid, terretonin (3), and 4-hydroxy-3-(3-methylbut-2-enyl)benzaldehyde (4). Chemical structures were unambiguously determined based on mass spectrometry and extensive 1D/2D NMR analyses experiments. Compounds (1–4) were assessed for their in vitro anti-inflammatory, antiallergic, and in silico COVID-19 main protease (M^pro) and elastase inhibitory activities. Among the tested compounds, only 1 revealed significant activities comparable to or even more potent than respective standard drugs, which makes butyrolactone I (1) a potential lead entity for developing a new remedy to treat and/or control the currently devastating and deadly effects of COVID-19 pandemic and elastase-related inflammatory complications. Full article

(This article belongs to the Special Issue Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career)

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17 pages, 4234 KiB

Open AccessArticle

Crassolide Suppresses Dendritic Cell Maturation and Attenuates Experimental Antiphospholipid Syndrome

by Chi-Chien Lin, Yu-Kang Chang, Shih-Chao Lin, Jui-Hsin Su, Ya-Hsuan Chao and Kuo-Tung Tang

Molecules 2021, 26(9), 2492; https://doi.org/10.3390/molecules26092492 - 24 Apr 2021

Cited by 8 | Viewed by 2087

Abstract

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by the production of β2-glycoprotein I (β2GPI)-dependent autoantibodies, with vascular thrombosis or obstetrical complications. Around 20% of APS patients are refractory to current treatments. Crassolide, a cembranoid diterpene extracted from soft corals, is a potential therapeutic candidate. Here, to examine the anti-inflammatory properties of crassolide, we first determined its effects on bone marrow-derived and splenic dendritic cells (DC). Specifically, we applied lipopolysaccharide (LPS) or β2GPI stimulation and measured the expressions of CD80 and CD86, and secretions of cytokines. We also determined in the OT-II mice, if bone marrow-derived DC was able to stimulate antigen-specific T cells. Moreover, we examined the therapeutic potential of crassolide postimmunization in a murine model of APS that depended on active immunization with β2GPI. The vascular manifestations were evaluated in terms of fluorescein-induced thrombi in mesenteric microvessels, whereas the obstetric manifestations were evaluated based on the proportion of fetal loss after pregnancy. We also measured blood titers of anti-β2GPI antibody, splenic cell proliferative responses and cytokine secretions after β2GPI stimulation ex vivo. Finally, we determined in these mice, hematological, hepatic and renal toxicities of crassolide. Crassolide after LPS stimulation suppressed DC maturation and secretion of tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-12 and IL-23, and downstream T cell activation. Crassolide could partially ameliorate both the vascular and obstetric manifestations of APS in BALB/c mice. Both blood titers of anti-β2GPI antibody and splenic cell proliferation after β2GPI stimulation were reduced. Splenic Th1 and Th17 responses were also lowered after β2GPI stimulation. Finally, within therapeutic doses of crassolide, we found no evidence of its toxicity. In conclusion, we showed the ability of crassolide to suppress DC and downstream T cell responses. Crassolide is therefore a potential candidate for adjunctive therapy in APS. Full article

(This article belongs to the Special Issue Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career)

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8 pages, 1387 KiB

Open AccessArticle

Generation of Unusual Aromatic Polyketides by Incorporation of Phenylamine Analogues into a C-Ring-Cleaved Angucyclinone

by Hua Xiao, Guiyang Wang, Zhengdong Wang, Yi Kuang, Juan Song, Jing Jin, Min Ye, Donghui Yang and Ming Ma

Molecules 2021, 26(7), 1959; https://doi.org/10.3390/molecules26071959 - 31 Mar 2021

Viewed by 1594

Abstract

Angucyclinones are aromatic polyketides that possess impressive structural diversity and significant biological activities. The structural diversity of these natural products is attributed to various enzymatic or nonenzymatic modifications on their tetracyclic benz(a)anthracene skeleton. Previously, we discovered an unusual phenylamine-incorporated angucyclinone (1) from a marine Streptomyces sp. PKU-MA00218, and identified that it was produced from the nonenzymatic conversion of a C-ring-cleaved angucyclinone (2) with phenylamine. In this study, we tested the nonenzymatic conversion of 2 with more phenylamine analogues, to expand the utility of this feasible conversion in unusual angucyclinones generation. The (3-ethynyl)phenylamine and disubstituted analogues including (3,4-dimethyl)phenylamine, (3,4-methylenedioxy)phenylamine, and (4-bromo-3-methyl)phenylamine were used in the conversion of 2, which was isolated from the fermentation of Streptomyces sp. PKU-MA00218. All four phenylamine analogues were incorporated into 2 efficiently under mild conditions, generating new compounds 3–6. The activation of 3–6 on nuclear factor erythroid 2-related factor 2 (Nrf2) transcription were tested, which showed that 4 possessing a dimethyl-substitution gave most potent activity. These results evidenced that disubstitutions on phenylamine can be roughly tolerated in the nonenzymatic reactions with 2, suggesting extended applications of more disubstituted phenylamines incorporation to generate new bioactive angucyclinones in the future. Full article

(This article belongs to the Special Issue Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career)

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17 pages, 2906 KiB

Open AccessArticle

Prodigiosin Sensitizes Sensitive and Resistant Urothelial Carcinoma Cells to Cisplatin Treatment

by Lena Berning, David Schlütermann, Annabelle Friedrich, Niklas Berleth, Yadong Sun, Wenxian Wu, María José Mendiburo, Jana Deitersen, Hannah U. C. Brass, Margaretha A. Skowron, Michèle J. Hoffmann, Günter Niegisch, Jörg Pietruszka and Björn Stork

Molecules 2021, 26(5), 1294; https://doi.org/10.3390/molecules26051294 - 27 Feb 2021

Cited by 13 | Viewed by 2529

Abstract

Cisplatin-based treatment is the standard of care therapy for urothelial carcinomas. However, complex cisplatin resistance mechanisms limit the success of this approach. Both apoptosis and autophagy have been shown to contribute to this resistance. Prodigiosin, a secondary metabolite from various bacteria, exerts different biological activities including the modulation of these two cellular stress response pathways. We analyzed the effect of prodigiosin on protein levels of different autophagy- and apoptosis-related proteins in cisplatin-sensitive and -resistant urothelial carcinoma cells (UCCs). Furthermore, we investigated the effect on cell viability of prodigiosin alone or in combination with cisplatin. We made use of four different pairs of cisplatin-sensitive and -resistant UCCs. We found that prodigiosin blocked autophagy in UCCs and re-sensitized cisplatin-resistant cells to apoptotic cell death. Furthermore, we found that prodigiosin is a potent anticancer agent with nanomolar IC₅₀ values in all tested UCCs. In combination studies, we observed that prodigiosin sensitized both cisplatin-sensitive and -resistant urothelial carcinoma cell lines to cisplatin treatment with synergistic effects in most tested cell lines. These effects of prodigiosin are at least partially mediated by altering lysosomal function, since we detected reduced activities of cathepsin B and L. We propose that prodigiosin is a promising candidate for the therapy of cisplatin-resistant urothelial carcinomas, either as a single agent or in combinatory therapeutic approaches. Full article

(This article belongs to the Special Issue Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career)

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33 pages, 3591 KiB

Open AccessArticle

40 Years of Research on Polybrominated Diphenyl Ethers (PBDEs)—A Historical Overview and Newest Data of a Promising Anticancer Drug

by Laura Schmitt, Ilka Hinxlage, Pablo A. Cea, Holger Gohlke and Sebastian Wesselborg

Molecules 2021, 26(4), 995; https://doi.org/10.3390/molecules26040995 - 13 Feb 2021

Cited by 17 | Viewed by 3193

Abstract

Polybrominated diphenyl ethers (PBDEs) are a group of molecules with an ambiguous background in literature. PBDEs were first isolated from marine sponges of Dysidea species in 1981 and have been under continuous research to the present day. This article summarizes the two research aspects, (i) the marine compound chemistry research dealing with naturally produced PBDEs and (ii) the environmental toxicology research dealing with synthetically-produced brominated flame-retardant PBDEs. The different bioactivity patterns are set in relation to the structural similarities and dissimilarities between both groups. In addition, this article gives a first structure–activity relationship analysis comparing both groups of PBDEs. Moreover, we provide novel data of a promising anticancer therapeutic PBDE (i.e., 4,5,6-tribromo-2-(2′,4′-dibromophenoxy)phenol; termed P01F08). It has been known since 1995 that P01F08 exhibits anticancer activity, but the detailed mechanism remains poorly understood. Only recently, Mayer and colleagues identified a therapeutic window for P01F08, specifically targeting primary malignant cells in a low µM range. To elucidate the mechanistic pathway of cell death induction, we verified and compared its cytotoxicity and apoptosis induction capacity in Ramos and Jurkat lymphoma cells. Moreover, using Jurkat cells overexpressing antiapoptotic Bcl-2, we were able to show that P01F08 induces apoptosis mainly through the intrinsic mitochondrial pathway. Full article

(This article belongs to the Special Issue Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career)

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9 pages, 1048 KiB

Open AccessArticle

New Polyenes from the Marine-Derived Fungus Talaromyces cyanescens with Anti-Neuroinflammatory and Cytotoxic Activities

by Hee Jae Shin, Cao Van Anh, Duk-Yeon Cho, Dong-Kug Choi, Jong Soon Kang, Phan Thi Hoai Trinh, Byeoung-Kyu Choi and Hwa-Sun Lee

Molecules 2021, 26(4), 836; https://doi.org/10.3390/molecules26040836 - 05 Feb 2021

Cited by 4 | Viewed by 2385

Abstract

Three new polyene compounds, talacyanols A–C (1–3), along with two known compounds, ramulosin (4) and eurothiocin A (5), were isolated from the marine fungus Talaromyces cyanescens derived from a seaweed Caulerpa sp. Structures of 1–5 were established by one-dimensional and two-dimensional (1D/2D) NMR, HR-ESIMS, and the modified Mosher’s methods, as well as comparison with previously reported literature data. All the compounds (1–5) were tested for their in vitro cytotoxic and anti-neuroinflammatory activities. Among them, 1 showed moderate cytotoxic activity against a panel of cancer cell lines (HCT-15, NUGC-3, NCI-H23, ACHN, PC-3, and MDA-MB-231) with GI₅₀ values ranging from 44.4 to 91.6 μM, whereas compounds 2 and 5 exhibited anti-neuroinflammatory effect without cytotoxicity against all the tested cell lines. Full article

(This article belongs to the Special Issue Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career)

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12 pages, 465 KiB

Open AccessArticle

Humic Acid Extracts Leading to the Photochemical Bromination of Phenol in Aqueous Bromide Solutions: Influences of Aromatic Components, Polarity and Photochemical Activity

by Hui Liu, Yingying Pu, Xiaojun Qiu, Zhi Li, Bing Sun, Xiaomei Zhu and Kaiying Liu

Molecules 2021, 26(3), 608; https://doi.org/10.3390/molecules26030608 - 25 Jan 2021

Cited by 5 | Viewed by 1819

Abstract

Dissolved organic matter (DOM) is considered to play an important role in the abiotic transformation of organobromine compounds in marine environment, for it produces reactive intermediates photochemically and is recognized as a significant source of reactive halogen species in seawater. However, due to the complex composition of DOM, the relationship between the natural properties of DOM and its ability to produce organobromine compounds is less understood. Here, humic acid (HA) was extracted and fractionated based on the polarity and hydrophobicity using silica gel, and the influences of different fractions (F_A, F_B and F_C) on the photochemical bromination of phenol was investigated. The structural properties of HA fractions were characterized by UV-vis absorption, Fourier transform infrared spectroscopy and fluorescence spectroscopy, and the photochemical reactivity of HA fractions was assessed by probing triplet dissolved organic matter (³DOM*), singlet oxygen (¹O₂) and hydroxyl radical (^•OH). The influences of HA fractions on the photo-bromination of phenol were investigated in aqueous bromide solutions under simulated solar light irradiation. F_A and F_B with more aromatic and polar contents enhanced the photo-bromination of phenol more than the weaker polar and aromatic F_C. This could be attributed to the different composition and chemical properties of the three HAs’ fractions and their production ability of ^•OH and ³DOM*. Separating and investigating the components with different chemical properties in DOM is of great significance for the assessment of their environmental impacts on the geochemical cycle of organic halogen. Full article

(This article belongs to the Special Issue Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career)

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13 pages, 1292 KiB

Open AccessArticle

Synthesis and Investigation of Tetrahydro-β-carboline Derivatives as Inhibitors of Plant Pathogenic Fungi

by Koonchira Buaban, Weerachai Phutdhawong, Thongchai Taechowisan and Waya S. Phutdhawong

Molecules 2021, 26(1), 207; https://doi.org/10.3390/molecules26010207 - 03 Jan 2021

Cited by 8 | Viewed by 3506

Abstract

A series of tetrahydro-ß-carbolines substituted with an alkyl or acyl side chain was synthesized and screened for its antifungal activity against plant pathogenic fungi (Bipolaris oryzae, Curvularia lunata, Fusarium semitectum, and Fusarium fujikuroi). The structure activity relationship revealed that the substituent at the piperidine nitrogen plays an important role for increasing antifungal activities. In this series, 2-octyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole (3g) displayed potent antifungal activities with a minimum inhibitory concentration of 0.1 μg/mL, including good inhibitory activity to the radial growth of fungus at a concentration of 100 μg/mL compared to amphotericin B. Full article

(This article belongs to the Special Issue Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career)

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16 pages, 7059 KiB

Open AccessArticle

Biomimetic Alginate/Gelatin Cross-Linked Hydrogels Supplemented with Polyphosphate for Wound Healing Applications

by Shunfeng Wang, Xiaohong Wang, Meik Neufurth, Emad Tolba, Hadrian Schepler, Shichu Xiao, Heinz C. Schröder and Werner E. G. Müller

Molecules 2020, 25(21), 5210; https://doi.org/10.3390/molecules25215210 - 09 Nov 2020

Cited by 17 | Viewed by 4423

Abstract

In the present study, the fabrication of a biomimetic wound dressing that mimics the extracellular matrix, consisting of a hydrogel matrix composed of non-oxidized and periodate-oxidized marine alginate, was prepared to which gelatin was bound via Schiff base formation. Into this alginate/oxidized-alginate-gelatin hydrogel, polyP was stably but reversibly integrated by ionic cross-linking with Zn²⁺ ions. Thereby, a soft hybrid material is obtained, consisting of a more rigid alginate scaffold and porous structures formed by the oxidized-alginate-gelatin hydrogel with ionically cross-linked polyP. Two forms of the Zn-polyP-containing matrices were obtained based on the property of polyP to form, at neutral pH, a coacervate—the physiologically active form of the polymer. At alkaline conditions (pH 10), it will form nanoparticles, acting as a depot that is converted at pH 7 into the coacervate phase. Both polyP-containing hydrogels were biologically active and significantly enhanced cell growth/viability and attachment/spreading of human epidermal keratinocytes compared to control hydrogels without any adverse effect on reconstructed human epidermis samples in an in vitro skin irritation test system. From these data, we conclude that polyP-containing alginate/oxidized-alginate-gelatin hydrogels may provide a suitable regeneratively active matrix for wound healing for potential in vivo applications. Full article

(This article belongs to the Special Issue Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career)

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9 pages, 1489 KiB

Open AccessArticle

Cytospyrone and Cytospomarin: Two New Polyketides Isolated from Mangrove Endophytic Fungus, Cytospora sp.

by Chengwen Wei, Qin Deng, Mengyu Sun and Jing Xu

Molecules 2020, 25(18), 4224; https://doi.org/10.3390/molecules25184224 - 15 Sep 2020

Cited by 20 | Viewed by 2116

Abstract

Two new polyketides, cytospyrone (1), cytospomarin (2), together with three known metabolites dimethoxyphtalide (3), integracin A (4) and integracin B (5), were isolated from the culture of Cytospora sp. from the Chinese mangrove Ceriops tagal. Their structures were elucidated by extensive spectroscopic analyses and time dependent density functional theory (TDDFT), calculation of electronic circular dichroism (ECD) and optical rotation (OR) data. Compound 2 displayed weak inhibitory activity against Escherichia coli GIM1.201 (minimum inhibitory concentration (MIC) value of 0.35 mM). Compounds 4 and 5 displayed significant cytotoxicity against human cancer cell line HepG2 (IC₅₀ values of 5.98 ± 0.12 µM and 9.97 ± 0.06 µM, respectively), more potent than the positive control 5-fluorouracil (IC₅₀ value of 43.50 ± 3.69 µM). Full article

(This article belongs to the Special Issue Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career)

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11 pages, 1717 KiB

Open AccessArticle

Benzyl Furanones and Pyrones from the Marine-Derived Fungus Aspergillus terreus Induced by Chemical Epigenetic Modification

by Jing-Shuai Wu, Xiao-Hui Shi, Ya-Hui Zhang, Chang-Lun Shao, Xiu-Mei Fu, Xin Li, Guang-Shan Yao and Chang-Yun Wang

Molecules 2020, 25(17), 3927; https://doi.org/10.3390/molecules25173927 - 27 Aug 2020

Cited by 15 | Viewed by 2854

Abstract

Chemical epigenetic modification on a marine-derived fungus Aspergillus terreus RA2905 using a histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA), resulted in a significantly changed metabolic profile. A chemical investigation of its ethyl acetate (EtOAc) extract led to the isolation of a racemate of benzyl furanone racemate (±)-1, which further separated chirally as a pair of new enantiomers, (+)- and (−)-asperfuranone (1), together with two new benzyl pyrones, asperpyranones A (2) and B (3). Their structures were elucidated by analysis of the comprehensive spectroscopic data, including one-dimensional (1D) and two-dimensional (2D) NMR, and HRESIMS. The absolute configurations were determined by electronic circular dichroism (ECD) calculation and single-crystal X-ray crystallographic experiment. The structures with benzyl furanone or benzyl pyrone skeletons were discovered from natural products for the first time. Compounds (±)-1, (+)-1, (−)-1, and 2 displayed the antifungal activities against Candida albicans with MIC values of 32, 16, 64, and 64 μg/mL and PTP1B inhibitory activities with the IC₅₀ values of 45.79, 17.32, 35.50, and 42.32 μM, respectively. Compound 2 exhibited antibacterial activity against Pseudomonas aeruginosa with the MIC value of 32 μg/mL. Full article

(This article belongs to the Special Issue Marine Natural Product Chemistry: A Themed Issue in Honor of Professor Peter Proksch on His Research Career)

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