Separation and configurational assignment of stereoisomeric phenalenones from the marine mangrove-derived fungus Penicillium herquei MA-370

Three new α-pyrone derivatives from the soil-derived fungus Penicillium herquei MA-370

Three new α-pyrone derivatives, annularins L-N (1-3), were isolated from the EtOAc extract of Penicillium herquei MA-370, a fungus obtained from the rhizospheric soil of the mangrove plant Rhizophora mucronata. The planar structures of compounds 1-3 were determined based on comprehensive spectral interpretation of the NMR and MS data. The absolute configuration of 1 was determined by X-ray crystallographic data and that of 2 was assigned by TDDFT calculations of its ECD spectrum and cotton effects comparison with those of 1. The antimicrobial activity of compounds 1-3 was evaluated.

Genomic characterization and identification of candidate genes for putative podophyllotoxin biosynthesis pathway in Penicillium herquei HGN12.1C

Previous studies have reported the functional role, biochemical features and synthesis pathway of podophyllotoxin (PTOX) in plants. In this study, we employed combined morphological and molecular techniques to identify an endophytic fungus and extract PTOX derivatives. Based on the analysis of ITS sequences and the phylogenetic tree, the isolate was classified as Penicillium herquei HGN12.1C, with a sequence identity of 98.58%. Morphologically, the HGN12.1C strain exhibits white colonies, short-branched mycelia and densely packed hyphae. Using PacBio sequencing at an average read depth of 195×, we obtained a high-quality genome for the HGN12.1C strain, which is 34.9 Mb in size, containing eight chromosomes, one mitochondrial genome and a GC content of 46.5%. Genome analysis revealed 10 genes potentially involved in PTOX biosynthesis. These genes include VdtD, Pinoresinollariciresinol reductase (PLR), Secoisolariciresinol dehydrogenase (SDH), CYP719A23, CYP71BE54, O-methyltransferase 1 (OMT1), O-methyltransferase 3 (OMT3), 2-ODD, CYP71CU and CYP82D61. Notably, the VdtD gene in fungi shares functional similarities with the DIR gene found in plants. Additionally, we identified peltatin, a PTOX derivative, in the HGN12.1C extract. Docking analysis suggests a potential role for the 2-ODD enzyme in converting yatein to deoxypodophyllotoxin. These findings offer invaluable insights into the synthesis mechanism of PTOX in fungi, shedding light on the relationship between host plants and endophytes.

Antimicrobial sesterterpenoids with a unique 5/8/6/5 tetracyclic carbon-ring-system and diepoxide polyketides from a deep sea-sediment-sourced fungus Chaetomium globosum SD-347

Two new sesterterpenoids, sesterchaetins A and B (1 and 2), and two new diepoxide polyketides, chaetoketoics A and B (3 and 4), were characterized from the culture extract of Chaetomium globosum SD-347, a fungal strain derived from deep sea-sediment. Their structures and absolute configurations were unambiguously determined by detailed NMR, mass spectra, and X-ray crystallographic analysis. Compounds 1 and 2 contained a distinctive 5/8/6/5 tetracyclic carbon-ring-system, which represented a rarely occurring natural product framework. The new isolates 1-4 exhibited selective antimicrobial activities against human and aquatic pathogenic bacteria and plant-pathogenic fungi.

Penicimides A and B, two novel diels-alder [4 + 2] cycloaddition ergosteroids from Penicillium herquei

Two novel naturally occurring [4 + 2] Diels-Alder cycloaddition ergosteroids (1 and 2), three undescribed oxidized ergosteroids (3-5), and eleven known analogs (6-16) were isolated from Penicillium herquei. Compounds 1 and 2 represent the first reported cycloadducts of a steroid with 1,4,6-trimethyl-1,6-dihydropyridine-2,5-dione or 4,6-dimethyl-1,6-dihydropyridine-2,5-dione to date. Compound 3 is the C-15 epimer of (22E,24R)-9α,11β-dihydroxyergosta-4,6,8(14),22-tetraen-3-one (14). The chemical structures of these compounds were elucidated through widespread spectroscopic analyses, mainly including HRESIMS and 1D and 2D NMR data, calculated 13C NMR-DP4+ analysis, and electronic circular dichroism (ECD) data analyses. Biological evaluations of Compounds 1-16 revealed that 3, 9-11, and 15 inhibited the production of NO in LPS-induced RAW264.7 cells with an IC50 value from 7.37 ± 0.69 to 38.9 ± 2.25 μM (the positive control dexamethasone IC50: 9.54 ± 0.71 μM). In addition, Compound 3 exhibited a potent inhibitory effect on the secretion of the proinflammatory cytokines TNF-α and IL-6, the transcription level of the proinflammatory macrophage markers TNF-α, and the expression of the iNOS protein.

ent-Herqueidiketal and epi-Peniciherqueinone Isolated from a Mushroom Derived Fungus Penicillium herquei YNJ-35

A new polyaromatic metabolite, ent-herqueidiketal (1), and a new phenalenone derivative, epi-peniciherqueinone (2), along with twelve known compounds 3-14, were isolated from the fungus Penicillium herquei YNJ-35, a symbiotic fungus of Pulveroboletus brunneopunctatus collected from Nangunhe Nature Reserve, Yunnan Province, China. The structures of 1-14 and the absolute configurations of 1 and 2 were determined by their spectroscopic data or by their single-crystal X-ray diffraction analysis or optical rotation values. Compound 1 showed strong antibacterial activity against Staphylococcus aureus (ATCC 29213) with minimum inhibitory concentration (MIC) of 8 μg/mL. In the cytotoxicity assays, compound 1 showed weak inhibitory activity against breast cancer MCF-7 and mice microglial BV2 cells with half maximal inhibitory concentration (IC50 ) of 17.58 and 29.56 μM; compound 14 showed stronger cytotoxicity against BV2 and MCF-7 cells with IC50 values of 6.57 and 10.26 μM.

A Review of the Chemistry and Biological Activities of Natural Colorants, Dyes, and Pigments: Challenges, and Opportunities for Food, Cosmetics, and Pharmaceutical Application

Natural pigments are important sources for the screening of bioactive lead compounds. This article reviewed the chemistry and therapeutic potentials of over 570 colored molecules from plants, fungi, bacteria, insects, algae, and marine sources. Moreover, related biological activities, advanced extraction, and identification approaches were reviewed. A variety of biological activities, including cytotoxicity against cancer cells, antioxidant, anti-inflammatory, wound healing, anti-microbial, antiviral, and anti-protozoal activities, have been reported for different pigments. Considering their structural backbone, they were classified as naphthoquinones, carotenoids, flavonoids, xanthones, anthocyanins, benzotropolones, alkaloids, terpenoids, isoprenoids, and non-isoprenoids. Alkaloid pigments were mostly isolated from bacteria and marine sources, while flavonoids were mostly found in plants and mushrooms. Colored quinones and xanthones were mostly extracted from plants and fungi, while colored polyketides and terpenoids are often found in marine sources and fungi. Carotenoids are mostly distributed among bacteria, followed by fungi and plants. The pigments isolated from insects have different structures, but among them, carotenoids and quinone/xanthone are the most important. Considering good manufacturing practices, the current permitted natural colorants are: Carotenoids (canthaxanthin, β-carotene, β-apo-8'-carotenal, annatto, astaxanthin) and their sources, lycopene, anthocyanins, betanin, chlorophyllins, spirulina extract, carmine and cochineal extract, henna, riboflavin, pyrogallol, logwood extract, guaiazulene, turmeric, and soy leghemoglobin.

Nine undescribed oxidized ergosterols from the endophytic fungus Penicillium herquei and their cytotoxic activity

A chemical investigation of the EtOAc extract of the endophytic fungus Penicillium herquei led to the isolation of nine undescribed oxidized ergosterols, penicisterols A-I (1-9), along with ten known analogs (10-19). Their structures and absolute configurations were elucidated by a combination of spectroscopic data analysis, quantum-chemical electronic circular dichroism (ECD) calculations and comparisons, [Rh₂(OCOCF₃)₄]-induced ECD experiments, DFT-calculated ¹³C chemical shifts and DP4+ probability analysis. Compound 1 was a rare example of ergosterol in which the bond between C-8 and C-9 is cleaved to form an enol ether. Moreover, compound 2 possessed a rare (2,5-dioxo-4-imidazolidinyl)-carbamic acid ester group substituted at C-3. All undescribed oxidized ergosterols (1-9) were evaluated for their cytotoxic activity against five cancer cell lines including 4T1 (mouse breast carcinoma), A549 (human pulmonary carcinoma), HCT-116 (human colorectal carcinoma), HeLa (human cervical carcinoma) and Hepg2 (human hepatoma carcinoma) cells. Compounds 2 and 3 displayed moderate cytotoxic activity against 4T1, A549 and HeLa cells, with IC₅₀ values ranging from 17.22 to 31.35 μM.

Marine natural products

Covering: January to December 2021This review covers the literature published in 2021 for marine natural products (MNPs), with 736 citations (724 for the period January to December 2021) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1425 in 416 papers for 2021), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of the number of authors, their affiliations, domestic and international collection locations, focus of MNP studies, citation metrics and journal choices is discussed.

A Pair of Chromone Epimers and an Acetophenone Glucoside from the Mangrove Endophytic Fungus Mycosphaerella sp. L3A1

Three new compounds, including a pair of chromone derivatives (1-2), and an acetophenone glucoside (3), together with three known compounds (4-6), were isolated from the mangrove endophytic fungus Mycosphaerella sp. L3A1. Their structures were elucidated by HR-ESI-MS analysis and extensive spectroscopic data. The absolute configurations of new compounds were determined using single-crystal X-ray diffraction analysis, electronic circular dichroism (ECD) calculations and chemical hydrolysis. In bioassays, compound 4 showed moderate cytotoxic activity against MDA-MB-435, HCT116, and SNB19 with IC₅₀ values in the range of 18.5-26.29 μM.

Natural products from mangrove sediments-derived microbes: Structural diversity, bioactivities, biosynthesis, and total synthesis

The mangrove forests are a complex ecosystem, and the microbial communities in mangrove sediments play a critical role in the biogeochemical cycles of mangrove ecosystems. Mangrove sediments-derived microbes (MSM), as a rich reservoir of natural product diversity, could be utilized in the exploration of new antibiotics or drugs. To understand the structural diversity and bioactivities of the metabolites of MSM, this review for the first time provides a comprehensive overview of 519 natural products isolated from MSM with their bioactivities, up to 2021. Most of the structural types of these compounds are alkaloids, lactones, xanthones, quinones, terpenoids, and steroids. Among them, 210 compounds are obtained from bacteria, most of which are from Streptomyces, while 309 compounds are from fungus, especially genus Aspergillus and Penicillium. The pharmacological mechanisms of some representative lead compounds are well studied, revealing that they have important medicinal potentials, such as piericidins with anti-renal cell cancer effects, azalomycins with anti-MRSA activities, and ophiobolins as antineoplastic agents. The biosynthetic pathways of representative natural products from MSM have also been summarized, especially ikarugamycin, piericidins, divergolides, and azalomycins. In addition, the total synthetic strategies of representative secondary metabolites from MSM are also reviewed, such as piericidin A and borrelidin. This review provides an important reference for the research status of natural products isolated from MSM and the lead compounds worthy of further development, and reveals that MSM have important medicinal values and are worthy of further development.

Secondary metabolites from mangrove-associated fungi: source, chemistry and bioactivities

Covering 1989 to 2020The mangrove forests are a complex ecosystem occurring at tropical and subtropical intertidal estuarine zones and nourish a diverse group of microorganisms including fungi, actinomycetes, bacteria, cyanobacteria, algae, and protozoa. Among the mangrove microbial community, mangrove associated fungi, as the second-largest ecological group of the marine fungi, not only play an essential role in creating and maintaining this biosphere but also represent a rich source of structurally unique and diverse bioactive secondary metabolites, attracting significant attention of organic chemists and pharmacologists. This review summarizes the discovery relating to the source and characteristics of metabolic products isolated from mangrove-associated fungi over the past thirty years (1989-2020). Its emphasis included 1387 new metabolites from 451 papers, focusing on bioactivity and the unique chemical diversity of these natural products.

New diphenyl ethers from a fungus Epicoccum sorghinum L28 and their antifungal activity against phytopathogens

The strategy "IEMAHC" (Induction of Endophyte Metabolism by Adding Host Components) was applied to the fermentation of the endophytic fungus Epicoccum sorghinum L28 from Myoporum bontioides by introducing guaiol, an ingredient of M. bontioides, into the cultivation medium, which resulted in the purification of nine new diphenyl ethers, epicoccethers A-I (1-9). Their structures were determined by overall spectroscopic analysis. HPLC-MS analysis revealed that compounds 5-7 were products generated by induction of guaiol. Compounds 6 and 7 are the first members containing an ester moiety formed by the natural long-chain fatty acid and the hydroxyl group in the phenylmethanol unit of the diphenyl ether class. The antifungal activities of compounds 1, 2, and 4-7 against Fusarium oxysporum were 1, 1, 2, 1, 2 and 4 times as high as those of the positive control triadimefon, respectively. Compounds 4 and 5 showed 1.6 times the antifungal activities of triadimefon towards Colletotrichum musae.

Five New Triene Derivatives from the Fungus Penicillium herquei JX4

Five undescribed triene derivatives, pinophols B-F (2-6), together with one known compound, pinophol A (1), were obtained from the mangrove endophytic fungus Penicillium herquei JX4. The structures of compounds 1-6 were elucidated using IR, HR-ESI-MS, and NMR methods. The absolute configurations of compounds 1-6 were confirmed by comparing their experimental or calculated ECD spectra. Pinophols C and D (3 and 4) showed inhibitory activities against LPS-induced NO production.

Structurally diverse alkaloids produced by Aspergillus creber EN-602, an endophytic fungus obtained from the marine red alga Rhodomela confervoides

Thirteen alkaloids, which include three new diketopiperazines, namely, 3-hydroxyprotuboxepin K (4), 3,15-dehydroprotuboxepin K (5), and versiamide A (6), together with ten known alkaloid derivatives (1-3 and 7-13), were isolated from the marine red algal-derived fungus Aspergillus creber EN-602. Versiamide A (6) represents the first example of a naturally occurring quinazolinone alkaloid with a diketopiperazine ring that is derived from phenylalanine (Phe) and leucine (Leu). The structures of these compounds were elucidated by detailed interpretation of their 1D/2D NMR spectroscopic and mass spectrometric data, while the absolute configurations of compounds 1-6 were established on the basis of X-ray crystallographic analysis and time-dependent density functional (TDDFT) calculations of the ECD spectra. Compounds 1, 2, and 4 exhibited inhibitory activity against the angiotensin converting enzyme (ACE) with IC₅₀ values of 11.2, 16.0, and 22.4 μM, respectively, and compounds 5 and 6 inhibited various aquatic bacteria with MIC values that ranged from 8 to 64 μg/mL. The intermolecular interactions and potential binding sites between compounds 1-6 and ACE were investigated via molecular docking simulations.