A new depsidone derivative from mangrove endophytic fungus Aspergillus sp. GXNU-A9

Identification and bioactivity evaluation of twelve previously undescribed depsidone derivatives from Garcinia oligantha

Phytochemical studies on the leaves and twigs of Garcinia oligantha Merr. led to the isolation of twelve previously undescribed depsidone derivatives (oliganthdepsidones A-L, 1-12). Their structures were elucidated by extensive spectroscopic analysis including 1H and 13C NMR, HSQC, HMBC and NOESY along with HRESIMS. The structures of oliganthdepsidones G and J were finally determined using DFT-NMR chemical shift calculations and DP4+ methods. Cytotoxicity test in four human cancer cell lines indicated that oliganthdepsidone F had relatively strong cytotoxic effect against A375 (melanoma), A549 (lung cancer), HepG2 (liver cancer), and MCF-7 (breast cancer) cell lines with IC50 of 18.71, 15.44, 10.92, and 15.90 μM, respectively. The dose- and time-dependent antiproliferative effects of oliganthdepsidone F on these cell lines were also observed by CCK-8 test. As determined by fluorescent microscopy and flow cytometry in these cell lines, oliganthdepsidone F could promote cell apoptosis, leading to the inhibition of cell proliferation. The results of wound healing assay and transwell assay showed that oliganthdepsidone F could inhibit the migration and invasion of A549 and MCF-7 cell lines in a concentration-dependent manner.

Two new polyketone derivatives from the mangrove endophytic fungus Aspergillus sp. GXNU TH4b

Two new polyketones, exserone B (1) and cytosporone F (2), along with three known metabolites, were isolated from the mangrove endophytic fungus Aspergillus TH4b. The structures of 1 and 2 were determined by detailed NMR, and MS spectroscopic data. The absolute configurations of 1 and 2 were determined by single crystal X-ray diffraction analysis and the combination of experimental ECD and computational ECD, respectively. Compounds 1-2 have strong inhibitory activity against citrus Psyllid (Diaphorina citri) with 95.4% and 93.7% lethal at 1000 mg/kg.

A new isoprenyl-phenol-type meroterpenoid from mangrove endophytic fungus Aspergillus sp. GXNU-Y65

Asperphenol A (1), a new isoprenyl-phenol-type meroterpenoid, was isolated from the mangrove endophytic fungus Aspergillus sp. GXNU-Y65 together with five known compounds (2-6). All structures were assigned using extensive NMR spectroscopic data and electronic circular dichroism (ECD) calculations. Compounds 1-6 were evaluated for their cytotoxic activity against A549 and T24 human cancer cell lines. Among them, compounds 1 and 5 exhibited moderate inhibitory activities against T24 cancer cell lines with the IC50 values of 26.71 and 43.50 μM, respectively.

A new chromone derivative from an endophytic Aspergillus sp. GXNU-B1

A new chromone derivative, aspergione A (1), along with seven known metabolites, was isolated from a mangrove endophytic fungus, Aspergillus sp. GXNU-B1, which was collected from mangrove Acanthus ilicifolius L. Their structures and the absolute configuration of 1 were elucidated based on the analysis of HR-ESI-MS, NMR, and ECD calculation. Compounds 1-8 were evaluated for their anti-inflammatory effects on the production of nitricoxide (NO). Compounds 1 and 8 have potent inhibitory effects against NO production in activated macrophages with IC50 values of 38.26 and 44.30 μM, respectively.

Mangrove-associated endomycota: diversity and functional significance as a source of novel drug leads

Endophytic fungi are known for their unprecedented ability to produce novel lead compounds of clinical and pharmaceutical importance. This review focuses on the unexplored fungal diversity associated with mangroves, emphasizing their biodiversity, distribution, and methodological approaches targeting isolation, and identification. Also highlights the bioactive compounds reported from the mangrove fungal endophytes. The compounds are categorized according to their reported biological activities including antimicrobial, antioxidant and cytotoxic property. In addition, protein kinase, α-glucosidase, acetylcholinesterase, tyrosinase inhibition, antiangiogenic, DNA-binding affinity, and calcium/potassium channel blocking activity are also reported. Exploration of these endophytes as a source of pharmacologically important compounds will be highly promising in the wake of emerging antibiotic resistance among pathogens. Thus, the aim of this review is to present a detailed report of mangrove derived endophytic fungi and to open an avenue for researchers to discover the possibilities of exploring these hidden mycota in developing novel drug leads.

Recent advances on natural depsidones: sources, biosynthesis, structure-activity relationship, and bioactivities

Depsidones are a class of polyphenolic polyketides that have been proposed to be biosynthesized from oxidative coupling of esters of two polyketidic benzoic acid derivatives. They are principally encountered in fungi and lichens. In addition to their diversified structural features, they revealed varied bioactivities such as antimicrobial, antimalarial, cytotoxic, anti-inflammatory, anti-Helicobacter pylori, antimycobacterial, antihypertensive, anti-diarrheal, antidiabetic, phytotoxic, anti-HIV, anti-osteoclastogenic, and butyrylcholinesterase, tyrosinase, hyaluronidase, and acetylcholinesterase inhibition. The current work was targeted to provide an overview on the naturally reported depsidones from various sources in the period from 2018 to the end of 2022 including their structures, biosynthesis, sources, and bioactivities, as well as the reported structure-activity relationship and semisynthetic derivatives. A total of 172 metabolites with 87 references were reviewed. The reported findings unambiguously demonstrated that these derivatives could be promising leads for therapeutic agents. However, further in-vivo evaluation of their potential biological properties and mechanistic investigations are needed.

A new lactone from mangrove endophytic fungus Aspergillus sp. GXNU-A9

A new lactone, asperlactone A (1), and four known lactone derivatives 2-5 were isolated from the mangrove endophytic fungus Aspergillus sp. GXNU-A9. Their structures were elucidated based on high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) datum, extensive nuclear magnetic resonance (NMR) spectroscopic analysis, and comparison with literature data. The structure of 1 was further confirmed by single-crystal X-ray diffraction analysis, and the absolute configuration of 1 was established. Compounds 1-5 were evaluated for their anti-inflammatory activities against nitric oxide (NO) production, and compounds 1-5 showed moderate inhibitory activities with IC₅₀ values ranging from 15.87 to 30.48 µM.

Asperphenyltones A and B: New Phenylfuropyridinone Skeleton from an Endophytic Aspergillus sp. GXNU-A1

Chemical investigation of the fermentation extract of the mangrove endophytic fungus Aspergillus sp. GXNU-A1, isolated from Acanthus ilicifolius L., discovered an undescribed pair of enantiomers (asperphenyltones A and B (±1)), together with four previously described metabolites: nodulisporol (2), isosclerone (3), 2,3,4-trihydroxy-6-(hydroxymethyl)-5-methylbenzyl alcohol (4), and 4,6-dihydroxy-5-methoxy-7-methyl-1,3-dihydroisobenzofuran (5). Analyses of the 1D and 2D NMR spectroscopic data of the compounds supported their structural assignments. The presence of the asperphenyltones A and B, which are a pair of enantiomers, was established by HR-ESI-MS, 1D and 2D NMR data and confirmed by single-crystal X-ray diffraction analysis. Metabolites 1-5 were evaluated for their anti-inflammatory effects on the production of nitric oxide (NO), and 1, 3, and 4 showed significant potential inhibitory activities against NO production in activated macrophages with IC₅₀ values of 26-40 μM, respectively.

Structural Characterization and Assessment of Anti-Inflammatory Activities of Polyphenols and Depsidone Derivatives from Melastoma malabathricum subsp. normale

The roots of Melastoma malabathricum subsp. normale (D. Don) Karst. Mey have been used in traditional ethnic medicine systems in China to treat inflammation-triggered ailments, such as trauma, toothache, and fever. Therefore, the aim of this study is to screen for compounds with anti-inflammatory activity in the title plant. The extract of M. malabathricum subsp. normale roots was separated using various chromatographic methods, such as silica gel, ODS C18, MCI gel, and Sephadex LH-20 column chromatography, as well as semi-preparative HPLC. One new complex tannin, named whiskey tannin D (1), and an undescribed tetracyclic depsidone derivative, named guanxidone B (2), along with nine known polyphenols (2–10) and three known depsidone derivatives (12–14) were obtained from this plant. The structures of all compounds were elucidated by extensive NMR and CD experiments in conjunction with HR-ESI-MS data. All these compounds were isolated from this plant for the first time. Moreover, compounds 1–4, 8, and 10–14 were obtained for the first time from the genus Melastoma, and compounds 1, 2, and 11–14 have not been reported from the family Melastomataceae. This is the first report of complex tannin and depsidone derivatives from M. malabathricum subsp. normale, indicating their chemotaxonomic significance to this plant. Compounds 1–12 were investigated for their anti-inflammatory activities on the production of the nitric oxide (NO) in lipopolysaccharide (LPS)-stimulated RAW264.7 cells, and compounds 1, 11, and 12 showed anti-inflammatory activities with IC₅₀ values of 6.46 ± 0.23 µM, 8.02 ± 0.35 µM, and 9.82 ± 0.43 µM, respectively. The structure–activity relationship showed that the catechin at glucose C-1 in ellagitannin was the key to its anti-inflammatory activity, while CH₃O- at C-16 of aromatic ring A in depsidone derivatives had little effect on its anti-inflammatory activity. The study of structure–activity relationships is helpful to quickly discover new anti-inflammatory drugs. The successful isolation and structure identification of these compounds, especially complex tannin 1, not only provide materials for the screening of anti-inflammatory compounds, but also provide a basis for the study of chemical taxonomy of the genus Melastoma.

The Endophytic Aspergillus Strains: A Bountiful Source of Natural Products

Fungi that invade plant inner tissues without inducing disease symptoms are known as fungal endophytes. They represent a promising and tremendous reservoir of natural products with valuable biological potentials for application in medicine, agriculture and industry. Among the numerous existing endophytic fungi, Aspergillus strains constitute one of the most prolific sources of secondary metabolites with diverse chemical classes and interesting biological activities. This review covers the literature of the year 2020, reporting the isolation of 202 compounds obtained from more than ten different endophytic Aspergillus species associated with different host plants. Analysis and interpretation of the collected data revealed that chemical investigation of endophytes belonging to the genus Aspergillus may greatly contribute in the discovery of potential drug leads. The isolated metabolites were chemically various and exhibited diverse biological activities such as antibacterial, anti-cancer, anti-plasmodial, anti-inflammatory, antioxidant, immunosuppressive and antifungal activities. Moreover, adoption of advanced technology in molecular biology together with modern chemical tools is anticipated to improve the discovery of new biopharmaceuticals from this valuable microbial world in the future.

Cytotoxic and antibacterial depsidones from the endophytic fungus Chaetomium brasiliense isolated from Thai rice

Four new depsidones, mollicellins V-Y (1-4), together with eight known depsidones (5-12) were isolated from the endophytic fungus, Chaetomium brasiliense, detached from stems of Thai rice. Their structures were determined by extensive spectroscopic methods. Mollicellins X, H, and F (3, 8 and 10) showed potent cytotoxicity against the human oral epidermoid carcinoma (KB) cell line, and mollicellin F (10) also showed a potent cytotoxicity against the human hepatocellular carcinoma (HepG2) cell line. Besides, mollicellin B (11) exhibited cytotoxicity against the colorectal adenocarcinoma (HT-29) cell line. Moreover, most of the isolated depsidones displayed potent antibacterial activity against Gram-positive bacteria, Bacillus cereus and Bacillus subtilis, and several of them showed moderate activity against Methicillin-resistant Staphylococcus aureus (MRSA) and clinical isolates of S. aureus. In addition, a few of them also showed moderate activity against a Gram-negative bacteria Pseudomonas aeruginosa.

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.