N-Hydroxypyridone alkaloids, chromone derivatives, and tetrahydroxanthones from the scale-insect pathogenic fungus Orbiocrella sp. BCC 33248

Okichromanone, a new antiviral chromanone from a marine-derived Microbispora

Okichromanone (1), a new chromanone, was isolated from the culture extract of a sponge-derived actinomycete Microbispora, along with known 1-hydroxyphenazine (2). Compound 1 was elucidated to exist as a mixture of two isomeric structures (1a and 1b) at a ratio of nearly 3:2. Compounds 1 and 2 showed anti HSV-I activity with IC50 values 40 and 86 μM, respectively, and anti HSV-II activity with IC50 values 59 and 123 μM, respectively.

Exploration of Potent Cytotoxic Molecules from Fungi in Recent Past to Discover Plausible Anticancer Scaffolds

Fungi are known to produce diverse scaffolds possessing unique biological activities, however, to date, no molecule discovered from a fungal source has reached the market as an anti-cancer drug. Every year number of cytotoxic molecules of fungal origin are getting published and critical analysis of those compounds is necessary to identify the potent ones. A review mentioning the best cytotoxic fungal metabolites and their status in the drug development was published in 2014. In this report, we have included 176 cytotoxic molecules isolated from fungi after 2014 and categorized them according to their potencies such as IC₅₀ values below 1 μM, 1-5 μM, and 5-10 μM. The emphasis was given to those 42 molecules which have shown IC₅₀ less than 1 μM and discussed to a great extent. This review shall provide potent scaffolds of fungal origin which can be given priority in the development as a drug candidate for cancer therapeutics.

Naturally Occurring Chromone Glycosides: Sources, Bioactivities, and Spectroscopic Features

Chromone glycosides comprise an important group of secondary metabolites. They are widely distributed in plants and, to a lesser extent, in fungi and bacteria. Significant biological activities, including antiviral, anti-inflammatory, antitumor, antimicrobial, etc., have been discovered for chromone glycosides, suggesting their potential as drug leads. This review compiles 192 naturally occurring chromone glycosides along with their sources, classification, biological activities, and spectroscopic features. Detailed biosynthetic pathways and chemotaxonomic studies are also described. Extensive spectroscopic features for this class of compounds have been thoroughly discussed, and detailed 13C-NMR data of compounds 1-192, have been added, except for those that have no reported 13C-NMR data.

Overview of the Antioxidant and Anti-Inflammatory Activities of Selected Plant Compounds and Their Metal Ions Complexes

Numerous plant compounds and their metal-ion complexes exert antioxidative, anti-inflammatory, anticancer, and other beneficial effects. This review highlights the different bioactivities of flavonoids, chromones, and coumarins and their metal-ions complexes due to different structural characteristics. In addition to insight into the most studied antioxidative properties of these compounds, the first part of the review provides a comprehensive overview of exogenous and endogenous sources of reactive oxygen and nitrogen species, oxidative stress-mediated damages of lipids and proteins, and on protective roles of antioxidant defense systems, including plant-derived antioxidants. Additionally, the review covers the anti-inflammatory and antimicrobial activities of flavonoids, chromones, coumarins and their metal-ion complexes which support its application in medicine, pharmacy, and cosmetology.

Generation of Stilbene Glycoside with Promising Cell Rejuvenation Activity through Biotransformation by the Entomopathogenic Fungus Beauveria bassiana

A stilbene glycoside (resvebassianol A) (1) with a unique sugar unit, 4-O-methyl-D-glucopyranose, was identified through biotransformation of resveratrol (RSV) by the entomopathogenic fungus Beauveria bassiana to obtain a superior RSV metabolite with enhanced safety. Its structure, including its absolute configurations, was determined using spectroscopic data, HRESIMS, and chemical reactions. Microarray analysis showed that the expression levels of filaggrin, HAS2-AS1, and CERS3 were higher, while those of IL23A, IL1A, and CXCL8 were lower in the resvebassianol A-treated group than in the RSV-treated group, as confirmed by qRT-PCR. Compound 1 exhibited the same regenerative and anti-inflammatory effects as RSV with no cytotoxicity in skin keratinocytes and TNF-α/IFN-γ-stimulated HIEC-6 cells, suggesting that compound 1 is a safe and stable methylglycosylated RSV. Our findings suggest that our biotransformation method can be an efficient biosynthetic platform for producing a broad range of natural glycosides with enhanced safety.

Xanthone glucoside from an insect pathogenic fungus Conoideocrella luteorostrata NBRC106950

A new compound, 3-O-(4-O-methyl-β-D-glucopyranosyl) xanthone (1) was isolated from the culture of Conoideocrella luteorostrata NBRC106950. The structure of 1 was mainly determined by ¹H, ¹³C, 2D-NMR and HREIMS spectral analyses. The absolute configuration of 4-O-methylglucopyranosyl moiety was determined by the optical rotation of aqueous layer of hydrolyzed 1 as D-configuration.

Polysubstituted Phenyl Glucosides Produced by the Fungus Metarrhizium anisopliae

Metarhizosides A–G (1–7), seven new polysubstituted phenyl glucosides, were isolated from the extracts of solid rice medium of a marine-derived fungus Metarrhizium anisopliae. Compounds 1–7 all contain a polysubstituted phenyl group and the sugar unit is identified as 4′-O-methyl-β-D-glucopyranose. Their structures were elucidated by NMR spectroscopy and chemical method. These compounds were evaluated for anti-inflammatory activity by using LPS-stimulated murine macrophage RAW 264.7 cells and the cytotoxicities against four human cancer cell lines.

Chromone and isocoumarin derivatives from the endophytic fungus Xylomelasma sp. Samif07, and their antibacterial and antioxidant activities

Five chromone derivatives, including 2,6-dimethyl-5-methoxyl-7-hydroxylchromone (1), 6-hydroxymethyleugenin (2), 6-methoxymethyleugenin (3), chaetoquadrin D (4), and isoeugenitol (5), and three isocoumarin congeners, namely diaporthin (6), 8-hydroxy-6-methoxy-3-methylisocoumarin (7), and 6-methoxymellein (8), were isolated from the culture of the endophytic fungus Xylomelasma sp. Samif07 derived from the medicinal plant Salvia miltiorrhiza Bunge. Among them, compound 1 was a new natural product. Their structures were determined by spectroscopic methods and comparison with the literature. The isolated compounds were evaluated for their antibacterial and antioxidant activities. Compound 5 showed notable antitubercular activity against Mycobacterium tuberculosis with MIC value of 10.31 µg/mL, while compounds 1-3, and 5-7 displayed inhibitory activities against the other bacteria with MIC range of 25 ∼ 100 µg/mL. Meanwhile, compound 6 showed potent hydroxyl radical-scavenging activity with EC₅₀ value of 15.1 µg/mL, while compounds 5-7 showed certain ferric reducing ability.