Diverse host-associated fungal systems as a dynamic source of novel bioactive anthraquinones in drug discovery: Current status and future perspectives

Discovery of natural anthraquinones as potent inhibitors against pancreatic lipase: structure-activity relationships and inhibitory mechanism

Obesity is acknowledged as a significant risk factor for various metabolic diseases, and the inhibition of human pancreatic lipase (hPL) can impede lipid digestion and absorption, thereby offering potential benefits for obesity treatment. Anthraquinones is a kind of natural and synthetic compounds with wide application. In this study, the inhibitory effects of 31 anthraquinones on hPL were evaluated. The data shows that AQ7, AQ26, and AQ27 demonstrated significant inhibitory activity against hPL, and exhibited selectivity towards other known serine hydrolases. Then the structure-activity relationship between anthraquinones and hPL was further analysed. AQ7 was found to be a mixed inhibition of hPL through inhibition kinetics, while AQ26 and AQ27 were effective non-competitive inhibition of hPL. Molecular docking data revealed that AQ7, AQ26, and AQ27 all could associate with the site of hPL. Developing hPL inhibitors for obesity prevention and treatment could be simplified with this novel and promising lead compound.

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.

Fungal Pigments: Carotenoids, Riboflavin, and Polyketides with Diverse Applications

Natural pigments and colorants have seen a substantial increase in use over the last few decades due to their eco-friendly and safe properties. Currently, customer preferences for more natural products are driving the substitution of natural pigments for synthetic colorants. Filamentous fungi, particularly ascomycetous fungi (Monascus, Fusarium, Penicillium, and Aspergillus), have been shown to produce secondary metabolites containing a wide variety of pigments, including β-carotene, melanins, azaphilones, quinones, flavins, ankaflavin, monascin, anthraquinone, and naphthoquinone. These pigments produce a variety of colors and tints, including yellow, orange, red, green, purple, brown, and blue. Additionally, these pigments have a broad spectrum of pharmacological activities, including immunomodulatory, anticancer, antioxidant, antibacterial, and antiproliferative activities. This review provides an in-depth overview of fungi gathered from diverse sources and lists several probable fungi capable of producing a variety of color hues. The second section discusses how to classify coloring compounds according to their chemical structure, characteristics, biosynthetic processes, application, and present state. Once again, we investigate the possibility of employing fungal polyketide pigments as food coloring, as well as the toxicity and carcinogenicity of particular pigments. This review explores how advanced technologies such as metabolic engineering and nanotechnology can be employed to overcome obstacles associated with the manufacture of mycotoxin-free, food-grade fungal pigments.

Recent advances in the identification of biosynthetic genes and gene clusters of the polyketide-derived pathways for anthraquinone biosynthesis and biotechnological applications

Natural anthraquinones are represented by a large group of compounds. Some of them are widespread across the kingdoms, especially in bacteria, fungi and plants, while the others are restricted to certain groups of organisms. Despite the significant pharmacological potential of several anthraquinones (hypericin, skyrin and emodin), their biosynthetic pathways and candidate genes coding for key enzymes have not been experimentally validated. Understanding the genetic and epigenetic regulation of the anthraquinone biosynthetic gene clusters in fungal endophytes would help not only understand their pathways in plants, which ensure their commercial availability, but also favor them as promising systems for prospective biotechnological production.

In silico, in vitro screening of antioxidant and anticancer potentials of bioactive secondary metabolites from an endophytic fungus (Curvularia sp.) from Phyllanthus niruri L

The main objective of this research work is to discover novel and efficient phytochemical substances from endophytic fungus found in medicinal plants. Curvularia geniculata L. (C. geniculata L.), an endophytic fungus isolated from Phyllanthus niruri L. (P. niruri L.), was tested against hepatoma cell lines (HepG2) in order to screen their antioxidant and anticancer potentials. The profiling of phytochemicals from the fungal extract was characterized using gas chromatography-mass spectrometry (GC-MS), and molecular docking was done for the identified compounds against one of the potential receptors predominantly present in the hepatocellular carcinoma cell lines. Among the phytochemicals found, 2-methyl-7-phenylindole had the highest binding affinity (- 8.8 kcal mol^-1) for the epidermal growth factor receptor (EGFR). The stability of 2-methyl-7-phenylindole in the EGFR-binding pockets was tested using in silico molecular dynamics simulation. The fungal extract showed the highest antioxidant activity as measured by DPPH, ABTS radical scavenging, and FRAP assays. In vitro cytotoxicity assay of fungal extract demonstrated the concentration-dependent cytotoxicity against HepG2 cells after 24 h, and the IC₅₀ (50% cell death) value was estimated to be 62.23 μg mL^-1. Typical morphological changes such as condensation of nuclei and deformed membrane structures are indicative of ongoing apoptosis. The mitochondria of HepG2 cells were also targeted by the endophytic fungal extract, which resulted in substantial generation of reactive oxygen species (ROS) leading to the destruction of mitochondrial transmembrane potential integrity. These outcomes suggest that the ethyl acetate extract of C. geniculata L. has the potential to be an antioxidant agent and further to be exploited in developing potential anticancer agents.