Undescribed benzophenone and xanthones from cave-derived Streptomyces sp. CB09001

Discovery of phenoxazine congeners as novel α-glucosidase inhibitors and identification of their biosynthetic gene cluster from Streptomyces sp. CB00316

α-Glucosidase is considered an ideal target for the treatment of type 2 diabetes mellitus. Streptomyces species are known to produce a plethora of bioactive metabolites. On the basis of genomic information, the one strain many compounds (OSMAC) strategy and various chromatographic separation techniques, two compounds, bezerramycin A (1) and elloxazinone A (2), were identified from among Streptomyces sp. CB00316 metabolites. The α-glucosidase inhibitory activities of the isolated compounds were evaluated and compound 2 showed the strongest activity, with an IC50 value of 74.31 ± 3.74 µM. In silico molecular docking and molecular dynamics simulations confirmed the in vitro activities of these α-glucosidase inhibitors. In addition, we investigated the biosynthetic gene clusters and metabolic pathways of compounds 1 and 2. These findings highlight the potential of phenoxazines as lead compounds to combat the development of type 2 diabetes.

Subterranean marvels: microbial communities in caves and underground mines and their promise for natural product discovery

Covering: 2014 to 2024Since the dawn of human history, caves have played an intimate role in our existence. From our earliest ancestors seeking shelter from the elements to more recent generations harnessing cave substances for medicinal purposes, caves have served as essential resources and havens. The last 40 years of geomicrobiology research has replaced the outdated perception of subterranean environments as lifeless and unchanging with the realization that vibrant microbial communities have adapted to thrive in extreme conditions over millions of years. The ability of subterranean microbial communities to withstand nutrient deprivation and darkness creates a unique reservoir of untapped biosynthetic potential. These communities offer exciting prospects for medicine (e.g., antimicrobial and antitumor therapies) and biotechnology (e.g., redox chemical properties and biomineralization). This article highlights the significance of caves and mines as reservoirs of microbial diversity, the potential impact of their bioactive compounds on the fields of healthcare and biotechnology, and the significant challenges that must be overcome to access and harness the biotechnological potential of subterranean microbial communities. Additionally, it emphasizes the conservation efforts needed to protect these delicate ecosystems, ensuring the preservation of both ancient traditions and tomorrow's medicines.

Analysis of the Setomimycin Biosynthetic Gene Cluster from Streptomyces nojiriensis JCM3382 and Evaluation of Its α-Glucosidase Inhibitory Activity Using Molecular Docking and Molecular Dynamics Simulations

The formation of atroposelective biaryl compounds in plants and fungi is well understood; however, polyketide aglycone synthesis and dimerization in bacteria remain unclear. Thus, the biosynthetic gene cluster (BGC) responsible for antibacterial setomimycin production from Streptomyces nojiriensis JCM3382 was examined in comparison with the BGCs of spectomycin, julichromes, lincolnenins, and huanglongmycin. The setomimycin BGC includes post-polyketide synthase (PKS) assembly/cycling enzymes StmD (C-9 ketoreductase), StmE (aromatase), and StmF (thioesterase) as key components. The heterodimeric TcmI-like cyclases StmH and StmK are proposed to aid in forming the setomimycin monomer. In addition, StmI (P-450) is predicted to catalyze the biaryl coupling of two monomeric setomimycin units, with StmM (ferredoxin) specific to the setomimycin BGC. The roles of StmL and StmN, part of the nuclear transport factor 2 (NTF-2)-like protein family and unique to setomimycin BGCs, could particularly interest biochemists and combinatorial biologists. α-Glucosidase, a key enzyme in type 2 diabetes, hydrolyzes carbohydrates into glucose, thereby elevating blood glucose levels. This study aimed to assess the α-glucosidase inhibitory activity of EtOAc extracts of JCM 3382 and setomimycin. The JCM 3382 EtOAc extract and setomimycin exhibited greater potency than the standard inhibitor, acarbose, with IC50 values of 285.14 ± 2.04 μg/mL and 231.26 ± 0.41 μM, respectively. Molecular docking demonstrated two hydrogen bonds with maltase-glucoamylase chain A residues Thr205 and Lys480 (binding energy = -6.8 kcal·mol-1), two π-π interactions with Trp406 and Phe450, and one π-cation interaction with Asp542. Residue-energy analysis highlighted Trp406 and Phe450 as key in setomimycin's binding to maltase-glucoamylase. These findings suggest that setomimycin is a promising candidate for further enzymological research and potential antidiabetic therapy.

Natural products with γ-pyrone scaffold from Streptomyces

The Streptomyces sp. is considered the vast reservoir of bioactive natural products belonging to different classes like polyketides, terpenoids, lanthipeptides, and non-ribosomal peptides to name a few. The ubiquitous distribution of the genus makes them capable of producing distinct compounds. Many of those compounds contain a unique γ-pyrone with various chemical structures and exhibit different bioactivities. One such class, nitrophenyl-γ-pyrone, constitutes different bioactive compounds isolated from Streptomyces sp. from different sources ranging from soil to marine environments. In addition, such compounds have antinematodal, cytotoxicity activities, and inhibition of adipogenesis. These compounds include aureothin (3), spectinabilin (7), and their derivatives. Moreover, there are other compounds like actinopyrones (11-16), benwamycins (22-23), and peucemycin and its derivatives (24-26) that also have antibacterial and anticancer activities. The other group classified as anthra-γ-pyrone has various bioactive natural products. For instance, tetrahydroanthra-γ-pyrone, shellmycin A-D (27-30) possess antibacterial as well as anticancer activities. In addition, the pluramycin family compounds belonging to anthra-γ-pyrone group also possess cytotoxic activity, for instance, kidamycin (31), rubiflavin, and their derivatives (33-37). Xanthones are another important group of natural products that also contain γ-pyrone ring producing different bioactivities. Albofungin (42) and its derivatives (43-46) belong to subgroup polycyclic tetrahydro xanthones that possess antibacterial, anticancer, and antibiofilm, antimacrofouling activities. Similarly, other compounds, belonging to this subgroup, exhibit different bioactivities like antifungal, antimalarial, and antibacterial activities and block transient receptor potential vanilloid 1 (TRPV1). These compounds include cervinomycins (48-55), citreamycins (56-57), sattahipmycin (59), and chrexanthomycins (60-63). This review gives succinct information on the γ-pyrone containing natural products isolated from Streptomyces sp. focusing on their structure and bioactivities. KEY POINTS: • The Streptomyces sp. is the producer of various bioactive natural products including the one with γ-pyrone ring. • These γ-pyrone compounds are structurally different and possess different bioactivities. • The Streptomyces has the potential to produce such compounds and the reservoir of these compounds is expected to increase in the future.

Pseudocercones A-C, three new polyketide derivatives from the endophytic fungus Pseudocercospora sp. TSS-1

Chemical investigation of an EtOAc extract of the endophytic fungus Pseudocercospora sp. TSS-1 led to the isolation of three new polyketide derivatives, including one benzophenon derivative (1), two spirocyclic polyketides (4 and 5), along with four known compounds (2, 3, 6 and 7). Their structures and the absolute configurations were characterized by means of NMR, HRESIMS, 13C NMR and theoretical electronic circular dichroism calculations. Furthermore, all compounds were evaluated for their antibacterial activity against four microbial pathogens (Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Escherichia coli), and compounds 1, 2, 3 and 5 displayed significant selective antibacterial activity against S. aureus with MIC values ranging from 3.9 to 7.8 µg/mL.

Muyocoxanthones O-S: Undescribed xanthones with antioxidative damage bioactivity to cardiomyocytes from the endophytic fungus Muyocopron laterale

The metabolites from the endophytic fungus Muyocopron laterale hosted in the medicinal plant Tylophora ovata were investigated, and five undescribed xanthones, muyocoxanthones O-S, along with seven known compounds were isolated. Their structures were elucidated by HR-ESI-MS, NMR, and ECD calculations. Compounds were evaluated for their anti-cardiomyocyte oxidative damage activity using a model of oxidative damage induced by cell hypoxia incubation. Muyocoxanthones O-Q and blennolide L exhibited moderate activity against oxidative damage to cardiomyocytes with relative viabilities of 62.4, 54.8, 60.3 and 54.9%, respectively.

Discovery of a DNA Topoisomerase I Inhibitor Huanglongmycin N and Its Congeners from Streptomyces sp. CB09001

Huanglongmycin (HLM) congeners G-N (7-14) were isolated from Streptomyces sp. CB09001. Among them, 10-12 possesses a tricyclic scaffold with benzene-fused pyran/pyrone, confirmed by X-ray single crystal diffraction analysis of 12. The structure-activity relationship study of 1, 13, and 14 revealed not only the stronger cytotoxicity of 14 against tested cancer cells but also the critical role of the C-7 ethyl group of 14 in its binding to the DNA-topoisomerase I complex.

Chemical constituents from the Streptomyces morookaensis strain Sm4-1986

Three new compounds, including 6-methoxy-3,4,5,7-tetramethylisochromane-3,8-diol (1), 3,4,5,7-tetramethylisochromane-3,6,8-triol (2), streptimidone derivative (3), along with ten known compounds (4-13) were isolated from the Streptomyces morookaensis strain Sm4-1986. Their chemical structures were established based on the information from UV, IR, NMR (¹H NMR, ¹³C NMR, ¹H-¹H COSY, HSQC, HMBC, NOESY), and mass spectroscopic. Moreover, all the isolated new compounds were evaluated for antibacterial activities (S. aureus, B. cereus, S. epidermids and methicillin-resistant S. aureus) and their cytotoxicities against MCF-7, A549, Hela tumor cell lines and Marc-145 normal cell line.