Streptoglycerides E-H, Unsaturated Polyketides from the Marine-Derived Bacterium Streptomyces specialis and Their Anti-Inflammatory Activity

Exploring Bioactive Potential of Streptomyces thinghirensis WAE1 from Wadi El-Natron, Egypt

This study aimed to investigate the bioactive metabolites produced by Streptomyces thinghirensis WAE1, an actinomycete isolated from El-Hamara Lake in Egypt. The discovery of new bioactive compounds from natural sources is crucial for the advancement of therapeutic treatments, and this study aimed to contribute to this field by exploring the potential of Streptomyces thinghirensis WAE1 as a source of such compounds. Streptomyces thinghirensis WAE1 was screened for its ability to produce antimicrobial, antioxidant, and anti-inflammatory metabolites. The results revealed that S. thinghirensis WAE1 exhibited strong antimicrobial activity against Streptococcus pneumoniae and moderate activity against Listeria monocytogenes, Staphylococcus aureus, and Candida albicans. Streptomyces thinghirensis WAE1 also displayed antioxidant activity through scavenging free radicals and chelating iron, and moderate anti-inflammatory activity as determined by its IC50 value. The isolate's demonstration of L-asparaginase activity suggests that S. thinghirensis WAE1 is a promising source of bioactive compounds with potential therapeutic uses. The high salinity and alkalinity of El-Hamara Lake, which create favorable conditions for the production of bioactive metabolites, further add to its potential as a source of actinomycetes strains with bioactive properties. These findings make both S. thinghirensis WAE1 and El-Hamara Lake valuable subjects for further exploration in the field of bioactive compounds.

Pyrrolidine, Piperazine, and Diazinane Alkaloids from the Marine Bacterium Strain Vibrio ruber ZXR-93

Four new alkaloids, vibripyrrolidine A (1), vibripiperazine A (2), and vibridiazinane A, B (3, 4), comprising one pyrrolidine, one piperazine, and two diazinane alkaloids, along with two known analogs (5, 6), were isolated from the marine bacterium Vibrio ruber ZXR-93 cultured in ISP2 medium. Their chemical structures were elucidated by analysis of their 1D and 2D NMR, mass spectra, and electronic circular dichroism (ECD) calculations. Compounds 1 and 3-6 showed vigorous antibacterial activity against Staphylococcus aureus, with MIC values ranging from 0.96 to 7.81 μg/mL. Moreover, compound 1 exhibited robust anti-inflammatory activity in vitro using the LPS-induced RAW264.7 macrophage model. All compounds also showed moderate antineoplastic activity against cervical cancer cells (HeLa) and gastric cancer cells (SGC-7901).

Recent Advances in Anti-Inflammatory Compounds from Marine Microorganisms

Marine microbial secondary metabolites with diversified structures have been found as promising sources of anti-inflammatory lead compounds. This review summarizes the sources, chemical structures, and pharmacological properties of anti-inflammatory natural products reported from marine microorganisms in the past three years (2021-2023). Approximately 252 anti-inflammatory compounds, including 129 new ones, were predominantly obtained from marine fungi and they are structurally divided into polyketides (51.2%), terpenoids (21.0%), alkaloids (18.7%), amides or peptides (4.8%), and steroids (4.3%). This review will shed light on the development of marine microbial secondary metabolites as potential anti-inflammatory lead compounds with promising clinical applications in human health.

Genome-guided discovery of two undescribed 6,6-spiroketal polyketides and stereochemical correction of bafilomycins P and Q from the marine-derived Streptomyces sp. SCSIO 66814

Bafilomycins are macrocyclic polyketides with intriguing structures and therapeutic value. Genomic analysis of Streptomyces sp. SCSIO 66814 revealed a type I polyketide synthase biosynthetic gene cluster (BGC), namely blm, which encoded bafilomycins and featured rich post-modification genes. The One strain many compounds (OSMAC) strategy led to the discovery of six compounds related to the blm BGC from the strain, including two previously undescribed 6,6-spiroketal polyketides, streptospirodienoic acids D (1) and E (2), and four known bafilomycins, bafilomycins P (3), Q (4), D (5), and G (6). The structures of 1 and 2 were determined by extensive spectroscopic analysis, quantum calculation, and biosynthetic analysis. Additionally, the absolute configurations of the 6/5/5 tricyclic ring moiety containing six consecutive chiral carbons in the putative structures of 3 and 4 were corrected through NOE analysis, DP4+ calculation, and single-crystal X-ray diffraction data. Bioinformatic analysis uncovered a plausible biosynthetic pathway for compounds 1-6, indicating that both streptospirodienoic acids and bafilomycins were derived from the same blm BGC. Additionally, sequence analysis revealed that the KR domains of module 2 from blm BGC was B1-type, further supporting the configurations of 1-4. Notably, compounds 3 and 4 displayed significant cytotoxic activities against A-549 human non-small cell lung cancer cells and HCT-116 human colon cancer cells.

The Plethora of Microbes with Anti-Inflammatory Activities

Inflammation, which has important functions in human defense systems and in maintaining the dynamic homeostasis of the body, has become a major risk factor for the progression of many chronic diseases. Although the applied medical products alleviate the general status, they still exert adverse effects in the long term. For this reason, the solution should be sought in more harmless and affordable agents. Microorganisms offer a wide range of active substances with anti-inflammatory properties. They confer important advantages such as their renewable and inexhaustible nature. This review aims to provide the most recent updates on microorganisms of different types and genera, being carriers of anti-inflammatory activity.

Marine natural products

Covering: January to the end of December 2022This review covers the literature published in 2022 for marine natural products (MNPs), with 645 citations (633 for the period January to December 2022) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, the submerged parts of mangroves and other intertidal plants. The emphasis is on new compounds (1417 in 384 papers for 2022), 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 NP structure class diversity in relation to biota source and biome is discussed.

Aspersterols A-D, Ergostane-Type Sterols with an Unusual Unsaturated Side Chain from the Deep-Sea-Derived Fungus Aspergillus unguis

Four previously undescribed ergostane-type sterols, aspersterols A-D (1-4), were isolated from a deep-sea-derived fungus, Aspergillus unguis IV17-109. The structures of the new compounds were determined by extensive analyses of their spectroscopic data, pyridine-induced deshielding effect, Mosher's method, and electronic circular dichroism calculations. The key feature of these sterols is the presence of a rare unsaturated side chain with conjugated double bonds at Δ¹⁷ and Δ²². The absolute configuration of C-24 in the side chain was determined by hydrogenation and comparing ¹³C NMR chemical shifts of the hydrogenated products with literature values. In addition, aspersterol A (1) is the second representative of anthrasteroids with a hydroxy group at the C-2 position. Compound 1 showed cytotoxicity against six cancer cell lines, with GI₅₀ values of 3.4 ± 0.3 to 4.5 ± 0.7 μM, while 2-4 showed anti-inflammatory activity, with IC₅₀ values ranging from 11.6 ± 1.6 to 19.5 ± 1.2 μM.

Unusual Secondary Metabolites from the Mangrove Ecosystems: Structures, Bioactivities, Chemical, and Bio-Syntheses

Mangrove ecosystems are widely distributed in the intertidal zone of tropical and subtropical estuaries or coasts, containing abundant biological communities, for example, mangrove plants and diverse groups of microorganisms, featuring various bioactive secondary metabolites. We surveyed the literature from 2010 to 2022, resulting in a collection of 134 secondary metabolites, and classified them into two major families in terms of the biological sources and 15 subfamilies according to the chemical structures. To highlight the structural diversity and bioactivities of the mangrove ecosystem-associated secondary metabolites, we presented the chemical structures, bioactivities, biosynthesis, and chemical syntheses.

Nitrogen-Containing Secondary Metabolites from a Deep-Sea Fungus Aspergillus unguis and Their Anti-Inflammatory Activity

Aspergillus is well-known as the second-largest contributor of fungal natural products. Based on NMR guided isolation, three nitrogen-containing secondary metabolites, including two new compounds, variotin B (1) and coniosulfide E (2), together with a known compound, unguisin A (3), were isolated from the ethyl acetate (EtOAc) extract of the deep-sea fungus Aspergillus unguis IV17-109. The planar structures of 1 and 2 were elucidated by an extensive analysis of their spectroscopic data (HRESIMS, 1D and 2D NMR). The absolute configuration of 2 was determined by comparison of its optical rotation value with those of the synthesized analogs. Compound 2 is a rare, naturally occurring substance with an unusual cysteinol moiety. Furthermore, 1 showed moderate anti-inflammatory activity with an IC₅₀ value of 20.0 µM. These results revealed that Aspergillus unguis could produce structurally diverse nitrogenous secondary metabolites, which can be used for further studies to find anti-inflammatory leads.