Extracellular carbohydrate metabolites from Streptomyces coelicolor A3(2)

New Anti-Inflammatory β-Resorcylic Acid Lactones Derived from an Endophytic Fungus, Colletotrichum sp

The endophytic fungus Colletotrichum gloeosprioides JS0419, isolated from the leaves of the halophyte Suaeda japonica, produced four new β-resorcylic acid derivatives, colletogloeopyrones A and B (1 and 2) and colletogloeolactones A and B (3 and 4), and seven known β-resorcylic acid lactones (RALs). The structures of these compounds were elucidated via analysis of the high-resolution mass spectrometry and nuclear magnetic resonance data. Compounds 1 and 2 showed a dihydrobenzopyranone ring with a linear C9 side chain, which is rarely observed in RALs. All isolated compounds were evaluated for their anti-inflammatory activities. Colletogloeopyrone A (1), monocillin II (5), and monocillin II glycoside (6) were effective in reducing nitric oxide production without cytotoxicity. They also inhibited the secretion of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), as demonstrated by the expression of mRNA corresponding to IL-6 and TNF-α. Mechanistically, compounds 5 and 6 significantly inhibited the protein expression of nuclear factor-κB, IκBα, IKKα/β, inducible nitric oxide synthase, and cyclooxygenase (COX)-2, whereas compound 1 only inhibited COX-2 expression. This study indicated that RAL-type compounds 1, 5, and 6 demonstrated potential anti-inflammatory activity by inhibiting the synthesis of pro-inflammatory cytokines.

Rare β-Resorcylic Acid Derivatives from a Halophyte-Associated Fungus Colletotrichum gloeosporioides JS0419 and Their Antifungal Activities

Six new β-resorcylic acid derivatives (1–5 and 7) were isolated from a halophyte-associated fungus, Colletotrichum gloeosporioides JS0419, together with four previously reported β-resorcylic acid lactones (RALs). The relative and absolute stereochemistry of 1 was completely established by a combination of spectroscopic data and chemical reactions. The structures of the isolated compounds were elucidated by analysis of HRMS and NMR data. Notably, compounds 1–3 had a β-resorcylic acid harboring a long unesterified aliphatic side chain, whereas the long aliphatic chains were esterified to form macrolactones in 4–9. Among the isolated compounds, monocillin I and radicicol showed potent antifungal activities against Cryptococcus neoformans, comparable to clinically available antifungal agents and radicicol showed weak antifungal activity against Candida albicans. These findings provide insight into the chemical diversity of fungal RAL-type compounds and their pharmacological potential.

Identification of Anomericity and Linkage of Arabinose and Ribose through Collision-Induced Dissociation

Arabinose and ribose are two common pentoses that exist in both furanose and pyranose forms in plant and bacteria oligosaccharides. In this study, each pentose isomer, namely α-furanose, β-furanose, α-pyranose, and β-pyranose, was first separated through high-performance liquid chromatography followed by an investigation of collision-induced dissociation in an ion trap mass spectrometer. The major dissociation channels, dehydration and cross-ring dissociation, were analyzed by using high-level quantum chemistry calculations and transition state theory. The branching ratio of major dissociation channels was governed by two geometrical features: one being the cis or trans configuration of O1 and O2 atoms determining dehydration preferability and the other being the number of hydroxyl groups on the same side of the ring as the O1 atom determining the preferability of cross-ring dissociation. The relative branching ratios of the major channels were used to identify anomericity and the linkages of arabinose and ribose. Arabinose in the β-configuration and ribose in the α-configuration are predicted to have larger relative dehydration branching ratios than arabinose in the α-configuration and ribose in the β-configuration, respectively. Arabinose and ribose at the reducing end of oligosaccharides with 1 → 2 (pyranose and furanose), 1 → 3 (pyranose and furanose), 1 → 4 (pyranose only), and 1 → 5 (furanose only) linkages are predicted to undergo ^0,2X, ^0,3X, ^0,2A, and ^0,2A/^0,3A cross-ring dissociation, respectively. Application of the dissociation mechanism to the disaccharide linkage determination is demonstrated.

Structuring Microbial Metabolic Responses to Multiplexed Stimuli via Self-Organizing Metabolomics Maps

Secondary metabolite biosynthesis in microorganisms responds to discrete chemical and biological stimuli; however, untargeted identification of these responses presents a significant challenge. Herein we apply multiplexed stimuli to Streptomyces coelicolor and collect the resulting response metabolomes via ion mobility-mass spectrometric analysis. Self-organizing map (SOM) analytics adapted for metabolomic data demonstrate efficient characterization of the subsets of primary and secondary metabolites that respond similarly across stimuli. Over 60% of all metabolic features inventoried from responses are either not observed under control conditions or produced at greater than 2-fold increase in abundance in response to at least one of the multiplexing conditions, reflecting how metabolites encode phenotypic changes in an organism responding to multiplexed challenges. Using abundance as an additional filter, each of 16 known S. coelicolor secondary metabolites is prioritized via SOM and observed at increased levels (1.2- to 22-fold compared with unperturbed) in response to one or more challenge conditions.

Production of specialized metabolites by Streptomyces coelicolor A3(2)

The actinomycetes are well-known bioactive natural product producers, comprising the Streptomycetes, the richest drug-prolific family in all kingdoms, producing therapeutic compounds for the areas of infection, cancer, circulation, and immunity. Completion and annotation of many actinomycete genomes has highlighted further how proficient these bacteria are in specialized metabolism, which have been largely underexploited in traditional screening programs. The genome sequence of the model strain Streptomyces coelicolor A3(2), and subsequent development of genomics-driven approaches to understand its large specialized metabolome, has been key in unlocking the high potential of specialized metabolites for natural product genomics-based drug discovery. This review discusses systematically the biochemistry and genetics of each of the specialized metabolites of S. coelicolor and describes metabolite transport processes for excretion and complex regulatory patterns controlling biosynthesis.

Isolation, structure, and antibacterial activities of lucensimycins D-G, discovered from Streptomyces lucensis MA7349 using an antisense strategy

Bacterial resistance to existing antibiotics continues to grow, necessitating the discovery of new compounds of this type. Antisense-based whole-cell target-based screening is a new and highly sensitive antibiotic discovery approach that has led to a number of new natural product antibiotics. Screening with a rpsD-sensitized strain led to the discovery of a number of natural product polyketides from Streptomyces lucensis. Complete workup of the fermentation extract of this strain allowed for the isolation of seven new compounds, lucensimycins A-G (1-3, 4a, 5-7), with varying degrees of antibacterial activities. Lucensimycin E (5) exhibited the best activity and showed MIC values of 32 microg/mL against Staphylococcus aureus and 8 microg/mL against Streptococcus pneumoniae. The isolation, structure elucidation, and antibacterial activities of four new members, lucensimycins D-G, are described. Lucensimycins D (4a) and E (5) are N-acetyl-l-cysteine adducts of lucensimycin A (1). Semisynthesis of lucensimycins D and E from lucensimycin A has also been described. Lucensimycins F and G are myo-inositolyl-alpha-2-amino-2-deoxy-l-idosyl amide derivatives of lucensimycins D and E, respectively. The relative configuration of these compounds was determined, in part, by molecular dynamics simulations.