Fuhang Song

Bioprospecting microbial natural product libraries from the marine environment for drug discovery

Marine microorganisms are fascinating resources due to their production of novel natural products with antimicrobial activities. Increases in both the number of new chemical entities found and the substantiation of indigenous marine actinobacteria present a fundamental difficulty in the future discovery of novel antimicrobials, namely dereplication of those compounds already discovered. This review will share our experience on the taxonomic-based construction of a highly diversified and low redundant marine microbial natural product library for high-throughput antibiotic screening. We anticipate that libraries such as these can drive the drug discovery process now and in the future.

Abyssomicins from the South China Sea deep-sea sediment Verrucosispora sp.: natural thioether michael addition adducts as antitubercular prodrugs

Tuberculosis (TB) is a leading cause of death in the world today, and is exacerbated by the prevalence of multi- (MDR-TB), extensively (XDR-TB), and totally (TDR-TB) drug resistant strains. Despite the threat to human health, existing frontline TB therapeutics remain constrained to a handful of vintage antibiotics prescribed in a combinatorial format to achieve efficacy. The current shortfall in antitubercular drugs demands urgent attention, to develop new antibiotics effective against all strains of tuberculosis.

Trichodermaketones A-D and 7-O-Methylkoninginin D from the Marine Fungus Trichoderma koningii

Five new polyketide derivatives, 7-O-methylkoninginin D (1) and trichodermaketones A-D (2-5), together with four known compounds, koninginins A, D, E, and F, were isolated from the marine-derived fungus Trichoderma koningii. Trichodermaketones A (2) and B (3) are unprecedented polyketides with a bistetrafuran-containing tricyclic skeleton. The chemical structures and absolute configurations of compounds 1-5 were elucidated by comparing with literature data and extensive spectroscopic methods, including 2D NMR and CD spectroscopic analysis. Compounds 1-5 were evaluated for action against bacteria and fungi and for synergistic antifungal activity. Compound 2 showed synergistic antifungal activity against Candida albicans with 0.05 microg/mL ketoconazole.

Amycolatopsis marina sp nov., an actinomycete isolated from an ocean sediment

A Gram-positive, aerobic, non-motile actinobacterium, designated strain Ms392A(T), was isolated from an ocean-sediment sample collected from the South China Sea. The isolate contained chemical markers that supported chemotaxonomic assignment to the genus Amycolatopsis. On the basis of an analysis of 16S rRNA gene sequence similarities, strain Ms392A(T) represents a novel subclade within the genus Amycolatopsis, with Amycolatopsis palatopharyngis 1BDZ(T) as its closest phylogenetic neighbour (99.4 % similarity). However, DNA-DNA hybridization demonstrated that strain Ms392A(T) was distinct from A. palatopharyngis AS 4.1729(T) (48.6 % relatedness). The polyphasic analysis demonstrated that the ocean isolate can be clearly distinguished from recognized species of the genus Amycolatopsis. Therefore, strain Ms392A(T) represents a novel species of the genus Amycolatopsis, for which the name Amycolatopsis marina sp. nov. is proposed. The type strain is Ms392A(T) (=CGMCC 4.3568(T) =NBRC 104263(T)).

Bioprospecting for antituberculosis leads from microbial metabolites

Microbial metabolites have been an important source of tuberculosis (TB) therapeutics, but the last truly novel drug that was approved for the treatment of TB was discovered 40 years ago. In light of the growing threat of multi-drug resistance, recent advances have been made to accelerate the discovery rate of novel TB drugs including diversifying strategies for environmental strains, and high-throughput screening assays. This review will discuss the approaches used in biodiversity- and taxonomy-guided microbial natural product library construction, specific cell-based and target-based high-throughput screening assays and early-stage dereplication processes by liquid chromatography-mass spectrometry (LC-MS). New antituberculosis natural products that have been recently discovered are highlighted.

New benzoate derivatives and hirsutane type sesquiterpenoids with antimicrobial activity and cytotoxicity from the solid-state fermented rice by the medicinal mushroom Stereum hirsutum

In addition to the fruiting bodies, mushroom mycelia can be used as functional foods and nutraceutical materials. In this study, two new benzoate derivatives (1 and 2) and three new sesquiterpenoids (3-5) were isolated from the mycelia of Stereum hirsutum. Their chemical structures were elucidated by NMR experiments. The absolute configuration in 3 was assigned by X-ray crystallographic analysis. In bioactivities evaluation, compounds 1 and 2 showed antimicrobial effects against methicillin-resistant Staphylococcusaureus, and S. aureus with the MIC values of 25.0μg/mL; compounds 1 and 3 inhibited the NO overproduction in the LPS-induced macrophages with the IC50 values of 19.17 and 15.44μM, and also displayed cytotoxicity against A549 and HepG2 with IC50 in the range of 10-50μM. These results support the usage of the mycelia of S. hirsutum as a good functional food.

Optimization for the Production of Surfactin with a New Synergistic Antifungal Activity

Background Two of our long term efforts are to discover compounds with synergistic antifungal activity from metabolites of marine derived microbes and to optimize the production of the interesting compounds produced by microorganisms. In this respect, new applications or mechanisms of already known compounds with a high production yield could be continually identified. Surfactin is a well-known lipopeptide biosurfactant with a broad spectrum of antimicrobial and antiviral activity; however, there is less knowledge on surfactin’s antifungal activity. In this study, we investigated the synergistic antifungal activity of C15-surfactin and the optimization of its production by the response surface method. Methodology/Principal Findings Using a synergistic antifungal screening model, we found that the combination of C15-surfactin and ketoconazole (KTC) showed synergistic antifungal effect on Candida albicans SC5314 when the concentrations of C15-surfactin and KTC were 6.25 µg/mL and 0.004 µg/mL, respectively. These concentrations were lower than their own efficient antifungal concentrations, which are >100 µg/mL and 0.016 µg/mL, respectively. The production of C15-surfactin from Bacillus amyloliquefaciens was optimized by the response surface methodology in shaker flask cultivation. The Plackett-Burman design found sucrose, ammonium nitrate and NaH2PO4.2H2O to have significant effects on C15-surfactin production. The optimum values of the tested variables were 21.17 g/L sucrose, 2.50 g/L ammonium nitrate and 11.56 g/L NaH2PO4·2H2O. A production of 134.2 mg/L, which were in agreement with the prediction, was observed in a verification experiment. In comparison to the production of original level (88.6 mg/L), a 1.52-fold increase had been obtained. Conclusion/Significance This work first found that C15-surfactin was an efficient synergistic antifungal agent, and demonstrated that response surface methodology was an effective method to improve the production of C15-surfactin.

Terpenoid and phenolic metabolites from the fungus xylaria sp. associated with termite nests.

Three new sesquiterpene acids, xylaric acids A–C (1–3, resp.), and a new tetralone (=3,4‐dihydronaphthalen‐1(2H)‐one) derivative, 4, along with nine known compounds, xylaric acid D (5), hydroheptelidic acid (6), gliocladic acid (7), chlorine heptelidic acid (8), trichoderonic acid A (9), 16‐(α‐D‐mannopyranosyloxy)isopimar‐7‐en‐19‐oic acid (10), 16‐(α‐D‐glucopyranosyloxy)isopimar‐7‐en‐19‐oic acid (11), 5‐carboxymellein (12), and naphthalen‐1,8‐diol 1‐O‐α‐D‐glucopyranoside (13) have been isolated from the solid culture of the ascomycete fungus Xylaria sp. associated with termite nest. The structures of these compounds were elucidated primarily by NMR experiments. The absolute configurations of compounds 1–3 and 5–9 were determined by combination of X‐ray data and CD spectral analysis. The absolute configuration of 4 was assigned by Snatzkes method. Compounds 8 and 11 showed slight cytotoxicities against two cell lines A549 and SGC7901.

Tricycloalternarenes F-H: three new mixed terpenoids produced by an endolichenic fungus Ulocladium sp. using OSMAC method.

Three new mixed terpenoids, tricycloalternarenes (TCAs) F-H (1-3), together with ten known tricycloalternarenes (4-13), were isolated from the Czapeks culture of an endophytic fungus Ulocladium sp. Their structures were identified by extensive spectroscopic experiments (NMR and MS) and comparison with literature data. TCA 1b (5) showed weak activity against the Bacille Calmette-Guerin strain with the MIC of 125μg/mL. TCA 9b (10) exhibited strong cytotoxic activity against Hela cell line with IC50 of 8.58μM.

Synergistic Effect of 14-Alpha-Lipoyl Andrographolide and Various Antibiotics on the Formation of Biofilms and Production of Exopolysaccharide and Pyocyanin by Pseudomonas aeruginosa

ABSTRACT Pseudomonas aeruginosa produces a biofilm that provides the bacteria with an effective barrier against antibiotics. Here, we investigated the synergy of various antibiotics with 14-alpha-lipoyl andrographolide (AL-1), focusing upon synthesis of the biofilm. AL-1 also inhibited the production of the exopolysaccharide and pyocyanin components. We propose that AL-1 may potentially serve as a cotherapy to combat P. aeruginosa.