Cyclic Peptides from the Soft Coral-Derived Fungus Aspergillus sclerotiorum SCSIO 41031

Three novel cyclic hexapeptides, sclerotides C–E (1–3), and a new lipodepsipeptide, scopularide I (4), together with a known cyclic hexapeptide sclerotide A (5), were isolated from fermented rice cultures of a soft coral-derived fungus: Aspergillus sclerotiorum SCSIO 41031. The structures of the new peptides were determined by 1D and 2D NMR spectroscopic analysis, Marfey’s method, ESIMS/MS analysis, and single crystal X-ray diffraction analysis. Scopularide I (4) exhibited acetylcholinesterase inhibitory activity with an IC50 value of 15.6 μM, and weak cytotoxicity against the human nasopharyngeal carcinoma cell line HONE-EBV with IC50 values of 10.1 μM.

Comparative Metabolomics Reveals Fungal Conversion of Co-Existing Bacterial Metabolites within a Synthetic Aspergillus-Streptomyces Community

In nature, secondary metabolites have been proven to be the essential communication media between co-occurring microorganisms and to influence their relationship with each other. In this study, we conducted a metabolomics survey of the secondary metabolites of an artificial co-culture related to a hydrothermal vent fungal–bacterial community comprising Aspergillus sclerotiorum and Streptomyces and their reciprocal relationship. The fungal strain was found to increase the secretion of notoamides and the compound cyclo(Pro-Trp) produced by the actinomycetes strain was discovered to be the responsible molecule. This led to the hypothesis that the fungi transformed cyclo(Pro-Trp) synthesized by the actinomycetes as the biosynthetic precursors of notoamides in the chemical communication. Further analysis showed Streptomyces sp. WU20 was efficient in transforming amino acids into cyclo(Pro-Trp) and adding tryptophan as well as proline into the chemical communication enhanced the induction of the notoamide accumulation. Thus, we propose that the microbial transformation during the synthetic metabolically-mediated chemical communication might be a promising means of speeding up the discovery of novel bioactive molecules. The objective of this research was to clarify the mechanism of microbial transformation for the chemical communication. Besides, this research also highlights the utility of mass spectrometry-based metabolomics as an effective tool in the direct biochemical analysis of community metabolites.

Antispasmodic Effect of Asperidine B, a Pyrrolidine Derivative, through Inhibition of L-Type Ca2+ Channel in Rat Ileal Smooth Muscle

Antispasmodic agents are used for modulating gastrointestinal motility. Several compounds isolated from terrestrial plants have antispasmodic properties. This study aimed to explore the inhibitory effect of the pyrrolidine derivative, asperidine B, isolated from the soil-derived fungus Aspergillus sclerotiorum PSU-RSPG178, on spasmodic activity. Isolated rat ileum was set up in an organ bath. The contractile responses of asperidine B (0.3 to 30 µM) on potassium chloride and acetylcholine-induced contractions were recorded. To investigate its antispasmodic mechanism, CaCl2, acetylcholine, Nω-nitro-l-arginine methyl ester (l-NAME), nifedipine, methylene blue and tetraethylammonium chloride (TEA) were tested in the absence or in the presence of asperidine B. Cumulative concentrations of asperidine B reduced the ileal contraction by ~37%. The calcium chloride and acetylcholine-induced ileal contraction was suppressed by asperidine B. The effects of asperidine B combined with nifedipine, atropine or TEA were similar to those treated with nifedipine, atropine or TEA, respectively. In contrast, in the presence of l-NAME and methylene blue, the antispasmodic effect of asperidine B was unaltered. These results suggest that the antispasmodic property of asperidine B is probably due to the blockage of the L-type Ca2+ channel and is associated with K+ channels and muscarinic receptor, possibly by affecting non-selective cation channels and/or releasing intracellular calcium.

Antifungal Activity of Silver Nanoparticles with the Potential to Control Fungal Contamination in the Male Inflorescences of Palmyra Palm

Fungal contamination of the male inflorescences of palmyra palm (Borassus flabellifer Linn.) is a serious problem during their storage prior being used as the raw material for making the local One-Tambon-One-Product, a cloth holder known as “Nguang Taan Hom” made by the Phutaan Entrepreneurship, Takua Thung District PhangNga Province, Thailand. Morphological and molecular techniques were used to identify the isolated fungi from male palmyra palm inflorescences. Three major strains: Aspergillus niger, Aspergillus fumigatus and Aspergillus sclerotiorum were studied for antifungal activities and the minimum inhibitory concentration (MIC) of silver nanoparticles (AgNPs) was found to range from 13.5–27 mg mL–1. Then, the efficiency of the AgNPs and silver nanoparticles stabilizing by Polyvinylpyrrolidone (AgNPs-PVP) on the male palmyra palm inflorescences was studied by constructing a chamber model over a period for 9 weeks. The results showed that the group inoculated with Aspergillus niger, Aspergillus fumigatus and Aspergillus sclerotiorum spores developed fungal growth after 4 weeks whereas no fungal growth was observed in the group treated with AgNPs and AgNPs-PVP at 27 μg/ mL until week 7, indicating that dipping with either AgNPs or AgNPs-PVP is able to inhibit the growth of the fungi which cause damage to raw materials and also threaten human health. Therefore, it can effectively extend the storage time of male palmyra inflorescences.

Evaluation of Metal Tolerance of Fungal Strains Isolated from Contaminated Mining Soil of Nanjing, China

Rapidly increasing industry has resulted in greater discharge of hazardous chemicals in the soil. In the current study, soil samples were collected from Nanjing mine (32°09′19.29″ N 118°56′57.04″ E) and subjected to heavy metal analysis and microbe isolation. A total of 460 fungi were isolated, and five of these were yeast strains. Most of the strains exhibited tolerance to one metal. Five multimetal tolerant strains were selected and identified as Aspergillus sclerotiorum, Aspergillus aculeatus, Komagataella phaffii, Trichoderma harzianum, and Aspergillus niger. Isolated strains were grown in high concentrations of cadmium (Cd), chromium (Cr) and lead (Pb), for induced-tolerance training. The tolerance index (TI) revealed the highest Cd tolerance of novel K. phaffii strain at 5500 ppm (TI: 0.2). K. phaffii also displayed resistance at 4000 ppm against Cr (TI: 0.32) and Pb (TI: 0.32). In contrast, tolerance training for A. niger was not that successful. K. phaffii also displayed the highest bioaccumulation capacity for Cd (25.23 mg/g), Cu (21.63 mg/g), and Pb (20.63 mg/g) at 200 ppm. Scanning electron microscopy (SEM) explored the morphological changes in the mycelia of stressed fungi. Results of this study describe this delicate approach to be species and metal dependent and suggest a potential utilization of this fungal strain for the bioremediation of contaminated soils.

Lovastatin Production by Aspergillus sclerotiorum Using Agricultural Waste

Research background. Lovastatin is a well-known drug used to reduce hypercholesterolaemia. However, the cost of lovastatin production is still high. Therefore, alternative low-cost carbon sources for the production of lovastatin are desirable.Experimental approach. Four different agricultural wastes, namely corn trunks, rice husks, wild sugarcane, and soya bean sludge, were tested separately as substrates to produce lovastatin using a new fungal strain, Aspergillus sclerotiorum PSU-RSPG 178, under both submerged and solid-state fermentation (SSF).Results and conclusions. Of these substrates and cultivation systems, soya bean sludge gave the highest lovastatin yield on dry mass basis of 0.04 mg/g after 14 days of SSF at 25 °C. Therefore, the soya bean sludge was separately supplemented with glucose, wheat flour, trace elements, palm oil, urea and molasses. The addition of the palm oil enhanced the lovastatin yield to 0.99 mg/g. In addition, the optimum conditions, which gave a lovastatin yield of (20±2) mg/g after 18 days of SSF, were soya bean sludge containing 80 % moisture (dry basis) at a ratio of soya bean sludge (g) to mycelial agar plugs of 1:4, and a ratio of soya bean sludge (g) to palm oil (mL) of 1:2. Besides, the lovastatin yields obtained from SSF using fresh or dry soya bean sludge were not significantly different.Novelty and scientific contribution. We conclude that A. sclerotiorum PSU-RSPG 178 has a good potential as an alternative strain for producing lovastatin using soya bean sludge supplemented with palm oil as a carbon source.

New Butenolides and Cyclopentenones from Saline Soil-Derived Fungus Aspergillus Sclerotiorum

Three new γ-hydroxyl butenolides (1–3), a pair of new enantiomeric spiro-butenolides (4a and 4b), a pair of enantiomeric cyclopentenones (5a new and 5b new natural), and six known compounds (6–11), were isolated from Aspergillus sclerotiorum. Their structures were established by spectroscopic data and electronic circular dichroism (ECD) spectra. Two pairs of enantiomers [(+)/(–)-6c and (+)/(–)-6d] obtained from the reaction of 6 with acetyl chloride (AcCl) confirmed that 6 was a mixture of two pairs of enantiomers. In addition, the X-ray data confirmed that 7 was also a racemate. The new metabolites (1−5) were evaluated for their inhibitory activity against cancer and non-cancer cell lines. As a result, compound 1 exhibited moderate cytotoxicity to HL60 and A549 with IC50 values of 6.5 and 8.9 µM, respectively, and weak potency to HL-7702 with IC50 values of 17.6 µM. Furthermore, compounds 1−9 were screened for their antimicrobial activity using the micro-broth dilution method. MIC values of 200 μg/mL were obtained for compounds 2 and 3 towards Staphylococcus aureus and Escherichia coli, while compound 8 exhibited a MIC of 50 μ/mL towards Candida albicans.