Antimicrobial Potential of Endophytic Fungi Derived from Three Seagrass Species: Cymodocea serrulata,Halophila ovalis and Thalassia hemprichii

Endophytic fungi from three commonly found seagrasses in southern Thailand were explored for their ability to produce antimicrobial metabolites. One hundred and sixty endophytic fungi derived from Cymodocea serrulata (Family Cymodoceaceae), Halophila ovalis and Thalassia hemprichii (Family Hydrocharitaceae) were screened for production of antimicrobial compounds by a colorimetric broth microdilution test against ten human pathogenic microorganisms including Staphylococcus aureus ATCC 25923, a clinical isolate of methicillin-resistant S. aureus, Escherichia coli ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Candida albicans ATCC 90028 and NCPF 3153, Cryptococcus neoformans ATCC 90112 and ATCC 90113 and clinical isolates of Microsporum gypseum and Penicillium marneffei . Sixty-nine percent of the isolates exhibited antimicrobial activity against at least one test strain. Antifungal activity was more pronounced than antibacterial activity. Among the active fungi, seven isolates including Hypocreales sp. PSU-ES26 from C . serrulata , Trichoderma spp. PSU-ES8 and PSU-ES38 from H . ovalis , and Penicillium sp. PSU-ES43, Fusarium sp. PSU-ES73, Stephanonectria sp. PSU-ES172 and an unidentified endophyte PSU-ES190 from T . hemprichii exhibited strong antimicrobial activity against human pathogens with minimum inhibitory concentrations (MIC) of less than 10 µg/ml. The inhibitory extracts at concentrations of 4 times their MIC destroyed the targeted cells as observed by scanning electron microscopy. These results showed the antimicrobial potential of extracts from endophytic fungi from seagrasses.     

Evaluation of in vitro alpha-glucosidase inhibitory,antimicrobial, and cytotoxic activities of secondary metabolites from the endophytic fungus,Nigrospora sphaerica,isolated from Helianthus annuus

This study aimed to evaluate alpha-glucosidase inhibition and antimicrobial activity as well as cytotoxic activity of extracts from the endophytic fungus, Nigrospora sp., isolated from leaves of Helianthus annuus, which is widely cultivated for food and used as a medicinal plant. The fungus (TSU-CS003) was identified based on internal transcribed spacer ribosomal DNA sequences and fungal biomass, and fermentation broth was subjected to extraction by solvents (hexane and ethyl acetate). All extracts were tested for their antimicrobial activity, alpha-glucosidase inhibition, and cytotoxicity activity. In addition, the active extract was analyzed by using gas chromatography mass spectrometry (GC-MS) TSU-CS003 was identified as Nigrospora sphaerica. The fermentation broth extract (BE) showed strong antimicrobial activity against Staphylococcus aureus and methicillin-resistant S. aureus (Gram-positive bacteria) with minimum inhibitory concentration (MIC) values in the range of 16–32 μg/mL and a few yeasts with MIC values ranging from 64 to 128 μg/mL, especially Talaromyces marneffei with an MIC value of 4 μg/mL. The effects of BE were observed by SEM. The results showed that this extract affected the cell morphology of T. marneffei. The half-maximal inhibitory concentration (IC50) of BE from alpha-glucosidase inhibition was recorded as 17.25 μg/mL and also showed significant cytotoxicity against A549 human cancer cell lines with an IC50 value of 22.41 μg/mL. Furthermore, BE was analyzed by using GC-MS and divided into three main compounds, including 5-pentyldihydrofuran-2(3H)-one, (Z)-methyl 4-(isobutyryloxy)but-3-enoate, and 2-phenylacetic acid. This was the first report of the endophytic fungus N. sphaerica from H. annuus. It is a potential source of active metabolites, which gave the strong antifungal activity, antioxidant activity, and cytotoxicity to A549 cancer cell lines.     

Isolation and antimicrobial activities of fungi derived from Nymphaea lotus and Nymphaea stellata

This study aimed to isolate fungi from leaves, petals, stalks and stamens of Nymphaea lotus and Nymphaea stellata and explore their bioactive potential with respect to antimicrobial activity and their cytotoxicity on human cell lines. The totals of 210 fungal isolates were obtained from 640 segments. The highest isolation rate was found in petal segments (0.44), while stamens yielded the lowest isolation rate (0.13). One hundred and ninety–five fungal extracts were evaluated for their efficiency against ten pathogenic microorganisms by colorimetric broth microdilution tests. Cell hexane extract from Eupenicillium levitum FNL036 (FNL036CH) gave the strongest antifungal activity against Cryptococcus neoformans and Talaromyces marneffei with minimum inhibitory concentration of 0.5?μg/mL and affected cell morphology of the test microorganisms. Moreover, this extract was non–cytotoxic to human embryonic kidney 293 (293T) and human keratinocytes (HaCAT) cell lines with 50% inhibitory concentration (IC₅₀) values above 100?μg/mL. This finding confirmed that fungi derived from these two Nymphaea species were a novel source of bioactive metabolites.