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.     

Isoflavone glycosides from Derris scandens

Five isoflavone glycosides, named derriscandenosides A–E (1–5), were isolated from the stems of Derris scandens, together with ten known compounds comprising one isoflavone, two benzoic acid derivatives, three glucosyl isoflavones and four rhamnosyl-(1→6)-glucosyl isoflavones. The structures of the glycosides were assigned on the basis of spectroscopic data, especially of the acetate derivatives. Three known rhamnosyl-(1→6)-glucosyl isoflavones isolated from a crude fraction were retested for hypotensive activity with varying results.     

Antimicrobial activity in cultures of endophytic fungi isolated from Garcinia species

The aim of the present study was to screen for antimicrobial activity in endophytic fungi isolated from surface sterilized leaves and branches of five Garcinia plants, G. atroviridis, G. dulcis, G. mangostana, G. nigrolineata and G. scortechinii, found in southern Thailand. Fermentation broths from 377 isolated fungi were tested for antimicrobial activity by the agar diffusion method. Minimum inhibitory concentrations (MICs) were obtained for crude ethyl acetate extracts. Seventy isolates (18.6%) displayed antimicrobial activity against at least one pathogenic microorganism, such as Staphylococcus aureus, a clinical isolate of methicillin-resistant S. aureus, Candida albicans and Cryptococcus neoformans. The results revealed that 6-10%, 1-2% and 18% of the crude ethyl acetate extracts inhibited both strains of S. aureus (MIC 32-512 microg mL(-1)), Ca. albicans and Cr. neoformans (MIC 64-200 microg mL(-1)), and Microsporum gypseum (MIC 2-64 microg mL(-1)), respectively. Isolates D15 and M76 displayed the strongest antibacterial activity against both strains of S. aureus. Isolates M76 and N24 displayed strong antifungal activity against M. gypseum. Fungal molecular identification based on internal transcribed spacer rRNA gene sequence analysis demonstrated that isolates D15 (DQ480353), M76 (DQ480360) and N24 (DQ480361) represented Phomopsis sp., Botryosphaeria sp. and an unidentified fungal endophyte, respectively. These results indicate that some endophytic fungi from Garcinia plants are a potential source of antimicrobial agents.     

Asperidines A–C,pyrrolidine and piperidine derivatives from the soil-derived fungus Aspergillus sclerotiorum PSU-RSPG178

One new pyrrolidine derivative, asperidine A (1), and two new piperidine derivatives, asperidines B (2) and C (3), were isolated from the soil-derived fungus Aspergillus sclerotiorum PSU-RSPG178 together with two known alkaloids. Compound 3 possessed an unprecedented 7-oxa-1-azabicyclo[3.2.1]octane skeleton with four chiral centers. Their structures were determined by spectroscopic evidence. The absolute configurations of compounds 2 and 3 were established using Mosher’s method and further confirmed for compound 3 by X-ray crystallographic data. Compound 2 dose-dependently inhibited the CFTR-mediated chloride secretion in T84 cells with an IC₅₀ value of 0.96?μM whereas 3 displayed the same activity with the IC₅₀ value of 58.62?μM. Compounds 2 and 3 also significantly reduced intracellular ROS under both normal and H₂O₂-treated conditions compared with their respective controls in a dose-dependent manner without cytotoxic effect on Caco-2 cells. In addition, compound 3 was inactive against noncancerous Vero cells whereas compound 2 was considered to be inactive with the IC₅₀ value of >10?μM.     

Lanostanes and friedolanostanes from the pericarp of Garcinia hombroniana

The CH2Cl2 extract from the pericarp of Garcinia hombroniana yielded three 17,14-friedolanostanes [(24E)-3alpha-hydroxy-17,14-friedolanostan-8, 14,24-trien-26-oic acid, methyl (24E)-3alpha,23-dihydroxy-17,14-friedolanostan-8,14,24 -trien-26-oate and methyl (24E)-3alpha,9,23-trihydroxy-17,14-friedolanostan-14,2 4-dien-26-oate] and two lanostanes [3beta- and 3alpha-hydroxy-23-oxo-9,16-lanostadien-26-oic acid]. The structure of (14E)-3alpha-hydroxy-17,14-friedolanostan-8,14,24-trie n-26-oic acid was determined using spectroscopic and X-ray analyses, while the structures of the other compounds were elucidated solely from analysis of spectroscopic data.     

α-Pyrone and seiricuprolide derivatives from the mangrove-derived fungi Pestalotiopsis spp. PSU-MA92 and PSU-MA119

Investigation of the mangrove-derived fungi Pestalotiopsis spp. PSU-MA92 and PSU-MA119 resulted in the isolation of three new α-pyrones, pestalotiopyrones A–C (1–3), and two new seiricuprolides, pestalotioprolides A (4) and B (5), together with two known compounds. Their structures were identified by analysis of spectroscopic data. Compound 5 was isolated as its diacetate derivative (6). The antibacterial and antifungal activities of 2 were evaluated.     

Anthraquinone derivatives from the mangrove-derived fungus Phomopsis sp. PSU-MA214

One new tetrahydroanthraquinone derivative, (2R,3S)-7-ethyl-1,2,3,4-tetrahydro-2,3,8-trihydroxy-6-methoxy-3-methyl-9,10-anthracenedione (1), together with five known anthraquinones (2–6), two known phenylethyl alcohols (7–8) and one known butanamide (9), were isolated from the mangrove-derived fungus Phomopsis sp. PSU-MA214. Their structures were established by spectroscopic evidence. Compound 1 is a rare ethyltetrahydroanthraquinone and exhibited weak cytotoxicity against breast cancer (MCF-7) cell lines and antibacterial activity against the standard Staphylococcus aureus ATCC25923 and methicillin-resistant S. aureus SK1.     

A dimeric chromanone and a phthalide: Metabolites from the seagrass-derived fungus Bipolaris sp. PSU-ES64

Two new metabolites, a dimeric chromanone, bipolarinone (1), and a phthalide, bipolarilide (2), as well as eight known compounds have been isolated from the seagrass-derived fungus Bipolaris sp. PSU-ES64. The structures were elucidated by analysis of spectroscopic data. The absolute configuration of 1 was determined by circular dichroism spectroscopy, Mosher's method, and NOEDIFF data. The antioxidant and antimicrobial activities of the isolated compounds were examined.     

Metabolites from the endophytic fungus Xylaria sp. PSU-D14

Glucoside derivatives, xylarosides A (1) and B (2), were isolated from the broth extract of the endophytic fungus Xylaria sp. PSU-D14 along with two known compounds, sordaricin (3) and 2,3-dihydro-5-hydroxy-2-methyl-4H-1-benzopyran-4-one (4). The structures were assigned by spectroscopic methods. Sordaricin (3), one of the known metabolites, exhibited moderate antifungal activity against Candida albicans ATCC90028 with a MIC value of 32 microg/ml.     

Tricycloalternarene derivatives from the endophytic fungus Guignardia bidwellii PSU-G11

Four new tricycloalternarene derivatives, guignarenones A–D (1–4), along with known (6S,9R)-vomifoliol were isolated from the endophytic fungus Guignardia bidwellii PSU-G11. Their structures were determined on the basis of spectroscopic data. The absolute configurations in 1 were assigned using a combination of the modified Mosher's method and NOEDIFF data. Compound 1 displayed mild cytotoxic activity against oral cavity cancer and African green monkey kidney fibroblast (Vero) cell lines.