Nematicidal Activity of Grammicin Biosynthesis Pathway Intermediates in Xylaria grammica KCTC 13121BP against Meloidogyne incognita

Grammicin, a polyketide metabolite produced by the endolichenic fungus Xylaria grammica KCTC 13121BP, shows strong nematicidal activity against Meloidogyne incognita. This study was performed to elucidate the grammicin biosynthesis pathway of X. grammica KCTC 13121BP and to examine the nematicidal activity of the biosynthesis intermediates and derivatives against M. incognita. Two grammicin biosynthesis intermediates were isolated from a T-DNA insertion transformant (strain TR-74) of X. grammica KCTC 13121BP and identified as 2-(hydroxymethyl)cyclohexa-2,5-diene-1,4-dione (compound 1) and 2,5-dihydroxybenzaldehyde (compound 2), which were also reported to be intermediates in the biosynthesis pathway of patulin, an isomer of grammicin. This indicates that the grammicin biosynthesis pathway overlaps almost with that of patulin, except for the last few steps. Among 13 grammicin biosynthesis intermediates and their derivatives (except grammicin), toluquinol caused the highest M. incognita J2 mortality, with an LC_{50/72 h} value of 11.13 µg/mL, which is similar to grammicin with an LC_{50/72 h} value of 15.95 µg/mL. In tomato pot experiments, the wettable powder type formulations (WP) of toluquinol (17.78 µg/mL) and grammicin (17.78 µg/mL) also effectively reduced gall formation on the roots of tomato plants with control values of 72.22% and 77.76%, respectively, which are much higher than abamectin (16.67%), but lower than fosthiazate (100%). The results suggest that toluquinol can be used directly as a biochemical nematicide or as a lead molecule for the development of new synthetic nematicides for the control of root-knot nematode diseases.     

Three new polyketides from fruiting bodies of the endophytic ascomycete Xylaria polymorpha

The isolation of three new secondary metabolites from the fruiting body of Xylaria polymorpha is described. The new compounds are of mixed biosynthetic origin consisting of a polyketide starter, extended with a methyl orsellinate unit and terminated hydrolytically or with an amine-containing terminal unit.     

Biosynthesis and mass spectral fragmentation pathways of 13C and 15N labeled cytochalasin D produced by Xylaria arbuscula

The fungus Xylaria arbuscula was isolated as an endophyte from Cupressus lusitanica and has shown to be a prominent producer of cytochalasins, mainly cytochalasins C, D and Q. Cytochalasins comprise an important class of fungal secondary metabolites that have aroused attention due to their uncommon molecular structures and pronounced biological activities. Due to the few published studies on the ESI‐MS/MS fragmentation of this important class of secondary metabolites, in the first part of our work, we studied the cytochalasin D fragmentation pathways by using an ESI‐Q‐ToF mass spectrometer coupled with liquid chromatography. We verified that the main fragmentation routes were generated by hydrogen and McLafferty rearrangements which provided more ions than just the ones related to the losses of H₂O and CO as reported in previous studies. We also confirmed the diagnostic ions at m /z 146 and 120 as direct precursor derived from phenylalanine. The present work also aimed the production of structurally diverse cytochalasins by varying the culture conditions used to grow the fungus X. arbuscula and further insights into the biosynthesis of cytochalasins. HPLC‐MS analysis revealed no significant changes in the metabolic profile of the microorganism with the supplementation of different nitrogen sources but indicated the ability of X. arbuscula to have access to inorganic and organic nitrogen, such as nitrate, ammonium and amino acids as a primary source of nitrogen. The administration of 2‐¹³C‐glycine showed the direct correlation of this amino acid catabolism and the biosynthesis of cytochalasin D by X. arbuscula , due to the incorporation of three labeled carbons in cytochalasin chemical structure. Copyright © 2017 John Wiley & Sons, Ltd.     

Xylaropyrones B and C,new γ-pyrones from the endophytic fungus Xylaria sp. SC1440

Two new γ-pyrones, xylaropyrones B (1) and C (2), together with three known compounds, xylaropyrone (3), annularin A (4) and annularin C (5), were isolated from solid cultures of the endophytic fungus Xylaria sp. SC1440. The structures of these compounds were determined mainly by analysis of their NMR spectroscopic data. The relative configurations of 1 and 2 were assigned on the basis of J-based configurational analysis, and the absolute configurations were established by experimental and TDDFT calculated ECD spectra. The isolated compounds were evaluated for cytotoxic and tyrosinase inhibitory activity.     

Chemical Constituents from the Fermented Mycelia of the Medicinal Fungus Xylaria nigripes

Nineteen compounds mainly including pyrrole‐containing alkaloids and phytosterols were isolated from the EtOH extract of the fermented mycelia of Xylaria nigripes, a precious medicinal fungus known as Wuling Shen in Chinese. On the basis of spectroscopic methods, the structures of the new naturally occurring compounds were determined to be (4S)‐3,4‐dihydro‐4‐(4‐hydroxybenzyl)‐3‐oxo‐1H‐pyrrolo[2,1‐c][1,4]oxazine‐6‐carbaldehyde ( 1 ), methyl (2S)‐2‐[2‐formyl‐5‐(hydroxymethyl)‐1H‐pyrrol‐1‐yl]‐3‐(4‐hydroxyphenyl)propanoate ( 2 ), and 3‐{4‐[(2R)‐(2,3‐dihydroxy‐3‐methylbutoxy]phenyl}‐7‐hydroxy‐4H‐chromen‐4‐one ( 3 ), respectively. The absolute configurations of 1 and 2 were deduced by the observed Cotton effects in their circular dichroism (CD) spectra, whereas that of the 1,2‐diol moiety in 3 was determined using the Snatzke's method. Their biological activities such as neuroprotective, anti‐neuroinflammatory, and cytotoxic properties were also reported.     

Antimalarial and cytotoxic constituents of Xylaria cf. cubensis PK108

Xylaria cf. cubensis PK108 was identified by its distinctive morphological characteristics and its internal transcribed spacers sequence analysis. The chromatographic separation and structural elucidation based on spectroscopic analysis of fungal crude extracts led to 10 compounds; tryptoquivaline L (1), fiscalin C (2), epi-fiscalin C (3), cytochalasin D (4), ergosterol (5), ergosterol peroxide (6), chevalone C (7), xylaranol B (8), helvolic acid (9) and cyclo-(l-Pro-l-Leu) (10). The bioassay screening showed that 4 displayed cytotoxicity against KB and NCI-H187 cancer cell lines with IC₅₀ values of 3.25 and 5.95 μg mL^? 1. 6 exhibited cytotoxicity against NCI-H187 with an IC₅₀ value of 5.81 μg mL^? 1. 7 and 9 showed antimalarial activity with IC₅₀ values of 25.00 and 6.25 μg mL^? 1, respectively. This result establishes Xylaria as broad spectrum bioactive compound producers.     

Secondary metabolites of Xylaria sp., an endophytic fungus from Taxus mairei

One new metabolite 3,7-dimethyl-9-(-2,2,5,5-tetramethyl-1,3-dioxolan-4-yl)nona-1,6-dien-3-ol, together with nine known compounds, were isolated from the strain Xylaria sp., an endophytic fungus of Taxus mairei. Their structures were deduced from 1D and 2D NMR data. In vitro cytotoxicity and antibacterial activity of these compounds were evaluated. Some of them exhibited substantial activity.     

Two new tetralone derivatives from the culture of Xylaria hypoxylon AT-028

Two new tetralone derivatives named xylariol A （1） and B （2） were isolated from the EtOAc extract of the culture broth of Xylaria hypoxylon AT-028 （Xylariaceae）, and their structures were elucidated by MS, 1R, 1D- and 2D-NMR spectra, and by X-ray diffraction analysis. 1 and 2 showed moderate cytotoxic activities against Hep G2 cells in the in vitro cytotoxic assay with IC50 values of 22.3 and 21.2 μg/mL, respectively.     

白蚁巢内生态环境与真菌优势种类

通过人工凋节CO_2分压、温湿度等条件,来探讨白蚁巢内的生态环境与真菌优势种类的关系。活巢内的优势种类小白球菌适应巢内的高浓度CO_2与高湿度,并与白蚁形成了和谐的共生关系;废巢里炭角菌占优势的原因主要是CO_2浓度的降低;离巢菌圃则由于低CO_2与低湿度而诱发了在蚁巢内处于休眠状态的多种半知菌生长。     

炭角菌深层发酵制品的抗氧化特性研究

用硅胶柱层析、顺相或反相MPLC，HPLC等方法对炭角菌深层发酵制品中的抗氧化物质进行分离筛选，用TLC及HPLC测定254nm的吸收检验其纯度，并用DPPH或Indophenol法对各单离物抗氧化活性进行了测定。在中性酯溶性抽提物的60％己烷／40％乙酸乙酯和40％己烷／60％乙酸乙酯部分获得纯度较大的抗氧化物质12个，在相同浓度下，B4－16，3－17－5的抗氧化活性比对照VE还要强，4－4－1，4－4－3，3－10－5的抗氧化活性与VE相近。说明炭角菌深层发酵菌粉具有较多的抗氧化成分，较高的抗氧化活力。