Guo-Bo Xu

A new alternariol glucoside from fungus Alternaria alternate cib-137

A new secondary metabolite, 2-O-methylalternariol 4-O-β-[4-methoxyl-glucopyranoside] (1), together with four known compounds alternariol methyl ether (2), altenuene (3), isoaltenuene (4) and 2-(2′S-hydroxypropyl)-5-methyl-7-hydroxychromone (5), was isolated from the fungus Alternaria alternate cib-137. Its structure was elucidated on the basis of spectroscopic data. Compounds 3 and 4 demonstrated moderate activity against Staphylococcus aureus.

Peniciside, a new triterpenoid glycoside, from the fungus Penicillium sp. 169

Peniciside, a new fernene triterpenoid glycoside, was isolated from the EtOAc extract of the solid-state fermented rice culture of the fungus Penicillium sp. 169. Its structure was elucidated on the basis of spectroscopic analysis, and the absolute configuration was determined by X-ray crystallographic analysis and chemical methods. Peniciside is the first example of a fernene triterpenoid glycoside with two hydroxyls at C-19 and C-20.

Two New Polyketide Metabolites Isolated from Paraconiothyrium brasiliense

Two new polyketide metabolites, named ethyl 8-hydroxy-9-oxo-9H-xanthene-1-carboxylate (1) and 1,8-dihydroxy-2-(1-hydroxyethyl)anthracene-9,10-dione (2), along with six known compounds, were isolated from the fungus Paraconiothyrium brasiliense. The structures of the new compounds were elucidated on the basis of 1D and 2D NMR experiments.

Analysis of Chaetoconvosins a and B Using Electrospray Ionization Quadrupole Time-of-Flight Mass Spectrometry

Two novel cytochalasins, chaetoconvosins A and B, isolated from Chaetomium convolutum were investigated using electrospray quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) in positive-ion mode. The main product ions in the high mass range for chaetoconvosins A and B are formed with the loss of H2O, CO, or both. The neutral loss of CH3NCO can be detected for chaetoconvosin B. However, their fragmentation patterns producing product ions in the low mass range vary greatly. It was found that hydroxyl or H atom linked to C1 is the key leading to the fragmentation differences. McLafferty-type rearrangement (producing the characteristic product ion at m/z 155), four-centered H rearrangement (generating m/z 193), and RDA reaction (producing m/z 203) are directly or indirectly related to the groups linked to C1. The identity of major product ions was supported by a D-labeling experiment.

A New Orsellinic Acid Derivative from the Fungus Chaetomium megalocarpum

A new orsellinic acid derivative, orsellide A1, together with orsellide A, orsellide D, and orsellinic acid, was isolated from the ethyl acetate extract of the solid-state fermented rice culture of the Chaetomium megalocarpum cib-135 fungus. The structure of orsellide A1 (1) was confirmed to be 2-O-(2,4-dihydroxy-6-methylbenzoyl)-6-deoxy-1-O-ethyl-3-keto-α-D-ribo-hexopyranoside on the basis of spectroscopic analysis.