Ochraceopyronide, a Rare α-Pyrone-C-lyxofuranoside from a Soil-Derived Fungus Aspergillus ochraceopetaliformis

Abstract

The fungal strain was isolated from a soil sample collected in Giza province, Egypt, and was identified as Aspergillus ochraceopetaliformis based on phenotypic and genotypic data. The ethyl acetate extract of the fungal strain exhibited promising activity levels against several pathogenic test organisms and through a series of 1H NMR guided chromatographic separations, a new α-pyrone-C-lyxofuranoside (1) along with four known compounds (2–5) were isolated. The planar structure of the new metabolite was elucidated by detailed analysis of its 1D/2D NMR and HRMS/IR/UV spectroscopic data, while the relative configuration of the sugar moiety was determined by a combined study of NOESY and coupling constants data, with the aid of theoretical calculations. The structures of the known compounds—isolated for the first time from A. ochraceopetaliformis—were established by comparison of their spectroscopic data with those in the literature. All isolated fungal metabolites were evaluated for their antibacterial and antifungal activities against six Gram-positive and Gram-negative bacteria as well as against three human pathogenic fungi.

Unravelling the Secrets of α‐Pyrones from Aspergillus Fungi: A Comprehensive Review of Their Natural Sources, Biosynthesis, and Biological Activities

“…Moreover, a chemical investigation of the ethyl acetate extract obtained from soil‐derived Aspergillus ochraceopetaliformis led to the discovery of an uncommon compound known as ochraceopyronide ( 47 ), which belongs to the rare class of α ‐pyrone‐C‐lyxofuranosides. The elucidation of its planar structure was achieved through a comprehensive analysis of its 1D/2D NMR and HRMS/IR/UV spectroscopic data [16] . At the same time, the relative configuration of the sugar moiety was achieved by combining data from NOESY and coupling constants, aided by theoretical calculations.…”

“…Ochraceopyronide (47) exerted weak antimicrobial effects against both gram-positive and gramnegative bacteria, as well as weak inhibitory activity against human pathogenic fungi. [16] (�)-usphenethylones A-C (48-50) (Figure 4), new heterodimeric polyketide enantiomers were isolated from the culture extract of Aspergillus ustus 3.3904. The absolute configuration of these compounds was established by X-ray diffraction analysis and ECD calculations.…”

“…At the same time, the relative configuration of the sugar moiety was achieved by combining data from NOESY and coupling constants, aided by theoretical calculations. Ochraceopyronide ( 47 ) exerted weak antimicrobial effects against both gram‐positive and gram‐negative bacteria, as well as weak inhibitory activity against human pathogenic fungi [16] . (±)‐usphenethylones A–C ( 48 – 50 ) (Figure 4), new heterodimeric polyketide enantiomers were isolated from the culture extract of Aspergillus ustus 3.3904.…”

“…Currently, α-pyrones constitute a promising class of natural products that are abundantly recovered from animals, plants, microorganisms, and insects, where they share several types of biological defense processes. [15] Specifically, α-pyrone-type natural products extensively exist in the fungal genera Aspergillus, [16][17] Phomopsis, [18] Alternaria, [12,19] Pestalotiopsis, [20] Dictyostelium, [21] and Xylaria. [22][23] According to the chemical structure (Figure 1), γ-pyrone is the vinylogous form of α-pyrone, which possesses a lactone ring.…”

“…The elucidation of its planar structure was achieved through a comprehensive analysis of its 1D/2D NMR and HRMS/IR/UV spectroscopic data. [16] At the same time, the relative configuration of the sugar moiety was achieved by combining data from NOESY and coupling constants, aided by theoretical calculations. Ochraceopyronide (47) exerted weak antimicrobial effects against both gram-positive and gramnegative bacteria, as well as weak inhibitory activity against human pathogenic fungi.…”