Sesquiterpenoids and Xanthones from the Kiwifruit-Associated Fungus Bipolaris sp. and Their Anti-Pathogenic Microorganism Activity

Abstract

Nine previously undescribed sesquiterpenoids, bipolarisorokins A–I (1–9); two new xanthones, bipolarithones A and B (10 and 11); two novel sativene-xanthone adducts, bipolarithones C and D (12 and 13); as well as five known compounds (14–18) were characterized from the kiwifruit-associated fungus Bipolaris sp. Their structures were elucidated by extensive spectroscopic methods, electronic circular dichroism (ECD), 13C NMR calculations, DP4+ probability analyses, and single crystal X-ray diffractions. Many compounds exhibited anti-pathogenic microorganism activity against the bacterium Pseudomonas syringae pv. actinidiae and four pathogenic microorganisms.

Terpenoids from Kiwi endophytic fungus Bipolaris sp. and their antibacterial activity against Pseudomonas syringae pv. actinidiae

“…Furthermore, the HMBC correlations from δ H 3.77 (3H, s, Me-19) and 4.58 (1H, dd, J = 5.8, 1.4 Hz, H-17) to δ C 174.2 (s, C-18) suggested that the connections among C-17, C-18 and C-19. The planar structure of 1 was thus deduced as shown in Figure 2 , resembling bipolarisorokin G ( 10 ) ( Yu et al, 2022 ). The ROESY correlations ( Figure 3 ) of H-13/H-8, H-13/H-6 and H-12/H-14 revealed that H-3, H-6, H-7 and H-8, were co-facial and assigned to be β -oriented.…”

“…In addition, the structures of five known compounds were identified as bipolarisorokin H ( 9 ), bipolarisorokin G ( 10 ), helminthosporol ( 11 ), helminthosporic acid ( 12 ) and fusaproliferin ( 13 ), by comparing the spectral data with those reported in the literature ( Osterhage et al, 2002 ; Abdel-Lateff et al, 2013 ; Liu et al, 2013 ; Yu et al, 2022 ). In this study, compounds 1 and 2 were isolated as methyl esters, which could be derived from the separation process since methanol was used as the solvent.…”

“…All compounds ( 1 – 13 ) were evaluated for their anti-Psa activity by using the method as described previously ( Yu et al, 2022 ). Streptomycin was used as the positive control.…”

“…Actinidae. The antibacterial assay was conducted by the previously described method ( Yu et al, 2022 ). The sample to be tested was added into a 96-well culture plate, and the final compound concentration range from 4 to 256 μ g/ml.…”

“…Is also an endophytic fungus that was characterized from health kiwi plant. Our previous chemical investigation on this fungus yielded a series sesquiterpenoids (bipolarisorokins A–I) and xanthones with anti-Psa properties from the liquid fermented extract ( Yu et al, 2022 ). In order to search for more anti-Psa agents from this fungus, we further investigated the fermentation products from the culture grown on rice medium.…”