Abstract
Investigation of the entomogenous fungus Setosphaeria rostrate LGWB-10 from Harmonia axyridis led to the isolation of four new isocoumarin derivatives, setosphlides A–D (1–4), and four known analogues (5–8). Their planar structures and the relative configurations were elucidated by comprehensive spectroscopic methods. The absolute configurations of isocoumarin nucleus for 1–4 were elucidated by their ECD spectra. The C-10 relative configurations for the pair of C-10 epimers (1 and 2) were established by comparing the magnitude of the computed 13C NMR chemical shifts (Δδcalcd.) with the experimental 13C NMR values (Δδexp.) for the epimers. All of the isolated compounds (1–8) were evaluated for their cytotoxicities against four human tumor cell lines MCF-7, MGC-803, HeLa, and Huh-7.Graphic
Highlights
Symbiosic microorganisms from insects, which are wellknown as a rich source of bioactive natural products, have attracted widespread attention [1,2,3]
Secondary metabolites from several fungal sources [5]. It made such a task extremely challenging to assign their absolute configurations, when a side chain attached to isocoumarin derivative nuclear, as the high free rotation of the stereogenic centers in chains [6]
During our ongoing search for bioactive compounds from fungi, Setosphaeria rostrate LGWB-10 was selected for chemical exploration based on HPLC–DAD and HPLC–MS analyses of its EtOAc extract
Summary
Symbiosic microorganisms from insects, which are wellknown as a rich source of bioactive natural products, have attracted widespread attention [1,2,3]. Due to the special environmental conditions, the bioactive natural products from symbiotic microorganisms as a rich source of various compounds with complex structures and excellent activities, may reshape the experts’ views on the drug ability of natural products [4]. Secondary metabolites from several fungal sources [5] It made such a task extremely challenging to assign their absolute configurations, when a side chain attached to isocoumarin derivative nuclear, as the high free rotation of the stereogenic centers in chains [6]. Eight isocoumarin derivatives, including four new setosphlides A–D (1–4) and four known analogues, (3R,4R)-4,8-dihydroxy-3-((R)-2-hydroxypentyl)6,7-dimethoxyisochroman-1-one (5) [5], (3R,4R)-4,8-dihydroxy-3-((R)-2-hydroxypentyl)-6,7-dimethoxyisochroman1-one (6) [5], (12R)-12-hydroxymonocerin (7) [7], and (12S)-12-hydroxymonocerin (8) [6] (Fig. 1) were isolated from Setosphaeria rostrate LGWB-10. We report the details of the isolation, structure elucidation, absolute configuration determination, and bioactivities of them
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