Structure elucidation of linear triquinane sesquiterpenoids, hirsutuminoids A-Q, from the fungus Stereum hirsutum and their activities

Abstract

Eighteen linear triquinane sesquiterpenoids (LTSs), including seventeen previously undescribed ones (hirsutuminoids A-Q), were isolated from the fermentation of the fungus Stereum hirsutum (Willd.) Pers. The structures and absolute configurations of the isolates were characterized by extensive spectroscopic analysis (1D, 2D NMR, and HRMS data), together with comparing the experimental and calculated data of both electronic circular dichroism and NMR data, as well as X-ray crystallography. Based on the literature survey and efforts on constructing the absolute configurations of these LTSs in this study, one empirical rule about the orientations of substitutions at C-2/C-3/C-7/C-9 was summarized. Anti-inflammatory and cytotoxic bioassays showed that only hirsutuminoid B inhibited the nitric oxide (NO) production in RAW 264.7 macrophages with an IC₅₀ value, 18.9 μM.

Keywords: Chemical investigation; Configuration elucidation; Linear triquinane sesquiterpenoids; NO production inhibition; Stereaceae; Stereum hirsutum (Willd.) Pers..