Clypeasterol, a novel aromatic ergosterol skeleton from the mushroom Entoloma clypeatum

Chemical investigation of the wild mushroom Entoloma clypeatum led to the isolation of one new A-nor B-aromatic C28 steroid (1), along with eight known compounds (2-9) from this mushroom. As far as we know, compound 1 represents an unprecedented type of natural product. The structure of the new compound was elucidated based on extensive spectroscopic data analysis of HR-ESI-MS, 1D, and 2D NMR, while the relative configuration was confirmed by NOESY correlations. In addition, the anti-inflammatory activity of compound 1 was evaluated against LPS induced NO production in RAW 264.7 macrophages. Compound 1 exhibited a moderate anti-inflammatory activity with an IC₅₀ value of 24.56 ± 1.72 μM.