Applanmerotic acids A and B, two meroterpenoid dimers with an unprecedented polycyclic skeleton from Ganoderma applanatum that inhibit formyl peptide receptor 2

Abstract

Two unprecedented Ganoderma meroterpenoid dimers, applanmerotic acids A and B (1 and 2), were isolated from the fruiting bodies of Ganoderma applanatum. Their structures including stereostructures were established by spectroscopic analysis and the quantum chemical calculation (calculated ¹³C NMR and electronic circular dichroism) method. Compound 1 was a pair of enantiomers and compound 2 represents the first example of a dimeric meroterpenoid with a 2-oxo-spiro[furo[3,2-b]benzofuran-3,2′-naphthalene] core. Their plausible biogenetic pathway was proposed, from which their key polycyclic cores were formed through an intermolecular Diels–Alder reaction. Compounds 1 and 2 showed anti-inflammatory activities with IC₅₀ values of 14.5 and 20.9 μM, respectively, by inhibiting the activation of FPR2 and the further competitive binding assay and molecular docking study indicated their action mechanism.