Polyoxygenated meroterpenoids and a bioactive illudalane derivative from a co-culture of Armillaria sp. and Epicoccum sp

Three novel polyoxygenated meroterpenoids, epiterenoids A–C ( 1–3 ), and a new illudalane derivative, armiloid A ( 4 ), were isolated from a liquid co-culture of Armillaria sp. and the endophytic fungus Epicoccum sp. YUD17002 associated with Gastrodia elata . Their structures were established by extensive spectroscopic analyses, X-ray crystal diffraction, and TDDFT-ECD calculations. Compounds 1–3 possessed a 5/6/4/5/5-fused pentacyclic ring scaffold. Plausible biosynthetic pathways for 1–4 are proposed. Compound 4 exhibited potent AChE inhibitory activity, with an IC 50 value of 4.91 μM.