Lanostanoid triterpenes from the fungus Rigidoporus microporus

Abstract

Five new lanostanoid triterpenes were isolated from the extract of R. microporus. Three of the metabolites (1-3) present a Δ^8,9 skeleton with an uncommon keto functionality at C-1. Another compound (4) has an unprecedented rearranged skeleton in which methyl-19 was transposed to C-1, with conjugated double bonds at Δ^1-10 and Δ^8-9. All of the compounds have hydroxylated or furane-cyclized side-chains. The structures were elucidated by spectroscopic methods, and the absolute configuration of the hydroxyl-bearing carbon in the side chain of compound 5 was established in silico. The metabolites were evaluated for their antifungal activity and the bioactivity as agonist/antagonists of the liver X receptors (LXRs). Compound 4 presents antifungal activity and compounds 3 and 5 are the agonists of LXRs.

Keywords: 1-methyl-19-nor-lanostane; 3-ketolanostanes; Rigidoporus microporus; antifungal activity; liver X receptors.