Erinacines as cyathane-xylosides are known to have potent stimulating activity for nerve-growth-factor synthesis. Our search for new cyathane metabolites from a liquid culture of Hericium erinaceum YB4-6237 resulted in the isolation of a new erinacine named erinacine Q (1). NMR spectrometry and a chemical derivation from erinacine P (2) determined the compound to be a derivative in which the formyl group of erinacine P had been reduced to the hydroxymethyl group. To clarify the biosynthetic relationship between erinacine Q and the others, [1'-13C]erinacine Q ([1'-13C]-1) was chemically derived from [1'-13C]erinacine P ([1'-13C]-2) which had been prepared by feeding [1-13C]-D-glucose to the basidiomycete. The biotransformation of labeled erinacine Q into [1'-13C]erinacine C ([1'-13C]-5) via [1'-13C]erinacine P in this basidiomycete was demonstrated by NMR spectrometry.