Biosynthesis of Antroquinonol and 4-Acetylantroquinonol B via a Polyketide Pathway Using Orsellinic Acid as a Ring Precursor in Antrodia cinnamomea

Antroquinonol (AQ) and 4-acetylantroquinonol B (4-AAQB), isolated from the mycelium of Antrodia cinnamomea, have a similar chemical backbone to coenzyme Q (CoQ). Based on the postulation that biosynthesis of both AQ and 4-AAQB in A. cinnamomea starts from the polyketide pathway, we cultivated this fungus in a culture medium containing [U- 13 C]oleic acid, and then we analyzed the crude extracts of the mycelium using UHPLC-MS. We found that AQ and 4-AAQB follow similar biosynthetic sequences as CoQ. Obvious [ 13 C 2 ] fragments on the ring backbone were detected in the mass spectrum for [ 13 C 2 ]AQ, [ 13 C 2 ]4-AAQB, and their [ 13 C 2 ] intermediates found in this study. The orsellinic acid, formed from acetyl-CoA and malonyl-CoA via the polyketide pathway, was found to be a novel benzoquinone ring precursor for AQ and 4-AAQB. The identification of endogenously synthesized farnesylated intermediates allows us to postulate the routes of AQ and 4-AAQB biosynthesis in A. cinnamomea .