Cyclization of xanthohumol as a strategy for its gas chromatographic analysis

Xanthohumol is a prenylated flavonoid present in female hop inflorescences, attracting scientific interest due to its diverse bioactive properties. Its high boiling point (576.5 °C) renders liquid chromatography the primary analytical technique for its determination in various matrices. This study is the first to demonstrate that xanthohumol can be successfully analyzed by gas chromatography after conversion to its cyclic pyran form via intramolecular addition of the phenolic OH group to the -C=C- bond. Experimental results indicate that BF₃·Et₂O is the most effective catalyst, enabling nearly complete transformation of xanthohumol into its pyran derivative. The developed method was validated, showing excellent linearity (R² ≥ 0.985), precision (< 6%), accuracy (> 95%), and low detection limits (< 0.13 μg/mL). Its applicability was confirmed through analyses of beer, dietary supplements, hop cones, and plasma samples containing xanthohumol. The described procedure can also be used for GC analysis of isoxanthohumol in the same matrices.