Investigation of the Quinone-quinone and Quinone-catechol products using 13C labeling, UPLC-Q-TOF/MS and UPLC-Q-Exactive Orbitrap/MS

Quinones are highly reactive oxidants and play an essential role in inducing quality deterioration of fruit and vegetable products. Here, a novel stable isotope-labeling approach in combination with high-resolution tandem mass spectrometry UPLC-Q-TOF/MS and UPLC-Q-Exactive Orbitrap/MS, was successfully applied in tracking quinone reaction pathways in both real wines and model reaction systems. Unexpectedly, the binding products of quinone-quinone and quinone-catechol that are not derived from either nucleophilic reaction or redox reaction were discovered and showed the significant high peak area. Self-coupling reactions of semiquinone radicals might provide a possible interpretation for the formation of quinone-quinone products, and a charge transfer reaction coupled with a complementary donor-acceptor interaction is feasibly responsible for the products with a quinone-catechol structure. These findings endow a new perspective for quinone metabolic pathway in foods.

Automated summary

A novel stable isotope-labeling approach combined with high-resolution mass spectrometry was used to track quinone reaction pathways in wines and model systems. Unexpected binding products of quinone-quinone and quinone-catechol were discovered, which were not derived from nucleophilic or redox reactions. Self-coupling of semiquinone radicals and charge transfer reactions were proposed as the possible mechanisms for the formation of these products. These findings provide new insights into the metabolic pathways of quinones in foods.