Anthocyanidins structural study using positive electrospray ionization triple quadrupole mass spectrometry and H/D...

Area of Science:

• Analytical Chemistry
• Natural Product Chemistry
• Computational Chemistry

Background:

• Anthocyanidins are natural colorants with complex structures.
• Understanding their fragmentation is crucial for mass spectrometry analysis.
• Previous studies lacked detailed mechanistic insights.

Purpose of the Study:

• To elucidate the fragmentation mechanisms of nonglycosylated anthocyanins (anthocyanidins).
• To validate proposed mechanisms using isotope labeling and computational thermochemistry.
• To provide a comprehensive understanding for mass spectrometry-based analysis.

Main Methods:

• Electrospray ionization triple quadrupole mass spectrometry (ESI-QqQ).
• Collision-induced dissociation (CID) experiments.
• Isotope labeling studies and B3LYP/6-311+G** ab initio calculations.

Main Results:

• Proposed fragmentation mechanisms including rearrangements, retro Diels-Alder, water loss, CO losses, and acylium ion formation.
• Computational studies indicated CO losses as the lowest energy fragmentation channel.
• Isotope labeling confirmed H/D exchange of hydroxyl protons.

Conclusions:

• A general fragmentation mechanism for anthocyanidins was proposed and corroborated.
• The study provides valuable insights into the mass spectrometry analysis of anthocyanidins.
• Fragmentation pathways are essential for structural elucidation of natural products.