Investigation of serum amino acids involved in gallic acid detoxification of formaldehyde by LC-MS/MS and neutral loss scan.

RATIONALE: Gallic acid is one of the most common polyphenols in natural products and human diet. The consumption of gallic acid reduces the incidence of cardiovascular diseases, chronic metabolic disorders and cancers. Most of previous publications focused on gallic acid's antioxidative or prooxidative properties. In the present work, gallic acid as a trapping agent of blood formaldehyde was investigated by LC-MS/MS and neutral loss scan.

METHODS: Serum samples incubated with gallic acid were subjected to an LTQ XL ion trap mass spectrometer for the LC-MS/MS analysis. The adduct ions of gallic acid-formadehyde-amino acids were explored by fragmentation pattern investigation and neutral loss scan experiments.

RESULTS: A series of Mannich adducts (namely, gallic acid-formadehyde-alanine, gallic acid-formadehyde-proline, gallic acid-formadehyde-leucine or gallic acid-formadehyde-isoleucine and gallic acid-formadehyde-phenylalanine) were identified as metabolites by neutral loss scan experiments.

CONCLUSIONS: This work demonstrated that serum amino acids are involved in gallic acid detoxification of formaldehyde. Because excessive formaldehyde in blood is implicated in a variety of disease pathologies, detoxification of formaldehyde, especially endogenous formaldehyde, may be another health beneficial effect of gallic acid. It also suggested that more attentions should be paid to Mannich-type metabolites of polyphenol-formadehyde-amino acid in the pharmacokinetics and bioavailability research of polyphenols.