Effect of phosphate on stability of pyridoxal in the presence of lysine

Tzou Chi Huang, Ming Hung Chen, Chi Tang Ho

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10 Scopus citations


The stability of the biologically active compound vitamin B6 in aqueous solution was investigated. Schiff base formation is the major reaction between the ε-amino group of lysine and the aldehyde group of both pyridoxal and pyridoxal phosphate. Model systems composed of equal molar concentrations of lysine with either pyridoxal or pyridoxal phosphate were used to study the effect of proton transfer on Schiff base formation. Pyridoxylidenelysine was found to be the major product in both lysine/pyridoxal and lysine/pyridoxal phosphate systems. Quantitation of residual pyridoxal and pyridoxal phosphate was conducted using an HPLC to evaluate the degradation of pyridoxal and pyridoxal phosphate. The results indicate both the free phosphate ion in the buffer system and the bound phosphate on pyridoxal phosphate can enhance the formation of the Schiff base. The phosphate group serves as both proton donor and acceptor, which catalyzes the Schiff base formation. The aldehyde group on pyridoxal phosphate was found to be much more reactive than that on pyridoxal. The bound phosphate group on pyridoxal phosphate, with proton donating and accepting groups in close proximity, can simultaneously donate and accept protons, thus enhancing Schiff base formation between the aldehyde group and the ε-amino group. The deterioration rate of pyridoxal phosphate was faster than that of pyridoxal in an aqueous system.

Original languageEnglish (US)
Pages (from-to)1559-1563
Number of pages5
JournalJournal of agricultural and food chemistry
Issue number3
StatePublished - Oct 2 2001

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Agricultural and Biological Sciences(all)


  • Phosphate
  • Pyridoxallysine
  • Pyridoxallysine phosphate
  • Schiff base

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