Concentrations of various forms of vitamin B6 in ginkgo seed poisoning.

A 2-year-old girl required medical attention for a sudden onset of repetitive tonic-clonic convulsions after ingesting 20-30 ginkgo seeds. Concentrations of the major forms of circulating vitamin B6, pyridoxal-5'-phosphate (PLP), pyridoxal (PL), and 4-pyridoxic acid, as well as the known ginkgo seed toxin 4'-O-methylpyridoxine (MPN) were measured in the serum and cerebrospinal fluid (CSF). PLP is an active form of vitamin B6 and necessary for γ-aminobutyric acid (GABA) production. High MPN concentrations were observed in both the serum and CSF. As the PLP to PL ratio was markedly decreased in serum and CSF examinations, we suspected the ratio to be important in GABA production. This case report provides novel information on the metabolism of vitamin B6 in humans as a result of ginkgo seed poisoning.