The serum 4-O-methylpyridoxine (MPN) levels in a 21 months-old patient with gin-nan food poisoning were determined by HPLC. The blood of the patient was taken at 8.5 and 15.5 h after taking about 50 ginkgo albumens. After deproteinization of the serum, the supernatant was pretreated with Sep-pak C18 cartridge and was applied to HPLC. HPLC was performed with a Hibar LiChrosorb RP-18 (4.0 mm i.d.×250 mm, 7μm) using a fluorescence detector (wave length of excitation and fluorescence ; 290 and 400 nm, respectively). The serum MPN level was determined by the absolute calibration method. The determination limit of MPN in the serum was 0.05 μg/ml. The serum MPN concentration was 0.09 μg/ml at 8.5 h after taking ginkgo seeds, and was less than the determination limit of MPN (0.05 μg/ml) at 15.5h. MPN, isolated from the seed of Ginkgo biloba L., is responsible for"gin-nan food poisoning, "and its cardinal symptoms are mainly tonic and/or clonic convulsions and loss of consciousness. Infants are particularly vulnerable. This method may be available for proving the gin-nan food poisoning, chemically.
