Analysis of Ginkgo biloba for the presence of ginkgotoxin and ginkgotoxin 5'-glucoside.
Hot water extracts of Ginkgo biloba seeds were analyzed for the presence of ginkgotoxin (4'-O-methylpyridoxine) by reversed-phase liquid chromatography (LC) using methanol-0.05M KH2PO4 (1 + 9, v/v) adjusted to pH 3 as mobile phase. Detection was by fluorescence (excitation 280 nm, emission 370 nm). A straight line calibration curve was obtained for the 10-100 ng injected. After addition of beta-glucosidase (37 degrees C/h), an earlier eluting peak disappeared and the ginkgotoxin peak increased. The identity of the ginkgotoxin was confirmed by LC/MS and LC/MS/MS. LC/MS/MS also confirmed the 5'-glucoside by comparison with the 3-glucoside. This is the first identification of a glucoside of ginkgotoxin in Ginkgo biloba. An unknown compound of MW 267 also observed in the Ginkgo biloba seed extract was shown not to be 3,5'-diacetylginkgotoxin by its different LC retention time. Extraction of ground Ginkgo biloba seeds with boiling water in a Soxhlet for 2 x 2 h yielded a total of 179 microg/g of free ginkgotoxin. The concentration in powder from Ginkgo biloba capsules was several times lower than this (17-64 microg/g) in 3 samples but higher in another (457 microg/g). Canned ginkgo seeds (white nuts) contained no detectable free ginkgotoxin but the glucoside was present. Different extraction times were studied: 0.5 h gave only 52 microg/g free ginkgotoxin in the ginkgo seeds. However, boiling an extract for 4 h showed about 15% loss of ginkgotoxin and its glucoside.
Scott
P M
PM
Health Canada, Health Protection Branch, Food Research Division, Ottawa, ON.
Lau
B P
BP
Lawrence
G A
GA
Lewis
D A
DA
D002853:Chromatography, Liquid; D020441:Ginkgo biloba / Q000737:chemistry*; D005960:Glucosides / Q000032:analysis*; D007202:Indicators and Reagents; D010946:Plants, Medicinal; D011725:Pyridines / Q000032:analysis*; D011736:Pyridoxine / Q000031:analogs & derivatives* / Q000032:analysis*; D012639:Seeds / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
C420694:3,5'-diacetylginkgotoxin; C406624:4'-O-methylpyridoxine; D005960:Glucosides; D007202:Indicators and Reagents; D011725:Pyridines; C420693:ginkgotoxin 5'-glucoside; D011736:Pyridoxine