Analysis of Ginkgo biloba for the presence of ginkgotoxin and ginkgotoxin 5'-glucoside

J AOAC Int. Nov-Dec 2000;83(6):1313-20.

Abstract

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.

MeSH terms

  • Chromatography, Liquid
  • Ginkgo biloba / chemistry*
  • Glucosides / analysis*
  • Indicators and Reagents
  • Plants, Medicinal*
  • Pyridines / analysis*
  • Pyridoxine / analogs & derivatives*
  • Pyridoxine / analysis*
  • Seeds / chemistry
  • Spectrometry, Mass, Electrospray Ionization

Substances

  • 3,5'-diacetylginkgotoxin
  • 4'-O-methylpyridoxine
  • Glucosides
  • Indicators and Reagents
  • Pyridines
  • ginkgotoxin 5'-glucoside
  • Pyridoxine