Analysis of Ginkgo biloba for the Presence of Ginkgotoxin and Ginkgotoxin 5′-Glucoside

Author:

Scott Peter M1,Lau Benjamin P-Y1,Lawrence Guillaume A1,Lewis David A1

Affiliation:

1. Health Canada, Health Protection Branch, Food Research Division, Address Locator 2203D, Ottawa, ON K1A 0L2, Canada

Abstract

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 β-glucosidase (37°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 × 2 h yielded a total of 179 μg/g of free ginkgotoxin. The concentration in powder from Ginkgo biloba capsules was several times lower than this (17–64 μg/g) in 3 samples but higher in another (457 μg/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 μg/g free ginkgotoxin in the ginkgo seeds. However, boiling an extract for 4 h showed about 15% loss of ginkgotoxin and its glucoside.

Publisher

Oxford University Press (OUP)

Subject

Pharmacology,Agronomy and Crop Science,Environmental Chemistry,Food Science,Analytical Chemistry

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