Comparison of phytochemical composition of Ginkgo biloba extracts using a combination of non-targeted and targeted analytical approaches

Bradley J Collins,Suramya Waidyanatha,Eugene F Derose,Robert E London,Cynthia V Rider,James M Harnly,Season P Kerns,Geoffrey Mueller,Kristin Aillon

doi:10.1007/s00216-020-02839-7

Abstract

Ginkgo biloba extract (GbE) is a dietary supplement derived from an ethanolic extract of Ginkgo biloba leaves. Unfinished bulk GbE is used to make finished products that are sold as dietary supplements. The variable, complex composition of GbE makes it difficult to obtain consistent toxicological assessments of potential risk. The National Toxicology Program (NTP) observed hepatotoxicity in its rodent studies of a commercially available, unfinished GbE product, but the application of these results to the broader GbE supplement market is unclear. Here, we use a combination of non-targeted and targeted chromatographic and spectrophotometric methods to obtain profiles of 24 commercially available finished GbE products and unfinished standardized and unstandardized extracts with and without hydrolysis, then used principal component analysis to group unfinished products according to their similarity to each other and to National Institute of Standards and Technology (NIST) standard reference materials (SRM), and the finished products. Unfinished products were grouped into those that were characteristic and uncharacteristic of standardized GbE. Our work demonstrates that different analytical approaches produced similar classifications of characteristic and uncharacteristic products in unhydrolyzed samples, but the distinctions largely disappeared once the samples were hydrolyzed. Using our approach, the NTP GbE was most similar to two unfinished GbE products classified as characteristic, finished products, and the NIST GbE SRM. We propose that a simple analysis for the presence, absence, or amounts of compounds unique to GbE in unhydrolyzed samples could be sufficient to determine a sample’s authenticity.Graphical abstract

Highlights

Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Health Sciences, Research Triangle Park, NC 27709, USA 4 U.S Department of Agriculture, Beltsville Human NutritionResearch Center, Methods and Applications Food Composition Lab, Beltsville, MD 20705, USABotanical dietary supplements are complex mixtures of variable composition
Flavonol glycoside content is determined after hydrolysis to convert the glycosides to the corresponding aglycones; Ginkgo biloba extract (GbE) products are often adulterated with cheaper botanical material containing individual flavonol glycosides or flavonols [9]
Chromatograms from samples were visually compared with the National Institute of Standards and Technology (NIST) unfinished GbE standard reference materials (SRM) (3247) and each other on the same X-Y scale for the presence or absence of peaks in each retention time range as well as peak shape and intensity

Summary

Introduction

A key challenge identified in the NTP botanical research program is comparing across these complex mixtures, both in the design phase when selecting an appropriate test article from the multitude of available products and subsequently in extending the toxicological evaluation results for a single reference sample to similar products in the marketplace. To address this challenge, the NTP has begun to assess the chemical and biological parameters needed to establish sufficient similarity between complex mixtures, and Ginkgo biloba extract (GbE) was selected as the first case study for this assessment [2]. Flavonol glycoside content is determined after hydrolysis to convert the glycosides to the corresponding aglycones (flavonols); GbE products are often adulterated with cheaper botanical material containing individual flavonol glycosides (e.g., rutin, the glycoside of quercetin) or flavonols (e.g., quercetin, the aglycone of rutin) [9]

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Conclusion