Proanthocyandidines from EGb 761​: pharmacological effect on learning and memory and oral bioavailability

EGb 761​, a dry extract from Ginkgo biloba leaves, is used for the treatment of declining cognitive performance. The extract is adjusted to 22.0 – 27.0% flavonoids, 5.4 – 6.6% terpene lactones and contains

4.5 – 9.5% of proanthocyanidines (PAC) and less than 5 ppm ginkgolic acids. We recently reported first evidence of pharmacological activity of a PAC fraction isolated from EGb 761​ [1]. In the present study, we aimed to further characterize the PAC fraction to identify PACs or associated metabolites linked to pharmacological activity. To this end, we assessed learning and memory in mice using the passive avoidance model. Metabolite profiles in plasma and brain of PAC-treated mice and from in-vitro gut microbiota experiments were examined by untargeted and targeted LC-(HR)-MS/MS. Our experiments revealed a dose- dependent amelioration of scopolamine induced amnesic effects by both EGb 761​ and PAC. Whereas no (conjugated)-PAC monomers were detectable, we observed a dose-dependent increase in other metabolites in plasma and brain of PAC-treated animals. In addition, a potential relevance of gut microbiota for PAC metabolisation was suggested by formation of low molecular weight metabolites from the mostly polymeric PAC fraction in the in-vitro experiments.

In conclusion, a PAC fraction isolated from EGb 761​ displays anti-amnesic effects in vivo that are probably mediated by strongly metabolised PAC rather than PAC monomers. Our results are consistent with the assumption that PACs contribute to the efficacy of EGb 761​.

Publication History

Article published online:
16 November 2023

• References

• 1 Sens-Albert C.. et al. Planta Med 2021; 87: PC5-1