Proanthocyanidines from EGb 761^® improve impaired short term memory

EGb 761^®, a dry extract from Ginkgo biloba leaves, is used for the treatment of declining cognitive performance. The extract is adjusted to contain 22.0–27.0% ginkgo flavonoids, 5.4–6.6% terpene lactones and less than 5ppm ginkgolic acids. Further, EGb 761^® contains about 7% proanthocyanidines (PAC) [1] with a yet unknown contribution to the efficacy of EGb 761^®. In the present work we aimed to assess the relevance of PAC constituents for the pharmacological activity of EGb 761^®. One hour before testing spontaneous alternation in the T-maze, NMRI mice received perorally either vehicle, donepezil (0.3mg/kg), EGb 761^® (10-300mg/kg), isolated PACs (3-300mg/kg), or two finished products with different Ginkgo extracts that showed eight-fold differences in PAC content but comparable levels of terpene lactones and ginkgo flavonoids (50mg/kg). 20 minutes prior to the session, mice were injected i.p. with 1mg/kg scopolamine to impair short term memory. Mice were observed for 20 trials and spontaneous alteration was documented. Both, EGb 761^® (ED₅₀=89mg/kg, E_max 90%, n=6) and its isolated PAC fraction (ED₅₀=43mg/kg, E_max 71%, n=7-14) dose-dependently attenuated the scopolamine-mediated impairment. Interestingly, treatment with a Ginkgo product with a high PAC content extract (EGb 761^®) showed better activity in reversing the scopolamine effect than a product with a low PAC content (63% vs. 34% inhibition).

In conclusion, we identified PACs as a novel, quantitatively relevant and pharmacologically active constituent of EGb 761^®.

All authors are employees of Dr. Willmar Schwabe GmbH & Co. KG, Germany.

Publikationsverlauf

Artikel online veröffentlicht:
13. Dezember 2021

• References

• 1 Kulić Ž. et al. Planta Med 2021