Substantial Differences in Proanthocyanidin Contents among Ginkgo biloba Leaf Extracts in Herbal Medicinal Products obtained from the German Market

Abstract

Pharmacologic activity of proanthocyanidins (PACs) in Ginkgo biloba leaf extract has recently been reported. The objective of the present study was to screen the PACs content in herbal medicinal products containing Ginkgo extracts. A recently published HPLC method for quantification of PACs in Ginkgo biloba leaf extract EGb 761 was adopted to be also suitable for finished herbal medicinal products. The method was applied to 14 products from the German market. For each product a set of 3 individual batches was purchased and analyzed. Substantial differences in PACs content were found among distinct products ranging from 0.30 % to 5.86 %. The batch-to-batch variability within each product was low. The highest concentrations are in a similar range as for example the amount of Ginkgo terpene trilactones specified in the monograph for Ginkgo biloba leaf extract in the Ph. Eur.. Although it has not yet been established whether and to which extent PACs contribute to the overall pharmacological or clinical efficacy of Ginkgo extracts, a potential impact on the purported benefits of different contents in PACs cannot be ruled out. Quality assessment of different Ginkgo extracts in future may include the PACs.