VERIFICATION OF AUTHENTICITY OF GINKGO BILOBA L. LEAF EXTRACT AND ITS PRODUCTS PRESENT ON THE CROATIAN MARKET BY ANALYSIS OF QUANTITY AND RATIO OF GINKGO FLAVONE GLYCOSIDES (QUERCETIN, KAEMPFEROL AND ISORHAMNETIN) TO TERPENE TRILACTONES TO THE EFFECT OF UNMASKING COUNTERFEIT DRUGS ENDANGERING PATIENT HEALTH

Ginkgo biloba L. is the eldest plant growing on the Earth; preparations made of its leaves and seeds represent an integral part of the Chinese medicine for over a millennium. The plant species was first discovered by Linnaeus in 1771, its name thereby originating from the Latin words bis (two) and lobus (lobe), which duly illustrate the specific shape of its leaf. Contemporary Ginkgo biloba L. plant based pharmaceuticals mostly comprise extracts recovered from leaves harvested during fall, when the concentration of active components reaches its peak. Recent investigations have managed to establish the chemical composition of the plant leaf, together with the mechanisms underlying its beneficial effects on rheological profile of the blood and acceleration of its flow. High price of these preparations and their vast popularity have soon become an incentive for counterfeiting Ginkgo biloba L. extracts and the release of bogus drugs comprising cheaper extracts coming from other plants. Namely, modern Ginkgo biloba L.-based medicinal products and food supplements comprise extracts recovered from the plant leaf that get to be standardized according to its key pharmacological active components, most often flavone glycosides (represented in the share of 22%-27%) and terpene trilactones (represented in the share of 6%-7%). The flavonoids that predominate such preparations and are most relevant from the pharmacological standpoint are quercetin, kaempferol and isorhamnetin, their total amount and mutual ratios, thereby being an unquestionable indicator of the extract authenticity. Therefore, most of the analyses aiming at verifying the authenticity of a given Ginkgo biloba L.-based product boil down to the analysis of these parameters. Counterfeiting involves partial or full replacement of the Ginkgo biloba L. extract (GBE) with a cheaper plant extract of a similar composition, the latter occasionally being enriched with an additional amount of flavonoids, most often quercetin, not originating from the Ginkgo biloba L. plant. The aim of this study was to verify the authenticity and quality of Ginkgo biloba L.-based products circulating on the Croatian market. To that effect, 10 samples of products produced by various manufacturers were analyzed in a certified laboratory. The parameters based on which the authenticity of the preparations was assessed were the shares of aglycones of typical ginkgo flavone glycosides, that is to say, quercetin, kaempferol and isorhamnetin, and mutual ratios of the established quantities of quercetin to kaempferol as the key clues to unmasking Ginkgo extracts counterfeiting. The amount of ginkgo flavone glycosides was established using high performance liquid chromatography. The analysis proved 80% of the samples analyzed to be conformant to the label statements as regards the total amount of flavone glycosides and their mutual ratios. In 20% of the samples, the ratio of quercetin to kaempferol deviated from normal values; on top of that, the presence of the phytoestrogen genistein, one of the components typically comprised by the Sophora japonica L. plant, was also proven, documenting counterfeiting of the GBE and its replacement by the Sophora japonica L. extracts in the samples under consideration. Due to the untrue label statements descriptive of these products, the information on the presence of pharmacologically active genistein was neglected to be mentioned despite its unfavorable health impact that can be expected in some consumer groups. The results of this study indicated the frequency of counterfeiting the Ginkgo biloba L.-based products found on the Croatian market to be deemed substantial. Therefore, a more rigorous and more thorough control of these products and sanctioning of irresponsible manufacturers and distributers is proposed, so as to contribute to a higher market representation of high-quality products, as well as to avoid health risks and downsize the rate of their counterfeiting.