The Impact of Vegetation Conditions of gingko Bilobaon their Antioxidant Ability and Cholinoesterase Inhibitory Effect
During two vegetation periods, hydrophilic and lipophilic fractions of green and yellow leaves of Gingko biloba were analyzed for their chemical constituents. Samples were analyzed via HPLC for the presence and content of selected flavonols, tocochromanol, ß-carotene and phytosterols with the GC method. Then, the antioxidant effect towards DPPH and ABTS radicals was studied. In both Rancimat tests antioxidant activity of hydrophilic and lipophilic fractions was measured.The evaluation of Gingko leaves extracts activity potential as acetylcholinesterase and butyrylcholinesterase inhibitors were estimated. It was found that the content of individual phytochemicals depended on the month of leaf harvesting and varieties depending on the lipophilic and hydrophilic fraction. Among the tocopherols analyzed, the presence of which was observed only in the lipophilic fraction, the dominant homologue was α-tocopherol, and among the phytosterol group sitosterol content was the highest. In green leaves, stigmasterol was found in trace amounts and. Gingko leaves extract posses antiradical-scavenging activity. Both fractions from ginkgoleaves imparted a significant protection factor against fat oxidation, as assessed with the Rancimat method. The best effect was shown by the lipophilic fraction from yellow ginkgo leaves.The highest inhibitory activity against AChE and BChE was observed for yellow leaves extracts. The test results confirmed that the leaves in the final phase of vegetation can be a raw material for obtaining extracts. Therefore, further work on assessing other environmental and agriculture factors on the properties of Ginkgo as a potential source of health promoting ingredients is recommended.