The growing interest in polyphenols of natural origin and their plant sources encourages the study of their chemical composition and biological activity. Propolis is widely used as a source of phenolic compounds. The aim of this study is to evaluate and compare the chemical composition, antioxidant activity and sun protection factor (SPF) of the ethanolic extracts of the poplar buds, birch buds and pine buds of propolis plant precursors collected in Lithuania. The IC50 concentration of the extracts was evaluated using DPPH and ABTS methods. Extracts of poplar buds, birch buds and propolis showed a lower IC50 concentration by ABTS and DPPH methods compared with pine buds extracts. Poplar buds and propolis extracts showed the highest SPF value, while birch and pine buds extracts showed a lower SPF value. High-performance liquid chromatography (HPLC) analysis results showed that phenolic acids, such as p-coumaric acid and cinnamic acid, and flavonoids, such as pinobanksin and pinocembrin, were identified in all the tested extracts. Salicin has been identified only in poplar buds extracts. The results of antioxidant activity showed that propolis poplar and birch buds are a promising source of biologically active polyphenols.

Oral bioavailability of flavonoids, including G. biloba extract, is limited due to their chemical complexity, which determines slow dissolution in vitro behavior of the extract. The overall research objective was to compare the effect of increasing freeze-dried G. biloba extract (GFD) concentrations in carboxymethyl cellulose (CMC) films on their mechanical properties, release profile of flavonoid glycosides, stability and disintegration time. Physicochemical evaluation of films was performed by SEM and FTIR. The mechanical properties and in vitro release profile of flavonoid glycosides from the prepared films were characterized in the study. The higher elongation at break and tensile strength values, quick release of flavonoids and good stability were observed in formulation, coded FRG—15 (the film contained 0.4 g of GFD, 0.3 g of glycerol and 2 g of 2% CMC), (p < 0.05). Dissolution rate tests showed that approximately 85% of loaded flavonoid glycosides had been released; the release profile of flavonoid glycosides from FRG-15 had levelled off after only 15 min. The results could lay the groundwork for further studies, concerning the development of sublingual films as G. biloba extract-based dosage forms, which might increase the multifunctional properties and pharmacological activity closer to the desired level.

The aim of our research is to investigate the qualitative and quantitative composition and antioxidant activity of flavonoids in leaf samples ofGinkgo bilobaL.(G. biloba)growing in Lithuania and also to provide practical recommendations for the pharmaceutical industry to determine the optimum harvesting time and growth location ofG. bilobaleaves. The obtained results indicate that the growth location and time of sample collection have a significant influence (p≤0.05) on the content of active compounds. July and August are the best months to harvestG. bilobaleaves for industry. To ensure the rational collection ofG. bilobaraw material, the location of plantations is recommended in the western and southwestern phytoregions. The obtained results also indicate that the flavonoid content inG. bilobaleaf has a significantly positive correlation (r=0.952,p≤0.001) with antioxidant activity. The aqueous acetonic extracts from green leaves scavenge radicals to a greater degree than those from yellowGinkgoleaves. The results of this investigation provide information regarding the most suitable Lithuanian growing location to produceG. bilobawith an optimized content of health-promoting compounds.

The aim of the present work was to improve and validate the HPLC-CUPRAC postcolumn method for the evaluation of active antioxidant markers from the acetonic extracts ofGinkgo bilobaleaves. Improvement of the HPLC online assay was performed by evaluating the suitable loop temperature, the reaction loop length, and the impact of flow rate. Separation of the analytes was performed by the HPLC method on an ACE C18 analytical column using a gradient elution program. The separated antioxidant markers in the extracts reacted with copper(II)-neocuproine (Cu(II)-Nc) reagent in the postcolumn reaction coil. The reagent was reduced by antioxidants to the copper(I)-neocuproine (Cu(I)-Nc) chelate with a maximum absorption at 450 nm. Validation experiments confirmed sufficient precision, sensitivity, and effectiveness of the corresponding method, which could be used for further evaluations of active antioxidant compounds in similar plant materials.