Subcritical Water as a Tool for Obtaining Extracts of Plant Secondary Metabolites with High Antioxidant Activity from Ginkgo biloba L. Leaves

Objective: This study aims to explore the potential of subcritical water (SCW) for the preparation of polyphenol-rich’s extracts leaves with high antioxidant activity from Ginkgo biloba (GB). Methods: Subcritical water (in the temperature range from 100 to 220°C) was used to extract secondary plant metabolites from GB’s leaves. UV/Vis spectrophotometry methods were used to study the dependence of the polyphenolic profile (the total sum of polyphenolic compounds, including flavonoids) and AOA of GB leaf extracts on the extraction method: in a subcritical water medium or water-alcohol (traditional) extraction. Results and Discussion: In the results, it is found that the use of a subcritical water medium for extraction processes allows not only to increase the extraction of secondary plant metabolites, but also to achieve changes in the properties of the obtained extracts—the content of polyphenolic compounds and AOA activity depend on the extraction conditions (subcritical water temperature). It was shown that the extract obtained from GB leaves in the SCW medium at 220°C contains the highest amount of polyphenolic compounds and demonstrates the highest AOA (EC₅₀ = 34.7 μg/mL) among the extracts obtained. Conclusions: The results demonstrate the prospects of using SCW to obtain extracts from GB’s leaves with a high content of polyphenols for the development of pharmaceuticals and food additives with high AOA.