Impact of Ethanol–Water Ratio on the Recovery of Major Biflavonoids from Ginkgo Leaves and Sarcotesta

Biflavonoids, or flavonoid dimers, are characteristic phytochemicals of ginkgo associated with various biological activities, yet they remain far less studied than monomeric flavonoids. For their effective industrial application, optimization of extraction conditions is essential. This study investigated the effect of ethanol–water ratio (0, 10, 30, 50, 70, and 96% ethanol) on the extraction efficiency of major ginkgo biflavonoids (amentoflavone, bilobetin, ginkgetin, isoginkgetin, and sciadopitysin). Three ginkgo tissue types, green leaves, yellow leaves, and sarcotesta, previously reported to accumulate biflavonoids, were analyzed. Biflavonoids were quantified by HPLC-DAD, and total polyphenol content and antioxidant activity were also determined. Biflavonoids were most abundant in yellow leaves, with sciadopitysin identified as the dominant compound. No biflavonoids were detected in water or 10% ethanol extracts, while 30% ethanol extracts contained detectable biflavonoids only in yellow leaves at low concentrations. For most biflavonoids, the highest concentrations were obtained using 70% and 96% ethanol. Considering comparable extraction efficiency and lower toxicity, 70% ethanol was identified as the most suitable solvent. These findings highlight the importance of tissue type and solvent composition for efficient biflavonoid extraction from ginkgo.