Neuroprotective, Anti-Hyperpigmentation, and Anti-Diabetic Effects and Bioaccessibility of Flavonoids in Ginkgo Leaf Infusions from Green and Yellow Leaves

Ginkgo (Ginkgo biloba L.) is a widely used medicinal plant, with its green spring leaves commonly utilized for preparing extracts with various therapeutic properties, and leaf infusions also frequently employed. This study aimed to evaluate the in vitro neuroprotective, anti-hyperpigmentation, anti-diabetic, and antioxidant activities, as well as the flavonoid content and its bioaccessibility, of ginkgo leaf infusions, comparing leaves collected in spring and autumn. Infusions made from yellow leaves, both those collected directly from the tree and fallen leaves, exhibited significantly higher total polyphenol content (3.2-fold and 2.5-fold, respectively) and flavonoid content (3.1-fold and 2.4-fold, respectively), along with greater flavonoid bioaccessibility in the salivary phase. These infusions also demonstrated enhanced tyrosinase inhibition (6.0-fold and 5.7-fold, respectively) and antioxidant activity (4.8-fold and 3.5-fold, respectively). Notably, infusions from fallen yellow leaves showed 2.5-fold higher acetylcholinesterase inhibition compared to spring leaf infusions, while α-glucosidase inhibition remained comparable across all samples. These findings suggest that yellow ginkgo leaves, including those that have fallen, could be considered a valuable material for making infusions with potential neuroprotective, anti-hyperpigmentation, and anti-diabetic properties.