Effect of Ginkgo biloba Leaf Flavonoids on the Growth and Enzymatic Oxidation Systems of Penicillium expansum

Blue mold caused by Penicillium expansum (P. expansum) causes severe fruit losses, and there is an urgent need to explore safe natural products to control post-harvest diseases and investigate potential antifungal mechanisms. In this study, flavonoids (GBLF) were extracted and purified from mature Ginkgo biloba leaves (GBL). According to an analysis of UV-visible spectroscopy, FTIR, and LC-MS, GBLF contained 10 flavonoids, including 8 quercetin and kaempferol derivatives. The inhibition halo diameter by GBLF ethanol solution reached a maximum of 11.2 ± 0.3 mm, which significantly inhibited the growth of P. expansum. In the GBLF ethanol solution treatment trial, the mycelial cells of P. expansum reached their maximum cell conductivity, protein leakage rate, and malondialdehyde (MDA) content at 48 h, with values of 3.89 ± 0.17 ms/cm, 5.22 ± 0.08 mg/L, and 5.76 ± 0.09 mmol/kg, respectively, which were 2.7, 13.74, and 4.76 times higher than those of the control. Compared with 12 h, the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in the enzyme antioxidant system were 3.38 ± 0.11 U/mg, 5.23 ± 0.09 U/mg, and 2.66 ± 0.10 U/mg, respectively, which decreased by 30.2