Five new ginkgolides from the seeds of Ginkgo biloba L.

Five previously undescribed compounds (1-5) and eight known ginkgolides (6-13) were isolated from the 95% ethanol extract of Ginkgo biloba L. seeds. Among the new compounds, one rare sesquiterpene lactone (compound 1) and four diterpene lactones (compounds 2-5) were identified and designated as bilobolide C, ginkgolide I, ginkgolide II, ginkgolide III, and ginkgolide IV, respectively. Compound purification was achieved using a combination of silica gel chromatography, octadecylsilyl (ODS) column chromatography, and preparative liquid chromatography. Structural elucidation was performed through comprehensive spectroscopic analysis-including one-dimensional (1H and 13C) and two-dimensional (COSY, HSQC, HMBC, ROESY) NMR, high-resolution electrospray ionization mass spectrometry (HRESIMS), infrared (IR), and ultraviolet (UV) spectroscopy-as well as electronic circular dichroism (ECD) calculations and single-crystal X-ray diffraction analysis, supplemented by comparison with reported literature data. The neuroprotective potential of all isolated compounds was evaluated against hydrogen peroxide (H2O2)-induced oxidative injury in rat pheochromocytoma (PC12) cells. Compounds 3, 7, 8, and 10 demonstrated significant neuroprotective activity, with EC50 values of 22.39 ± 6.98, 15.10 ± 3.68, 33.64 ± 4.06, and 30.62 ± 1.18 μM, respectively.