Elucidation of micromolecular phenylpropanoid and lignan glycosides as the main antioxidants of Ginkgo seeds

Ginkgo biloba L. is a widely used medicinal plant that has a high concentration of its bioactive components, flavonoids and ginkgolides, in its leaves. Gingko seeds are also consumed as a functional food and medicine throughout the world to slow the ageing process. However, there have been few phytochemical studies of the phenylpropanoids from Ginkgo seeds. To elucidate the active components, we studied the antioxidant activities and related main compounds in Ginkgo seeds. Four main phenylpropanoids and lignans were isolated and identified from the antioxidative fraction and their antioxidant activities were measured. An HPLC/DAD-Q-TOF-MS/MS method was developed to identify the other minor phenylpropanoid and lignan glycosides to elucidate the antioxidant profile of Gingko seeds. Four compounds were identified by NMR and mass data, three of which (8, 17, and 28) exhibited substantial antioxidant activities (IC50: 67-100 μM). Sixteen minor compounds were tentatively identified based on their tandem mass spectrometry data and the fragmentation of four isolated standards from antioxidative n-butanol fraction. Fifteen compounds were reported in Ginkgo seeds for the first time, and compound 16 was tentatively identified as a new chemical structure. Thus, understanding their antioxidant profiles will lay the foundation for research and development of the health benefits of Ginkgo seeds.