Natural flavonoids function as chemopreventive agents from Gancao (Glycyrrhiza inflata Batal)

• Natural flavonoids function as chemopreventive agents from Chinese licorice.
• The chemical profile of the effective part was elucidated as 24 flavonoids.
• Major components 8, 12 and 20 could be potential NQO1 inducers and tumour angiogenesis inhibitors.

Bioactivity guided assay of Gancao showed the flavonoids as being effective in its extract, which contained 24 flavonoids, including isoflavones (1–4), flavanones (5–7), chalcones (8–17), and flavones (18–24). Components 1, 5, 6, 7, 8, 9, 19, 21, and 22 were for the first time identified in licorice. NQO1 and tumour angiogenesis assay suggested three effective flavonoids, α, 4, 2′, 4′ – tetrahydroxydihydrochalcone (8), licochalcone A (12), and licoflavone B (20) as being responsible for the chemopreventive effect. Furthermore, AutoDock 4.2 was employed for molecular docking to clarify the interaction between bioactive flavonoids and NQO1. HPLC analysis was performed to determine the contents of 8, 12 and 20. Therefore the chemical and biological results indicated that flavonoids from the residue of Gancao are promising natural cancer chemopreventive agents.