Abstract:Sea buckthorn leaves are rich in flavonoids; nevertheless, in the past, the leaves were mostly discarded as waste after processing, resulting in a waste of resources. Herein, Chinese sea buckthorn leaves were used for flavonoid extraction. Microwave-assisted ethanol solvent extraction, isoelectric precipitation, and ion-exchange resin purification of flavonoids were optimized by response surface methodology, and the composition of the extracted flavonoids were identified by ultra-performance liquid chromatography-high-resolution mass spectrometry. The highest total flavonoid yield (70.98%) and associated flavonoid content (42.11%) were obtained when the processing conditions are as follow: solid-to-liquid ratio of 1:30 (g/mL), alkali dissolution at 92 ℃ and pH 9.50, and acid precipitation at pH 2.70. A total of 15 flavonoids were identified in the sea buckthorn leaf. In particular, rutin, quercetin-3-rhamnoside, quercetin-3-O-glucopyranoside, and quercetin accounted for 89.67% of the total flavonoid content. The herein proposed method can be used to extract and refine high-purity flavonoid products from sea buckthorn leaves, thereby contributing to the field of fine processing and utilization of sea buckthorn leaf resources in the future.
