Abstract: [Objective] Xinjiang medicine mulberry branches are characterized by their strong antioxidation, but have been untapped as by-products which are annually and largely produced in sericulture. Study on separating and identifying antioxidant active component from Xinjiang medicine mulberry branches can reveal their physical basis of antioxidation, and provide a theoretical foundation for discovery of new natural antioxidant component and for exploitation of Xinjiang medicine mulberry. [Method] The components in medicine mulberry branches are extracted with 70% ethanol and concentrated by reducing pressure at low temperature. Together with DPPH (1, 1-diphenyl-2 picrylhydrazyl), TLC (thin layer chromatography) was applied in activity detection, while ultraviolet spectrophotometry was used to detect the active substances with 10% sulfuric acid-ethanol solution coloration. Based on the activity tracking, separation and purification of the antioxidant compound in medicine mulberry branches were achieved by different organic solvents extraction and segmentation, repeated silica gel column chromatography, gel column chromatography and thin-layer chromatography. With deuterated chloroform as the solvent and TMS (tetramethylsilane) as the internal standard substance, the MS (mass spectra) and NMR (nuclear magnetic resonance) techniques were employed to make spectrum and structure analysis on the compound, and then DPPH free radical and OH free radical scavenging, as well as the total reducing power assay are proceeded with the synthetic antioxidant BHT as a control. [Results] The deep yellow powder, freely soluble in methanol and ethyl acetate, was separated from Xinjiang medicine mulberry branches with ethyl acetate extraction. According to its physical and chemical properties, the powder is classified as flavonoids by preliminary judgment, and then with spectral data analysis by MS, ¹H-NMR, ¹³C-NMR, and DEPT, it was finally identified as the known compound, sanggenon A, and its molecular formula is C₂₅H₂₄O₇, with the molecular weight of 436 Dalton. The antioxidant activity study showed that the IC₅₀ values of scavenging DPPH radical and OH radical were 50.3 mg·L^-1 and 96.5 mg·L^-1, respectively (the IC₅₀ values of the control BHT were 64.2 mg·L^-1 and 231.6 mg·L^-1, respectively). The total reducing power is significantly higher than the control BHT. [Conclusion] The antioxidant component, Sanggenon A, is firstly separated from mulberry branches in this study, which expands the sources of raw materials for extraction and separation of the component. In addition, this study provides theoretical basis for the further study of Sanggenon A and for exploitation of medicine mulberries that, as a forestry resource, are widely cultivated in the region of Xinjiang. The mechanism of the Sanggenon A production in mulberry branches remains further study.

Key words: Xinjiang medicine mulberry, branch, sanggenon A, separation and identification, flavonoid, antioxidant activity