Supercritical fluid extraction of flavonoids from Eucommia ulmoides leaves and antioxidant activities before and after purification

Total flavonoids were extracted from Eucommia ulmoides leaves using Supercritical fluid extraction and purified with AB-8 macroporous resin. In order to contrast the antioxidant activities of flavonoids before and after purification, three antioxidative tests including 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH·), superoxide radicals and xanthine oxidase, have been used in this study. The results indicated that the antioxidant capacities of purified flavonoids are stronger than the crude flavonoids from Eucommia ulmoides leaves. For the crude flavonoids, IC₅₀ of scavenging DPPH· and superoxide radicals were 0.21 mg/mL and 4.38 mg/mL. IC₅₀ for inhibiting XOD was 7.5 mg/mL. But for the purified flavonoids, IC₅₀ was found to be 0.14 mg/mL, 3.37 mg/mL and 1.2 mg/mL respectively.