Studies on the Free Radical Scavenging Activity and Transition Metal Ion Chelation Ability of the Extracts from Osmanthus fragrans Seeds

Abstract

Green and aubergine Osmanthus fragrans seeds were extracted with ethanol using ultrasoundassisted extraction. The free radical scavenging activity (FRSA) and transition metal ion chelation ability of green Osmanthus fragrans seeds extract (GE) and aubergine Osmanthus fragrans seeds extract (AE) were evaluated. Both of GE and AE showed good free radical scavenging activity and GE displayed stronger free radical scavenging activity than the synthetic antioxidant butylated hydroxytoluene (BHT) in ABTS• assay, with the IC₅₀ 8.06 μg mL^-1. The binding constants K_a (and fluorescence quenching constants K_sv) of GE and AE, binded with Fe(II), Cu(II) and Cu(I) ion, were in the range of 1.04 × 10³-4.00 × 10⁴ M^-1 (2.04 × 10²-5.15 × 103 M^-1), indicating that both GE and AE were good ion chelator and hence may play a vital role in modulating the body's transition metal ion homeostasis.