Antioxidant properties and quantification of phenolic compounds from safflower (Carthamus tinctorius L.) seeds

The antioxidant properties of twelve phenolic compounds, including matairesinol 4'-O-beta-D-glucoside, 8'-hydroxy-arctigenin 4'-O-beta-D-glucoside, matairesinol, 8'-hydroxyarctigenin, N-feruloyiserotonin 5-O-beta-D-glucoside, N-(p-coumaroyl)-serotonin-5-O-beta-D-glucoside, N-feruloylserotonin, N-(p-coumaroyl)serotonin, luteolin 7-O-beta-D-glucoside, luteolin, acacetin 7-O-beta-glucuronide, and acacetin, isolated from defatted safflower (Carthamus tinctorius L.) seeds were evaluated with regard to the DPPH, superoxide and hydroxyl radicals. Additionally, levels of phenolic compounds were determined by HPLC in two cultivars of safflower seeds. Among them, four serotonin derivatives showed potent DPPH (IC50=10.83-21.75 mu M) and hydroxyl (IC50=75.93-374.63 mu M) radical scavenging activities, and their activities were significantly stronger than that of alpha-tocopherol. Four flavonoids (IC50=170.65-275.83 mu M) and four lignans (IC50=114.22-406.10 mu M) exhibited significant superoxide and hydroxyl radical scavenging activities, respectively, whereas these compounds contained less activity toward the DPPH and hydroxyl radicals than serotonin derivatives. The levels of serotonin derivatives, lignans and flavonoids in safflower seeds of two cultivars ranged from 49.30 to 260.40, 3.72 to 158.90, and 11.72 to 214.97 mg% (dry base), respectively. Of the two cultivars, 'Cheongsu' had somewthat higher concentrations of phenolic compounds than 'Uisan'. These results suggest that phenolic compounds in safflower seeds may play a role as protective phytochemical antioxidants against reactive oxygen-mediated pathological diseases.