Antioxidant activities of the constituents of Picris echoides

Abstract

Some flavonoids with antioxidant properties from the aerial parts of the plant species Picris echoides (family Asteraceae) were identified. Upon chromatography, the ethyl acetate extract afforded flavonoids, such as flavone apigenin (1) and its glucoside, cosmosiin (2), as well as common plant constituents from this family, flavonol galetin (3 3,4?,5,6,7-pentahydroxyflavone) and 4,4?,6,7-tetrahydroxyaurone (4). The structure of the aurone 4 has not been described so far in the literature and presented a very rare type of aurone skeleton. The structures of the isolated compounds were determined by interpretation of their physical and spectral data. The antioxidant activities of different extracts from Picris echoides were measured by the Schaal oven test at 60 ?C and by the Rancimat method at 100 ?C.Water/ethanol extracts (2:8, v/v), in concentrations of 0.02 and 0.05 %, showed lower activity than commercial tocopherol (Tch). On the contrary, the purified ethyl acetate extracts showed a strong concentration-dependent antioxidant effect. The investigation demonstrated that galetin was the main flavonol from this origin. According to the results of the two methods, galetin (3) showed a two-fold better activity than didTch and a lower activity than did butylated hydroxyanisole (BHA). The aurone 4 exhibited significantly lower antioxidant activity than did galetin at the same concentration level. Thus, the plant species P. echoides is a new and favorable source of natural lipid antioxidants.