Identifying the impact of ultrasound-assisted extraction on polysaccharides and natural antioxidants from Eucommia ulmoides Oliver

摘要

Ultrasound-assisted technique has been developed as complementary method to extract natural antioxidants and polysaccharides from Eucommia ulmoides Oliver. Additionally, polysaccharides were characterized by sugar analysis, FTIR, and GPC. The contents of eight main bioactive molecules were identified and quantified by HPLC. The results showed that ultrasound improved the yield and selectivity of the antioxidants and that the chemical properties of the polysaccharides were modified slightly. The contents of phenolics, flavonoids, and bioactive compounds were increased after ultrasonic treatment, but the increment varied between the different tissue parts. Meanwhile, aucubin and chlorogenic acid were the uppermost bioactive constituents of barks and leaves, respectively. The polysaccharides prepared with ultrasound exhibited slightly higher molecular weights (32,125-91,800g/mol) as compared to the fractions prepared without ultrasound (17,995-21,410g/mol). The extracts from leaves showed significant inhibitory activity, with radical scavenging index ranging from 3.22 to 4.17, which was higher than that of extracts from cortex (1.01-1.32), suggesting that the leaves exhibited much higher antiox-idant activity than raw cortex. The in vitro antioxidant activity of concentrates correlated with their phenolic content.