The antioxidant activities of flavonoids in Jerusalem artichoke ( L.) leaves and their quantitative analysis.

The main targets of this work were to evaluate the antioxidative properties of flavonoids in Jerusalem artichoke ( L.) leaves and quantitatively determine their contents. 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis (3-ethylbenzothiazoline)-6-sulphonic acid (ABTS) and hydroxyl free radicals scavenging assays were performed to determine their antioxidative capacities. The validated ultra high-performance liquid chromatography-quadrupole-time-of-flight/mass spectrometry (UHPLC-Q-TOF/MS) method was subsequently applied to the quality evaluation of eleven batches of Jerusalem artichoke leaves grown in different habitats at different harvesting time. Results indicated that two flavonoids isolated from Jerusalem artichoke leaves showed stronger antioxidant effects than the positive control, butylated hydroxytoluene (BHT). And the total contents of the two flavonoids in the Jerusalem artichoke leaves of flowering stage from Dalian, Liaoning Province, China, were the highest, their contents varied significantly depending on region and harvesting time. This study indicated that the leaves of Jerusalem artichoke possessed excellent antioxidant properties, highlighting their candidacy as natural antioxidants, which could be utilized therapeutically to protect the body from diseases caused by oxidative stress.