Bioactive Compound and Antioxidant Activity of Sunchoke (Helianthus tuberosus L.) at Different Harvest Times

Abstract

The Sunchoke or Jerusalem artichoke (Helianthus tuberosus) tubers were harvested 14, 16, 18 and 20 weeks after planting at Ubon Ratchathani province, Thailand. This work investigated bioactive compounds and antioxidant activities of Sunchoke harvested at different times after planting and prepared by infusion with water, ethanol and acetone. The study of bioactivity of Sunchoke revealed that the extraction with water was appropriate application. Phenolic content ranged from 2.49 to 4.44 mg GAE/g sample. Flavonoid content ranged from 21.06 to 195.30 mg QE/g sample. It was found that Sunchoke water extract showed the highest total phenolic and flavonoid contents. Antioxidant activities of all three extracts were evaluated using DPPH, ABTS, reducing power and ion-chelating capacity assays. Sunchoke water extract displayed the highest antioxidant activities. An increase in bioactive compound and antioxidant activity was observed for late-harvested (20 weeks) tubers. Therefore, 20 weeks seem to be the optimum harvest time for locally grown Sunchoke on the basis of the amounts of high bioactive compound and antioxidant activity.