Introduction
Plants contain a large variety of phytonutrients, of which many have antioxidant properties. Antioxidant compounds include vitamins, phenols carotenoids and flavonoids. Phenolics are secondary plant metabolites found in the majority of herbs, vegetables, and tea. In recent years many studies have demonstrated that free radicals are the leading cause of degenerative disease. Plant antioxidants work as singlet and triplet oxygen quenchers, free radical scavengers, peroxide decomposers and enzyme inhibitors. Many of these protective biological effects are attributed to polyphenol contents of plants. The demand for natural antioxidants (plant phenolics) has increased tremendously over the past five years. New phenolic products are continuously been developed and consumed. Our results have good significance, as this study provided economic and efficient ways to enhance phenolic content for commercial use. Helianthus tuberosus L. (Asteraceae), also known as Jerusalem artichoke and an important industrial crop, is a sunflower species originating from the eastern North America. It has been naturalized and cultivated widely across the tropical, temperate, boreal and arid to semi-arid zones. Jerusalem artichoke has both economic and ecological values. Given its wide ecological adaptation (it is resistant to drought, salt, cold and wind stress), Jerusalem artichoke has been used in food, pharmaceutical, feed, sugar, paper, cosmetics, and bioethanol industry, and in desert and tideland control.