Effect of Drying Methods on Phytochemicals, Antioxidant Activity and Total Phenolic Content of Dandelion Leaves

Taraxacum officinale is globally used both as a vegetable and as a herb for medical and therapeutic purposes; hence the need to investigate its phytonutrients. The aim of this study was to evaluate the effects of different drying methods (hot-air drying, solar drying and freeze-drying) on the phytochemicals as well as total phenolics content and antioxidant capacity of dandelion leaves. The fresh dandelion leaves had high contents of total phenolics (7.78 mg GAE/ g) on dry weight basis. They exhibited high antioxidant activity (397.94%, %inhibition of DPPH) measured by DPPH assay. Drying methods caused a significant decrease in total phenolics and antioxidant capacity of dandelion leaves. Drying by freeze drying and solar drying had the lowest adverse effects on antioxidant capacities of dandelion leaves while drying by hot-air at 60°C cannot be a competitive process for preserving antioxidants and antioxidant capacity of dandelion leaves. The changes in the antioxidant capacity due to the drying methods were positively correlated with the content of phenolics. Therefore, it can be suggested that special care should be taken when processing method is selected for the exploration of dandelion leaves.