Optimization infusions conditions for improving phenolic content and antioxidant activity in Sideritis scardica tea using response surface methodology

Sideritis scardica (Mountain Tea), an endemic plant of the Balkan Peninsula, is generally acknowledged as a very popular consumed beverage with multiple pharmacological properties including antioxidant activity. This study was designed to optimize the infusion conditions, aiming to maximize the phenolic compounds and antioxidant activity of the tea-infusion, made from different parts of Sideritis plants. The influence of different infusion temperatures (60, 80 and 93 degrees C) and steeping times (10, 20 and 30 min) either as aerial parts or as stems, flowers, leaves of Sideritis plants was determined using response surface methodology. The results showed good fit of data and the optimal infusion conditions were steeping time no more than 10 min and temperature water ranged between 87.5-99.8 degrees C for all infusions under investigation. The highest bioactive content and antioxidant activity was exhibited in leaves infusions followed by flower, aerial parts, and stems. Under this condition, chlorogenic acid was detected as the major phenolic acids in all Sideritis infusions. Moreover, the most abundant minerals were recorded in the order: K > P > Ca > Mg > Na > Fe. Stems tea-infusions contained the highest amount of minerals followed by those obtained from flowers, aerial parts and leaves, respectively.