Total Polyphenolic Content and Antioxidant Activity of Different Extracts from Sideritis scardica

Abstract

Sideritis scardica is an endemic plant in Bulgaria traditionally used for its therapeutic properties. It has a wide composition of biologically active substances such as polyphenolic compounds, flavonoids, and organic acids. Its antioxidant activity has been well documented in recent decades and is considered a possible principle in the treatment and prevention of inflammatory and neurodegenerative diseases. The influence of the solvent and extraction approach on the yield, total polyphenolic, and flavonoid content, and antioxidant activity in Sideritis scardica extracts were evaluated. Water, acetone, and water-ethanol mixtures (20%, 50%, and 70% ethanol) were used as solvents to extract bioactive compounds from the plant material. The applied extraction procedures included infusion, decoction, maceration, as well as green extraction techniques such as ultrasonic and microwave irradiation. The highest values for total polyphenols and total flavonoids were demonstrated in 70% ethanol extracts, followed by other water-ethanol mixtures and water decoctions. The microwave and ultrasonic irradiations reduced the extraction time, as the value of phenolic content in these extracts was the highest. The results showed that the highest extraction yields are obtained with 50% and 70% ethanol maceration, followed by aqueous infusion. The highest antioxidant potential was found in extractions with water and 70% ethanol solution, where the amount of polyphenols was also sufficient. A positive correlation between polyphenol content and antioxidant activity was observed. Therefore, extracts of Sideritis scardica are a rich source of polyphenols with pronounced antioxidant properties.