Effect of extraction solvents on polyphenol content and antioxidant activity of carob tree (Ceratonia siliqua L.) leaves

Abstract

Carob tree (Ceratonia siliqua L.) is widely used in traditional medicine and food. The aim of this study was to determine the most appropriate extraction solvent to optimize the extraction of polyphenols and flavonoids from the leaves, in order to obtain the highest antioxidant activity. In this context, the effects of six different solvents (100% methanol, 100% ethanol, 100% acetone, 50% (v/v) aqueous methanol, 50% (v/v) aqueous ethanol and 50% (v/v) aqueous acetone) with different polarities on the polyphenol content and antioxidant activity of carob tree leaf extracts were investigated. The total polyphenol and total flavonoid contents, as well as the antioxidant activity determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method of the extracts were evaluated. The results showed that carob tree leaves extracted with 100% methanol presented the highest values in terms of total polyphenol content (11.33± 0.08 mg EAG/g DM), total flavonoid content (8.55± 0.34 mg EC/g DM) and DPPH inhibition percentage (79.29 ± 3.75%). High positive correlations between total polyphenols, total flavonoids and antioxidant activity of carob tree leaf extracts were also observed. These results indicate that carob tree leaf extract obtained using an appropriate extraction solvent was able to enhance the protective effect against oxidative damage associated with free radicals.