Effects of Different Extraction Methods and Solvents on the Phenolic Composition and Antioxidant Activity of Silybum Marianum Leaves Extracts

Abstract

Objective: The objectives of this study were essentially to evaluate the best technique for extracting phenolic compounds from Silybum marianum leaves.
 Subjects and Methods: Two extraction methods (maceration and decoction), using four extraction solvents. The efficiency of the extraction methods was estimated by quantifying the total polyphenol contents by the Folin -Ciocalteu method and by determining the antioxidant power of the various extracts by the ability to trap the free radical DPPH °, and the influence of these parameters on the antioxidant activity.
 Results: The results showed that the extracts of the leaves by maceration have contained the highest percentage yield (24.68%); the highest content in the aqueous -methanol polyphenols extract (18.75 ± 0.55 mg GAE / g DW ) against the decoction is more effective for the extraction of flavonoids and condensed tannins. The highest content of flavonoids had been recorded for the aqueous- ethanolic extract (5.08 ± 0.57 CE mg / g DW). The water had the highest content of condensed tannin (03.86 ± 0.22 TAE / g DW). On the other hand, the aqueous -ethanolic and aqueous -methanol extract of the leaves obtained by maceration have the best antioxidant capacity (73.84 ± 5.90 EAG / g DW and 73.64 ± 5.93 mg EAG / g DW respectively) and the aqueous extract of the leaves by decoction had a better antiradical power (48.64 μg / ml).
 Conclusion: The extraction of phenolic compounds from Silybum marianum leaves was strongly influenced by the type of solvent and the extraction method. In addition, it is very difficult to choose an appropriate extraction solvent for all plant samples.