Biological activities and chemical analysis of phenolic and flavonoid components ofThymus hirtusWilld. andThymus lanceolatusDesf. extracts

Abstract

This work deals with the determination of the antioxidant and antimicrobial effects of the hydro-methanolic extract and its fractions of the aerial parts of two medicinal species of thyme: Thymus hirtus Willd and Thymus lanceolatus Desf. A chemical analysis by colorimetric and chromatographic methods was also carried out on the various extracts prepared. The results show that the polyphenol contents of diethyl ether and ethyl acetate extracts of Thymus hirtus are the highest (261.66 ± 3.66 and 272.80 ± 8.88 mgEAG/g.d.e, (respectively) while the largest amounts of flavonoids were observed in diethyl ether and chloroform extracts of Thymus lanceolatus (3.39 ± 0.03 and 3.13 ± 0.08 mg EQ/g.d.e, respectively). High performance liquid chromatography (HPLC) analysis of the hydro-methanolic extract revealed its richness in phenolic acids. Concerning antioxidant activity, the diethyl ether fraction of Thymus hirtus was found to be more active than other extracts and demonstrated strong free radical scavenging activity (SC 50 = 13.12 μg/mL) with very high protective capacity of the β- carotene–linoleic acid system (96.65 ± 0.720%). As for the antimicrobial activity, extracts of the species Thymus lanceolatus were the most active and the strains Staphylococcus aureus and Umpelopsis ramaniana were the most sensitive with an MIC (minimum inhibition concentration) ranging from 0.391 to 0.098 mg/mL.