Influence of extraction solvents on total phenolic content and antioxidant activity of Tunisian Thymbra capitata (L.) Cav. aerial parts extracts

Natural compounds from the Lamiaceae family (thyme, sage and rosemary) have been reported in several studies for their antioxidant, anti-inflammatory, antimicrobial, antidiabetic, antiaging and anti-carcinogenic properties.Among the sources of these bioactive molecules, the Thymus genus is particularly noted for its long history of use for different food, pharmaceutical and medicinal purposes, which could be attributed to its polyphenolic compounds.The objective of this study is to evaluate the effect of solvents (water, ethanol, methanol) on extract yields, total phenolic content (TPC), total flavonoid content (TFC) and antioxidant potential of Tunisian Thymbra capitata (L.) Cav.aerial parts.The highest extract yield was obtained from hydroethanolic extract (9.4 mg dry extract per gram dry plant weight, mg DE/g DW) followed by hydromethanolic (8.2 mg DE /g DW) and aqueous extract (7.4 mg DE/g DW).The TPC, evaluated by the Folin-Ciocalteau method, reached the values of 30.20 mg gallic acid equivalent per gram dry extract (mg GAE/g DE), 32.14 mg GAE/g DE and 30.31 mg GAE/g DE of aqueous, hydroethanolic and hydromethanolic thyme extracts, respectively.The highest TFC (16.20 mg quercetin equivalent per gram dry extract, mg QE/g DE) was recorded in hydroethanolic extract, followed by hydromethanolic (11.29 mg QE/g DE) and aqueous extract (4.18 mg QE/g DE).The thyme extract showed strong antioxidant activity with the methanolic extract showing the highest activity reflected by IC50 value of 15.44 µg/mL.The results reveal that thyme aerial parts extracts have proven to be an effective potential source of polyphenols, as natural antioxidants, which is beneficial to human health, and could be useful in replacing or even decreasing synthetic antioxidants in foods, cosmetics and pharmaceutical products.