Evaluation of 33 medicinal plant extracts for the antioxidant capacity and total phenols.

The total phenolic content and related total antioxidant capacity of 33 medicinal plants were analyzed. The total phenols were measured by Folin-Ciocalteau assay. The total antioxidant capacity (TAC) was estimated by Ferric Reducing/Antioxidant Power (FRAP), CUPRAC and DPPH assay. The total phenolic content of medicinal plant infusions ranged from 84 to 1168 μmol Trolox/g.The results for the total antioxidant capacity ranged from 33 to 206 μmol Trolox/g for TAC FRAP , from 29 to 515 μmol Trolox/g for TAC CUPRAC and from 0.3 to 81.3% for DPPH. There was not very good linear correlation between total phenolic content and FRAP (R 2 = 0.5061). Better correlation was noticed between total phenolic content and CUPRAC (R 2 = 0.8828). According to their total antioxidant capacity, 33 medicinal plant samples can be divided into four groups: (1) very high total phenols (>1000 μmol Trolox/g) and TAC FRAP (183-184 μmol Trolox/g), n = 2; (2) high total phenols (759-834 μmol trolox/g) and TAC FRAP (182-206 μmol Trolox/g), n = 5; (3) medium and low total phenols (635-202 μmol Trolox/g) and TAC FRAP (82-202 μmol Trolox/g), n = 20 and (4) very low total phenols (<181 μmol Trolox/g) and TAC FRAP (<101 μmol Trolox/ g), n=6. The highest total polyphenols, TAC FRAP , TAC CUPRAC and TAC DPPH values were obtained for Epilobium montanum, followed very close by Melissae folium.