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 (TAG) 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 mu mol Trolox/g. The results for the total antioxidant capacity ranged from 33 to 206 mu mol Trolox/g for TAC(FRAP), from 29 to 515 Knot 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 mu mol Trolox/g) and TAC(FRAP) (183-184 mu mol Trolox/g), n = 2; (2) high total phenols (759-834 mu mol Trolox/g) and TAC(FRAP) (182-206 mu mol Trolox/g), n = 5; (3) medium and low total phenols (635-202 mu mol Trolox/g) and TAC(FRAP) (82-202 mu mol Trolox/g), n = 20 and (4) very low total phenols (<181 mu mol Trolox/g) and TAC(FRAP) (<101 mu mol 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.