Antioxidant activity and phenolic compounds in 32 selected herbs

Total equivalent antioxidant capacities (TEAC) and phenolic contents of 32 spices extracts from 21 botanical families grown in Poland were investigated. The total antioxidant capacity was estimated by the following methods: ABTS+ (2,2′azinobis-(3-ethylbenzthiazoline-6-sulfonic acid)), DPPH (1,1-diphenyl-2-picrylhydrazyl radical) and ferric reducing/antioxidant power (FRAP) expressed as TEAC. The total phenolics were measured using a Folin–Ciocalteu assay. Qualitative and quantitative analyses of major phenolics by reverse-phase high-performance liquid chromatography (RP-HPLC) were also used. Major phenolic acids identified in analyzed species were caffeic, p-coumaric, ferulic and neochlorogenic, while predominant flavonoids were quercetin, luteolin, apigenin, kaempferol and isorhamnetin. Myricetin was detected only in Epilobium hirsutum. Many investigated spices had high levels of phenolics and exhibited high antioxidant capacity. The TEAC values of the spices ranged from 1.76 to 346 μM trolox/100 g dw, from 7.34 to 2021 μM trolox/100 g dw, and 13.8 to 2133 μM trolox/100 g dw for ABTS+, DPPH and FRAP, respectively. The total phenolic content, measured using a Folin–Ciocalteu assay, ranged from 0.07 to 15.2 mg of gallic acid equivalents (GAE)/100 g dw. The herbs with the highest TEAC values were Syzygium aromaticum, E. hirsutum and the species belonging to the Labiatae and Compositae family. A positive relationship between TEAC (ABTS+ and FRAP) values and total phenolic content, measured by HPLC, was found only in family groups with many representative herbs within Labiatae and Compositae.