Achillea millefolium L. s.l. herb extract: Antioxidant activity and effect on the rat heart mitochondrial functions

► Antiradical activity of Achillea millefolium herb extract (YE) is due to phenolics. ► YE significantly decreases H 2O 2 production in rat heart mitochondria. ► Higher amounts of YE induce the decrease in State 3 respiration rate in mitochondria. ► YE had no effect on the integrity of the inner mitochondrial membrane. An extract of Achillea millefolium herb (YE) was investigated for antioxidant activity using chemical and biological assays. Qualitative and quantitative analysis of some major phenolics was carried out by HPLC. An on-line HPLC-DPPH assay showed that YE possesses significant antiradical activity which is due to the presence of active components amongst phenolic compounds. Furthermore, direct effects of YE and a mixture of its identified phenolic compounds (MPC) on isolated rat heart mitochondrial function were investigated. We found that YE in concentration-dependent manner induce a decrease in State 3 respiration rate without any changes in the integrity of inner mitochondrial membrane. Thus, pyruvate oxidation was affected only by the highest used YE concentrations; meanwhile succinate oxidation was reduced even at lower YE concentrations. MPC had no effect on mitochondrial State 3 respiration rate. Fluorimetric measurements demonstrated that YE at concentrations that had no effect on the State 3 respiration rate significantly decreased H 2O 2 production in mitochondria.