Motherwort herb or Macae or Rubim (Leonurus sibiricus L.) is used in folk medicine in the form of teas for postpartum bleeding, excessive menstruation as well as against edema, abscesses and renal, cardiovascular and liver problems. The infusion of leaves and flowers are used to combat vomiting and diarrhea. The objective of this study was to determine the concentration of total phenolic compounds, derivates flavonoids, reducing ability and antioxidant activity of fresh leaves of L. sibiricus. Fully expanded leaves picked in orchards, in a shading area and high irrigation, in October, in Mariana (Brazil). Voucher specimen of propagative material was prepared and is deposited in the UFOP Herbarium (OUPR). Eat the fresh leaves made up the ethanolic extract was made by remaceration, until exhaustion. The solvent (40 °C) was then evaporated to give the dried extract. The yield of the extract was calculated as a function of the initial mass of fresh leaves and solvent. Phenolic compounds were determined by Folin-Ciocalteu, flavonoid derivatives by hydrochloric vanillin, antioxidant by DPPH and reducing power by ferric chloride and β-carotene by linoleic acid. The yield of the ethanolic extract of fresh leaves of L. sibiricus was 10.80%. The contents of phenolic compounds, flavonoids, antioxidant activity and reducing power were PC = 160.3733 ± 5.7607 mg.g-1 (R2 = 0.99); Flav = 27 ± 5,5740 mg.g-1 (R2 = 0.998), AAT0 = 61.87 ± 0.69% and AAT30 = 81.90 ± 0.59%. β-carotene = 66.45 ± 0.84% (BHA = 87.06 ± 2.31% control). Low concentrations of fresh leaf extract of L. sibiricus had antioxidant activity equivalent to BHA control, thus being able to prevent the oxidation of free radicals, corroborating popular use with the potential of the species as cardioprotective and hepatoprotective, hypocholesterolemic and hypoglycemic.
