Deetermination of qualitative composition of phenolic compounds and antioxidant activity in vitro of Ilex paraguariensis A.St.-Hil. leaves samples extracts

Introduction. Ilex paraguaruiensis A.St.-Hil. is a plant in the family Aquifoliaceae DC. ex A.Rich., which is dominated by the genus Ilex L., the largest genus of woody dioecious plants in the class Magnoliopsida (Dicotyledones) [1]. Medicinal plant raw material consists of dried and coarsely crushed Ilex paraguariensis leaves, often with some stem pieces and fine dust—just as nature delivers them after gentle processing [2]. Its health promoting effects come from flavonoids, caffeine and phenolic acids found in I. paraguariensis leaves extracts [3-5]. Aim. In this research, we investigate variation of the total phenolic content, total flavonoid content and antioxidant activity in vitro of I. paraguariensis leaves samples obtained from different producers. Methods. The total phenolic content was determined using Folin–Ciocâlteu assay and expressed in mg of gallic acid equivalent per g (mg GAE/g) [6]. The total flavonoid content was ascertained using spectrophotometric methodology described by Urbonavičiūtė et al. and expressed mg of rutin equivalent per g (mg RE/g) [7]. The antiradical activity in vitro of I. paraguariensis samples extracts was determined using ABTS radical cation scavenging assay [8]. The reduction activity in vitro was evaluated by spectrophotometric CUPRAC assay [9]. The antioxidant activity in vitro of tested extracts was expressed in µmol of Trolox equivalent per g (µmol TE/g). All data were recalculated for the dry weight. Results. The total phenolic content in I. paraguariensis leaves smaples varied from 56.59±4.08 mg GAE/g to 106.60±1.75 mg GAE/g with the highest content found in a sample N2 collected in Argentina. The coefficient of variation was 21.88%. The total flavonoid content varied from 10.47±0.76 mg RE/g to 24.64±1.42 mg RE/g, highest content found in a sample N2. The coefficient of variation was 32.32%. The antiradical activity in vitro using ABTS assay varied between 37.17±2.28 µmol TE/g to 202.38±0.75 µmol TE/g, coefficient of variation was 78.71%. The strongest antiradical activity in vitro was indicated in sample N2. The reducing activity in vitro varied from 274.53±6.06 µmol TE/g to 947.54±15.02 µmol TE/g, strongest was also sample N2. Coeficient of variation of tested extracts was 42.59%. Conclusions. The results of our research have shown that all investigated samples of I. paraguariensis leaves extracts contain phenolic compounds and possess antioxidant (both, antiradical and reducing) activities. The strongest reducing and antiradical activity in vitro and the highest total phenolic content and total flavonoid content determined in the sample N2 from Argentina.