Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
A study of antioxidant activity and acetylcholineste ase (AChE) inhibitory activity of aqueous tea infusions prepared from walnut (Juglans regia L.), peppermint (Mentha×piperita L.), strawberry (Fragaria×ananassa L.), lemon balm (Melissa officinalis L.), sage (Salvia officinalis L.), and immortelle (Helichrysum arenarium (L.) Moench.) is presented here. Chemical composition of selected aqueous tea infusions was determined by high-performance liquid chromatography with photodiode-array method (HPLC-PDA), and the following phenolic compounds were identified as dominant: rosmarinic acid, gallic acid (not identified in walnut and sage), caffeic acid (in sage and peppermint), neochlorogenic acid, 3-p-coumaroylquinic acid and quercetin 3-galactoside (in walnut) and luteolin 7-O-glucoside (in sage). Antioxidant activity of the selected aqueous tea infusions was measured using low-density lipoprotein (LDL) oxidation method, 2,2\u27-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging test, β-carotene bleaching method, and Rancimat method (induction period of lard oxidation). Strawberry and lemon balm aqueous infusions completely inhibited LDL oxidation at the concentration of 0.005 g/L in the reacting system. Very long prolongation of the lag phase was achieved with peppermint and sage aqueous infusions. All tested infusions in the concentration range of 0.05–2.85 g/L showed very pronounced effect of DPPH scavenging activity (90–100 %) as well as the inhibition of β-carotene bleaching (89–100 %). In pure lipid medium, used in Rancimat method, sage and immortelle at the concentration of 0.16 % (by mass) had the highest ability to inhibit lipid peroxidation process. Screening of the AChE inhibitory activity by Ellman´s method showed that the strongest inhibition was obtained with walnut and strawberry aqueous infusions at the concentration of 1.36 g/L in the reacting system. The presented results suggest that natural antioxidants could be useful and merit further investigations in the treatment and prevention of Alzheimer’s disease.Svrha je istraživanja bila odrediti antioksidacijsko djelovanje i sposobnost inhibicije enzima acetilkolinesteraze u vodenim infuzijama oraha (Juglans regia L.), paprene metvice (Mentha × piperita L.), jagode (Fragaria × ananassa L.), matičnjaka (Melissa officinalis L.), kadulje (Salvia officinalis L.) i smilja (Helichrysum arenarium (L.) Moench.). HPLC-PDA analizom utvrđeno je da u vodenim infuzijama odabranih biljaka najviše ima fenolnih kiselina (ružmarinske, galne, kafeinske, neoklorogenske i 3-p-kumaroil-kinske kiseline), te flavonola (kvercetin-3-galaktozid i luteolin-7-glukozid). Antioksidacijsko djelovanje vodenih infuzija određeno je LDL metodom (sprječavanje oksidacije lipoproteina male gustoće), DPPH metodom, metodom izbjeljivanja ß-karotena i Rancimat metodom (produženi proces oksidacije masti). Utvrđeno je da vodene infuzije jagode i matičnjaka potpuno sprječavaju oksidaciju LDL-a pri koncentraciji od 0,005 g/L u sustavu, te da je izrazito produžena lag faza tijekom oksidacije LDL-a uzrokovana djelovanjem vodenih infuzija paprene metvice i kadulje. Nadalje, testirane infuzije u rasponu koncentracija od 0,05 do 2,85 g/L pokazale su jako visoki stupanj uklanjanja DPPH radikala (90-100 %) i sprječavanja izbjeljivanja ß-karotena (89-100 %). Rancimat metodom utvrđeno je da vodene infuzije kadulje i smilja (masenog udjela od 0,16 %) najviše utječu na odgađanje procesa oksidacije masti. Inhibicija enzima acetilkolinesteraze pomoću testiranih vodenih infuzija određena je Ellmanovom metodom, pri čemu su vodene infuzije oraha i jagode (u koncentraciji od 1,36 g/L u sustavu) pokazale najveći stupanj inhibicije acetilkolinesteraze. Dobiveni rezultati upućuju na to da prirodni antioksidansi svojim djelovanjem mogu pridonijeti poboljšanju terapije i prevenciji Alzheimerove bolesti
