Antioxidant Activity of Aqueous Tea Infusions Prepared from Oregano, Thyme and Wild Thyme

Abstract

Različitim metodama istražen je odnos antioksidativne aktivnosti i kemijskog sastava infuza mravinca, timijana i majčine dušice. Spektrofotometrijskim metodama određena je koncentracija ukupnih fenola, flavonoida, katehina i antocijanina. Infuz mravinca imao je najveću koncentraciju ukupnih fenola (12500 mg/L) i flavonoida (9000 mg/L), izraženu kao galna kiselina. HPLC-PDA metodom određivanja polifenolnih spojeva dokazano je da u infuzu ima najviše ružmarinske kiseline (u mg/g), i to 123,11 u infuzu mravinca; 17,45 u infuzu timijana i 93,13 u infuzu majčine dušice. Antioksidativna aktivnost infuza istražena je pomocu četiri metode: metodom izbjeljivanja b-karotena, metodom uklanjanja 2,2\u27-difenil-1- pikrilhidrazil (DPPH) radikala, metodom s reaktivnim spojevima tiobarbiturne kiseline (TBARS metoda) i metodom određivanja indukcijskog vremena oksidacije masti (Rancimat metoda). Rezultati su uspoređeni s prirodnim (askorbinska kiselina i a-tokoferol) i sintetskim antioksidansima - butiliranim hidroksitoluenom (BHT) i butiliranim hidroksianisolom (BHA). Primjenom triju metoda (izbjeljivanjem b-karotena, metodom uklanjanja DPPH radikala i Rancimat metodom) dokazano je da infuza mravinca ima najveću antioksidativnu aktivnost, dok su timijan i majčina dušica pokazali slabiju i relativno sličnu antioksidacijsku aktivnost.Using a multiple-method approach, antioxidant activity of aqueous tea infusions prepared from oregano (Origanum vulgare L. ssp. hirtum), thyme (Thymus vulgaris L.) and wild thyme (Thymus serpyllum L.) were tested in relation to their chemical composition. Total phenolic, flavonoid, catechin and anthocyanin content was determined by spectrophotometric methods. Oregano aqueous tea infusion had the highest amount of total phenols (12 500 mg/L gallic acid equivalent, GAE) and flavonoids (9000 mg/L GAE). Identification of polyphenolic compounds in aqueous tea infusions by HPLC-PDA analysis showed a dominant presence of rosmarinic acid (in mg/g): 123.11 in oregano, 17.45 in thyme and 93.13 in wild thyme. Antioxidant activity of aqueous tea infusions was evaluated using four antioxidative methods (the b-carotene bleaching method (BCB), the 2,2’-diphenyl-1- -picrylhydrazyl (DPPH) radical scavenging method, the thiobarbituric acid reactive species (TBARS assay) and the induction period of lard oxidation (Rancimat assay)). The results were compared with natural (ascorbic acid and a-tocopherol) and synthetic antioxidants, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA). Oregano aqueous tea infusion showed the strongest antioxidant activity using three methods (the b-carotene bleaching method, DPPH radical scavening method and Rancimat assay), while thyme and wild thyme showed weaker and relatively similar antioxidant activity