POLYPHENOLS AND MINERALS IN INFUSIONS OF OLIVE LEAVES - INFLUENCE OF LEAVES STORAGE TIMES

U ovom su radu istraživani neki aspekti pripremanja biljnih infuzija od lista masline sorte Leccino korisni u praktičnoj primjeni, kao što su utjecaj stupnja usitnjenosti lišća te vremena i oblika čuvanja lišća na prelazak fenolnih i mineralnih tvari u vruću vodenu otopinu. Fenolne tvari određivane su tekućinskom kromatografijom visoke djelotvornosti (HPLC), a mineralni je sastav određivan induktivno spregnutim plazma masenim spektrometrom. Rezultati rada pokazali su da vanilinska kiselina i diosmetin nisu detektirani ni u jednoj od provedenih analiza. Ekstrakcija fenolnih tvari metanolom kod netom osušenih listova učinkovitija je od ekstrakcije vrućom vodom za oko 33%. Ekstrakcija vrućom vodom iz netom osušenih mljevenih listova je oko 4 puta učinkovitija u odnosu na rezani oblik, ali nakon dvomjesečnog čuvanja između rezanog i cjelovitog oblika lista nema značajnih razlika. Uslijed dvomjesečnog čuvanja osušenih listova masa fenolnih tvari ekstrahiranih vrućom vodom smanjila se za oko 6% u odnosu na početne razine. Konzumiranjem jedne šalice infuzije pripremljene s 200 mL vruće vode i 2 do 4 g osušenog, različito usitnjenog i do dva mjeseca čuvanog lista masline sorte Leccino moguće je unijeti 10 do 20 puta više bioaktivnih fenola od minimuma (5 mg) za koji je kod djevičanskih maslinovih ulja odobrena zdravstvena tvrdnja o doprinosu zaštiti lipida u krvi od oksidacijskog stresa. Jedna šalica infuzije uglavnom sadrži manje od 1% preporučenog dnevnog unosa željeza, cinka i selenija te ne predstavlja značajan prehrambeni izvor ovih elemenata.In this paper, some aspects of preparation of herbal infusions from olive leaves of Leccino variety useful in practical application are investigated, like the influence of the degree of leaf fragmentation and time and form of leaf storage on the transition of phenolic and mineral substances into hot aqueous solution. Phenolic substances were determined by high-performance liquid chromatography (HPLC), and the mineral composition was determined by inductively coupled plasma mass spectrometer. The results showed that vanillic acid and diosmetin were undetected in any of the performed analyses. The extraction of phenolic substances with methanol in freshly dried leaves is about 33% more efficient than hot water extraction. Hot water extraction from freshly dried ground leaves is about four times more efficient compared to the cut form, but after two months of storage, there are no significant differences between the cut and whole leaf shape. Due to two months of dried leaves storage, the mass of phenolic substances extracted with hot water decreased by about 6% compared to the initial levels. By consuming one cup of infusion prepared with 200 mL of hot water and 2 to 4 g of dried olive leafs of the Leccino variety, variously chopped and stored for up to two months, it is possible to ingest 10 to 20 times more bioactive phenols than the minimum (5 mg) specified for virgin olive oils approved health claim related to the oxidative stress protection of blood lipids. One cup of infusion generally contains less than 1% of the recommended daily intake of iron, zinc, and selenium and is not a significant dietary source of these elements