Total phenolic and flavonoid contents of in vitro cultured Stevia rebaudiana (Bert)

Stevia rebaudiana Bertoni je višegodišnja biljka slatkog okusa iz porodice Asteraceae. Podrijetlom je iz Paragvaja, gdje se više od 1500 godina koristi kao zaslađivač. U listovima vrste se nalaze steviozidi koji su ujedno i glavni izvor slatkoće. Suhi ekstrakti listova stevije također sadrže flavonoide, fenole i mnoge druge spojeve. Ciljevi istraživanja bili su utvrditi utjecaj sastava hranjive podloge i regulatora rasta na klijanje i multiplikaciju te na sadržaj ukupnih fenola i flavonoida u različitim biljnim tkivima vrste S. rebaudiana. Sjemenke su sterilizirane i nasađene na hranjive podloge MS i ½ MS uz dodatak regulatora rasta benzil-aminopurina (BA) i giberelinske kiseline (GA3) u različitim koncentracijama. Izdanci su presađeni na hranjive podloge za multiplikaciju te su nakon toga presađeni na hranjive podloge za zakorijenjivanje. Biljni materijal (list, kalus, korijen) za analizu fenola i flavonoida uziman je nakon četiri tjedna rasta. Klijanje najbolje potiče dodatak hormona GA3+BA, dok rast najbolje potiče hormon GA3. Najviše fenola i flavonoida je zabilježeno u kalusu na podlogama s dodatkom indol-3-octene kiseline (IAA) i BA, dok je najmanje zabilježeno u korijenu. Veća koncentracija IAA potiče pohranu fenola u kalusu, a smanjuje u listu, dok je pri većoj koncentraciji indol-3-maslačne kiseline (IBA) zabilježeno suprotno. Povećanje koncentracije IAA smanjuje količinu flavonoida u listu, dok povećanje koncentracije IBA povećava koncentraciju flavonoida i u listu i u kalusu.Stevia rebaudiana Bertoni is a sweet flavoured perennial plant from the family Asteraceae. It originated in Paraguay where it is used as a sweetener for more than 1500 years. The main source of sweetness are steviosides, which are found in leaves. Dry leaf extracts also contain flavonoids, phenols and many other compounds. The aims of this research were to determine the influence of the nutrient composition and growth hormones on seed germination and multiplication, as well as on the total content of phenols and flavonoids in different plant tissues of species S. rebaudiana. Following sterilizazion, the seeds were germinated on full or half-strength Murashige and Skoog (MS) media supplemented with growth regulators gibberellic acid (GA3) alone or in combination with 6-benzyl aminopurine (BA) in different concentrations. Nodal explants were transplanted on multiplication media and then rooted. Best seed germination is achieved by combination of GA3 and BA and best induction of growth by GA3. The highest content of phenols and flavonoids was achieved in callus tissue using combination of ndole-3-acetic acid (IAA) and BA, while the lowest was detected in roots. Higher concentration of IAA stimulates phenol storage in callus, and inhibits in leaf, while higher concentration of indole-3-butyric acid (IBA) does the opposite. Higher concentration of IAA inhibits flavonoids storage in leaf, while higher concentration of IBA hormone stimulates storage of flavonoids in both leaf and callus tissue