Phenolic compounds and antioxidant activity in blackthorn fruits (Prunus spinosa L.) and in their nectars and syrup

U plodu trnine (Prunus spinosa L.) dva različita stupnja zrelosti, nektarima i sirupu trnine analizirani su fizikalno-kemijski sastav (ukupna i topljiva suha tvar, pH, ukupna kiselost, šećeri), fenolni spojevi (ukupni i pojedinačni), antioksidativna aktivnost i senzorske karakteristike. Ukupni fenoli, flavonoidi i neflavonoidi određeni su primjenom spektrofotometrijskih metoda, dok su pojedinačni fenolni spojevi (flavan-3-oli, flavonoli, procijanidini i hidroksicimetne kiseline) određeni primjenom tekućinske kromatografije visoke djelotvornosti uz UV- Photo Dioda Array detekciju (HPLC-UV/PDA). Antioksidativna aktivnost plodova i proizvoda mjerena je spektrofotometrijski primjenom 1,1-difenil-2-pikrilhidrazil radikala (DPPH) i 2,2`,-azinobis(3-etilbenzotiazolin-6-sulfonska kiselina) radikal kationa (ABTS). Najveća količina ukupnih i pojedinačnih fenolnih spojeva određena je u plodu trnine ubrane poslije prvog mraza, u listopadu. Njihova količina tijekom prerade u nektare i sirup bitno se smanjila. Plodovi trnine ubrani u studenom također su sadržavali manje količine fenolnih spojeva. U istraživanim uzorcima najzastupljeniji fenolni spojevi bili su: neoklorogenska kiselina, (-)-epikatehin i kvercetin-3-rutinozid. U svim uzorcima određena je visoka antioksidativna aktivnost, a naročito u plodovima trnine ubranim u listopadu. Rezultati dobiveni u ovom radu pokazuju da plodovi trnine i proizvodi dobiveni iz nje mogu biti važan izvor biološki aktivnih spojeva s izrazitom antioksidativnom aktivnošću.Blackthorn (Prunus spinosa L) fruits harvested at two stages of maturity, their nectars and syrup, were assayed for physico-chemical composition (total and soluble dry matter, pH, total acidity and sugars), phenolics (total and single), antioxidant activity and sensory characteristic. Total phenols, flavonoids and non-flavonoids were determined using spectrophotometric methods, whereas single phenols (flavan-3-ols, flavonols, procyanidins and hydroxycinamic acid) were determined using HPLC with UV-VIS Dioda Array detection. Antioxidant activity was evaluated by spectrophotometric methods against stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and 2,2`,-azino-di(3-ethylbenzothiazolin-6-sulfonic acid) radical cation (ABTS). The highest amount of total and single phenolic compounds was determined in blackthorn fruits harvested after 1st frost, in October. Their amounts significantly decreased during processing into nectars and syrup. Blackthorn fruits harvested in November also contained remarkable lower amounts of phenolic compounds. The most abundant phenolics in investigated samples were: neochlorogenic acid, (-)-epicatechin and quercetin-3-rutinoside. In all investigated samples an evident antioxidant activity was observed, especially in blackthorn fruits harvested in October. The results obtained in this study suggested that blackthorn fruits and their products may be important source of biologically active compounds with pronounced antioxidant activity