Phenolic content and antioxidant capacity of istrian olive leaf infusions

Abstract

The influence of commonly used steeping times and leaf size on the phenolic content and antioxidant capacity of olive leaf infusions from three Istrian olive cultivars (Buža, Rosinjola and Istarska Bjelica) were studied. Infusions were prepared from whole, rough or finely ground olive leaves immersed in boiled water for 5, 15, or 30 minutes. Extraction efficiency was quantified in terms of the total phenolic, flavonoid, non-flavonoid contents and antioxidant capacity. The phenolic content was primarily affected by infusion time, followed by particle size. The highest total values of phenolic and non-flavonoids were determined in finely ground leaf infusions from cultivars Rosinjola and Buža, while the highest total flavonoids value was detected in Istarska Bjelica after 30 minutes infusion. Particle size provided the highest effect on antioxidant capacity in all cultivars, exhibiting higher values in finely ground leaf infusions. The Rosinjola and I. Bjelica infusions exhibited the highest antioxidant capacity according to ABTS and FRAP assay, respectively. Antioxidant capacity in investigated olive infusions was correlated to TP and TNF, while TF had poor or no effect except in Rosinjola infusions. The results indicate that olive leaves infusion from three Istrian olive cultivars could be a valuable supplement to a daily intake of bioactive compounds.