Phenolic composition of Croatian olive leaves and their infusions obtained by hot and cold preparation

Abstract

Leaves and infusions of six Croatian olive cultivars grown in an organic orchard under the same agronomic conditions were characterised by high-performance liquid chromatography-ultraviolet/visible spectrophotometry (HPLC-UV/VIS). The total identified phenols in leaves ranged from 3 818 mg 100 g<sup>–1</sup> [cultivar Istarska crnica (IC)] to 10 572 mg 100 g<sup>–1</sup> of dry mass [cultivar Oblica (OB)]. The canonical discriminant analysis (CDA) provided a distinct separation of cultivars based on leaves' phenolic profiles. Hot- and cold-water infusions (200 mL) were prepared from 1 g of dry leaves. The average transfer rate of the total phenols in the cold-water infusions was 40% (25 °C/30 min), while in the hot-water infusions was 63% (75 °C/3 min) and 76% (100 °C/3 min). Although the cold-water infusions had the lowest transfer rate, they contained important levels of hydroxytyrosol derivatives ranging from 16.6 mg 200 mL<sup>–1</sup> to 36.5 mg 200 mL<sup>–1</sup> depending on the cultivar. Therefore, both hot and cold preparations are effective in obtaining antioxidant-rich natural beverages.