Determination of Antioxidant, Phenolic Compound and Mineral Contents in Olive Leaves by Chromatographic and Spectrophotometric Methods

In this study, changes in total phenolic content, total flavonoids, tannin content and phenolic constituents, and mineral content of the leaves of five olive varieties (Ayvalık, Gemlik, Sarıulak, Çöpaşı and Delice) collected in Mersin province in Turkey were investigated. Tannin contents of olive leaves extracts were determined to be between 1.73 (Sarıulak) and 5.33% (Çöpaşı). Total phenolic and flavonoid amounts in olive leaves were assayed to be between 2122.02 (Sarıulak) and 2338.69 mgGAE/100 g (Çöpaşı), and between 9010.71 (Sarıulak) and 18,910.71 mg quercetin equivalent/100 g (Çöpaşı), respectively. Also, the antioxidant activities of methanol extracts of the olive leaves were discovered to be between 0.85 mmolTE/kg (Gemlik) and 21.04 mmolTE/kg (Sarıulak). The phenolic components of the olive leaves studied showed differences depending on the variety of olive. Catechin, rutin, and 3,4-dihydroxybenzoic acid were the most abundant phenolics in leaf extracts. Also, “Delice” olive leaves in the wild form generally had more caffeic acid, syringic acid and rutin, compared to the other olive varieties studied. While the olive leaves were determined to be high in macroelements, the microelement contents detected in olive leaves were low. In general, there was a linear connection between the total phenols and antioxidant activities of leaf samples. This connection was also exhibited between the total flavonoid content and antioxidant activities of olive leaves (except for Sarıulak).