Wild versus Cultivated Olive Leaves Extracts: Antioxidant Activity, Analysis of Total Phenolics and Oleoropein Content

Abstract

Olive leaves are being used in the last decades as a potential source of beneficial compounds in medicines, cosmetics, and food industry. In this work a comparison between Palestinian wild and cultivated olive leaves extracts obtained using different solvent systems under different conditions was performed. The crude extracts were studied for their total phenol and oleuropein content, in addition to their antioxidant activity which was evaluated using DPPH free radical scavenging method and by studying their effect in stabilization of olive oil samples towards oxidation. The stability of olive oil samples enriched with extract additives was estimated by measuring peroxide values, absorption coefficients K270 and K232. The results showed that olive oil stabilizing effect of crude extract was higher than that of commonly used synthetic antioxidants such as BHT. The wild leaves extracts exhibited higher levels of DPPH inhibition than cultivated. The metabolic extract of cultivated olive leaves at pH 7 has higher total phenol content and exhibits better oil stabilizing effect in comparison to other extracts. The identification and quantization of the major phenol component of these extracts (oleuropein) was performed using TLC and HPLC. It was shown that wild olive leaves have higher oleuropein content (23.9%) than cultivated which have oleuropein content of (6.8%). The highest oleuropein content was found in wild olive leaves extract by using methanol-water 80:20 at pH = 3 and 48 h.