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.
