Abstract:

The purpose of this study was to evaluate the antioxidant and antibacterial activities of oleuropein from olive
leaves. The antioxidant activity in vitro was analyzed by total antioxidant capacity and total reducing power. Filter paper
disc method was used to determine the antibacterial activity against Escherichia coli, Staphylococcus aureus and Bacillus
subtilis. Dilution method was used to analyze the effects of oleuropein on bacterial growth curves for determining the
minimum inhibitory concentrations (MIC). The results showed that oleuropein exhibited stronger total antioxidant capacity
and reducing power than BHT in the concentration range of 0.02?0.08 mg/mL. Oleuropein had inhibitory effect on the
three species of bacteria, and the logarithmic growth phases of the bacteria were correspondingly delayed with increasing
concentration. Oleuropein had the strongest inhibitory effect on Escherichia coli, with an inhibitory zone diameter (d) of
(20.77±0.47) mm and MIC of 0.025 mg/mL. Staphylococcus aureus revealed high sensitivity (d ＝ (19.23 ± 0.44) mm ＞ 15 mm)
with MIC of 0.05 mg/mL. However, Bacillus subtilis had moderate sensitivity (d ＝ (11.48 ± 0.60) mm ＜ 15 mm), with
MIC of 0.4 mg/mL. These results confirmed that oleuropein had strong antioxidant and antibacterial activities.

Key words: olive leave, oleuropein, antioxidant activity, antimicrobial activity, total reducing power