The Olive Leaf Extract Induced Phenoloxidase Activity Changes in Galleria mellonella Hemolymph

Since the fruits and leaves of the Olive (Olea europea) tree, which grows naturally in Mediterranean countries, are thought to be beneficial for many diseases, it is widely used in folk medicine in these countries. Olive leaf extract has been used in the treatment of many diseases such as malaria, high fever, heart diseases and cancer. The greater wax moth Galleria mellonella (Lepidoptera: Pyralidae) is frequently used in invertebrate immunity studies due to its similarity to the mammalian natural immune system. Melanization occurs when quinone precursors are converted to melanin and inactive profenoloxidase to phenoloxidase enzyme. In this study, the phenoloxidase activity of G. mellonella hemolymph larvae injected with olive leaf extract in different doses was determined by ELISA microplate reader at 492 nm absorbance. The findings obtained from this study showed that olive leaf extract increased phenoloxidase activity at a dose of 0.001 mg mL-1. Lower doses of 0.001 mg mL-1 did not cause changes in phenoloxidase activity compared to the untreated and Dimethyl Sulfoxide (DMSO) groups. The highest olive leaf extract dose of our study is 0.01 mg mL-1 and the larvae did not survive for 24 hours over those doses. The results of our study show that olive leaf supports humoral immune responses when used in low doses.