In Vitro Antioxidant, Antimicrobial and Antiproliferative Activities of Olive Leaves (Olea europaea L. var. europaea) Collected from Derik, Turkiye

Abstract

In this study, the antimicrobial, antioxidant, and antiproliferative activities of the methanol and hexane extracts of Olea europaea L. var. europaea were evaluated. Both extracts had broad-spectrum antimicrobial activity, with the methanol extract showing the highest inhibition. The largest inhibition zones in the methanol extract were recorded at 500 mu g/mL for Candida albicans (28.52 +/- 1.34 mm), Streptococcus pyogenes (27.48 +/- 0.09 mm), and Escherichia coli (22.09 +/- 2.11 mm). Methanol and hexane extracts showed the lowest MIC values against C. albicans. Methanol extract provided higher antimicrobial activity in general, especially lower MIC values against S. pyogenes, E. coli and C. albicans. Strong concentration-dependent scavenging ability was demonstrated by antioxidant tests. The hexane extract demonstrated 37-66% and 54-91% DPPH and ABTS radical scavenging activities, respectively, whereas the methanol extract demonstrated 74-83% and 35-68%. Both extracts decreased the proliferation of colon cancer cell lines in a dose, and time-dependent manner. Cell viability was most significantly reduced by the methanol extract, which reached 9.43% at 200 mu g/mL after 72 h in Caco2 cells (p < 0.0001). Hexane extract also inhibited cell proliferation, but to a lesser degree. Phytochemical profiling revealed that both extracts contained different phytochemicals. The most abundant components in the methanol extract included oleuropein, quercetin, and emodin, while quercetin 3-rutinoside, astragalin, and isoquercitrin were detected in the hexane extract. The findings indicate that Olea europaea leaf extracts exhibit antimicrobial, and antioxidant properties, as well as antiproliferative activities against cancer cells, suggesting their potential as a significant source of bioactive compounds for future pharmaceutical applications. Additional in vivo and clinical studies are necessary to validate these effects.