Assessment of Olea europaea L. fruit extracts: Phytochemical characterization and anticancer pathway investigation

Olea europaea L. has been widely used as an advantageous rich source of bioactive compounds of high economic value leading to its use in pharmaceutical, cosmetic, and agriculture industries. Ethanolic extracts of olive fruits from three different cultivars (OFE) were studied for their phytochemical contents and were investigated for antioxidant activities and anticancer potential. Major polyphenols detected in these extracts were tyrosol, hydroxytyrosol, oleuropein, rutin, quercetin and glucoside forms of luteolin and apigenin. All these compounds have shown to significantly contribute to the antioxidant activity of OFE, which was evaluated by DPPH and ABTS assays. Proliferation of hepatic and colon cancer cells, HepG2 and Caco-2, were shown to be sensitive to OFE with IC₅₀ less than 1.6mg/ml for all tested extracts. Moreover, flow cytometry analysis showed that OFE induced cell cycle arrest in the S-phase within both HepG2 and Caco-2 cells. This has triggered a cell death mechanism as shown by DNA fragmentation, expression of p53 and phosphorylation level of Akt and Erk proteins. Interestingly, these extracts could be further used as a potential source of natural compounds with both antioxidant and anticancer effects.