Antioxidant Activity and Chemical Components as Potential Anticancer Agents in the Olive Leaf (Olea europaea L. cv Leccino.) Decoction

Abstract

Epidemiological studies have shown that a reduced risk of chronic diseases such as cancer and cardiovascular diseases is correlated with a regular consumption of fruits and vegetable, many of which are rich in polyphenols. The additive and synergistic effect of phytochemicals in fruits and vegetables may reduce chronic diseases related to oxidative stress in human body. Olea europaea L. leaf are rich in phenolic components, which have been proposed to play a role in cancer prevention. The purpose of this study was to identify the main components in the Olea europaea L. leaf (cv. Leccino) preserved during the decoction preparation, in order to delineate the antioxidant activities of the crude extracts and its isolated compounds by using different in vitro assays including DPPH radicalscavenging capacity, total antioxidant capacity (TAC), xanthine oxidase (XO) inhibitory effect and the ability to delay the linoleic acid peroxidation process (ALP). The aqueous decoction was partitioned obtaining four extracts and the n-butanol extract showed the highest antioxidant activity and the highest total phenolic content. Phytochemical investigation leads to the isolation of thirteen secondary metabolites including simple phenolics, flavonoids, secoiridoids whose structures were elucidated by spectroscopic data (1D and 2D NMR) and spectrometric techniques. A significant free radical scavenging effect against DPPH has been evidenced in fraxamoside (1) (EC50 62.6 µM) and taxifolin (5) (EC50 50.0 µM), isolated for the first time from the water decoction. The most active compound in the TAC evaluation, was the 3,4 dihydro-phenyl glycol (8) (0.90 caffeic acid equiv.) while taxifolin and fraxamoside resulted as the most efficient inhibitors of XO activity (IC50 2.7 and 5.2 µM, respectively). Secoxyloganin (4), oleuropein (2) and tyrosol (6) showed the highest ALP activity. This study adds to the growing body of data supporting the bioactivities of phytochemicals and their potential impact on human health.

Bioavailability of Bioactive Molecules from Olive Leaf Extracts and its Functional Value

“…Moreover, European Food Safety Authority (EFSA) has recently accepted the olive leaf aqueous extract as a safe product and, therefore, the olive leaf extract could be used as food additive. In fact, olive leaf extract contain many potentially bioactive compounds that may have antioxidant, antihypertensive, antiatherogenic, antiinflammatory, anticancer, hypoglycemic, and hypocholesterolemic properties (De Marino et al, 2014;Fakhraei et al, 2014;Olmez et al, 2015;Kishikawa et al, 2015).…”

Evidence to Support the Anti-Cancer Effect of Olive Leaf Extract and Future Directions

“…Several studies have demonstrated that the phenolic compounds from OLE may display a synergistic effect when in the same proportions as occurring naturally in the olive leaf. The secoiridoids, flavonoids and other phenols in OLE provide a stronger anti-microbial and antioxidant effect when working together, as opposed to the phenolics independently [59,75,76]. Through the use of different antioxidant assays it was determined that OLE flavonoids, simple phenols and secoiridoids utilize different mechanisms to exert an anti-oxidant effect [75], which at least in part explains their additive effect.…”

Beneficial effects of oleuropein on glucose uptake and on parameters relevant to the normal homeostatic mechanisms of glucose regulation in rat skeletal muscle

“…The beneficial effects of these extracts have been attributed to the content of polyphenols, among them oleuropein. Oleuropein, a heterosidic ester of elenolic acid and dihydroxyphenylethanol, is the most abundant (60-90 mg/g) phenolics found in olive fruit and leaves (De Marino et al, 2014;Rigacci & Stefani, 2016) and has been reported to exhibit various therapeutic and pharmacological properties (Barbaro et al, 2014;Bulotta et al, 2014), including its ability to suppress hyperglycemia in various diabetic models. Much of these studies have been carried out either in cell lines (Hadrich et al, 2016) or in vivo model (Al-Azzawie & Alhamdani, 2006;Jemai, El Feki, & Sayadi, 2009;Sangi, Sulaiman, El-Wahab, Ahmedani, & Ali, 2015).…”