Olea europaea L

Micucci, M., Bolchi, C., Budriesi, R., Cevenini, M., Maroni, L., Capozza, S., Chiarini, A., Pallavicini, M. & Angeletti, A., 2020, Antihypertensive phytocomplexes of proven efficacy and well-established use: Mode of action and individual characterization of the active constituents, Phytochemistry (112222) 170, pp. 1-19 : 8

2.10. Olea europaea L

In folk medicine, this tree is mainly considered useful due to its diuretic, hypotensive, emollient, febrifuge and tonic actions and for urinary and bladder infections treatment.

Olea europaea L . leaves extract was shown to inhibit K + -induced contraction in guinea pigs ileum and aorta, suggesting a calcium antagonistic effect (Scheffler et al., 2008; Micucci et al., 2015). The vasorelaxant and antihypertensive effects of O. europaea leaves extract were confirmed also by in vivo studies (Romero et al., 2016) and clinical trials (Susalit et al., 2011). The antihypertensive effect of the extract can be also related to factors involving reversal of vascular changes contributing to L-NAME-induced hypertension (Khayyal et al., 2002).

Quite recently, the combination of O. europaea leaves and H. sabdari ff a flowers (13:2, respectively) has been proposed with the aim to obtain a mixture endowed with higher activity than the single components. In particular, it has been demonstrated that this mixture exerts a negative inotropic activity comparable to the singular phytocomplexes, and, at the same time, is endowed of additional properties such as vasorelaxant and a mild negative chronotropic-effect as well as higher in vitro cytoprotective and antioxidant activity (Micucci et al., 2015). On the basis of these results, a possible nutraceutical use of the above formulation for the management of preclinical hypertension has been suggested, especially in consideration of its antihypertensive effects along with its good toxicologic profile (Campbell et al., 2015). The combination of H. sabdari ff a flowers and O. europaea leaves (2:1 respectively) is able to normalize in vivo BP in L-NAME-mediated hypertension. In this experimental model, the combination can also improve hepatic and renal dysfunction (Abdel-Rahman et al., 2017). Olive oil may also contribute providing cardiovascular beneficial effects, preventing LDL oxidation and maintaining normal blood HDL cholesterol concentrations as it contains oleuropein and hydroxytyrosol (Clodoveo et al., 2016; Roselli et al., 2017). According to EFSA, in fact, the daily administration of hydroxytyrosol (5 mg) and its derivatives prevents LDL oxidation (Scientific opinion, EFSA Journal 2011, 9, 2033). In both leaves extract and olive oil, oleuropein and hydroxytyrosol have been demonstrated to be the main constituents responsible for the antihypertensive effects and cardiovascular benefits ( Fig. 10 ). Hydroxytyrosol protects against the impairing effects of oxidative stress on the NO • -mediated relaxation of isolated rat aorta (Rietjens et al., 2007) and exhibits analogous antioxidant effects in vivo as demonstrated by studies on rats treated with cyclosporine, which causes oxidative stress, haemodynamic alterations and renal damages (Capasso et al., 2008). Recent reports have confirmed the beneficial antioxidant properties of hydroxytyrosol (Hu et al., 2014) and its ability to improve endothelial function and to lower systolic blood pressure in a diet-induced rat model of metabolic syndrome (Poudyal et al., 2017). Oleuropein attenuates, through ACE inhibition, the cardiac remodelling after infarction leading to excessive heart fibrosis (Mnafgui et al., 2015) and diminishes the increased ROS production in the hypothalamic paraventricular nucleus, associated to hypertension, by improving mitochondrial function (Sun et al., 2017).

Figures

Fig. 10. The main constituents responsible for the cardiovascular benefits of O. europaeaL.