Effects of high dose olive leaf extract on haemodynamic and oxidative stress parameters in normotensive and spontaneously hypertensive rats

Abstract

The antihypertensive activity of olive leaf extract (OLE), a natural antioxidant is recognized, but its influence on the cardiovascular system when administered in a high dose has not yet been investigated. The aim of the present study was to determine the acute effects of excessive intake of standardized OLE on blood pressure, heart rate and oxidative status in both spontaneously hypertensive rats and normotensive Wistar rats. The systolic arterial pressure and heart rate were measured using a tail-cuff and pneumatic pulse detector before and 60 and 120 min after intragastric OLE administration. The activities of catalase, glutathione peroxidase, superoxide dismutase (SOD) and glutathione reductase in erythrocytes, as well as lipid peroxidation in plasma (pTBARS) were measured spectrophotometrically at the same time points. A high-dose of OLE did not influence blood pressure, heart rate or pTBARS in normotensive rats, while the SOD, catalase and glutathione reductase activities were significantly increased. The same dose significantly decreased blood pressure in hypertensive rats, but increased the pTBARS and SOD activity. Excessive oral intake of OLE induced moderate hypotensive effects only in spontaneously hypertensive rats, suggesting the absence of harmful hemodynamic effects after an oral overdose in both rat strains. However, its pro-oxidative role when given in a high dose in hypertensive organisms should not be neglected.

In vitro antioxidant activity of olive leaf extract (Olea europaea L.) and its protective effect on oxidative damage in human erythrocytes

“…Recent studies have shown that olive leaves have high contents of bioactive compounds, including phenolic compounds, with diverse biological properties, such as antioxidant, antimicrobial, antiviral, anti-inflammatory, in addition to regulating blood pressure and cholesterol levels in animals [ 2 , 3 ]. Thus, the research community's interest in olive leaves and their extracts has intensified in recent years because of the olive's great potential for use in medicine and the pharmaceutical industry [ 4 , 5 ]. Furthermore, a previous study verified the effective antioxidant activity of olive leaf extract as a potential natural functional ingredient in food products [6] .…”

Thyroid-Modulating Activities of Olive and Its Polyphenols: A Systematic Review

“…Olive leaves also contain similar polyphenols and phytochemicals to olive oil but with a much higher oleuropein concentration [ 41 , 42 ]. Olive leaf extracts could reduce oxidative stress in rats [ 96 , 97 ]. Daily consumption of 50 mL of oleuropein-rich EVOO could increase the plasma’s total antioxidant capacity and enzyme levels among the elderly [ 32 ].…”

Highly potent antioxidant Olea europaea L. leaf extract affects carotid and renal haemodynamics in experimental hypertension: the role of oleuropein

“…On the other hand, in OLE25 group, blood pressure was also decreased, but at the expense of significant peripheral vasodilation (decreased total peripheral resistance), without altering the CO or HR. Previously, we demonstrated that acute oral administration of 2 g/kg of OLE reduces SAP in SHR (Dekanski et al, 2014[ 8 ]), and that 30 min duration of antihypertensive action of OLE (50 mg/kg) is NO-independent, whereby retaining antihypertensive effect occurs even after the blocked synthesis of NO, indicating that OLE in a dose of 50 mg/kg achieves blood pressure-lowering by mechanisms other than NO (Miloradović et al, 2013[ 27 ]). The ACE inhibitory activity of OLE, concurrent with the calcium channel blocking activity, as a result of the synergistic activity of OP and other components of OLE, was assumed by Susalit et al (2011[ 40 ]) in the clinical study in which the antihypertensive effect of OLE and captopril were compared.…”