**1. Introduction**

CVD is one of the most common causes of death in the world [1]. Some disorders such as HTN, type 2 diabetes mellitus (DM2), hypercholesterolemia, atherosclerosis and inflammatory disorders can increase the risk of CVD [2]. Among these disorders, HTN is one of the most common diseases imposed by modern lifestyle in terms of decreased physical activity and unbalanced lipid-rich diet [3].

It is estimated that around 30% of the world population will get involved with HTN by 2025 [4]. HTN gradually develops without notice, hence possibly aggravating such fatal diseases as CVD and chronic heart failure (CHF) [3]. There are several risk factors for HTN, such as family history, genetic and environmental factors [4]. The prevalence in females is dependent on age. In other words, prevalence of HTN in women >50 years old strongly increases. For instance, high blood pressure ratio

in women compared with men increments from 0.6 to 0.7 at the age of 30 years old, reaching 1.1 to 1.2 at the age of 65 years old [5]. CVD risks augment throughout the blood pressure range, which begins at 115/75 mmHg. The blood pressure which is higher than 140/90 mmHg needs intervention [3].

Drugs decreasing blood pressure including angiotensin-converting enzyme (ACE) inhibitors, angiotensin-receptor blockers (ARBs), calcium channel blockers (CCBs), α-blockers and diuretics dwindle the complications of HTN [6]. However, most patients suffer from enhanced adverse drug reactions even in common doses and medication costs because of needing ≥2 drugs to attain blood pressure goals (< 140/90 mmHg or <130/80 mmHg in DM or chronic kidney disease) [6]. Whilst chemical drugs are necessary for treating and dominating the cardiovascular risk factors mentioned in the previous lines, diet also plays an important role in modulating them.

The Mediterranean diet is one of the most supreme in the world in terms of preventing chronic illnesses, such as CVD [2, 7, 8]. The bulk of the Mediterranean diet originates from plant sources of which olive tree products are the quintessential ingredient [9].

Olive tree (Olea europaea) belongs to genus Olea of the Oleaceae family [10]. The parts used in olive tree are leaf, fruit and skin. In ancient times, people applied olive tree, particularly olive leaves to treat fever, gout, wounds, diabetes, atherosclerosis and HTN [3, 11]. As a matter of fact, the leaf of the olive tree has several beneficial effects on human health attributed, in part, to hypocholesterolemic, antioxidant, antimicrobial, hypoglycaemic, anti-inflammatory, anti-atherosclerotic, and especially anti-hypertensive effects [1, 7, 12]. The uses of olive leaf for humans are abundant. However, our aim is to focus on the anti-hypertensive yield.
