Introduction
Herbal therapy is an important part of medicine due to its safety and low side effects [1]. Nowadays, many people prefer to use medicinal herbs. In their opinion, herbals are safe and have lower unwanted side effects [2-7]. Apium graveolens , generally known as “celery” has many health benefits and is a pharmaceutical herb used as a food supplement [8]. Organs of celery, such as seeds, stems, leaves, roots, and stalks, contain ingredients with antibacterial, anti‐inflammatory, antioxidant, antifungal, antitumor, and insecticidal properties [9]. Celery can play a role in the control of BP, serum lipid, and diabetes [10, 11]. Compared to other parts of the plant, celery seeds have more effective ingredients [12, 13]. The celery seeds contain various active ingredients, including luteolin, d-limonene, phthalides, apigenin, hesperitin, rosmarinic acid, linalool, and quercetrin [14-16]. The pharmacological mechanisms of these active ingredients are discovered and reported in previous studies [17-20]. Celery contains a group of phytochemicals called phthalides, e.g. 3-n-butylphthalide (NBP), which are from the most active components in celery seed. NBP helps control stress hormones which contribute to high BP and reduces bad cholesterol [21, 22]. No significant toxicologically sub-chronic effects of oral celery were investigated in rats [23]. One of the therapeutic properties of celery seed is the hepatoprotective effect which is reported in some works. [24], cognitive strengthening [22, 25], neuroprotective effects [22] and anti-hyperglycemic [26]. The most remarkable therapeutic property of celery reported in the studies is blood pressure (BP) reduction [27-29]. There is not enough information on the safety evaluation of celery seed in humans for assurance as a medication. This clinical trial study was conducted to evaluate, for short-term, safety of celery seed extract in hypertensive patients in a randomized, triple-blind, placebo-controlled, cross-over clinical trial. The biochemical and mineral parameters were assessed four times during the study for each patient. The results were promising and indicated the safety of celery seed extract as a drug supplement in the management of hypertension.