The present study aims to evaluate the efficacy of treatment with an oral Nigella sativa (NS) seed oil in hypertensive patients. Subjects will be informed that they may take NS oil or placebo in the informed consent. Therefore, patients aren't aware of their therapeutic group they will be assigned. In addition, neither patients nor medical staff will be aware of the type of oils in the container (Ns oil or placebo). Only the researcher is aware of the code written on the container of the oils; so, this study is a double-blind, parallel clinical trial. Hypertensive patients with SBP /DBP ≥ 140/90 mmHg were eligible for inclusion. Patients who smoke and patients who consume antioxidant products aren't enrolled in the study. One hundred of patients attending the Quaem outpatient’s clinic who meet our inclusion criteria will take part in this study. By using random numbers (created by computer) subjects will randomly allocate to one of two experimental groups: a placebo and a test group. Thus, 50 cases in each treatment arm receive placebo or NS oil. In the intervention group, 5 ml oral NS oil is administered daily for 8 weeks. Patients in the control group receive placebo in the same way. Systolic and diastolic pressure (during intervention) and serum Malondialdehyde [MDA] (before and 8 weeks after intervention) will be checked as primary outcomes.