This study compared the antihypertensive effects of captopril alone to coadministration of Hibiscus sabdariffa aqueous extract plus captopril on blood pressure and RAAS biomarkers such as plasma renin level, serum ACE activity, and plasma angiotensin II level in the two-kidney-one-clip (2K1C) rat model of hypertension. The gene discussed is AGT; the disease is hypertensive disorder.