Hibiscus sabdariffa (Roselle/Karkade) as a Complementary Antihypertensive Agent: A Narrative Review of Pharmacological Mechanisms, Clinical Evidence, and Public Health Implications for Saudi Arabia

Background: Hypertension is a major public health burden in Saudi Arabia.Estimates vary by measurement method, age denominator, and survey year: self-reported physician-diagnosed prevalence in adults aged ≥15 years was 9.2% in the 2017 General Authority for Statistics Household Health Survey, whereas measured blood pressure data from the 2019 Kingdom of Saudi Arabia World Health Survey yielded a crude prevalence of 12.7% among adults aged ≥18 years, rising to approximately 22% on age-standardisation.Awareness, treatment, and blood pressure control rates remain suboptimal.Hibiscus sabdariffa L. (Hs), known locally as karkade, is herbal beverage plant of the Malvaceae family with a longstanding history of traditional use for blood pressure management across the wider Arab region.Objective: To synthesise the current evidence on the pharmacological mechanisms, clinical efficacy, safety profile, and drug-interaction potential of Hibiscus sabdariffa in hypertension management, and to outline a research agenda relevant to the Saudi Arabian context.Methods: Peer-reviewed literature was identified through PubMed, Scopus, Web of Science, and the Cochrane Database of Systematic Reviews.Priority was given to randomised controlled trials (RCTs), systematic reviews, metaanalyses, and mechanistic studies published between 2004 and 2026.No formal PRISMA screening, duplicate review, or risk-of-bias appraisal was performed; the review is therefore a structured narrative synthesis rather than a systematic review.Results: Several complementary pharmacological pathways may contribute to Hs antihypertensive activity, including angiotensin-converting enzyme (ACE) inhibition, nitric oxide-mediated vasodilation, calcium channel modulation, diuretic effects, antioxidant activity, and lipid metabolism regulation.Evidence from RCTs and meta-analyses suggests that Hs may reduce systolic and diastolic blood pressure, although estimates vary substantially across preparations, doses, populations, and study designs.The magnitude of pooled reduction reported in recent meta-analyses (systolic blood pressure approximately -6 to -8 mmHg versus placebo) overlaps with the size effect seen with some low-dose antihypertensive interventions, but direct therapeutic equivalence has not been established and an earlier Cochrane review reached more cautious conclusions.The safety profile is generally favourable in short-to medium-term studies, although long-term safety and human pharmacokinetic interaction data remain insufficient.Conclusion: Hibiscus sabdariffa may serve as a culturally familiar adjunct to lifestyle modification in hypertension, but it is not a substitute for guideline-directed pharmacotherapy.Evaluation within structured lifestyle-modification programmes is justified, particularly through locally conducted Saudi clinical trials.