Hypertension is a major global contributor to cardiovascular morbidity and mortality. Although antihypertensive medications are widely used, many individuals continue to experience incomplete blood pressure control or medication-related side effects. Natural polyphenols, such as quercetin, lycopene and French maritime pine bark extract, have shown promising effects on oxidative stress, endothelial inflammation and vascular function in individual clinical and preclinical studies. These mechanisms are directly relevant to hypertension biology and suggest potential value as adjunct therapies.
However, despite a growing number of studies, the evidence remains fragmented. Existing research varies widely in study design, dosage, populations and reported outcomes, and no up-to-date systematic review has synthesised these findings or evaluated the overall certainty of the evidence. As a result, the clinical relevance and consistency of effects across studies are unclear.
Objectives:
To systematically evaluate the effects of quercetin, lycopene and pine bark extract on blood pressure and hypertension-related biomarkers, and to determine whether current evidence supports their potential use alongside standard antihypertensive treatments.
Methods:
A PRISMA-guided search will be conducted in PubMed, MEDLINE and the Cochrane Library (2005–2025) to identify randomised controlled trials, controlled observational studies and relevant preclinical models. Data will be extracted using standardised templates and synthesised descriptively. Where appropriate, pooled effect estimates will be calculated through meta-analysis. Study quality and risk of bias will be assessed using Cochrane RoB2 and SYRCLE tools, and certainty of evidence evaluated using GRADE.
Outcomes:
Primary outcome: systolic blood pressure.
Secondary outcomes: diastolic blood pressure, oxidative stress markers (e.g., ROS), endothelial inflammation and vascular function.
This outcome of the proposed project will address the current evidence gap by providing the first structured synthesis of polyphenol supplementation for hypertension management, offering clearer insight into their potential benefits and limitations as adjunct therapies.