Hibiscus is a tropical wild plant rich in organic acids, polyphenols, anthocyanins, polysaccharides, beneficial for the cardiovascular system.
Meta analyses and randomised controlled trials show that daily consumption of hibiscus tea significantly lowered blood pressure greater than the control groups.
Extracts showed antibacterial, anti-oxidant, nephro and hepato-protective, renal/diuretic effect, effects on lipid metabolism, anti-diabetic and anti-hypertensive effects among others but it seems the greatest effect is that of lowering blood pressure.
Reference: https://pubmed.ncbi.nlm.nih.gov/25875025/