Abstract:
Ethnopharmacological relevance: Since ancient times, Hibiscus sabdariffa L. calyces
have been used as a folk remedy for the treatment of hypertension. However, it is
questionable as to whether there is a difference in the antihypertensive activity of the
hot or cold aqueous extracts.
Aim of the study: We designed this study to specify the best method for water extraction
of the antihypertensive metabolites of H. sabdariffa and to confirm their in vivo
antihypertensive capabilities.
Materials and methods: The powdered dried calyces of H. sabdariffa were
independently extracted with cold and hot water. A comparative study was performed
between the cold and hot aqueous extracts of H. sabdariffa based on evaluation of the
in vitro renin and angiotensin-converting enzyme (ACE) inhibition activities. Additionally,
both extracts were subjected to an in vivo study for the evaluation of their antihypertensive
activities in L-Nw-Nitro arginine methyl ester (L-NAME)–induced hypertensive rats. Further,
a metabolomics study was also performed for both extracts to identify their chemical
constituents.Results: The cold and hot extracts significantly reduced the angiotensin II, ACE, and
aldosterone levels in the plasma. Furthermore, in the myocardium and aorta, decreased
iNOS (inducible nitric oxide synthase) levels and elevated eNOS (endothelial nitric oxide
synthase), as well as the rise in plasma NO levels, were reported with both extracts, but
better results were displayed with the hot extract, leading to a potential antihypertensive
effect. Additionally, the cold and hot Hibiscus extracts induced a cardioprotective effect
through reducing necrosis, inflammation, and vacuolization that results from the induction
of hypertension, an effect that was more prominent with the hot extract. Moreover, a
comprehensive metabolomics approach using ultra-performance liquid chromatography
coupled to tandem mass spectrometry (UPLC–MS/MS) was able to trace the metabolites
in each extraction.
Conclusion: The extracts showed different anthocyanin and phenolic compounds, but
the hot extract showed higher contents of specific phenolics to which the superior
antihypertensive and cardioprotective activities could be related.
