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.
Highlights
Hypertension is characterized by persistent high blood pressure (BP), as indicated by 130 mmHg or more for systolic BP or diastolic BP of 80 mmHg or greater according to The American College of Cardiology (ACC) 2017 guidelines
The analysis revealed the presence of different classes of metabolites, including sugars, organic and phenolic acids, flavonoids, and anthocyanins
The hot aqueous extract of Hibiscus sabdariffa recorded the best activity in lowering the high blood pressure and restoring the normal histology of the heart compared to the cold extract and captopril
Summary
Hypertension is characterized by persistent high blood pressure (BP), as indicated by 130 mmHg or more for systolic BP or diastolic BP of 80 mmHg or greater according to ACC 2017 guidelines. Hypertension is considered a global health concern with major impact on morbidity and mortality, showing high prevalence in developing countries (20–30%), especially for older generations (Holm et al, 2006). Among the pharmacological drug classes used are diuretics, calcium channel blockers, β-blockers, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers, vasodilators, and centrally acting medications (Jackson and Bellamy, 2015). These medications help in controlling the high blood pressure, their side effects include dizziness, headache, dry cough, nausea, and tiredness, which restrict their use, raising the need for alternative treatments (Jackson and Bellamy, 2015). Many people in developing countries prefer to use herbal medicine due to its affordability and broad safety profile
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