Abstract
Simple SummaryHypericum revolutum (HR) is reported to produce vasodilating activity in phenylephrine-precontracted aortae, where the chloroform fraction is the most potent. Chemical investigation of this fraction yielded two new compounds, revolutin (1) and hyperevolutin C (2), along with three known metabolites, β-sitosterol (3), euxanthone (4), and 2,3,4-tirmethoxy xanthone (5). Isolated compounds 1, 2, 3, and 5 produce vasodilation activities that are dependent on endothelial nitric oxide release.Vasodilators are an important class in the management of hypertension and related cardiovascular disorders. In this regard, the chloroform fraction of Hypericum revolutum (HR) has been reported to produce vasodilating activity in phenylephrine-precontracted aortae. The current work aims to identify the active metabolites in the chloroform fraction of HR and illustrate the possible mechanism of action. The vasodilation activities were investigated using the isolated artery technique. NO vascular release was assessed by utilizing the NO-sensitive fluorescent probe DAF-FM. Free radical scavenging capacity was assessed utilizing DPPH. Chemical investigation of this fraction yielded two new compounds, revolutin (1) and hyperevolutin C (2), along with three known metabolites, β-sitosterol (3), euxanthone (4), and 2,3,4-tirmethoxy xanthone (5). Compounds 1, 2, 3, and 5 showed significant vasodilation activities that were blocked by either endothelial denudation or L-NAME (nitric oxide synthase inhibitor), pointing towards a role of endothelial nitric oxide in their activities. In confirmation of this role, compounds 1–3 showed a significant release of NO from isolated vessels, as indicated by DAF-FM. On the other hand, only compound 5 showed free radical scavenging activities, as indicated by DPPH. In conclusion, isolated compounds 1, 2, 3, and 5 produce vasodilation activities that are dependent on endothelial nitric oxide release.
Highlights
Elevated blood pressure is a serious disorder that underlies other cardiovascular diseases and is a direct complication of metabolic disorders such as diabetes and metabolic syndrome
We have previously reported a significant vasodilating activity of the chloroform fraction of H. revolutum, produced in phenylephrine-precontracted aortae [14]
The current work represents the first evaluation of the bioactive compounds from H. revolutum that are responsible for vasodilation activities; we investigate the mechanism of action
Summary
Elevated blood pressure is a serious disorder that underlies other cardiovascular diseases and is a direct complication of metabolic disorders such as diabetes and metabolic syndrome. Hypertension can be due to increased heart stimulation or, most likely, increased peripheral resistance and endothelial dysfunction [1]. Endothelial dysfunction has a crucial role in the progression of hypertension by affecting vascular relaxation and constriction. The endothelium-dependent vasodilatation regulatory system controls vascular function mainly through the release of nitric oxide (NO) [2,3]. Endothelial dysfunction can lead to a significant decrease in the bioavailability of nitric oxide, causing vasodilatation impairment in affected individuals [2]. Regular medicine has many drawbacks that encourage researchers to find safer compounds for hypertension [1]. Herbal drugs are popularly dispensed for treating various ailments owing to their efficiency and comparatively moderate cost and fewer side effects
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