Mechanisms of action of Panax notoginseng ethanolic extract for its vasodilatory effects and partial characterization of vasoactive compounds

Naodesheng decoction regulating vascular function via G-protein-coupled receptors: network analysis and experimental investigations

Introduction: Ischemic stroke (IS) is a detrimental neurological disease with limited treatment options. Recanalization of blocked blood vessels and restoring blood supply to ischemic brain tissue are crucial for post-stroke rehabilitation. The decoction Naodesheng (NDS) composed of five Chinese botanical drugs, including Panax notoginseng (Burk.) F. H. Chen, Ligusticum chuanxiong Hort., Carthamus tinctorius L., Pueraria lobata (Willd.) Ohwi, and Crataegus pinnatifida Bge., is a blood-activating and stasis-removing herbal medicine commonly used for the clinical treatment of cerebrovascular diseases in China. However, the material basis of NDS on the effects of blood circulation improvement and vascular tone regulation remains unclear. Methods: A database comprising 777 chemical metabolites of NDS was constructed. Then, the interactions between various herbal metabolites of NDS and five vascular tone modulation G-protein-coupled receptors (GPCRs), including 5-HT1AR, 5-HT1BR, β2-AR, AT1R, and ETBR, were assessed by molecular docking. Using network analysis and vasomotor experiment of the cerebral basilar artery, the potential material basis underlying the vascular regulatory effects of NDS was further explored. Results: The Naodesheng Effective Component Group (NECG) was found to induce relaxation of rat basilar artery rings precontracted using Endothelin-1 (ET-1) and KCl in vitro in a dose-dependent manner. Several metabolites of NDS, including C. tinctorius, C. pinnatifida, and P. notoginseng, were found to be the main plant resources of metabolites with high docking scores. Furthermore, several metabolites in NDS, including formononetin-7-glucoside, hydroxybenzoyl-coumaric anhydride, methoxymecambridine, puerarol, and pyrethrin II, were found to target multiple vascular GPCRs. Metabolites with moderate-to-high binding energy were verified to have good rat basilar artery-relaxing effects, and the maximum artery relaxation effects of all three metabolites, namely, isorhamnetin, kaempferol, and daidzein, were found to exceed 90%. Moreover, metabolites of NDS were found to exert a synergistic effect by interacting with vascular GPCR targets, and these metabolites may contribute to the cerebrovascular regulatory function of NDS. Discussion: The study reports that various metabolites of NDS contribute to its vascular tone regulating effects and demonstrates the multi-component and multi-target characteristics of NDS. Among them, metabolites with moderate-to-high binding scores in NDS may play an important role in regulating vascular function.

Evaluation of vasodilatory effect and antihypertensive effect of chrysin through in vitro and sub-chronic in vivo study

Chrysin, a bioflavonoid belonging to the flavone, occurs naturally in plants such as the passionflower, honey and propolis. Few studies have demonstrated that chrysin can promote vasorelaxant activities in rats' aorta and mesenteric arteries. To date, no research has explored the signalling system routes that chrysin may utilise to produce its vasorelaxant action. Therefore, this study aimed to investigate the underlying mechanisms involved in chrysin-induced vasorelaxant in rats' aortic rings and assess the antihypertensive effect of chrysin in spontaneously hypertensive rats (SHRs). The findings revealed that chrysin utilised both endothelium-dependent and endothelium-independent mechanisms. The presence of L-NAME (endothelial NO synthase inhibitor), ODQ (sGC inhibitor), methylene blue (cGMP lowering agent), 4-AP (voltage-gated potassium channel inhibitor), atropine (muscarinic receptors inhibitor) and propranolol (β-adrenergic receptors inhibitor) significantly reduced the chrysin's vasorelaxant action. Furthermore, chrysin can reduce intracellular Ca²⁺ levels by limiting the extracellular intake of Ca²⁺ through voltage-operated calcium channels and blocking the intracellular release of Ca²⁺ from the sarcoplasmic reticulum via the IP₃ receptor. These indicate that chrysin-induced vasorelaxants involved NO/sGC/cGMP signalling cascade, muscarinic and β-adrenergic receptors, also the potassium and calcium channels. Although chrysin had vasorelaxant effects in in vitro studies, the in vivo antihypertensive experiment discovered chrysin does not significantly reduce the blood pressure of SHRs following 21 days of oral treatment. This study proved that chrysin utilised multiple signalling pathways to produce its vasorelaxant effect in the thoracic aorta of rats; however, it had no antihypertensive effect on SHRs.

Ajuga bracteosa Exerts Antihypertensive Activity in l-NAME-Induced Hypertension Possibly through Modulation of Oxidative Stress, Proinflammatory Cytokines, and the Nitric Oxide/Cyclic Guanosine Monophosphate Pathway

Ajuga bracteosa has been used in traditional medicine to treat hypertension and other ailments. The present study has been designed to investigate the beneficial effects of A. bracteosa in l-nitro arginine methyl ester (l-NAME)-induced hypertensive rats. Hypertension was induced by intraperitoneal injection of l-NAME (185 μmol kg^-1 i.p.). The aqueous methanol extract of A. bracteosa (AMEAB, 250 and 500 mg kg^-1) and coumarin (30 and 70 mg kg^-1) were administered orally from day 8 to day 35 of the study. In vivo antihypertensive activity was assessed by measuring the blood pressure using a PowerLab data system. The effects of the AMEAB and coumarin on nitric oxide (NO), cyclic guanosine monophosphate (cGMP), interleukin-6 (IL-6), the tumor necrosis factor (TNF-α), and oxidative stress markers were also assessed using kit methods. Phytochemical profiling of the AMEAB was carried out through high-performance liquid chromatography (HPLC) where quercetin, gallic acid, caffeic acid, vanillic acid, benzoic acid, syringic acid, p-coumaric acid, and ferulic acid were labeled as plant constituents including coumarin. The AMEAB and coumarin significantly reduced blood pressure at the tested doses of 500 and 70 mg kg^-1, respectively. Serum levels of NO and cGMP were found to be significantly increased in AMEAB- and coumarin-treated groups when compared with only l-NAME-challenged rats. In addition, a marked decrease was noticed in the serum concentrations of proinflammatory cytokines (IL-6 and TNF-α) in AMEAB- and coumarin-treated rats. Moreover, in AMEAB- and coumarin-treated animals, a noticeable improvement was observed in the levels of antioxidant enzymes including catalase, superoxide dismutase, and malonaldehyde, and the total oxidant status when compared with those of only l-NAME-challenged rats. The data of real-time polymerase chain reaction (RT-PCR) experiments supported that the antihypertensive and anti-inflammatory activities of the AMEAB and coumarin are possibly mediated through modulation of endothelial nitric oxide synthase (eNOS), angiotensin-converting enzyme (ACE), nuclear factor (NF)-kB, and COX-2 gene expressions. This study concludes that A. bracteosa possesses an antihypertensive effect mediated through the modulation of the antioxidant, anti-inflammatory, and NO/cGMP pathways, thus providing a rationale to the antihypertensive use of A. bracteosa in traditional medicine.

In Silico Screening of Off-line Comprehensive Two-Dimensional Counter-current Chromatography with Liquid Chromatography for Four Saponins Isolation

Be restrained by the limited peak capacity, one dimension chromatography usually leads to an unsatisfactory separation with low purity of compounds in a complex mixture. To obtain more highly pure targets for standard reference and to discover new substances for structural elucidation, two-dimensional chromatography is more and more prevalent in many fields. As few metrics on assessment of preparative capability of two-dimensional chromatographic separations is reported, a methodology of in silico screening of various two-dimensional chromatographic separations with a minimal number of experiments was demonstrated in this work, which was based on three descriptors including the occupation rate of peaks and system homogeneity of a two-dimensional separation space, and the minimal distance of all nearest-neighbor distances of peaks. Combining the advantages of counter-current chromatography and liquid chromatography, we elaborated the methodology by employing off-line comprehensive two-dimensional counter-current chromatography with liquid chromatography to be in silico screened for separation of four saponins from Panax notoginseng at analytical scale to simulate the case of preparative scale transfer. The predictive results were presented by two-dimensional contour plots and verified by experiments. The result showed that the experimental results were in general accord with the predictive results. This article is protected by copyright. All rights reserved.

Bioactive Natural Products against Systemic Arterial Hypertension: A Past 20-Year Systematic and Prospective Review

Background. Systemic arterial hypertension is one of the most common cardiovascular risks, corresponding to 45% of deaths involving CVDs. The use of natural products, such as medicinal plants, belongs to a millennial part of human therapeutics history and has been employed as an alternative anti-hypertensive treatment. Objective. The present review aims to prospect some natural products already experimentally assayed against arterial hypertension through scientific virtual libraries and patent documents over the past 20 years. Search strategy. This is a systematic review of the adoption of the PRISMA protocol and a survey of the scientific literature that synthesizes the results from published articles between 2001 and 2020 concerning the use of medicinal plants in the management of hypertension, including which parts of the plant or organism are used, as well as the mechanisms of action underlying the anti-hypertensive effect. Furthermore, a technological prospection was also carried out in patent offices from different countries in order to check technologies based on natural products claimed for the treatment or prevention of hypertension. Inclusion criteria. Scientific articles where a natural product had been experimentally assayed for anti-hypertensive activity (part of plants, plant extracts, and products derived from other organisms) were included. Data extraction and analysis. The selected abstracts of the articles and patent documents were submitted to a rigorous reading process. Those articles and patents that were not related to anti-hypertensive effects and claimed potential applications were excluded from the search. Results. Eighty specimens of biological species that showed anti-hypertensive activity were recovered, with 01 representative from the kingdom Fungi and 02 from the kingdom Protista, with emphasis on the families Asteraceae and Lamiaceae, with 6 representatives each. Leaves and aerial parts were the most used parts of the plants for the extraction of anti-hypertensive products, with maceration being the most used extraction method. Regarding phytochemical analyses, the most described classes of biomolecules in the reviewed works were alkaloids, terpenes, coumarins, flavonoids, and peptides, with the reduction of oxidative stress and the release of NO among the mechanisms of action most involved in this process. Regarding the number of patent filings, China was the country that stood out as the main one, with 813 registrations. Conclusion. The anti-hypertensive activity of natural products is still little explored in Western countries. Besides, China and India have shown more results in this area than other countries, confirming the strong influence of traditional medicine in these countries.

The predominance of endothelium-derived relaxing factors and beta-adrenergic receptor pathways in strong vasorelaxation induced by 4-hydroxybenzaldehyde in the rat aorta

4-hydroxybenzaldehyde (4HB), known as ρ-hydroxybenzaldehyde, is commonly present in traditional Chinese medicine herb, most frequently used for hypertension treatment. This research aims to determine the potency of 4HB's vasorelaxant action. In the study, the vasodilation effect of 4HB was evaluated using in vitro isolated rat aortic rings assay. The aortic rings were pre-incubated with respective antagonists before being pre-contracted with phenylephrine (PE) and challenged with various concentrations of 4HB for mechanistic action studies. R_max (maximal vasodilation) and pEC₅₀ (negative logarithm of half-maximal effective concentration) values of each experiment were determined for comparison purposes. 4HB caused vasodilation on endothelium-intact aortic rings which pre-contracted with PE (pEC₅₀ = 3.53 ± 0.05, R_max = 100.95 ± 4.25%) or potassium chloride (pEC₅₀ = 2.96 ± 0.13, R_max = 72.13 ± 4.93%). The vasodilation effect of 4HB was significantly decreased in the absence of an endothelium (pEC₅₀ = 2.21 ± 0.25, R_max = 47.96 ± 4.16%). The atropine, 4-aminopyridine, Nω-nitro-L-arginine methyl ester, glibenclamide, and propranolol significantly reduced the vasorelaxation effect of 4HB. Besides that, 4HB blocked the voltage-operated calcium channel (VOCC) and regulated the intracellular Ca²⁺ release from the sarcoplasmic reticulum (SR) in the aortic ring. Thus, the results indicated that 4HB exerted its vasodilatory effect via cGMP and β₂ pathways, M₃-dependent PLC/IP₃ pathways, and potassium and calcium channels.

Vasorelaxant effect of 5,7,4'- Trihydroxyflavanone (Naringenin) via endothelium dependent, potassium and calcium channels in Sprague Dawley rats: Aortic ring model

Naringenin is a naturally occurring flavanone (flavonoid) known to have bioactive effects on human health. It has been reported to show cardiovascular effects. This study aimed to investigate the possible vasorelaxant effect of naringenin and the mechanism behind it by using a Sprague Dawley rat aortic ring assay model. Naringenin caused significant vasorelaxation of endothelium-intact aortic rings precontracted with phenylephrine (pD₂ = 4.27 ± 0.05; R_max = 121.70 ± 4.04%) or potassium chloride (pD₂ = 4.00 ± 0.04; R_max = 103.40 ± 3.82%). The vasorelaxant effect decreased in the absence of an endothelium (pD₂ = 3.34 ± 0.10; R_max = 62.29 ± 2.73%). The mechanisms of the vasorelaxant effect of naringenin in the presence of antagonists were also investigated. Indomethacin, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, atropine, 4-aminopyridine, Nω-nitro-l-arginine methyl ester, glibenclamide and propranolol significantly reduced the relaxation stimulated by naringenin in the presence of endothelium. Besides that, the effect of naringenin on the voltage-operated calcium channel (VOCC) in the endothelium-intact aortic ring was studied, as was intracellular Ca²⁺ release from the sarcoplasmic reticulum (SR) in the endothelium-denuded aortic ring. The results showed that naringenin also significantly blocked the entry of Ca²⁺ via the VOCC, SERCA/SOCC and suppressed the release of Ca²⁺ from the SR. Thus, the vasorelaxant effect shown by naringenin mostly involve the COX pathway, the endothelium-dependent pathway via NO/sGC/prostaglandin, calcium and potassium channels.

Discovery of trans-3,4,4'-trihydroxystilbene as new lead vasorelaxant agent for antihypertensive drug development

AIMS

The structure-vasorelaxant activity relationships (SARs) assessment in previous study has found that trans-3,4,4'-trihydroxystilbene (344OH) could potentially act as a vasorelaxing agent with demonstration of over 2-fold maximal relaxation (Rmax) compared to its analogue, resveratrol. The present study focuses on the mechanism of actions and pathways employed by 344OH and compared to its analogue to further speculate the SAR of stilbenoids towards vasorelaxation.

MATERIALS AND METHODS

The 344OH employed in present study was synthesized based on the protocol in previous study. The vascular responses towards the cumulative addition of 344OH were evaluated using in vitro rat aortic rings assays.

KEY FINDINGS

The pEC50 and Rmax values were found to be 4.33 ± 0.05 and 106 ± 3.99%, respectively. Results showed that the vasorelaxation of 344OH were predominated by G-protein-coupled muscarinic- (M3) and β2-adrenergic receptors, followed by PGI2/AC/cAMP- and NO/sGC/cGMP-dependent pathways. It was also identified that 344OH employed voltage-activated- (Kv), calcium-activated- (Kca) and inwardly-rectifying (Kir) potassium channels and act as an antagonist for both VOCC and IP3R while regulating the action potential in the vasculature.

SIGNIFICANCE

The different position of hydroxyl substituent located in A-ring of the stilbenoid backbone in 344OH compared to resveratrol resulted in a significant difference in mechanistic actions that lead to 344OH's fast-acting and less time-dependent vasorelaxation behaviour. This has substantially increased the potential of 344OH to be developed as an effective antihypertensive drug in future. Present findings further strengthen our inferences where the SARs study approach should be carried out as the mainstream methodology in future drug development research.

Genes Induced by Panax Notoginseng in a Rodent Model of Ischemia-Reperfusion Injury

Stroke is a cerebrovascular disease that results in decreased blood flow. Although Panax notoginseng (PN), a Chinese herbal medicine, has been proven to promote stroke recovery, its molecular mechanism remains unclear. In this study, middle cerebral artery occlusion (MCAO) was induced in rats with thrombi generated by thread and subsequently treated with PN. After that, staining with 2,3,5-triphenyltetrazolium chloride was employed to evaluate the infarcted area, and electron microscopy was used to assess ultrastructural changes of the neurovascular unit. RNA-Seq was performed to determine the differential expressed genes (DEGs) which were then verified by qPCR. In total, 817 DEGs were identified to be related to the therapeutic effect of PN on stroke recovery. Further analysis by Gene Oncology analysis and Kyoto Encyclopedia of Genes and Genomes revealed that most of these genes were involved in the biological function of nerves and blood vessels through the regulation of neuroactive live receptor interactions of PI3K-Akt, Rap1, cAMP, and cGMP-PKG signaling, which included in the 18 pathways identified in our research, of which, 9 were reported firstly that related to PN's neuroprotective effect. This research sheds light on the potential molecular mechanisms underlying the effects of PN on stroke recovery.

Chemical components of ginseng, their biotransformation products and their potential as treatment of hypertension

Ginseng is an ancient perennial herb belonging to the family Araliaceae and genus Panax which has been used for medical therapeutics for thousands of years, particularly in China and other Asian cultures although increasing interest in ginseng has recently emerged in western societies. Ginseng is a complex substance containing dozens of bioactive and potentially effective therapeutic compounds. Among the most studied are the ginsenosides, which are triterpene saponins possessing a wide array of potential therapeutic effects for many conditions. The quantity and type of ginsenoside vary greatly depending on ginseng species and their relative quantity in a given ginseng species is greatly affected by extraction processes as well as by subjecting ginseng to various procedures such as heating. Adding to the complexity of ginsenosides is their ability to undergo biotransformation to bioactive metabolites such as compound K by enteric bacteria following ingestion. Many ginsenosides exert vasodilatating effects making them potential candidates for the treatment of hypertension. Their vascular effects are likely dependent on eNOS activation resulting in the increased production of NO. One proposed end-mechanism involves the activation of calcium-activated potassium channels in vascular smooth cells resulting in reduced calcium influx and a vasodilatating effect, although other mechanisms have been proposed as discussed in this review.

25-OH-PPD inhibits hypertrophy on diabetic cardiomyopathy via the PI3k/Akt/GSK-3β signaling pathway

The present study investigated the inhibitory effects and the associated mechanism of the compound 25-OH-PPD (PPD) on cardiac hypertrophy, fibrosis and inflammation. The signaling pathways associated with diabetic mellitus cardiomyopathy (DMCM) were investigated using a rat model. DMCM Sprague-Dawley rats were induced by injection of streptozotocin. The animals were divided into 5 groups as follows: Normal group (NG group), diabetic group, PPD treatment group, PPD/LY294002 group (inhibitor of PI3K/Akt) and PPD/LiCl group [inhibitor of glycogen synthase kinase (GSK) 3β]. The studies were carried out during the 12 weeks following induction of diabetes and the levels of plasma brain natriuretic peptide (BNP), creatine phosphokinase isoenzyme (CK-MB) were measured. In addition, the volume of myocardial collagen fraction (CVF) was tested. The expression levels of the inflammatory cytokines, including transforming growth factor beta 1 (TGF-β1), connective tissue growth factor (CTGF), cell adhesion molecules α-smooth muscle actin (α-SMA) and vascular adhesion molecule 1 (VCAM-1) and associated signaling proteins (Akt, GSK-3β) were measured by biochemical analyses. The levels of BNP and CK-MB, the volume of CVF, the expression levels of TGF-β1, CTGF, α-SMA and VCAM-1 in the diabetic group were higher compared with those of the normal control group (P<0.05). Conversely, the levels of these molecules were significantly decreased in the PPD treatment groups (P<0.05). The aforementioned effects were partially eliminated in the PPD/LY294002 and PPD/LiCl groups. In addition, PPD treatment significantly increased the expression levels of p-Akt and decreased the levels of phosphorylated GSK-3β compared with those of the DMCM group (P<0.05). The data demonstrated that the protective effects of 25-OH-PPD against DMCM may be attributed to the PI3k/Akt/GSK-3β signaling pathway, via the suppression of the α-SMA/VCAM axis and the downregulation of TGF-β1 and CTGF expression.

Underlying mechanism of vasorelaxant effect exerted by 3,5,7,2',4'-pentahydroxyflavone in rats aortic ring

Morin (3,5,7,2',4'-pentahydroxyflavone) is a yellow coloured natural flavonoid found in plants of the Moraceae family. This favonoid is easily sources from readily available fruits, vegetables and eve certain beverages. Among the sources that was identified, it is clear that morin is most abundantly found in almond, old fustic, Indian guava, and Osage orange. Multiple studies have suggested that morin has multiple therapeutic actions and possess potential to be a functional potent drug. Previous studies demonstrated that morin is capable of resolving deoxycorticosterone acetate-salt-induced hypertension and possess strong vasorelaxant properties. However, the exact mechanisms remains unknown. Therefore, this study is designed to investigate the in vitro mechanism of morin-induced vasorelaxant effects. The underlying mechanisms of morin's vasorelaxant activities were evaluated on thoracic aortic rings isolated from Sprague-Dawley rats. Results from the study demonstrated morin causing vasodilatory reaction in phenylephrine and potassium chloride pre-contracted endothelium-intact aortic rings with the effect being significantly affected in endothelium-denuded aortic rings. Pre-incubation of the aortic rings with ODQ (selective cGMP-independent sGC inhibitor), indomethacin (nonselective COX inhibitor), L-NAME (endothelial nitric oxide inhibitor), propranolol (β₂-adrenegic receptors blocker), and atropine (muscarinic receptors blocker) significantly reduced the vasorelaxant effect of morin. It was also found to be able to reduce the intracellular calcium level by blocking VOCC and calcium intake from the extracellular environment and the intracellular release of calcium from the sarcoplasmic reticulum. The present study showed that the vasorelaxant effect of morin potentially involves the NO/sGC, muscarinic receptors, β₂-adrenegic receptors, and calcium channels.

New flavonoid-based compound synthesis strategy for antihypertensive drug development

Hypertension is one of the leading causes of mortality in relation to the cardiovascular conditions and easily the most overlooked and poorly managed disease in mankind. With well over 200 drugs available in the market globally, there is still an urgency to search for antihypertensive alternatives due to the subpar efficacy and unwarranted side effects of the current choices. Present studies reported over 250 types of plant-derived compounds were being investigated for potential pharmacological effects on the vasculature in the last 3 decades. There were numerous literatures that claimed various compounds exhibiting vasorelaxant properties to a certain extent with low numbers of these compounds being successfully adapted into the current medicinal practice for treatment of hypertension. The issue is the scarcity of reviews that summarizes the discovery of this field and the lack of thorough comparison of these compounds to identify which of these vasodilators should be the next face of hypertension management. Thus, this review is aiming towards identifying the relationship between a major class of plant-derived compounds, flavonoid's activity as a vasodilator with their signalling pathways and their structural characteristics according to their vasorelaxant properties. Interestingly, we found that both nitric oxide and voltage-operated calcium channels pathways, and two of the flavonoid's structural characteristics play crucial roles in eliciting strong vasorelaxant effects. We have faith that the insights of this review will serve as a reference for those researching similar topics in the future and potentially lead to the development of more promising antihypertensive alternative.