Asiatic Acid Reduces Blood Pressure by Enhancing Nitric Oxide Bioavailability with Modulation of eNOS and p47phox Expression in l -NAME-induced Hypertensive Rats

Exploring the effects of vasoactive constituents in large cardamom: implications for the anti-hypertensive effect via eNOS coupling pathway - an in-vitro study in rat endothelial cells

Endothelial dysfunction, linked to reduced eNOS expression and nitric oxide (NO) availability, contributes to cardiovascular diseases (CVDs). Large cardamom exhibits antihypertensive effects by augmenting NO levels and antioxidant activity. To decipher its mechanisms, selected constituents were docked with eNOS-associated target genes such as GTP cyclohydrolase I (GTPCH-1) and (dihydrofolate reductase [DHFR]). Endothelial damage induced by L-NAME and fructose was countered by assessing nitric oxide metabolites (NOx), tetrahydrobipterin (BH4 levels), GCH-I expression and super oxide dismutase (SOD) activity after constituent incubation. Cyanidin-3-O-glucoside and petunidin-3-O-glucoside notably restored impaired vascular markers in both models. These phytoconstituents are likely to activate GCH-BH4-eNOS pathways, upregulating SOD and NO expression, maintaining endothelial integrity. Large cardamom's antihypertensive effects may stem from these components, synergistically enhancing endothelial NO release via the eNOS pathway.

Limonin ameliorates cardiovascular dysfunction and remodeling in hypertensive rats

AIMS

Limonin is a tetracyclic triterpenoid isolated from citrus fruits. Here, the effects of limonin on cardiovascular abnormalities in nitric oxide-deficient rats induced by N^ω-Nitrol-arginine methyl ester (L-NAME) were explored.

MAIN METHODS

Male Sprague Dawley rats were given L-NAME (40 mg/kg, drinking water) for 3 weeks and then treated daily with polyethylene glycol (vehicle), limonin (50 or 100 mg/kg) or telmisartan (10 mg/kg) for two weeks.

KEY FINDINGS

Limonin (100 mg/kg) markedly reduced L-NAME-induced hypertension, cardiovascular dysfunction and remodeling in rats (P < 0.05). Increases in systemic angiotensin-converting enzyme (ACE) activity and angiotensin II (Ang II) and a reduction in circulating ACE2 were restored in hypertensive rats treated with limonin (P < 0.05). Reductions in antioxidant enzymes and nitric oxide metabolites (NOx) and increases in oxidative stress components induced by L-NAME were relieved by limonin treatment (P < 0.05). Limonin suppressed the increased expression of tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 in cardiac tissue and circulating TNF-α in rats that received L-NAME (P < 0.05). Changes in Ang II receptor type I (AT1R), Mas receptor (MasR), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB) and NADPH oxidase subunit 2 (gp91^phox) protein expression in cardiac and aortic tissue were normalized by limonin (P < 0.05).

SIGNIFICANCE

In conclusion, limonin ameliorated L-NAME-induced hypertension, cardiovascular dysfunction and remodeling in rats. These effects were relevant to restorations of the renin-angiotensin system, oxidative stress and inflammation in NO-deficient rats. The molecular mechanisms are associated with the modulation of AT1R, MasR, NF-ĸB and gp91^phox protein expression in cardiac and aortic tissue.

Synergistic Combination of Luteolin and Asiatic Acid on Cervical Cancer In Vitro and In Vivo

Cervical cancer is an important issue globally because it is the second most common gynecological malignant tumor and conventional treatment effects have been shown to be limited. Lut and AsA are plant-derived natural flavonoid and triterpenoid products that have exhibited anticancer activities and can modulate various signaling pathways. Thus, the aim of the present study was to evaluate whether Lut combined with AsA could enhance the anticancer effect to inhibit cervical cancer cell proliferation and examine the underlying molecular mechanisms in vitro and in vivo. The results of a CCK-8 assay showed that Lut combined with AsA more effectively inhibited the proliferation of CaSki and HeLa cells than Lut or AsA treatment alone. Lut combined with AsA caused apoptosis induction and sub-G1-phase arrest in CaSki and HeLa cells, as confirmed by flow cytometry, mitoROS analysis, antioxidant activity measurement and western blot assay. In addition, Lut combined with AsA significantly inhibited the cell migration ability of CaSki and HeLa cells in a wound-healing assay. Furthermore, Lut combined with AsA induced apoptosis and inhibited migration through downregulated PI3K/AKT (PI3K, AKT and p70S6K), JNK/p38 MAPK and FAK (integrin β1, paxillin and FAK) signaling and upregulated ERK signaling. In an in vivo study, Lut combined with AsA markedly inhibited cervical cancer cell-derived xenograft tumor growth. Collectively, the present study showed that Lut combined with AsA may be used as an anticancer agent to improve the prognosis of cervical cancer. Indeed, with additional research to develop standardized dosages, Lut and AsA combination therapy could also be applied in clinical medicine.

Bioactivities and mechanisms of dietary proanthocyanidins on blood pressure lowering: A critical review of in vivo and clinical studies

Proanthocyanidins, widespread in natural plant sources, are bioactive substances that exhibit broad benefits to human health. Of note, proanthocyanidins have been reported to lower blood pressure and prevent hypertension, but a critical review of this is lacking. In this review, information on the basic structures and absorption of dietary proanthocyanidins as well as their bioactivities and related mechanisms on the lowering of blood pressure derived via in vivo and clinical studies are summarized. Clinical studies have shown that proanthocyanidins have a pronounced blood pressure-lowering effect, effectively preventing hypertension and reducing the occurrence of cardiovascular and cerebrovascular diseases. The potential mechanisms, which are herein reviewed in detail, involve the improvement of vascular function, reduction of oxidative stress and inflammation, and modulation of lipid metabolism. Taken together, this work provides information for a better understanding of the antihypertensive effects of proanthocyanidins, which may promote their use to reduce the risk of developing hypertension.

Effects of Thai native chicken breast meat consumption on serum uric acid level, biochemical parameters, and antioxidant activities in rats

This study aimed to evaluate the effect of a high protein diet comprising breast meat from commercial broiler (BR), Thai native (PD), and commercial broiler × Thai native crossbred (KKU-ONE) chicken on serum uric acid, biochemical parameters, and antioxidant activities in rats. Male Sprague–Dawley rats were divided into four groups. The control group received a standard chow diet, and the other three groups were fed a high protein diet (70% standard diet + 30% BR, PD, or KKU-ONE chicken breast) for five weeks. The PD- and KKU-ONE-fed rats had lower plasma total cholesterol and triglyceride levels than the control rats. A decrease in HDL-c was also observed in rats fed a diet containing BR. Liver weight, liver enzyme, plasma ALP, xanthine oxidase activity, serum uric acid, creatinine, superoxide production, and plasma malondialdehyde levels increased in BR-fed rats. The findings of this study might provide evidence to support the use of Thai native and Thai native crossbred chicken breast meat as functional foods.

Nobiletin resolves left ventricular and renal changes in 2K-1C hypertensive rats

This study investigated the effects of nobiletin on cardiorenal changes and the underlying mechanisms involved in two-kidney, one-clip (2K-1C) hypertension. 2K-1C rats were treated with nobiletin (15 or 30 mg/kg/day) or losartan (10 mg/kg/day) for 4 weeks (n = 8/group). Nobiletin (30 mg/kg) reduced high levels of blood pressure and circulating angiotensin II and angiotensin-converting enzyme activity in 2K-1C rats. Left ventricular (LV) dysfunction and remodelling in 2K-1C rats were alleviated in the nobiletin-treated group (P < 0.05). Nobiletin reduced the upregulation of Ang II type I receptor (AT₁R)/JAK (Janus kinase)/STAT (signal transducer and activator of transcription) protein expression in cardiac tissue of 2K-1C rats (P < 0.05). The reduction in kidney function, and accumulation of renal fibrosis in 2K-1C rats were alleviated by nobiletin (P < 0.05). Overexpression of AT₁R and NADPH oxidase 4 (Nox4) protein in nonclipped kidney tissue was suppressed in the nobiletin-treated group (P < 0.05). The elevations in oxidative stress parameters and the reductions in antioxidant enzymes were attenuated in 2K-1C rats treated with nobiletin (P < 0.05). In summary, nobiletin had renin-angiotensin system inhibitory and antioxidant effects and attenuated LV dysfunction and remodelling via restoration of the AT₁R/JAK/STAT pathway. Nobiletin also resolved renal damage that was related to modulation of the AT₁R/Nox4 cascade in 2K-1C hypertension.

Centella asiatica (L.) Urb. Prevents Hypertension and Protects the Heart in Chronic Nitric Oxide Deficiency Rat Model

Background: Hypertension is a major risk factor for cardiovascular disease (CVD), which is the number one cause of global mortality. The potential use of natural products to alleviate high blood pressure has been demonstrated to exert a cardioprotective effect. Centella asiatica (L.) Urb. belongs to the plant family Apiaceae (Umbelliferae). It contains a high amount of triterpenoid and flavonoid that have antioxidant properties and are involved in the renin-angiotensin-aldosterone system which is an important hormonal system for blood pressure regulation. Objective: This study aimed to investigate the effects of C. asiatica ethanolic extract on blood pressure and heart in a hypertensive rat model, which was induced using oral N(G)-nitro-l-arginine methyl ester (l-NAME). Methods: Male Sprague-Dawley rats were divided into five groups and were given different treatments for 8 weeks. Group 1 only received deionized water. Groups 2, 4, and 5 were given l-NAME (40 mg/kg, orally). Groups 4 and 5 concurrently received C. asiatica extract (500 mg/kg, orally) and captopril (5 mg/kg, orally), respectively. Group 3 only received C. asiatica extract (500 mg/kg body weight, orally). Systolic blood pressure (SBP) was measured at weeks 0, 4, and 8, while serum nitric oxide (NO) was measured at weeks 0 and 8. At necropsy, cardiac and aortic malondialdehyde (MDA) contents, cardiac angiotensin-converting enzyme (ACE) activity, and serum level of brain natriuretic peptide (BNP) were measured. Results: After 8 weeks, the administrations of C. asiatica extract and captopril showed significant (p < 0.05) effects on preventing the elevation of SBP, reducing the serum nitric oxide level, as well as increasing the cardiac and aortic MDA content, cardiac ACE activity, and serum brain natriuretic peptide level. Conclusion: C. asiatica extract can prevent the development of hypertension and cardiac damage induced by l-NAME, and these effects were comparable to captopril.

Actions and Therapeutic Potential of Madecassoside and Other Major Constituents of Centella asiatica: A Review

Centella asiatica is a popular herb well-known for its wide range of therapeutic effects and its use as a folk medicine for many years. Its therapeutic properties have been well correlated with the presence of asiaticoside, madecassoside, asiatic and madecassic acids, the pentacyclic triterpenes. The herb has been extensively known to treat skin conditions; nevertheless, several pre-clinical and clinical studies have scientifically demonstrated its effectiveness in other disorders. Among the active constituents that have been identified in Centella asiatica, madecassoside has been the subject of only a relatively small number of scientific reports. Therefore, this review, while including other major constituents of this plant, focuses on the therapeutic potential, pharmacokinetics and toxicity of madecassoside.

Aqueous extract of large cardamom inhibits vascular damage, oxidative stress, and metabolic changes in fructose-fed hypertensive rats

PURPOSE

Since metabolic abnormalities such as elevated glucose level and imbalanced lipid profiles increase the risk for hypertension and cause endothelial dysfunction, we evaluated the effect of aqueous extract of large cardamom (AELC) on fructose-induced metabolic hypertension and oxidative stress.

METHODS

The male Sprague-Dawley rats were divided into 6 groups with 5 rats in each group, and each group was fed with 10% fructose in drinking water for 8 weeks. Starting from week 5, animals were treated with 50, 100, and 200 mg/kg/day AELC or Losartan (10 mg/kg/day). Systolic, diastolic, and mean arterial blood pressure was measured once in every seven days using the tail-cuff method. Vascular function, plasma nitric oxide (NO), glucose, lipid profiles, serum biochemical, and anti-oxidant parameters were also evaluated.

RESULTS

Rats fed with fructose showed higher blood pressure, serum cholesterol, and triglyceride levels, but decreased in the AELC or Losartan treatment group. Treatments with AELC prevented exaggerated plasma glucose and oxidative stress and restored the nitric oxide level in fructose-fed rats. Besides, it also reduced vascular proliferation and improved the relaxation response of acetylcholine in the aorta pre-contracted with phenylephrine.

CONCLUSION

In summary, the obtained results suggest that AELC can prevent and reverse the high blood pressure induced by fructose, probably by restoring nitric oxide level and by improving altered metabolic parameters.

Diosmetin attenuates metabolic syndrome and left ventricular alterations via the suppression of angiotensin II/AT receptor/gp91phox/p-NF-κB protein expression in high-fat diet fed rats

Diosmetin, a monomethoxyflavone, is isolated from citrus fruits. The objective of this research was to test the biological role of diosmetin on parameters of metabolic syndrome (MS) and left ventricular (LV) alterations in rats fed with a high-fat (HF) diet. MS was induced by feeding male Sprague-Dawley rats with a HF diet plus 15% fructose in drinking water for 16 weeks. MS rats were given diosmetin (20 or 40 mg per kg per day) or metformin (100 mg per kg per day) for the final four weeks. Diosmetin attenuated signs of MS including, hypertension, hyperglycemia, insulin resistance, and dyslipidemia in rats that received the HF diet (p < 0.05). A decreased stroke volume, ejection fraction, fractional shortening, LV hypertrophy and fibrosis present in the MS group were alleviated by diosmetin treatment (p < 0.05). Diosmetin also suppressed angiotensin-converting enzyme activity, plasma angiotensin II (Ang II) levels and angiotensin II type 1 (AT1) receptor protein expression in MS rats. Increases in superoxide (O2˙-) formation, plasma malondialdehyde, plasma nitrate and nitrite and gp91phox expression induced by a HF diet were ameliorated in the diosmetin treated group. Inflammation indicated by an increased phospho nuclear factor kappa B (p-NF-κB) protein expression and cardiac TNF-α concentration was reduced in MS rats receiving diosmetin (p < 0.05). Metformin also attenuated MS, cardiac abnormalities relevant to decreasing the renin-angiotensin system stimulation, reactive oxygen species and inflammation in MS rats (p < 0.05). Diosmetin alleviated MS and LV dysfunction and remodeling in HF diet-induced MS rats. These results could be associated with the suppression of the Ang II/AT1 receptor/gp91phox/p-NF-κB protein pathway.

Butterfly Pea Flower (Clitoria ternatea Linn.) Extract Ameliorates Cardiovascular Dysfunction and Oxidative Stress in Nitric Oxide-Deficient Hypertensive Rats

In this study, we examine whether Clitoria ternatea Linn. (CT) can prevent Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME)-induced cardiac and vascular dysfunction in rats. Male Sprague Dawley rats were given L-NAME (40 mg/kg, drinking water) and orally administered with CT extract (300 mg/kg/day) or lisinopril (2.5 mg/kg/day) for 5 weeks. The main phytochemical components of the CT extract were found to be flavonoids. The CT extract alleviated the high blood pressure in rats receiving L-NAME. Decreased vasorelaxation responses to acetylcholine and enhanced contractile responses to sympathetic nerve stimulation in aortic rings and mesenteric vascular beds of L-NAME treated rats were ameliorated by CT extract supplementation. Left ventricular hypertrophy and dysfunction were developed in L-NAME rats, which were partially prevented by CT extract treatment. The CT extract alleviated upregulated endothelial nitric oxide synthase expression, decreased plasma nitrate/nitrite levels, and increased oxidative stress in L-NAME rats. It suppressed high levels of serum angiotensin-converting enzyme activity, plasma angiotensin II, and cardiac angiotensin II type 1 receptor, NADPH oxidases 2, nuclear factor-kappa B, and tumor necrosis factor-alpha expression. The CT extract, therefore, partially prevented L-NAME-induced hypertension and cardiovascular alterations in rats. These effects might be related to a reduction in the oxidative stress and renin-angiotensin system activation due to L-NAME in rats.

Genistein Prevents Nitric Oxide Deficiency-Induced Cardiac Dysfunction and Remodeling in Rats

Genistein is an isoflavone found in soybeans. This study evaluates the protective effects of genistein on N^ω-nitro-L-arginine methyl ester hydrochloride (L-NAME)-induced hypertension, cardiac remodeling, and dysfunction in rats. Male Wistar rats were treated with L-NAME 40 mg/kg/day together for 5 weeks, with or without genistein at a dose of 40 or 80 mg/kg/day or lisinopril 5 mg/kg/day (n = 8 per group). Genistein prevented L-NAME-induced hypertension in rats. Increases in the left ventricular weight, metalloproteinase-2, metalloproteinase-9, and collagen type I intensity were observed in L-NAME rats, and these changes were attenuated in the genistein-treated group. Genistein reduced circulating angiotensin-converting enzyme activity and angiotensin II concentrations in L-NAME rats. L-NAME increased plasma and cardiac malondialdehyde and vascular superoxide generations, as well as reductions of serum and cardiac catalase activities in rats. Plasma nitrate/nitrite were protected in the genistein-treated group. Genistein prevented the L-NAME-induced overexpression of angiotensin II receptor type I (AT₁R), nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit 2 (gp91^phox), and transforming growth factor beta I (TGF-β1) in hypertensive rats. In conclusion, genistein exhibited a cardioprotective effect in hypertensive rats in this study. The molecular mechanisms might be mediated by suppression of oxidative stress through the Ang II/AT₁R/NADPH oxidase/TGF-β1 signaling pathway.

Influence of Asiatic acid on cell proliferation and DNA damage in vitro and in vivo systems

Asiatic acid (AA) is a triterpene with promising pharmacological activity. In the present study, in vitro and in vivo assays were conducted to understand the effect of AA on cell proliferation and genomic instability. AA was cytotoxic to human tumor cell lines (M059J, HeLa, and MCF-7), with IC₅₀ values ranging from 13.91 to 111.72 µM. In the case of M059J, AA exhibited selective cytotoxicity after 48 h of treatment (IC₅₀  = 24 µM), decreasing the percentage of cells in the G0/G1 phase, increasing the percentage of cells in the S phase, and inducing apoptosis. A significant increase in chromosomal damage was observed in V79 cell cultures treated with AA (40 µM), revealing genotoxic activity. In contrast, low concentrations (5, 10, and 20 µM) of AA significantly reduced the frequencies of micronuclei induced by the mutagens doxorubicin (DXR), methyl methanesulfonate, and hydrogen peroxide. A reduction of DXR-induced intracellular free radicals was found in V79 cells treated with AA (10 µM). The antigenotoxic effect of AA (30 mg/kg) was also observed against DXR-induced chromosomal damage in Swiss mice. Significant reductions in p53 levels were verified in the liver tissue of these animals. Taken together, the data indicate that AA exerted antiproliferative activity in M059J tumor cells, which is probably related to the induction of DNA damage, leading to cell cycle arrest and apoptosis. Additionally, low concentrations of AA exhibited antigenotoxic effects and its antioxidant activity may be responsible, at least in part, for chemoprevention.

Cratoxylum formosum dyer extract alleviates testicular damage in hypertensive rats

The effects of a Cratoxylum formosum (Jack) Dyer ssp. (CF) extract on testicular damage were assessed in hypertensive rats. N^ω -nitro-L-arginine methyl ester hydrochloride (L-NAME; 40 mg kg^-1  day^-1 ) was administered for 5 weeks to induce hypertension in male Sprague-Dawley rats, and treated with CF extract (100, 300 or 500 mg kg^-1  day^-1 ) or sildenafil (5 mg kg^-1  day^-1 ) during the final 2 weeks (n = 8/group). Biochemical components of the CF extract were identified and mainly contained phenolic compounds. The CF extract significantly reduced systolic blood pressure and alleviated impaired sperm quality and seminiferous tubular morphology in hypertensive rats. CF extract restored reduced serum testosterone and protein expression of steroidogenic acute regulatory protein (StAR), nuclear factor erythroid-related factor 2 (Nrf2), and haem oxygenase 1 (HO-1) in L-NAME rats. Hypertensive rats presented decreased antioxidant enzyme activities, and increased testicular and plasma malondialdehyde (MDA) levels and superoxide production, all of which were normalised by CF extract. Furthermore, endothelial nitric oxide synthase (eNOS) expression in testicular tissue and plasma nitrate/nitrite levels were restored in hypertensive rats administered CF extract. Conclusion: CF extract alleviated testicular damage in hypertensive rats. Potential molecular mechanisms may involve suppression of oxidative stress and restoration of StAR, Nrf2, HO-1 and eNOS expression in hypertensive rats.

Hesperidin inhibits L-NAME-induced vascular and renal alterations in rats by suppressing the renin-angiotensin system, transforming growth factor-β1, and oxidative stress

The protective effect of hesperidin on vascular and renal alterations and possible underlying mechanisms involved in N^ω -nitro-L-arginine methyl ester hydrochloride (L-NAME)-induced hypertensive rats were investigated in this study. Male Sprague-Dawley rats were administered L-NAME (40 mg/kg/day), L-NAME plus hesperidin (30 mg/kg/day), and L-NAME plus captopril (2.5 mg/kg/day) for 5 weeks. Hesperidin and captopril significantly prevented L-NAME-induced hypertension, vascular and renal dysfunction, intrarenal artery remodelling, glomerular extracellular matrix accumulation, and renal fibrosis. The preventive treatment with hesperidin and captopril also significantly decreased serum angiotensin-converting enzyme activity and plasma transforming growth factor-β1 (TGF-β1) levels and downregulated angiotensin II receptor type I and TGF-β1 protein expression in the kidneys. In addition, decreased malondialdehyde levels and increased superoxide dismutase activity in the plasma and kidney were observed after co-treatment with hesperidin or captopril. These findings suggest that hesperidin inhibits L-NAME-induced vascular and renal alterations in rats. The possible mechanism may be related to the suppression of the activation of the renin-angiotensin system and expression of TGF-β1, and reduction of oxidative stress.

Syzygium gratum Extract Alleviates Vascular Alterations in Hypertensive Rats

Background and Objectives: Syzygium gratum (SG) is a local vegetable and widely consumed in Thailand. Previously, a strong antioxidative effect of SG extract has been reported. The effects of SG extract on hypertension have remained unknown. The effect of SG aqueous extract on blood pressure and vascular changes were examined in L-NAME-induced hypertensive rats (LHR), and its potential active constituents were also explored. Materials and Methods: Male Sprague Dawley rats were allocated to control, L-NAME (40 mg/kg/day), L-NAME + SG (100, 300, 500 mg/kg/day), or captopril (5 mg/kg/day) groups. The components of SG extract were analyzed. Results: The analysis of aqueous SG extract was carried out using HPLC-Mass spectroscopy, and phenolic compounds could be identified as predominant components which might be responsible for its antihypertensive effects observed in the LHR model (p < 0.05). Additionally, SG extract also improved vascular responses to acetylcholine and decreased vascular remodeling in LHR (p < 0.05). Enhancements of eNOS expression and plasma nitric oxide metabolite levels, and attenuation of angiotensin converting enzyme (ACE) activity and plasma angiotensin II levels were observed in the LHR group treated with SG. Moreover, SG exhibited strong antioxidant activities by reducing vascular superoxide generation and systemic malondialdehyde in LHRs. Captopril suppressed high blood pressure and alleviated vascular changes and ACE activity in LHRs, similar to those of the SG extract (p < 0.05). Conclusion: Our results suggest that the SG extract exhibited antihypertensive effects, which is relevant to alleviation of vascular dysfunction and vascular remodeling of LHRs. These effects might be mediated by phenolic compounds to inhibit ACE activity and scavenge reactive oxygen species in LHR.

Recent Advances in the Knowledge of Naturally-derived Bioactive Compounds as Modulating Agents of the Renin-angiotensin-aldosterone System: Therapeutic Benefits in Cardiovascular Diseases

BACKGROUND

One of the biggest challenges to public health worldwide is to reduce the number of events and deaths related to the cardiovascular diseases. Numerous approaches have been applied to reach this goal, and drug treatment intervention has been indispensable along with an effective strategy for reducing both cardiovascular morbidity and mortality. Renin-angiotensin-aldosterone system (RAAS) blockade is currently one of the most important targets of cardiovascular drug therapy. Many studies have proven the valuable properties of naturally-derived bioactive compounds to treat cardiovascular diseases.

METHODS

The goal of this review, therefore, is to discuss the recent developments related to medicinal properties about natural compounds as modulating agents of the RAAS, which have made them an attractive alternative to be available to supplement the current therapy options.

RESULTS

Data has shown that bioactive compounds isolated from several natural products act either by inhibiting the angiotensin-converting enzyme or directly by modulating the AT1 receptors of angiotensin II, which consequently changes the entire classical axis of this system.

CONCLUSION

While there are a few evidence about the positive actions of different classes of secondary metabolites for the treatment of cardiovascular and renal diseases, data is scarce about the clinical assays established to demonstrate their value in humans.

Lancemaside A from Codonopsis lanceolata prevents hypertension by inhibiting NADPH oxidase 2-mediated MAPK signalling and improving NO bioavailability in rats

OBJECTIVES

This study investigated whether lancemaside A (LMA) can prevent hypertension and assessed the mechanisms of action of LMA in rats.

METHODS

Hypertension was induced by chronic immobilization stress and nicotine administration. Hypertensive vehicle rats were treated with LMA (1, 20, or 40 mg/kg) or nifedipine (10 mg/kg) as a positive control daily for 3 weeks.

KEY FINDINGS

In hypertensive vehicle rats, LMA dose-dependently reduced systolic blood pressure. LMA doses of 20 and 40 mg/kg reduced the aortic expression of nicotinamide adenine dinucleotide phosphate oxidase (NOX)2 (both P < 0.01), and 40 mg/kg LMA reduced serum malondialdehyde (P < 0.01). Serum nitrite levels were significantly higher in LMA treated rats than in hypertensive vehicle rats, with LMA doses of 20 and 40 mg/kg reducing the expression of endothelial nitric oxide synthase in rat aortas (P < 0.001 and P < 0.01, respectively). LMA also reduced the aortic levels of nuclear factor kappa B and the activation of the three isoforms of mitogen-activated protein kinase (MAPK).

CONCLUSIONS

Lancemaside A prevents hypertension in rats by inhibiting the activation of MAPK signalling and the impairment in nitric oxide bioavailability due to NOX2-mediated oxidative stress. Thus, LMA may act as a preventive agent for hypertension.

Nobiletin alleviates vascular alterations through modulation of Nrf-2/HO-1 and MMP pathways in l-NAME induced hypertensive rats

Nobiletin alleviates l-NAME-induced vascular dysfunction and remodeling and superoxide production in rats.

Protective effect of Xin-Ji-Er-Kang on cardiovascular remodeling in high salt-induced hypertensive mice

The aim of the present study was to investigate the effects of Xin-Ji-Er-Kang (XJEK) on high salt-induced hypertensive mice. Mice with high-salt diet-induced hypertension were divided into four groups: Control (standard diet alone for 8 weeks), model (diet containing 8% NaCl for 8 weeks and intragastric administration of distilled water for the last 4 weeks), XJEK + high-salt-treated (diet containing 8% NaCl for 8 weeks and intragastric administration of XJEK for the last 4 weeks) and irbesartan + high-salt-treated (diet containing 8% NaCl for 8 weeks with intragastric administration of irbesartan for the last 4 weeks). The hemodynamic index and cardiac pathological changes in the hypertensive mice were then examined. An aortic ring apparatus was used to detect acetylcholine-dependent endothelium relaxation function. Colorimetric analysis was applied to determine serum nitric oxide (NO), superoxide dismutase activity and malondialdehyde content; ELISA was employed to measure brain natriuretic peptide, serum angiotensin II (Ang II), endothelin-1 content and aldosterone; and immunohistochemistry was used to detect the expression of endothelial nitric oxide synthase (eNOS), interleukin (IL)-1β, IL-10 and tumor necrosis factor (TNF)-α in cardiac tissues. XJEK improved the heart systolic and diastolic function, ameliorated hemodynamic parameters and cardiovascular remodeling indices, blunted the cardiac pathological changes and improved endothelial dysfunction (ED) via boosting eNOS activity, promoting NO bioavailability and decreasing serum Ang II content. Furthermore, treatment with XJEK inhibited the increase of IL-1β and TNF-α expression and the decrease of IL-10 expression in cardiac tissues, and ameliorated oxidative stress status. Therefore, XJEK exerted protective effects against high salt-induced hypertension and cardiovascular remodeling in mice via improving ED, restoring pro- and anti-inflammatory factor balance and decreasing oxidative stress.

Effects of glycyrrhizin on the pharmacokinetics of asiatic acid in rats and its potential mechanism

CONTEXT

Asiatic acid has been reported to possess a wide range of pharmacological activities.

OBJECTIVE

This study investigates the effects of glycyrrhizin on the pharmacokinetics of asiatic acid in rats and its potential mechanism.

MATERIALS AND METHODS

The pharmacokinetics of orally administered asiatic acid (20 mg/kg) with or without glycyrrhizin pretreatment (100 mg/kg/day for seven days) were investigated using a LC-MS method. Additionally, the Caco-2 cell transwell model and rat liver microsome incubation systems were used to investigate the potential mechanism of glycyrrhizin's effects on the pharmacokinetics of asiatic acid.

RESULTS

The results showed that the C_max (221.33 ± 21.06 vs. 324.67 ± 28.64 ng/mL), AUC_0-inf (496.12 ± 109.31 vs. 749.15 ± 163.95 μg·h/L) and the t_1/2 (1.21 ± 0.27 vs. 2.04 ± 0.32 h) of asiatic acid decreased significantly (p < 0.05) with the pretreatment of glycyrrhizin. The oral clearance of asiatic acid increased significantly from 27.59 ± 5.34 to 41.57 ± 9.19 L/h/kg (p < 0.05). The Caco-2 cell transwell experiments indicated that glycyrrhizin could increase the efflux ratio of asiatic acid from 1.63 to 2.74, and the rat liver microsome incubation experiments showed that glycyrrhizin could increase the intrinsic clearance rate of asiatic acid from 138.32 ± 11.20 to 221.76 ± 16.85 μL/min/mg protein.

DISCUSSION AND CONCLUSIONS

In conclusion, these results indicated that glycyrrhizin could decrease the system exposure of asiatic acid, possibly by inducing the activity of P-gp or CYP450 enzyme.

Pentacyclic triterpenes: New tools to fight metabolic syndrome

BACKGROUND

Metabolic syndrome is a combination of dysregulated cardiometabolic risk factors characterized by dyslipidemia, impaired glucose tolerance, insulin resistance, inflammation, obesity as well as hypertension. These factors are tied to the increased risk for type-II diabetes and cardiovascular diseases including myocardial infarction in patients with metabolic syndrome.

PURPOSE

To review the proposed molecular mechanisms of pentacyclic triterpenes for their potential use in the metabolic syndrome.

METHODS

PubMed, Science Direct, and Google Scholar database were searched from commencement to April 2018. Following keywords were searched in the databases with varying combinations: "metabolic syndrome", "pentacyclic triterpenes", "transcription factors", "protein kinase", "lipogenesis", "adipogenesis", "lipolysis", "fatty acids", "gluconeogenesis", "cardiovascular", "mitochondria", "oxidative stress", "pancreas", "hepatic cells", "skeletal muscle", "3T3-L1", "C2C12", "obesity", "inflammation", "insulin resistance", "glucose uptake", "clinical studies" and "bioavailability".

RESULTS

Pentacyclic triterpenes, such as asiatic acid, ursolic acid, oleanolic acid, 18β-glycyrrhetinic acid, α,β-amyrin, celastrol, carbenoxolone, corosolic acid, maslinic acid, bardoxolone methyl and lupeol downregulate several metabolic syndrome components by regulating transcription factors, protein kinases and enzyme involved in the adipogenesis, lipolysis, fatty acid oxidation, insulin resistance, mitochondria biogenesis, gluconeogenesis, oxidative stress and inflammation.

CONCLUSION

In vitro and in vivo studies suggests that pentacyclic triterpenes effectively downregulate various factors related to metabolic syndrome. These phytochemicals may serve as promising candidates for clinical trials for the management of metabolic syndrome.

Hesperidin Prevents Nitric Oxide Deficiency-Induced Cardiovascular Remodeling in Rats via Suppressing TGF-β1 and MMPs Protein Expression

Hesperidin is a major flavonoid isolated from citrus fruits that exhibits several biological activities. This study aims to evaluate the effect of hesperidin on cardiovascular remodeling induced by n-nitro l-arginine methyl ester (l-NAME) in rats. Male Sprague-Dawley rats were treated with l-NAME (40 mg/kg), l-NAME plus hesperidin (15 mg/kg), hesperidin (30 mg/kg), or captopril (2.5 mg/kg) for five weeks (n = 8/group). Hesperidin or captopril significantly prevented the development of hypertension in l-NAME rats. l-NAME-induced cardiac remodeling, i.e., increases in wall thickness, cross-sectional area (CSA), and fibrosis in the left ventricular and vascular remodeling, i.e., increases in wall thickness, CSA, vascular smooth muscle cells, and collagen deposition in the aorta were attenuated by hesperidin or captopril. These were associated with reduced oxidative stress markers, tumor necrosis factor-alpha (TNF-α), transforming growth factor-beta 1 (TGF-β1), and enhancing plasma nitric oxide metabolite (NOx) in l-NAME treated groups. Furthermore, up-regulation of tumor necrosis factor receptor type 1 (TNF-R1) and TGF- β1 protein expression and the overexpression of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) was suppressed in l-NAME rats treated with hesperidin or captopril. These data suggested that hesperidin had cardioprotective effects in l-NAME hypertensive rats. The possible mechanism may involve antioxidant and anti-inflammatory effects.

Asiatic acid stabilizes cytoskeletal proteins and prevents TNF-α-induced disorganization of cell-cell junctions in human aortic endothelial cells

Endothelial hyperpermeability represents an initiating step in early atherosclerosis and it often occurs as a result of endothelial barrier dysfunction. Asiatic acid, a major triterpene isolated from Centella asiatica (L.) Urban, has previously been demonstrated to protect against tumor necrosis factor (TNF)-α-induced endothelial barrier dysfunction. The present study aimed to investigate the mechanisms underlying the barrier protective effect of asiatic acid in human aortic endothelial cells (HAECs). The localization of F-actin, diphosphorylated myosin light chain (diphospho-MLC), adherens junctions (AJs) and tight junctions (TJs) was studied using immunocytochemistry techniques and confocal microscopy. Their total protein expressions were examined using western blot analysis. The endothelial permeability was assessed using In Vitro Vascular Permeability Assay kits. In addition, intracellular redistribution of the junctional proteins was evaluated using subcellular fractionation kits. We show that asiatic acid stabilized F-actin and diphospho-MLC at the cell periphery and prevented their rearrangement stimulated by TNF-α. However, asiatic acid failed to attenuate cytochalasin D-induced increased permeability. Besides, asiatic acid abrogated TNF-α-induced structural reorganization of vascular endothelial (VE)-cadherin and β-catenin by preserving their reticulum structures at cell-cell contact areas. In addition, asiatic acid also inhibited TNF-α-induced redistribution of occludin and zona occludens (ZO)-1 in different subcellular fractions. In conclusion, the barrier-stabilizing effect of asiatic acid might be associated with preservation of AJs and prevention of TJ redistribution caused by TNF-α. This study provides evidence to support the potential use of asiatic acid in the prevention of early atherosclerosis, which is initiated by endothelial barrier dysfunction.

Neuroprotective Properties of Asiatic Acid against 5-Fluorouracil Chemotherapy in the Hippocampus in an Adult Rat Model

5-fluorouracil or 5-FU (a chemotherapeutic medication) has been revealed to induce memory deficits in many cancer patients. Asiatic acid (AA) is a triterpenoid extract from Centella asiatica. This compound can ameliorate intracellular oxidative stress caused by chemotherapy drugs. Recent studies have shown that AA is capable of inhibiting neuronal generation and memory deficit produced by 5-FU chemotherapy. This study aimed to assess the molecular mechanisms of AA related to hippocampal neurogenesis and memory in rats receiving 5-FU. Male Sprague Dawley rats were given AA (30 mg/kg) orally and given 5-FU (25 mg/kg) by i.v. injection 5 times. Some rats were given AA for 20 days before and during 15-FU treatment (preventive), some received AA for 20 days after 5-FU treatment (recovery), and some underwent treatment with AA throughout the time of the experiment (throughout) for 40 days. Treatment with 5-FU caused significant reductions in Notch1, sex determining region Y-box 2 (SOX2), nestin, doublecortin (DCX), and nuclear factor erythroid 2-related factor 2 (Nrf2) levels within the hippocampus. In addition, 5-FU significantly increased p21 positive cell number in the subgranular zone (SGZ) and malondialdehyde (MDA) levels in the hippocampus. Administration with both AA and 5-FU in prevention and throughout was able to prevent decreases in Notch1 SOX2, nestin, DCX, and Nrf2 caused by 5-FU. Treatment with AA also led to decreases in p21 positive cells and MDA levels in the hippocampus. These findings exhibit that AA has the ability to counteract the down-regulation of neurogenesis within the hippocampus and memory deficits caused by 5-FU via inhibiting oxidative stress and increasing neuroprotective properties.

Effects of oligomeric grape seed proanthocyanidins on L-NAME-induced hypertension in pregnant mice: Role of oxidative stress and endothelial dysfunction

The aim of this study was to investigate the effects of Grape Seed Proanthocyanidins (GSP) on Nω-Nitro-L-arginine methyl ester-induced hypertension in pregnant mice. Fifty Kunming mice were randomized into control, control + GSP, model, and model + GSP. Three weeks later, the artery systolic blood pressure was examined and the related pathological changes were detected. Aorta relaxation function was assessed by aorta ring apparatus. Blood urea nitrogen and serum creatinine were measured by an automatic biochemistry analyzer. Colorimetric analysis, enzyme-linked immunosorbent assay, immunofluorescence, and western blot were applied to detect related indicator in serum, cardiac, and kidney tissues. The results showed that GSP treatment for 3 weeks could improve cardiovascular and kidney remodeling indexes and decrease blood urea nitrogen and serum creatinine content in serum, as well as could ameliorate oxidative stress status and endothelial dysfunction. Therefore, it is for the first time found that GSP exerts protective effect against Nω-Nitro-L-arginine methyl ester-induced hypertension in pregnant mice, which provided a theoretical basis for potential application in the clinic.

Pharmacological Review on Asiatic Acid and Its Derivatives: A Potential Compound

Natural triterpenes represent a group of pharmacologically active and structurally diverse organic compounds. The focus on these phytochemicals has been enormous in the past few years, worldwide. Asiatic acid (AA), a naturally occurring pentacyclic triterpenoid, is found mainly in the traditional medicinal herb Centella asiatica. Triterpenoid saponins, which are the primary constituents of C. asiatica, are commonly believed to be responsible for their extensive therapeutic actions. Published research work has described the molecular mechanisms underlying the various biological activities of AA and its derivatives, which vary for each chronic disease. However, a compilation of the various pharmacological properties of AA has not yet been done. Herein, we describe in detail the pharmacological properties of AA and its derivatives that inhibit multiple pathways of intracellular signaling molecules and transcription factors that are involved in the various stages of chronic diseases. Furthermore, the pharmacological activities of AA were compared with two natural compounds: curcumin and resveratrol. This review summarizes the research on AA and its derivatives and helps to provide future directions in the area of drug development.

Indonesian herbal medicine prevents hypertension-induced left ventricular hypertrophy by diminishing NADPH oxidase-dependent oxidative stress

Indonesian herbal medicine Centella asiatica, Justicia gendarussa and Imperata cylindrica decoction (CJID) are known to be efficacious for hypertension. Oxidative stress plays an important role in hypertension-induced left ventricular hypertrophy (H-LVH). This study evaluated whether CJID inhibit cardiac remodeling in spontaneously hypertensive rats (SHRs) through mechanism of oxidative stress-related cardiac-NADPH oxidase (NOXs) pathway: NOX1, NOX2 and NOX4. Forty-weeks-old SHRs and normotensive-WKY rats, were both randomly divided into 2 groups: CJID and control. All rats were treated for 5 weeks. Systolic blood pressure (SBP) and heart rate (HR) were measured. LV morphology, function and performance were assessed by histological staining and echocardiography. Serum and cardiac superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were assessed. Cardiac superoxide and hydrogen peroxide (H₂O₂) productions, protein expressions of SOD2, SOD3, NOX1, NOX2 and NOX4 were also determined. We found that SBP and HR were significantly decreased in SHRs-treated group. Echocardiography showed that CJID significantly improved LV morphometry and function. CJID decreased MDA level, but increased SOD activity. Cardiac superoxide and H₂O₂ generation were decreased in SHRs-treated group. CJID caused cardiac SODs expressions to be increased but NOXs expressions to be suppressed. In conclusion, CJID prevents H-LVH by reducing reactive oxygen species production via the NOXs-dependent pathway.

Effect of asiatic acid on the Ang II-AT1R-NADPH oxidase-NF-κB pathway in renovascular hypertensive rats

Asiatic acid, a triterpenoid compound derived from Centella asiatica, has been demonstrated to have antioxidant and anti-inflammatory effects. The present study evaluated the effects of asiatic acid on hemodynamic alterations, renin-angiotensin system (RAS), oxidative stress, and inflammation in 2K-1C hypertensive rats. Renovascular hypertension was induced in male Sprague-Dawley rats and treated with vehicle, asiatic acid (30 mg/kg/day), or captopril (5 mg/kg/day) for 4 weeks. We observed that 2K-1C hypertensive rats exhibited hemodynamic alterations such as high blood pressure, heart rate, hindlimb vascular resistance, and low hindlimb blood flow. Signs of RAS activation, such as increased plasma angiotensin II and serum angiotensin-converting enzyme activity, enhanced AT₁R protein expression, and suppressed AT₂R expression was observed in 2K-1C hypertensive rats. Overproduction of vascular superoxide, high levels of plasma MDA, low levels of plasma nitric oxide metabolites (NOx), and upregulation of gp91^phox protein expression were observed in hypertensive rats. Furthermore, inflammation was observed in hypertensive rats, as evidenced by increased plasma TNF-α, NF-κB, and phospho-NF-κB protein expression. Asiatic acid or captopril alleviated hemodynamic alterations, RAS activation, oxidative stress, and inflammation in 2K-1C hypertensive rats. These findings indicate that asiatic acid is an antihypertensive agent that ameliorates hemodynamic alterations in 2K-1C hypertensive rats. This effect may involve one or both of the following mechanisms: the direct effect of asiatic acid on RAS activation, oxidative stress and inflammation, and/or asiatic acid acting as an ACE inhibitor agent to inhibit the Ang II-AT₁R-NADPH oxidase-NF-κB pathway.

Asiatic acid attenuates renin-angiotensin system activation and improves vascular function in high-carbohydrate, high-fat diet fed rats

Background

In the rat model of high carbohydrate, high fat (HCHF) diet-induced metabolic syndrome (MS), previous studies have found that asiatic acid has an antihypertensive effect. In this study, we investigated effects of asiatic acid on vascular structure, vascular function and renin-angiotensin system (RAS) in HCHF diet-induced MS rats.

Methods

Male Sprague–Dawley rats were divided into three treatment groups for the 15 week study: a control group fed a normal diet, a MS group fed HCHF diet plus 15 % fructose in their drinking water for 15 weeks, and an asiatic acid treated group that received a HCHF diet plus fructose for 15 weeks and also received orally administered asiatic acid (20 mg/kg BW/day) for the final 3 weeks. Vascular structure and function were investigated. AT₁ receptor expression in aortic tissues and eNOS protein expression in the mesenteric arteries were detected. The levels of serum angiotensin (Ang) II, angiotensin converting enzyme (ACE) and plasma norepinephrine (NE) were measured. The differences among treatment groups were analyzed by one-way analysis of variance (ANOVA) followed by post-hoc Bonferroni tests.

Results

At the end of the study, all rats fed a HCHF diet exhibited signs of MS including, hypertension, dyslipidemia and insulin resistance. Vascular remodeling in large and small arteries, overexpression of AT₁ receptor, and high levels of serum Ang II and ACE were also observed in MS group (p < 0.05). Contractile responses to sympathetic nerve stimulation were enhanced relating to high plasma NE level in MS rats (p < 0.05). The response to exogenous NE was not changed in the mesenteric bed. Vasorelaxation responses to acetylcholine were blunted in thoracic aorta and mesenteric beds, which is consistent with downregulation of eNOS expression in MS rats (p < 0.05). Restoration of metabolic alterations, hemodynamic changes, RAS and sympathetic overactivity, increased plasma NE, endothelium dysfunction, and downregulation of eNOS expression was observed in the asiatic acid treated group (p < 0.05). However, asiatic acid failed to alleviate vascular remodeling in MS rats.

Conclusion

Our findings suggest that the observed antihypertensive effect of asiatic acid in MS rats might be related to its ability to alleviate RAS overactivity and improve vascular function with restoration of sympathetic overactivity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1100-6) contains supplementary material, which is available to authorized users.

Synergistic Antihypertensive Effect of Carthamus tinctorius L. Extract and Captopril in L-NAME-Induced Hypertensive Rats via Restoration of eNOS and AT₁R Expression

This study examined the effect of Carthamus tinctorius (CT) extract plus captopril treatment on blood pressure, vascular function, nitric oxide (NO) bioavailability, oxidative stress and renin-angiotensin system (RAS) in N^ω-Nitro-l-arginine methyl ester (l-NAME)-induced hypertension. Rats were treated with l-NAME (40 mg/kg/day) for five weeks and given CT extract (75 or 150 or 300 or 500 mg/kg/day): captopril (5 mg/kg/day) or CT extract (300 mg/kg/day) plus captopril (5 mg/kg/day) for two consecutive weeks. CT extract reduced blood pressure dose-dependently, and the most effective dose was 300 mg/kg/day. l-NAME-induced hypertensive rats showed abnormalities including high blood pressure, high vascular resistance, impairment of acetylcholine-induced vasorelaxation in isolated aortic rings and mesenteric vascular beds, increased vascular superoxide production and plasma malondialdehyde levels, downregulation of eNOS, low level of plasma nitric oxide metabolites, upregulation of angiotensin II type 1 receptor and increased plasma angiotensin II. These abnormalities were alleviated by treatment with either CT extract or captopril. Combination treatment of CT extract and captopril normalized all the abnormalities found in hypertensive rats except endothelial dysfunction. These data indicate that there are synergistic antihypertensive effects of CT extract and captopril. These effects are likely mediated by their anti-oxidative properties and their inhibition of RAS.

Asiatic acid inhibits left ventricular remodeling and improves cardiac function in a rat model of myocardial infarction

Left ventricular remodeling results in cardiac dysfunction and accounts for the majority of the morbidity and mortality following myocardial infarction (MI). The aim of the present study was to investigate the effect of asiatic acid (AA) on cardiac function and left ventricular remodeling in a rat model of MI and explore the underlying mechanisms. Rats were subjected to coronary artery ligation to model MI and orally treated with AA. After 4 weeks, cardiac function was assessed by echocardiography. Cardiomyocyte cross-sectional area was recorded, and the expression levels of a number of inflammatory cytokines were detected using ELISA. The degree of interstitial fibrosis was determined by evaluating the mRNA expression levels of collagen II and III. Western blot analysis was performed to detect the expression levels of total and phosphorylated p38 MAPK and ERK1/2, to investigate whether they are involved in the mechanism underlying the effect of AA on the heart. Rats subjected to MI displayed significantly impaired cardiac function compared with those subjected to a sham procedure, while this change was reversed by treatment with AA. Furthermore, AA markedly inhibited cardiac hypertrophy, reduced the mRNA expression levels of inflammatory cytokines and decreased interstitial fibrosis in the infarct border zone of MI model rats compared with those in vehicle-treated MI model rats. Furthermore, the phosphorylation of p38 MAPK and ERK1/2 was blocked by AA in the MI rats but not in the sham rats. In summary, AA treatment preserved cardiac function and inhibited left ventricular remodeling, potentially by blocking the phosphorylation of p38 MAPK and ERK1/2 in the infarct border zone of the ischemic myocardium, indicating that AA may be a novel candidate for development as a therapy for MI.

Ellagic Acid Prevents L-NAME-Induced Hypertension via Restoration of eNOS and p47phox Expression in Rats

The effect of ellagic acid on oxidative stress and hypertension induced by Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) was investigated. Male Sprague-Dawley rats were administrated with L-NAME (40 mg/kg/day) for five weeks. L-NAME induced high systolic blood pressure (SBP) and increased heart rate (HR), hindlimb vascular resistance (HVR) and oxidative stress. Concurrent treatment with ellagic acid (7.5 or 15 mg/kg) prevented these alterations. Co-treatment with ellagic acid was associated with up-regulation of endothelial nitric oxide synthase (eNOS) protein production and alleviation of oxidative stress as indicated by decreased superoxide production in the vascular tissue, reduced plasma malondialdehyde levels, reduced NADPH oxidase subunit p47phox expression and increased plasma nitrate/nitrite levels. Our results indicate that ellagic acid attenuates hypertension by reducing NADPH oxidase subunit p47phox expression, which prevents oxidative stress and restores NO bioavailability.