In vitro screening of traditional medicines for anti-hypertensive effect based on inhibition of the angiotensin converting enzyme (ACE)

Bioactive molecules from terrestrial and seafood resources in hypertension treatment: focus on molecular mechanisms and targeted therapies

Hypertension (HTN), a complex cardiovascular disease (CVD), significantly impacts global health, prompting a growing interest in complementary and alternative therapeutic approaches. This review article seeks to provide an up-to-date and thorough summary of modern therapeutic techniques for treating HTN, with an emphasis on the molecular mechanisms of action found in substances found in plants, herbs, and seafood. Bioactive molecules have been a significant source of novel therapeutics and are crucial in developing and testing new HTN remedies. Recent advances in science have made it possible to understand the complex molecular mechanisms underlying blood pressure (BP)-regulating effects of these natural substances better. Polyphenols, flavonoids, alkaloids, and peptides are examples of bioactive compounds that have demonstrated promise in influencing several pathways involved in regulating vascular tone, reducing oxidative stress (OS), reducing inflammation, and improving endothelial function. The article explains the vasodilatory, diuretic, and renin-angiotensin-aldosterone system (RAAS) modifying properties of vital plants such as garlic and olive leaf. Phytochemicals from plants are the primary in traditional drug development as models for novel antihypertensive drugs, providing diverse strategies to combat HTN due to their biological actions. The review also discusses the functions of calcium channel blockers originating from natural sources, angiotensin-converting enzyme (ACE) inhibitors, and nitric oxide (NO) donors. Including seafood components in this study demonstrates the increased interest in using bioactive chemicals originating from marine sources to treat HTN. Omega-3 fatty acids, peptides, and minerals obtained from seafood sources have anti-inflammatory, vasodilatory, and antioxidant properties that improve vascular health and control BP. Overall, we discussed the multiple functions of bioactive molecules and seafood components in the treatment of HTN.

Vasorelaxant property of 2-phenyl ethyl alcohol isolated from the spent floral distillate of damask rose (Rosa damascena Mill.) and its possible mechanism

ETHNOBOTANICAL RELEVANCE

Rosa damascena Mill. (Rosaceae), commonly known as damask rose, is an ancient medicinal and perfumery plant used in Traditional Unani Medicine due to various therapeutic effects, including cardiovascular benefits.

AIM OF THE STUDY

This study aimed to evaluate the vasorelaxant effect of the 2-phenyl ethyl alcohol (PEA) isolated from the spent flowers of R. damascena which remain after the extraction of essential oil.

MATERIALS AND METHODS

The freshly collected flowers of R. damascena were hydro-distilled in a Clevenger's type apparatus to extract the rose essential oil (REO). After removing the REO, the spent-flower hydro-distillate was collected and extracted with organic solvents to yield a spent-flower hydro-distillate extract (SFHE), which was further purified by column chromatography. The SFHE and its isolate were characterized by gas chromatography (GC-FID), gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR) techniques. The PEA, isolated from SFHE, was evaluated for vasorelaxation response in conduit blood vessels like rat aorta and resistant vessels like mesenteric artery. The preliminary screening of PEA was done in aortic preparation pre-constricted with phenylephrine. Further, a concentration-dependent relaxation response to PEA has been elicited in both endothelium-intact and endothelium-denuded arterial rings, and the mode of action was explored.

RESULTS

The SFHE revealed the presence of PEA as the main constituent (89.36%), which was further purity by column chromatography to a purity of 95.0%. The PEA exhibited potent vasorelaxation response both in conduit vessels like the rat aorta and resistance vessels like the mesenteric artery. The relaxation response is mediated without any involvement of vascular endothelium. Further, TEA sensitive BKca channel was found to be the major target for PEA-induced relaxation response in these blood vessels.

CONCLUSIONS

The spent flowers of R. damascena, which remain after the extraction of REO, could be used to extract PEA. The PEA possessed marked vasorelaxation properties in both aorta and mesenteric artery and showed promise for development into an herbal product against hypertension.

Angiotensin-converting enzyme inhibitors from plants: A review of their diversity, modes of action, prospects, and concerns in the management of diabetes-centric complications

Angiotensin-converting enzyme (ACE) inhibitors are antihypertensive medications often used in the treatment of diabetes-related complications. Synthetic ACE inhibitors are known to cause serious side effects like hypotension, renal insufficiency, and hyperkalaemia. Therefore, there has been an intensifying search for natural ACE inhibitors. Many plants or plant-based extracts are known to possess ACE-inhibitory activity. In this review, articles focusing on the natural ACE inhibitors extracted from plants were retrieved from databases like Google Scholar, PubMed, Scopus, and Web of Science. We have found more than 50 plant species with ACE-inhibitory activity. Among them, Angelica keiskei, Momordica charantia, Muntingia calabura, Prunus domestica, and Peperomia pellucida were the most potent, showing comparatively lower half-maximal inhibitory concentration values. Among the bioactive metabolites, peptides (e.g., Tyr-Glu-Pro, Met-Arg-Trp, and Gln-Phe-Tyr-Ala-Val), phenolics (e.g., cyanidin-3-O-sambubioside and delphinidin-3-O-sambubioside), flavonoids ([-]-epicatechin, astilbin, and eupatorin), terpenoids (ursolic acid and oleanolic acid) and alkaloids (berberine and harmaline) isolated from several plant and fungus species were found to possess significant ACE-inhibitory activity. These were also known to possess promising antioxidant, antidiabetic, antihyperlipidemic and anti-inflammatory activities. Considering the minimal side effects and lower toxicity of herbal compounds, development of antihypertensive drugs from these plant extracts or phytocompounds for the treatment of diabetes-associated complications is an important endeavour. This review, therefore, focuses on the ACE inhibitors extracted from different plant sources, their possible mechanisms of action, present status, and any safety concerns.

Evaluation of anti-hypertensive activity of ancient Unani cardiovascular drug “Saad Kufi” (Cyperus scariosus) in adrenaline-induced hypertensive rats

Background

Saad Kufi (Cyperus scariosus R.Br) is a hardy grass-like perennial plant that belongs to the family Cyperaceae. Ibn Sina (Avicenna), the most significant thinkers and writers of the Islamic Golden Age first time systematized the individual cardiac drugs in “Risala Advia Qalbia,” which deals with 63 cardiac drugs which are claimed to be beneficial for heart ailments as well as for psychiatric ailments. He described Saad as a root of a plant that is nodular, long, and slender and resembles the wheat plant. The roots which used medicinally are thick, elongated, slender, and color black and has an aromatic smell with a pungent taste. An antihypertensive effect of 50% ethanolic extract of Saad Kufi (Cyperus scariosus R.Br) [EESK] was evaluated in adrenaline-induced hypertension in Wistar albino rats. The induction of systolic blood pressure (SBP) and the percentage of inhibition was measured in EESK (15 and 25 mg/100 g, orally) with standard as Metoprolol (0.5 mg/100 g) orally, using tail-cuff apparatus with AD instrument power lab to evaluate the antihypertensive effect.

Results

EESK significantly decreased the induction in SBP as compared to disease control rats (p < 0.05), and there is a significant increase in the percentage of inhibition in SBP in EESK and metoprolol-treated rats as compared to the disease control group (p < 0.05).

Conclusion

Result data suggest that EESK possess significant antihypertensive activity in adrenaline-induced hypertensive rats.

Bioactivity of the Geranium Genus: A Comprehensive Review

BACKGROUND

Plants from the Geranium genus, which comprises about 400 species, have been used since ancient times in the practice of traditional medicines throughout the world. Therefore, herbal preparations based on Geranium species have found wide usage for the treatment of a variety of ailments. The aim of this work is to present a review, as comprehensive as possible, of the studies concerning different biological activities of Geranium species.

METHODS

Relevant data were obtained through systematic computer searches from major reputed scientific databases, particularly Web of Science and Scopus. Occasionally, information issued in primary sources not covered by these databases was also included provided published as peer-reviewed literature. This review covers the literature disclosed till the end of 2018.

RESULTS

Accompanying the increasing interest in herbal medicines in general, the evaluation of the biological properties of medicinal plants from the Geranium genus has been addressed thoroughly, mostly over the last two decades. Geranium species are endowed with a number of different biological activities. Herein, we present a survey of the results of the studies concerning these different biological activities.

CONCLUSION

Most studies found in the literature effectively contribute to scientifically validate the beneficial properties of Geranium plants claimed by traditional medicines and medical herbalism and demonstrate that many of them possess evident therapeutic properties.

Pharmacological Evaluation of Gut Modulatory and Bronchodilator Activities of Achyranthes aspera Linn

Achyranthes aspera L. is traditionally used to relieve constipation, diarrhea, and asthma. Its crude extract (Aa.Cr) was evaluated through in vivo and ex vivo experiments to rationalize these medicinal uses of A. aspera and to provide their scientific basis. Aa.Cr, at 3 and 10 mg/kg, increased fecal output, similar to castor oil, whereas at 30, 100, 300, and 700 mg/kg, it protected against castor oil-induced diarrhea in mice when administered orally. Aa.Cr caused spasmogenic effect on rabbit jejunum and guinea pig ileum preparations, which was partially inhibited by atropine while completely blocked by cyproheptadine preincubation. Aa.Cr also relaxed high K⁺ (80 mM)-induced contraction in rabbit jejunum. Aa.Cr inhibited CCh (100 μg/kg)-induced bronchospasm in rats, similar to aminophylline. Like dicyclomine, Aa.Cr relaxed high K⁺ and CCh (1 μM)-induced contractions in guinea pig trachea and caused rightwards parallel shift of CCh concentration-response curves at the lower concentrations followed by non-parallel shift at the higher concentrations. On activity-directed fractionation, spasmogenic and spasmolytic activities of Aa.Cr were concentrated in aqueous and organic fraction, respectively. This study suggests the presence of dose-specific laxative and antidiarrheal effects in A. aspera, possibly mediated through cyproheptadine-sensitive receptors and dual cholinergic and calcium channel blockade, respectively. The latter combination is also a suggested mechanism underlying its bronchodilator effect. Copyright © 2017 John Wiley & Sons, Ltd.

Review of Angiotensin-converting Enzyme Inhibitory Assay: Rapid Method in Drug Discovery of Herbal Plants

The renin-angiotensin-aldosterone system is a signaling pathway which responsible in the blood pressure regulation. Angiotensin-converting enzyme (ACE) is one of the key elements responsible for the hypertensive mechanism. It converts angiotensin-I to angiotensin-II. The discovery history of the ACE inhibitory activity assay method has been through a long stage for decades and development continues until today. The ACE inhibitory activity has become an effective screening method in the search for new antihypertensive agents from herbal plants. Some of in vitro assay methods were used to examine the activity of ACE inhibitors based on the substrate usage, such as; Cushman and Cheung Method using a substrate hippuryl-histidyl-leucine (HHL), Holmquist method using a substrate furanacryloyl-tripeptide, Elbl and Wagner method using a substrate benzoil-[l-14C] glicyl-L-histidine-L-leucine, Carmel and Yaron method using a substrate o-aminobenzoylglycyl-p-nitrophenylalanilproline, and Lam method using 3-hydroxybutyrylglycyl-glycyl-glycine as substrate. Several different methods to measure the results of enzymatic reactions or separating substrate with products, including spectrophotometric, fluorometric, high-performance liquid chromatography, electrophoresis, and radiochemistry. Application of the test method for screening the ACE inhibitors activity and investigation of active compounds from natural products can be done easily with this method, it is very helpful in research because the results obtained are simple, accurate, and rapid.

Inhibition of Angiotensin Converting Enzyme, Angiotensin II Receptor Blocking, and Blood Pressure Lowering Bioactivity across Plant Families

Hypertension is a major risk factor for coronary heart disease, kidney disease, and stroke. Interest in medicinal or nutraceutical plant bioactives to reduce hypertension has increased dramatically. The main biological regulation of mammalian blood pressure is via the renin-angiotensin-aldosterone system. The key enzyme is angiotensin converting enzyme (ACE) that converts angiotensin I into the powerful vasoconstrictor, angiotensin II. Angiotensin II binds to its receptors (AT1) on smooth muscle cells of the arteriole vasculature causing vasoconstriction and elevation of blood pressure. This review focuses on the in vitro and in vivo reports of plant-derived extracts that inhibit ACE activity, block angiotensin II receptor binding and demonstrate hypotensive activity in animal or human studies. We describe 74 families of plants that exhibited significant ACE inhibitory activity and 16 plant families with potential AT1 receptor blocking activity, according to in vitro studies. From 43 plant families including some of those with in vitro bioactivity, the extracts from 73 plant species lowered blood pressure in various normotensive or hypertensive in vivo models by the oral route. Of these, 19 species from 15 families lowered human BP when administered orally. Some of the active plant extracts, isolated bioactives and BP-lowering mechanisms are discussed.

Phytochemical and in vitro and in vivo biological investigation on the antihypertensive activity of mango leaves (Mangifera indica L.)

AIMS

The aim of this study was to investigate the antihypertensive effect of leaves Mangifera indica L. using in vitro and in vivo assays.

METHODOLOGY

The ethanol extract of leaves of M. indica was fractionated to dichloromethanic, n-butyl alcohol and aqueous fractions. The chemical composition of ethanolic extract and dichloromethanic fraction were evaluated by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Antioxidant activity was evaluated in the DPPH scavenging activity assay. Angiotensin-converting enzyme (ACE) inhibitory activity was investigated using in vitro and in vivo assays. The chronic antihypertensive assay was performed in spontaneously hypertensive rats (SHRs) and Wistar rats treated with enalapril (10 mg/kg), dichloromethanic fraction (100 mg/kg; twice a day) or vehicle control for 30 days. The baroreflex sensitivity was evaluated through the use of sodium nitroprusside and phenylephrine. Cardiac hypertrophy was evaluated by morphometric analysis.

RESULTS

The dichloromethanic fraction exhibited the highest flavonoid, total phenolic content and high antioxidant activity. Dichloromethanic fraction elicited ACE inhibitory activity in vitro (99 ± 8%) similar to captopril. LC-MS/MS analysis revealed the presence of ferulic acid (48.3 ± 0.04 µg/g) caffeic acid (159.8 ± 0.02 µg/g), gallic acid (142.5 ± 0.03 µg/g), apigenin (11.0 ± 0.01 µg/g) and quercetin (203.3 ± 0.05 µg/g). The chronic antihypertensive effects elicited by dichloromethanic fraction were similar to those of enalapril, and the baroreflex sensitivity was normalized in SHR. Plasma ACE activity and cardiac hypertrophy were comparable with animals treated with enalapril.

CONCLUSIONS

Dichloromethanic fraction of M. indica presented an antihypertensive effect, most likely by ACE inhibition, with benefits in baroreflex sensitivity and cardiac hypertrophy. Altogether, the results of the present study suggest that the dichloromethanic fraction of M. indica leaves may have potential as a promoting antihypertensive agent.

Reasons why Thai patients with chronic kidney disease use or do not use herbal and dietary supplements

BACKGROUND

Despite a high prevalence of herbal and dietary supplement use (HDS) in pre-dialysis patients, the reasons are unknown as to why they decide to use HDS. Objectives of the cross-sectional and qualitative studies were to determine reasons for the use and non-use of HDS in Thai patients with chronic kidney disease (CKD).

METHODS

This prospective study recruited 421 patients with stage 3-5 CKD from two kidney clinics in Thailand, and 357 were followed up regarding their HDS use over 12 months. Patients receiving renal replacement therapy at baseline were excluded. Participants were interviewed at baseline and in the twelfth month regarding their HDS use, and reasons for their use or non-use of HDS. Among HDS users, 16 patients were enrolled in a qualitative study and were interviewed using eight-open ended questions about reasons for HDS use. Descriptive and thematic analyses were performed.

RESULTS

Thirty-four percent of patients with CKD consistently used HDS over the 12 months and 17% of all patients intermittently took them during the follow-up period. At baseline, family or friends' recommendation was the most common reason for HDS use (35%), followed by having a perception of benefits from using HDS (24%). During the follow-up period, perceived benefits of HDS was a frequently reported reason for either continuing with HDS use (85%) or starting to use HDS (65%). Negative experience from using HDS influenced patients to stop using them (19%). Although the main reason for non-use of HDS was trust in a doctor or effectiveness of conventional medicine (32%), doubt about the benefits from HDS or concerns about negative effects were frequently reported reasons for non-use (23%). Doctor's recommendations to avoid using HDS were the main influence for non-users (19%) and for those who had stopped using HDS (23%). The media and patients' social network had an impact on HDS use.

CONCLUSIONS

Patients who perceived benefits from HDS use were more likely to use HDS, whilst non-users had negative attitudes towards HDS. Health professionals therefore should educate patients and their relatives about the risks and benefits from using HDS.

Effect ofVaccinium ashei readeLeaves on Angiotensin Converting Enzyme Activityin Vitroand on Systolic Blood Pressure of Spontaneously Hypertensive Ratsin Vivo

The hypotensive effects of Vaccinium ashei reade (blueberry) leaves were studied in vitro and in vivo. Blueberry leaf showed a strong inhibitory effect on angiotensin-converting enzyme activity in vitro. Additionally, feeding of blueberry leaf suppressed the development of essential hypertension in spontaneously hypertensive rats in vivo. These results promise the use of blueberry leaf as a source of dietary hypotensive components.

Traditional chinese medicine syndromes for essential hypertension: a literature analysis of 13,272 patients

Background. To simplify traditional Chinese medicine syndrome differentiation and allow researchers to master syndrome differentiation for hypertension, this paper retrospectively studied the literature and analyzed syndrome elements corresponding to hypertension syndromes. Methods. Six databases including PubMed, EMBASE, Chinese Bio-Medical Literature Database, Chinese National Knowledge Infrastructure, Chinese Scientific Journal Database, and Wan-fang Data were searched from 1/January/2003 to 30/October/2013. We included all clinical literature testing hypertension syndromes and retrospectively studied the hypertension literature published from 2003 to 2013. Descriptive statistics calculated frequencies and percentages. Results. 13,272 patients with essential hypertension were included. Clinical features of hypertension could be attributed to 11 kinds of syndrome factors. Among them, seven syndrome factors were excess, while four syndrome factors were deficient. Syndrome targets were mainly in the liver and related to the kidney and spleen. There were 33 combination syndromes. Frequency of single-factor syndromes was 31.77% and frequency of two-factor syndromes was 62.26%. Conclusions. Excess syndrome factors of hypertension patients include yang hyperactivity, blood stasis, phlegm turbidity, internal dampness, and internal fire. Deficient syndrome factors of hypertension patients are yin deficiency and yang deficiency. Yin deficiency with yang hyperactivity, phlegm-dampness retention, and deficiency of both yin and yang were the three most common syndromes in clinical combination.

Inhibitory effect of ethyl acetate extract of Aristolochia yunnanensis on cardiac fibrosis through extracellular signal-regulated kinases 1/2 and transforming growth factor β/small mother against decapentaplegic signaling pathways

Aristolochia yunnanensis, known as Nan Mu Xiang in traditional Chinese medicine, has long been used to treat hypertension and chest pain. In this study, the effect of ethyl acetate extract of Nan Mu Xiang (NMX) on cardiac fibrosis was assessed in vitro by cultured adult rat cardiac fibroblasts with angiotensin II (AngII) stimulation, and in vivo by rats with abdominal aorta constriction (AAC). In cultured adult rat cardiac fibroblasts stimulated by AngII, NMX inhibited cardiac fibroblast proliferation, reduced the expression of fibronectin, α-smooth muscle actin (α-SMA), and transforming growth factor β (TGF-β) in a dose-dependent manner; and suppressed AngII-induced phosphorylation of extracellular signal-regulated kinase (ERK)1/2, C- rapidly accelerated fibrosarcoma (C-Raf), and small mother against decapentaplegic (Smad) 2. Similar results were also observed in AAC rats with intraperitoneal injection of NMX, which not only ameliorated myocardial fibrosis, but also improved cardiac function. The therapeutic effect of NMX on myocardial fibrosis is attributed mainly to the inhibition of ERK and the TGF-β/Smad signaling pathways. NMX may be a promising potential drug candidate for myocardial fibrosis.

Asiatic acid alleviates hemodynamic and metabolic alterations via restoring eNOS/iNOS expression, oxidative stress, and inflammation in diet-induced metabolic syndrome rats

Asiatic acid is a triterpenoid isolated from Centella asiatica. The present study aimed to investigate whether asiatic acid could lessen the metabolic, cardiovascular complications in rats with metabolic syndrome (MS) induced by a high-carbohydrate, high-fat (HCHF) diet. Male Sprague-Dawley rats were fed with HCHF diet with 15% fructose in drinking water for 12 weeks to induce MS. MS rats were treated with asiatic acid (10 or 20 mg/kg/day) or vehicle for a further three weeks. MS rats had an impairment of oral glucose tolerance, increases in fasting blood glucose, serum insulin, total cholesterol, triglycerides, mean arterial blood pressure, heart rate, and hindlimb vascular resistance; these were related to the augmentation of vascular superoxide anion production, plasma malondialdehyde and tumor necrosis factor-alpha (TNF-α) levels (p<0.05). Plasma nitrate and nitrite (NOx) were markedly high with upregulation of inducible nitric oxide synthase (iNOS) expression, but dowregulation of endothelial nitric oxide synthase (eNOS) expression (p<0.05). Asiatic acid significantly improved insulin sensitivity, lipid profiles, hemodynamic parameters, oxidative stress markers, plasma TNF-α, NOx, and recovered abnormality of eNOS/iNOS expressions in MS rats (p<0.05). In conclusion, asiatic acid improved metabolic, hemodynamic abnormalities in MS rats that could be associated with its antioxidant, anti-inflammatory effects and recovering regulation of eNOS/iNOS expression.

Angiotensin Converting Enzyme Inhibition Activity of Fennel and Coriander Oils from India

Foeniculum vulgare Mill and Coriandrum sativum L. are very popular spices in Indian kitchens. The present study was an attempt to evaluate the angiotensin converting enzyme (ACE) inhibition and antioxidant activity of the standardized oils of F. vulgare and C. sativum by an UV method using hippuryl-L-histidyl-L-leucine (HHL) as substrate. Standardization of the oils and identification of the chemical-markers (linalool and anethole) present in them was performed through HPLC and GC-MS. Coriander oil showed the higher ACE inhibition with an IC50 value of 34.8 ± 2.3 μg/mL, than fennel oil with an IC50 value of 40.7 ± 3.5 μg/mL. Both oils showed strong DPPH radical scavenging activity. This finding suggests that coriander and fennel oils can be potential leads for the management of hypertension as an ACE inhibitor.

Zingiber officinale extract exhibits antidiabetic potential via modulating glucose uptake, protein glycation and inhibiting adipocyte differentiation: an in vitro study

BACKGROUND

Ginger, the rhizome of Zingiber officinale Roscoe (Zingiberaceae), a perennial herbaceous plant is native to Southern Asia. Study was aimed to evaluate antioxidant and antidiabetic potential of ginger extract and its characterization. Possible mode of action to elicit antidiabetic activity was also evaluated.

METHODS AND RESULTS

Ethyl acetate extract of ginger (EAG) was evaluated for its antioxidant activity in terms of DPPH radical scavenging potential with an IC₅₀ value of 4.59 µg/ml. Antidiabetic activity of EAG was evaluated by estimating antiglycation potential (IC₅₀ 290.84 µg/ml). HPLC profiling of EAG revealed the presence of phenolic components, gingerol and shoagol as major constituents. After determining sub-toxic concentration of EAG (50 µg/ml), efficacy of extract to enhance glucose uptake in cell lines were checked in L6 mouse myoblast and myotubes. EAG was effective at 5 µg/ml concentration in both cases. Antibody based studies in treated cells revealed the effect of EAG in expressing Glut 4 in cell surface membrane compared to control.

CONCLUSION

The antidiabetic effect of ginger was experimentally proved in the study and has concluded that the activity is initiated by antioxidant, antiglycation and potential to express or transport Glut4 receptors from internal vesicles.

Aqueous extract of Boerhaavia diffusa root ameliorates ethylene glycol-induced hyperoxaluric oxidative stress and renal injury in rat kidney

INTRODUCTION

Boerhaavia diffusa Linn. (Nyctaginaceae) is widely used in traditional Indian medicines against renal afflictions including calcium oxalate (CaOx) urolithiasis and is known for antioxidant activity.

OBJECTIVE

The present study was designed to investigate the ameliorating effect of aqueous extract of B. diffusa roots (BDE) in hyperoxaluric oxidative stress and renal cell injury.

MATERIAL AND METHODS

In vitro antioxidant activity of BDE was estimated in terms of total phenolic content and 1,1-diphenyl-2-picryl hydrazyl free radical scavenging activity. Wistar albino rats were given 0.75% v/v ethylene glycol in drinking water to induce chronic hyperoxaluria and simultaneously BDE was given to nephrolithiasic treated rats at the dose of 100 and 200 mg/kg b.w. orally for 28 days. Urinary volume, oxalate, serum creatinine, blood urea nitrogen (BUN), malondialdehyde (MDA) and antioxidant enzyme (SOD, CAT, GST, GPx) were evaluated.

RESULTS AND DISCUSSION

BDE extract was found to posses a high total phenolic content and exhibited significant free radicals scavenging activity. Oxalate excretion significantly increased in hyperoxaluric animals as compared to control which was protected in BDE-treated animals. BDE treatment significantly reduced level of MDA and improved the activity of antioxidant enzymes followed by reduction in BUN and serum creatinine. In addition, BDE reduced the number of CaOx monohydrate crystals in the urine. Histological analysis depicted that BDE treatment inhibited deposition of CaOx crystal and renal cell damage.

CONCLUSION

The present study reveals that antioxidant activity of BDE significantly protects against hyperoxaluric oxidative stress and renal cell injury in urolithiasis.

Evaluation of antidiabetic potential of selected traditional Chinese medicines in STZ-induced diabetic mice

AIMS

Traditional Chinese medicine (TCM) has been used for treating complex chronic diseases owing to their fewer side-effects, better patient tolerance and relatively less cost. The present work was carried out to study the anti-diabetic efficacy and mechanisms of 34 TCMs.

MATERIALS AND METHODS

Streptozotocin (STZ)-diabetic mice were orally administrated with corresponding herbal solution once a day for 4 weeks. At the end of experiment, the level of plasma glucose, malondialdehyde (MDA), the activity of superoxide dismutase (SOD) and the serum aldose reductase (AR) were determined, the effects of TCM extract on α-glucosidase and angiotensin-converting enzyme (ACE) in vitro were also evaluated.

RESULTS

13 out of the 34 herbs showed a statistically significant plasma glucose lowering action compared with the diabetic control group. Biochemical analysis revealed that Atractylodes macrocephala, Codonopsis pilosula, Dioscorea opposite, Flos lonicerae and Pueraria lobata may retard the progression of diabetes via reduce the blood glucose level and prevent the increase of AR activity. Other tested herbs, such as Ramulus cinnamomi, Cinnamomum cassia, and Eucommia ulmoides, showed the antidiabetic ability by either prevent the decrease in SOD activity or suppress the increase of MDA. Zymologic assay reveals that Pueraria lobata and Anemarrhena asphodeloides showed the highest inhibition against α-glucosidase and ACE respectively. Interestingly, the post-treatment glucose levels and AR activity were positively correlated with kidney/body weight of 34 herbs treated diabetic mice (p = 0.02, 0.04 respectively).

CONCLUSIONS

Several potential antidiabetic herbs derived from Chinese traditional pharmacopeia such as Dioscorea opposite, Pueraria lobata, Codonopsis pilosula and Ramulus cinnamomi, have been found to exert a beneficial action on diabetes and diabetic complications via multi-mechanisms.

An efficient plant regeneration system through callus for Pseudarthria viscida (L.) Wright and Arn., a rare ethnomedicinal herb

The purpose of this study was to develop a protocol to induce high frequency of callus and subsequent plantlet regeneration for Pseudarthria viscida; an important medicinal plant. The cotyledonary node and young leaf pieces (1 × 0.5 cm, length × breadth) were used as explants for callus induction and subsequent shoot regeneration and adventitious roots induction from the shoots. The best results were achieved on the following media: (1) 96 % callus induction from cotyledonary node explants on MS medium supplemented with 1.5 mgl(-1) 2, 4 dichlorophenoxyacetic acid (2, 4-D) and 0.5 mgl(-1) 1-naphthalene acetic acid (NAA), (2) 97 % shoot regeneration from cotyledonary node derived calli with an average of 44.9 shoots per explant on MS medium fortified with 3.0 mgl(-1) N6-benzylaminopurine (BA) and 1 mgl(-1) NAA,37 (3) 98 % rooting with an average number of 3.3 roots per shoot on MS medium containing indole-3-butyric acid (IBA) or NAA (0.5-4 mgl(-1)) after 45 days. The plantlets were transferred to the field after acclimatization. Of the 40 plantlets transplanted to the soil, 29 survived (72.5 %).

Angiotensin-converting enzyme inhibitory activity of Viscum triflorum is host plant-dependent

CONTEXT

Viscum triflorum DC. (Viscaceae) is a hemiparasitic plant used in traditional medicine on Réunion Island as a remedy to treat hypertension.

OBJECTIVE

The in vitro angiotensin-converting enzyme (ACE) inhibitory activity of extracts of V. triflorum and the corresponding host plant species were examined to evaluate the use as a remedy against hypertension, and to investigate whether the host plants have an influence on the activity.

MATERIALS AND METHODS

Aqueous, ethanol and acetone extracts of 24 leaf samples of V. triflorum and the corresponding host plants, representing 10 plant species, were prepared. The ACE inhibitory activities of the extracts were measured by HPLC using dansyltriglycine as substrate.

RESULTS AND CONCLUSION

Water extracts of Viscum samples from only two of the 10 host plants, namely Acacia heterophylla Willd. (Fabaceae) and Sophora denudata Bory (Fabaceae), showed significant inhibitory activity, ≥ 50% inhibition in a concentration of 0.33 mg crude plant extract in 1 mL test solution. From the two mentioned host plant species activity was only detected in the water extract from one of the six samples of A. heterophylla. Three host species showed pronounced activity without any detection of activity in the samples of V. triflorum. The results support the traditional use provided that V. triflorum is collected from A. heterophylla or S. denudata.

Evaluation of the effects of Olea europaea L. subsp. africana (Mill.) P.S. Green (Oleaceae) leaf methanol extract against castor oil-induced diarrhoea in mice

OBJECTIVES

Olea europaea L. subsp. africana (Mill.) P.S. Green is widely used in South Africa by traditional medicine practitioners to treat diarrhoea. However, little is known scientifically about this South African species in the treatment of diarrhoea. The main aim of the study therefore was to investigate the antidiarrhoeal effect of the leaf methanol extract of the plant species in mice.

METHODS

The antidiarrhoeal activity of the leaf methanol extract of O. europaea subsp. africana was studied using a castor oil-induced diarrhoeal test. The antipropulsive activity of the plant extract was also investigated using the charcoal meal transit test. Standard methods were used to investigate the acute toxicity and effect of O. europaea subsp. africana on castor oil-induced intraluminal fluid accumulation.

RESULTS

Leaf methanol extract of O. europaea subsp. africana and loperamide, a standard antidiarrhoeal drug, significantly reduced the number of diarrhoeal episodes induced by castor oil, significantly decreased the stool mass, significantly delayed the onset of the diarrhoea and protected the animals against castor oil-induced diarrhoea. Both O. europaea subsp. africana and loperamide significantly decreased the gastrointestinal transit of charcoal meal and castor oil-induced intraluminal fluid accumulation in mice. The LD50 value was found to be 3475 mg/kg (p.o.).

CONCLUSIONS

The results obtained suggest that the leaf methanol extract of O. europaea subsp. africana has an antidiarrhoeal property and that, given orally, it may be non-toxic and/or safe in mice.

Development of a fast liquid chromatography/mass spectrometry screening method for angiotensin-converting enzyme (ACE) inhibitors in complex natural mixtures like snake venom

A new robust high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS)-based screening method for angiotensin-converting enzyme (ACE)-inhibiting substances in crude samples is described. The ACE assay is carried out in a typical offline setup by incubation of the samples with ACE and angiotensin I (AI), followed by stopping the reaction with acetonitrile containing val(5)-AI serving as internal standard (I.S.). AI and the product angiotensin II (AII) are extracted from the incubation mixture by turbulent-flow chromatography (TFC) applied in backflush mode as online solid-phase extraction and are directly quantified by ESI(+)-MS. The presence of ACE inhibitors (ACEi) is detected by an increase in AI signal intensity and a corresponding decrease of AII signal, as compared to the blank assay. The overall time of analysis of the TFC/ESI-MS method was 5 min, thus making the described setup suitable for a rapid screening method. The assay was validated using a known ACE inhibitor and the IC(50) values found were in good accordance with a common HPLC/UV method and literature data. The method was successfully applied for the screening of size-exclusion chromatography fractions of the venom of the pitviper Bothrops moojeni. Three of 18 analyzed fractions inhibited ACE, due to peptides present as components of this snake venom. These compounds were extracted from the two most-active fractions by means of TFC and isolated by means of HPLC. Three peptides with ACE inhibitory activity were characterized and their structures were elucidated with ESI-MS/MS-based de novo sequencing to be ZKWPPGKVPP, ZKWPRPGPEIPP and ZNWPRPGPEIPP, respectively (Z = pyroglutamic acid).

Angiotensin-converting enzyme inhibition by Brazilian plants

The potential antihypertensive activity of Brazilian plants was evaluated in vitro by its ability to inhibit the angiotensin-converting enzyme (ACE). Forty-four plants belonging to 30 families were investigated. Plants were selected based on their popular use as antihypertensive and/or diuretics. The following plants presented significant ACE inhibition rates: Calophyllum brasiliense, Combretum fruticosum, Leea rubra, Phoenix roebelinii and Terminalia catappa.

Inhibition of angiotensin converting enzyme (ACE) by flavonoids isolated from Ailanthus excelsa (Roxb) (Simaroubaceae)

In our screening program for antihypertensive properties of plants, the leaves of Ailanthus excelsa (Roxb), a plant used in Egyptian traditional medicine, were analysed. Chromatographic separation of A. excelsa MeOH extract yielded six flavonoids for the first time from this species, namely apigenin, luteolin, kaempferol-3-O-alpha-arabinopyranoside, kaempferol-3-O-beta-galactopyranoside, quercetin-3-O-alpha-arabinopyranoside and luteolin-7-O-beta-glucopyranoside. The in vitro hypotensive activities of the MeOH extract and the isolated compounds were elucidated. All the flavonoids tested exhibited ACE inhibitory activity, in particular the most active compound was kaempferol-3-O-beta-galactopyranoside with an IC(50) value of 260 microm.

The hypotensive mechanisms for the aqueous stem bark extract of Musanga cecropioides in Sprague-Dawley rats

The present study was designed to evaluate the hypotensive properties and the mechanisms of action of the stem bark aqueous extract of Musanga cecropioides R.Br. Apud Tedlie (MCW) in anesthetized rats of Sprague-Dawley strain, through an invasive direct blood pressure measuring procedure. Thirty adult rats, weighing 150-230 g, were grouped into five groups of six rats each. The effects of the intravenous graded doses (0.0005-0.05 mg/kg) of the extract on the blood pressure indices were investigated. Its underlying mechanisms were also studied using additional five groups of rats. The results showed that the extract caused a dose dependent fall in the systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure and heart rate of the rats. Bilateral carotid artery occlusion (BCO) caused a reflex increase in mean arterial pressure and heart rate which were significantly attenuated by the extract injection. Angiotensin Converting Enzyme (ACE) blockade with 5 mg/kg of Captopril and cholinergic blockade with 0.2 mg/kg of atropine significantly attenuated the hypotensive response to MCW. However, the pattern of MAP fall in rats pretreated with a combination of Promethazine (1 mg/kg) and Cimetidine (15 mg/kg) was not significant. The results of the study was able to demonstrate dose dependent hypotensive effect of MCW and that its vasorelaxant effects may be through inhibition of sympathetic, cholinergic control of the arterial pressure and most significantly through ACE blockade. However, the phytochemical, elemental and toxicological studies of this potential antihypertensive still needed to be investigated.

Adriamycin induced myocardial failure in rats: Protective role of Centella asiatica

Generation of reactive oxygen species and mitochondrial dysfunction has been implicated in adriamycin induced cardiotoxicity. Mitochondrial dysfunction is characterized by the accumulation of oxidized lipids, proteins and DNA, leading to disorganization of mitochondrial structure and systolic failure. The present study was aimed to evaluate the efficacy of Centella asiatica on the mitochondrial enzymes; mitochondrial antioxidant status in adriamycin induced myocardial injury. Adriamycin (2.5 mg/kg body wt., i.p.) induced mitochondrial damage in rats was assessed in terms of decreased activities (p<0.05) of cardiac marker enzymes (lactate dehydrogenase, creatine phosphokinase, amino transferases), TCA cycle enzymes (isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, malate dehydrogenase, respiratory marker enzymes (NADH-dehydrogenase, cytochrome-C-oxidase), mitochondrial antioxidant enzymes (GPx, GSH, SOD,CAT) and increased (p<0.05) level of lipid peroxidation. Mitochondrial damage was confirmed by transmission electron microscopic examination. Pre-co-treatment with aqueous extract of Centella asiatica (200 mg/kg body wt, oral) effectively counteracted the alterations in mitochondrial enzymes and mitochondrial defense system. In addition, transmission electron microscopy study confirms the restoration of cellular normalcy and accredits the cytoprotective role of Centella asiatica against adriamycin induced myocardial injury. Our results demonstrated elevated oxidative stress and mitochondrial dysfunction in adriamycin treated rats. Moreover, on the basis of our findings it may be concluded that the aqueous extract of C. asiatica not only possesses antioxidant properties but it may also reduce the extent of mitochondrial damage.

ACE inhibitory activity in enzymatic hydrolysates of insect protein

In this paper, ACE inhibitory activity in insect protein hydrolyzed by various enzymes (gastrointestinal proteases, alcalase, and thermolysin) is reported for the first time. Four insects of different insect orders were tested: Spodoptera littoralis (Lepidoptera), Bombyx mori (Lepidoptera), Schistocerca gregaria (Orthoptera), and Bombus terrestris (Hymenoptera). ACE inhibitory activity was measured by two different methods: a spectrophotometric method using FAPGG (2-furanacryloyl-phenylalanyl-glycyl-glycine) as substrate, and an HPLC method using dansyltriglycine (DTG) as substrate. Hydrolysis of the insect protein resulted in an increased ACE inhibitory activity. Overall, the highest ACE inhibitory activity was obtained after gastrointestinal digestion. These results suggest a role for insect protein as antihypertensive component in functional foods and nutraceuticals. Furthermore, the ACE inhibitory activity differed according to the method used. As a consequence, there is a need to standardize methodologies to evaluate ACE inhibitory activity.

Validation of a colorimetric assay for the in vitro screening of inhibitors of angiotensin-converting enzyme (ACE) from plant extracts

A new method for the in vitro screening of plant extracts with potential angiotensin-converting enzyme (ACE) inhibitory activity is proposed. The method is based on the cleavage of the substrate hippuryl-glycyl-glycine by ACE and subsequent reaction with trinitrobenzenesulfonic acid to form 2,4,6-trinitrophenyl-glycyl-glycine, whose absorbance is determined at 415 nm in a microtitre plate reader. Rabbit lung dehydrated by acetone was employed as an enzyme source. Validation of the method showed satisfactory intra-day (CV = 7.63%) and inter-day precision (CV = 13.61%), recovery (97-102.1%), sensitivity (IC50 = 14.1 nmol/l) and linearity in the range 7.5-120 mmol/l of glycyl-glycine (r2 = 0.9921). Besides, the method showed good correlation with a HPLC assay already established for the screening of ACE inhibitors (r = 0.9935 and 0.9034, respectively, for captopril solutions and for plant extracts). The method involves only inexpensive reagents and apparatus.

Antifungal properties of Pseudarthria viscida

The extracts of leaf, root, stem, and the callus obtained from Pseudarthria viscida showed significant inhibitory activity against some fungal pathogens causing major diseases in crop plants and stored food grains.

Rapid detection and identification of angiotensin-converting enzyme inhibitors by on-line liquid chromatography–biochemical detection, coupled to electrospray mass spectrometry

An analytical method based on on-line liquid chromatography-biochemical detection (LC-BCD) coupled to electrospray mass spectrometry was developed for the detection and identification of angiotensin-converting enzyme (ACE) inhibitors in complex mixtures, such as hydrolyzed whey proteins. ACE inhibitory activity was detected by coupling a homogeneous, substrate conversion based bioassay on-line to high-performance liquid chromatography (HPLC). Chemical information was obtained by directing part of the HPLC effluent towards a mass spectrometer. After correlating the biochemical and chemical data, the accurate molecular masses of the bioactive peptides were used as search queries in protein databases. Combined with the recorded mass spectrometry (MS)-MS fingerprints, bioactive peptides were selected from the database search results. The results of LC-BCD-MS analyses were verified by establishing a bioactivity balance. Reference samples, containing several peptides at concentration levels similar to those observed in the hydrolyzed milk samples, were analyzed by LC-BCD-MS. High recoveries of biological activity were obtained, indicating that the correct ACE inhibitors were identified and that no co-elution of significantly bioactive molecules had occurred. Approximately, 30 ACE inhibitors were detected and identified. IC50 values of ACE inhibitors, reported in literature, ranged between 43 and 580 microM.

Effects of berberine on angiotensin-converting enzyme and NO/cGMP system in vessels

The present study was designed to examine the relaxant and anticonstrictive effects of berberine in the isolated thoracic aorta in rats. Intravenous injection of berberine lowered the mean arterial pressure (MAP) of anesthesized rats in a dose-dependent manner. The angiotensin-converting enzyme (ACE) activities were inhibited significantly by the addition of berberine in a dose-dependent manner of which the IC50 value of berberine for ACE was 42 micrograms/ml (125 microM). In the endothelium-intact rings, angiotensin I-induced contraction was markedly attenuated by prior exposure of aortic rings to berberine. Treatment of the intact aortic rings with berberine (10 micrograms/ml) increased the NOx and cGMP productions relative to the vehicle-treated group. Berberine induced a dose-dependent relaxation in phenylephrine-precontracted aortic rings, but NG-nitro-L-arginine methyl ester (L-NAME)-pretreated intact aortic rings or functional removal of the endothelium attenuated the berberine-induced relaxation without an effect on maximum response. These results suggest that berberine has a hypotensive effect, at least in part, via the inhibition of ACE and direct release of NO/cGMP in the vascular tissues.

Angiotensin converting enzyme inhibitory phenylpropanoid glycosides from Clerodendron trichotomum

The stems of Clerodendron trichotomum have been traditionally used for treatment of hypertension in far East Asia including China, Korea, and Japan. Bioassay-guided fractionation and purification of the EtOAc-soluble extract of Clerodendron trichotomum afforded acteoside (1), leucosceptoside A (2), martynoside (3), acteoside isomer (4), and isomartynoside (5). The angiotensin converting enzyme (ACE) activities were significantly inhibited by the addition of these phenylpropanoid glycosides (1-5) in a dose-dependent manner of which IC(50) values were 373+/-9.3 microg/ml, 423+/-18.8 microg/ml, 524+/-28.1 microg/ml, 376+/-15.6 microg/ml, 505+/-26.7 microg/ml, respectively. These results suggest that the antihypertensive effect of Clerodendron trichotomum may be, at least in part, due to ACE inhibitory effect of phenylpropanoid glycosides.

Antihypertensive effects of tannins isolated from traditional Chinese herbs as non-specific inhibitors of angiontensin converting enzyme

The tannins are natural polyphenols, able to precipitate water-soluble alkaloids and possess an inhibitory action on the angiotensin converting enzyme (ACE). We identified 18 polyphenolic compounds (tannins) from Chinese herbs and examined the in vitro effects of these tannins on ACE activity, including determination of the 50% inhibitory concentrations (IC50), specificity and mode of inhibition. We also assessed the in vivo inhibitory effect of the tannins on angiotensin I-induced blood pressure elevation in spontaneously hypertensive rats (SHR). Nine tannins with an IC50 <200 microM for ACE inhibitors were identified belonging to three tannin classes: caffeoylquinates, flavan-3-ols and gallotannins. In vitro, we found caffeoylquinates chelate the ACE zinc cofactor. Two of the flavan-3-ols: epigallocatechin-3-O-gallate and epigallocatechin-3-O-methylgallate, and one of gallotannin: 1, 2, 3, 4, 6-penta-O-galloyl-beta-D-glucose were non-specific inhibitors because also reduced the activity of trypsin and chymotrypsin. The ACE inhibition of 1, 2, 3, 4, 6-penta-O-galloyl-beta-D-glucose was also reduced after addition of bovine serum albumin, suggesting a non-specific mode of action. In vivo, 1,2,3,6-tetra-O-galloyl-beta-D-glucose and epigallocatechin-3-O-methylgallate had a strong dose-dependent hypotensive effect reducing the blood pressure significantly in the SHR with infusion of the angiotensin I. These findings indicate that some of the tannins isolated from herbs inhibit ACE activity non-specifically. The ACE inhibitory effect of these tannins may explain the hypotensive effects of some traditional Chinese herbs.

Antihypertensive, antiatherosclerotic and antioxidant activity of triterpenoids isolated from Olea europaea, subspecies africana leaves

For the first time a biossay-directed study of triterpenoids isolated from the leaves of Olea europaea from Greece, from wild African olive and from a cultivar of O. europaea grown in Cape Town was reported. The experiment was undertaken since our preliminary analyses showed that the African wild olive leave is rich in triterpenoids and contain only traces of the glycoside oleuropein, which is typical for the European olive leaves. The isolate of the African wild olive leaves (AO) used in the experiments was found to contain 0.27% 1:1 mixture of oleanolic acid and ursolic acid, named oleuafricein. The isolate of Greek olive leaves (GO) was found to contain 0.71% oleanolic acid, and the Cape Town cultivar (CT) contained 2.47% oleanolic acid. No ursolic acid was found in either GO or CT. The antihypertensive, diuretic, antiatherosclerotic, antioxidant and hypoglycemic effects of authentic oleanolic and ursolic acid and the three isolates (GO, AO and CT) were studied on Dahl salt-sensitive (DSS), insulin-resistant rat genetic model of hypertension. All three isolates, in a dose 60 mg/kg b.w. for 6 weeks treatment, prevented the development of severe hypertension and atherosclerosis and improved the insulin resistance of the experimental animals. GO, OA and CT isolates could provide an effective and cheap treatment of this particular, most common type of salt-sensitive hypertension in the African population.

Effect of quercetin on plasma extravasation in rat CNS and dura mater by ACE and NEP inhibition

The effects of quercetin on substance P-induced plasma protein extravasation (PE) in the rat dura mater, cerebellum, olfactory bulb and cortex and also its modulation by endopeptidases, angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) were studied. PE was assessed by photometric measurement of extravasated Evans blue. Substance P (SP) and NEP or ACE inhibitors increased the PE in dura mater. Pretreatment with captopril or phosphoramidon potentiated PE induced by SP in the dura mater and cerebellum, respectively. Quercetin increased the PE in the dura mater, cerebellum and cortex. Further results suggested that the PE induced by SP in the dura mater was enhanced by pretreatment with quercetin, similar to that observed with selective peptidase inhibitors. Quercetin-stimulated extravasation in all tissues was abolished by NK-1 receptor blockade. These results suggest that quercetin increases PE in the dura mater and CNS tissues by inhibiting NEP and/or ACE, showing that the effect induced in the dura mater, cerebellum and cortex occurs through endogenous SP accumulation.

Effects of bulb of Fritillaria ussuriensis maxim. on angiotensin converting enzyme and vascular release of NO/cGMP in rats

The present study was designed to investigate whether the Bulbus Fritillaria shows a hypotensive effect via the angiotensin converting enzyme (ACE) inhibition and elicit NO/cGMP release in rat aortic rings. Intravenous injection of Bulbus Fritillaria water extract lowered the mean arterial pressure of anesthetized rats in a dose-dependent manner. The ACE activities were inhibited significantly by the additions of ethylacetate and butanol extracts from Bulbus Fritillaria, of which IC(50) values were 292 and 320 microg/ml, respectively. Moreover, angiotensin I-induced vasoconstriction was also strongly inhibited by the additions of ethylacetate and butanol extracts from Bulbus Fritillaria. In order to assess whether NO production was induced by Bulbus Fritillaria extracts, we directly measured NO and cGMP production levels from the aortic ring elicited by extracts of Bulbus Fritillaria. Our results showed that the hexane, butanol, and water extracts of Bulbus Fritillaria increased NO and cGMP productions in intact vascular tissue. These findings suggest that Bulbus Fritillaria extracts have a hypotensive effect in rats via the inhibition of ACE activity and direct release of NO/cGMP in the vascular tissue.

Vasodilating properties of extracts from the leaves of Musanga cecropioides (R. Brown)

The mechanisms of action involved in the hypotensive properties of the aqueous extract of the leaves of Musanga cecropioides were investigated. The effect of the aqueous leaf extract of M. cecropioides, found to contain mostly saponins, flavonoids and procyanidins, was investigated on vascular smooth muscle and also in an in vivo direct invasive blood pressure study in both normotensive and hypertensive rats. The hypotensive or antihypertensive properties of the extracts appear to be due partly to a direct or indirect vasodilator effect and also to some alpha(1)- and beta(2)-adrenergic blocking effects. The extract also exhibited significant endothelium-dependent vascular smooth muscle relaxation, accounted for by the release of nitric oxide (NO), and induced significant angiotensin converting enzyme (ACE) inhibitory effects thereby supporting its vasodilator mechanism of action.

Effect of quercetin on tachykinin-induced plasma extravasation in rat urinary bladder

The effect of quercetin on substance P-induced plasma extravasation in rat urinary bladder and its modulation by endogenous peptidases in conscious rats was studied. Plasma protein extravasation (PE) was assayed by measurement of extravasated Evans blue dye (microg/g dry tissue). Intravenous injection of substance P (SP, 10 nmol/kg) significantly increased PE in the urinary bladder. PE evoked by SP was increased significantly by quercetin (20 mg/kg, p.o.) pretreatment in the urinary bladder (73.5 +/- 4.9 to 152.2 +/- 9.9). Pretreatment with captopril, an angiotensin-converting enzyme (ACE) inhibitor (10 nmol/kg, i.v.), or with phosphoramidon, a neutral endopeptidase (NEP) inhibitor (2.5 micromol/kg, i.v.) also potentiated the SP-induced PE in urinary bladder, 286.2 +/- 20.4 and 323.3 +/- 34.0, respectively. Quercetin did not show any effect on neurokinin-A (NKA, 10 nmol/kg, i.v.) -induced plasma extravasation. The present study demonstrates that quercetin potentiates the PE induced by substance P in the urinary bladder. These effects suggest that this flavonoid might cause inhibition of NEP and/or ACE.

Search for potential angiotensin converting enzyme (ACE)-inhibitors from plants

MeOH extracts, fractions and pure substances from Musanga cecropioides, Cecropia species and Crataegus oxyacantha /C. monogyna were screened by using an in vitro bio-assay based on the inhibition of Angiotensin Converting Enzyme (ACE), as measured from the enzymatic cleavage of the chromophore-fluorophore-labelled substrate dansyltriglycine into dansylglycine and diglycine. Phenolic acids showed no significant ACE-inhibition whereas flavonoids and proanthocyanidins demonstrated inhibitory activity at 0.33 mg/ml using this test system.

Screening the Brazilian flora for antihypertensive plant species for in vitro angiotensin-I-converting enzyme inhibiting activity

The evaluation of several antihypertensive activity of Brazilian plant species was performed using in vitro inhibition of the angiotensin I-converting enzyme (ACE). Nineteen species belonging to 13 families were investigated. Plants were selected based on their use as diuretics and on a chemosystematic consideration. Extracts of the following species presented the highest ACE inhibition rate, at concentrations of 0.33 mg/ml: Ouratea semiserrata (Mart. & Nees) Engl. stems (68%), Cuphea cartagenesis (Jacq.) Macbride leaves (50%) and Mansoa hirsuta DC. leaves (54%). Some hypotheses about the nature of the compounds that may be responsible for the activity of these species are discussed in the paper.

An ethnopharmacological survey for potential angiotensin converting enzyme inhibitors from Indian medicinal plants

Plants used in different traditional systems of Indian medicine and some relatives/substitutes have been investigated for their angiotensin converting enzyme (ACE) inhibitory activity. They were selected on the basis of their usage as cardiotonics, diuretics and other uses related to the symptoms of hypertension. Out of the 73 species investigated, 22 showed more than 50% ACE inhibitory activity.

Ethnomedical information and in vitro screening for angiotensin-converting enzyme inhibition of plants utilized as traditional medicines in Gujarat, Rajasthan and Kerala (India)

Plants utilized as traditional medicines in India have been investigated for their ability to inhibit the angiotensin converting enzyme (ACE). In total, 75 species belonging to 42 families have been investigated and new ethnomedical information has been obtained for 41 species. Four species were found to possess a high ACE inhibiting ability and were low in their tannin content.

Plants from Réunion Island with alleged antihypertensive and diuretic effects--an experimental and ethnobotanical evaluation

Eighty species of vascular plants were collected on Reunion Island and tested for their ability to inhibit the angiotensin converting enzyme (ACE), which plays an important role in the regulation of blood pressure and diuresis. Of these species, 26 serve as antihypertensive remedies in traditional medicine, and 38 as diuretics-10 of the 64 species have both alleged antihypertensive and diuretic effects. Of the species examined, 26 have not been reported to have any of these effects. Plant material was extracted with both acetone, ethanol and water, and samples were considered active if ACE inhibition was 50% or more in one of the extracts. Of the species with alleged antihypertensive or diuretic effect, 44% proved active. Of the species with no report of such effects, 31% proved active. There were no overall differences in the range of inhibition of the three extracts, but amongst the species considered active there was a strong negative correlation between inhibition of acetone and water extracts. A statistical analysis of the results demonstrated clear differences between plants with alleged antihypertensive effects, diuretic effects, and no alleged use with respect to inhibition of the three extracts.