Cardioactive compounds from Eremophila species

The Differences of Mechanisms in Antihypertensive and Anti-Obesity Effects of Eucommia Leaf Extract between Rodents and Humans

In the 1970s, Eucommia leaf tea, known as Tochu-cha in Japanese, was developed from roasted Eucommia leaves in Japan and is considered as a healthy tea. The antihypertensive, diuretic, anti-stress, insulin resistance improving, and anti-obesity effects of Eucommia leaf extract have been reported. However, the identification and properties of the active components as well as the underlying mechanism of action are largely unknown. In this review, we summarize studies involving the oral administration of geniposidic acid, a major iridoid component of Eucommia leaf extract which increases plasma atrial natriuretic peptide (ANP) on the atria of spontaneously hypertensive rats (SHR) by activating the glucagon-like peptide-1 receptor (GLP-1R). To achieve the antihypertensive effects of the Eucommia leaf extract through ANP secretion in humans, combining a potent cyclic adenosine monophosphate phosphodiesterase (cAMP-PDE) inhibitor, such as pinoresinol di-β-d-glucoside, with geniposidic acid may be necessary. Changes in the gut microbiota are an important aspect involved in the efficacy of asperuloside, another component of the Eucommia leaf extract, which improves obesity and related sequelae, such as insulin resistance and glucose intolerance. There are species differences of mechanisms associated with the antihypertensive and anti-obesity effects between rodents and humans, and not all animal test results are consistent with that of human studies. This review is focused on the mechanisms in antihypertensive and anti-obesity effects of the Eucommia leaf extract and summarizes the differences of mechanisms in their effects on rodents and humans based on our studies and those of others.

Phytochemistry, Medicinal Properties, Bioactive Compounds, and Therapeutic Potential of the Genus Eremophila (Scrophulariaceae)

The genus Eremophila (family Scrophulariaceae) consists of approximately 200 species that are widely distributed in the semi-arid and arid regions of Australia. Multiple Eremophila spp. are used as traditional medicines by the First Australians in the areas in which they grow. They are used for their antibacterial, antifungal, antiviral, antioxidant, anti-diabetic, anti-inflammatory, and cardiac properties. Many species of this genus are beneficial against several diseases and ailments. The antibacterial properties of the genus have been relatively well studied, with several important compounds identified and their mechanisms studied. In particular, Eremophila spp. are rich in terpenoids, and the antimicrobial bioactivities of many of these compounds have already been confirmed. The therapeutic properties of Eremophila spp. preparations and purified compounds have received substantially less attention, and much study is required to validate the traditional uses and to highlight species that warrant further investigation as drug leads. The aim of this study is to review and summarise the research into the medicinal properties, therapeutic mechanisms, and phytochemistry of Eremophila spp., with the aim of focussing future studies into the therapeutic potential of this important genus.

Serrulatane diterpenoids with unusual side chain modifications from root bark of Eremophila longifolia

The plant genus Eremophila is endemic to Australia and widespread in arid regions. Root bark extract of Eremophila longifolia (R.Br.) F.Muell. (Scrophulariaceae) was investigated by LC-PDA-HRMS, and dereplication suggested the presence of a series of diterpenoids. Using a combination of preparative- and analytical-scale HPLC separation as well as extensive 1D and 2D NMR analysis, the structures of 12 hitherto unreported serrulatane diterpenoids, eremolongine A-L, were established. These structures included serrulatanes with unusual side chain modifications to form hitherto unseen skeletons with, e.g., cyclopentane, oxepane, and bicyclic hexahydro-1H-cyclopenta[c]furan moieties. Serrulatane diterpenoids in Eremophila have recently been shown to originate from a common biosynthetic precursor with conserved stereochemical configuration, and this was used for tentative assignment of the relative and absolute configuration of the isolated compounds. Triple high-resolution α-glucosidase/α-amylase/PTP1B inhibition profiling demonstrated that several of the eremolongines had weak inhibitory activity towards targets important for management of type 2 diabetes.

Phenolic Plant Extracts Induce Sirt1 Activity and Increase Antioxidant Levels in the Rabbit's Heart and Liver

Background

Several dietary phytochemicals potentially regulate the equilibrium between oxidant and antioxidant species. The aim of this study was to evaluate the effects of Lippia citriodora, Raphanus sativus, and Solanum lycopersicum on blood parameters, oxidative/antioxidant status, and SIRT1 activity in the rabbit's heart and liver.

Methods

Twenty rabbits were divided into 4 groups of 5 animals each. The control group (CN) received a feed without any additives. One intervention group received a supplement containing verbascoside (VB), another Raphanus sativus extract (RAP), and lastly lycopene (LYC). Oxidant-antioxidant parameters and SIRT1 activity were measured in plasma and in the heart and liver, respectively.

Results

The treatment with VB, RAP, and LYC resulted in a marked improvement in the blood lipid and glycaemic profile in respect to CN. VB was the most effective, but all three plant extracts induced a significant reduction in oxidant parameters as well as an increase in antioxidant tissue activity and vitamin A and E levels. SIRT1 activity was significantly increased in both VB and LYC compared to CN, but the increased levels in the VB group were far the highest. The multivariate analysis suggests that the benefits of VB, particularly the antiglycaemic and antioxidant effects, might be mediated by increasing SIRT1 activity.

A Review on the Phytochemistry, Pharmacology, Pharmacokinetics and Toxicology of Geniposide, a Natural Product

Iridoid glycosides are natural products occurring widely in many herbal plants. Geniposide (C17H24O10) is a well-known one, present in nearly 40 species belonging to various families, especially the Rubiaceae. Along with this herbal component, dozens of its natural derivatives have also been isolated and characterized by researchers. Furthermore, a large body of pharmacological evidence has proved the various biological activities of geniposide, such as anti-inflammatory, anti-oxidative, anti-diabetic, neuroprotective, hepatoprotective, cholagogic effects and so on. However, there have been some research articles on its toxicity in recent years. Therefore, this review paper aims to provide the researchers with a comprehensive profile of geniposide on its phytochemistry, pharmacology, pharmacokinetics and toxicology in order to highlight some present issues and future perspectives as well as to help us develop and utilize this iridoid glycoside more efficiently and safely.

Antibacterial Nerol Cinnamates from the Australian Plant Eremophila longifolia

Two new antimicrobial agents, neryl ferulate (1) and neryl p-coumarate (2), were identified using bioassay-guided isolation from the leaves of Eremophila longifolia, which is a medicinal plant used by some Australian Aboriginal communities. Although gradual autoxidation of the nerol subunit hindered the initial attempts to purify and characterize 1 and 2, it was found that the autoxidation could be stopped through storage under argon at -20 °C. Biological evaluation showed that neryl ferulate (1) had moderate activity against various Gram-positive bacteria, while neryl p-coumarate (2) was active only against Enterococcus faecium.

Rapid screening and identification of the differences between metabolites of Cistanche deserticola and C. tubulosa water extract in rats by UPLC-Q-TOF-MS combined pattern recognition analysis

Cistanches Herba is a famous traditional Chinese medicine that has been in use for treating kidney deficiency, impotence, female infertility, morbid leucorrhea, profuse metrorrhagia, and senile constipation. With the exception of studies available for a few single active ingredients such as echinacoside, acteoside, and poliumoside, comprehensive and systematic studies on in vivo metabolism of Cistanches Herba are lacking despite its widespread clinical application. There is no comparative study yet on the metabolites resulting from the traditional usage of Cistanche deserticola and C. tubulosa water extract - two species that are recorded in Chinese Pharmacopoeia. This further restricts research on the therapeutic effect of Cistanches Herba to a great extent. In this study, a robust and unbiased UPLC-Q-TOF-MS combined pattern recognition analysis (orthogonal partial least squared discriminant analysis, OPLS-DA) was employed to rapidly screen prototype components and metabolites of C. deserticola and C. tubulosa water extract in rat urine, feces, and serum. A total of 71 metabolites from C. deserticola including 25 prototype components and 46 metabolites, and 45 metabolites from C. tubulosa including 18 prototype components and 27 metabolites were tentatively identified. Out of these, 10 metabolites were characterized for the first time in these two species. Results of this study indicate that phenylethanoid glycosides (PhGs) are mainly metabolized into degradation products in the gastrointestinal tract of rats. The chemical components cistanoside B, C, D, and E exist only in C. deserticola and release methylated hydroxytyrosol (HT) following metabolism. This factor contributes to the difference between metabolites of C. deserticola and C. tubulosa water extract in rats and is responsible for the differential therapeutic effect that these two species of Cistanches Herba have on the same diseases.

Antibacterial constituents of Eremophila alternifolia: An Australian aboriginal traditional medicinal plant

ETHNOPHARMACOLOGICAL RELEVANCE

For traditional medicinal purposes Aboriginal Australians have utilised numerous plant species, Eremophila alternifolia is among the most prominent. Traditionally, fresh leaves, leaf-infusions and handmade leaf-pastes have been used as both external and internal preparations to provide relief from a variety of conditions. Preparations of the species have been used to treat various infections of skin, eyes and throat including the treatment of septic wounds. These usages suggest that the plant contains antibacterial compounds; however, to date they have not been isolated and identified.

AIM OF THE STUDY

The present study aimed to identify antibacterial compounds from this important traditionally recorded medicinal species.

MATERIALS AND METHODS

Bioassay-guided fractionation was used to isolate compounds from the crude leaf-extract. Antibacterial activity of pure compounds was assessed through broth microdilution method by determining both minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). Structure elucidation was performed using spectroscopic techniques such as 1D and 2D nuclear magnetic resonance spectroscopy and high resolution mass spectrometry.

RESULTS

Four compounds have been isolated from the leaf-extract; they include previously known flavanones [pinobanksin (1), pinobanksin-3-acetate (2) and pinobanksin-3-cinnamate (3)] and a serrulatane diterpene, 8-hydroxyserrulat-14-en-19-oic acid (4). While compound 4 had been found in other Eremophilas, flavanones 2 and 3 are identified for the first time from the genus Eremophila. The flavanone 3 is the most promising antibacterial compound with significant activity (10-20µM) against strains of the Gram-positive bacterium Staphylococcus aureus including methicillin resistant and biofilm forming strains. No activity was observed for any isolated compounds against the Gram-negative bacterium Escherichia coli.

CONCLUSION

The antibacterial activity of the crude extract of E. alternifolia and of the isolated compounds against Gram-positive bacteria provides a Western scientific explanation of the therapeutic modality of this plant species in traditional Aboriginal medicinal practice.

Isolation and characterisation of (-)-genifuranal: the principal antimicrobial component in traditional smoking applications of Eremophila longifolia (Scrophulariaceae) by Australian aboriginal peoples

ETHNOPHARMACOLOGICAL SIGNIFICANCE

Eremophila longifolia is considered by some Australian Aboriginal tribal groups to be among the most significant of the medicinal plants in contemporary and traditional use. Usage modalities traditionally involved lipophilic extraction into animal fats and most importantly, ceremonial or medicinal smoking applications, involving the fumigation of mothers and infants following childbirth or boys following circumcision. An attempt was made to replicate the smoking modalities used by Australian Aboriginal people in the laboratory to identify bioactive compounds.

MATERIALS AND METHODS

Two methods were used to produce smoke extracts; smoke was channelled through a condenser then bubbled into solvent, or bubbled directly into H2O then partitioned into chloroform followed by butanol. Extracts were used, firstly for antimicrobial screening using micro-titre plate broth dilution to produce minimum inhibitory concentrations (MIC), and secondly for chemical analysis. Structure elucidation of an abundant compound isolated from the smoke extract was performed using 2D-NMR and derivatisation.

RESULTS

Significant antimicrobial activity (<1.0 mg/ml) was produced using the smoke extracts against the Gram-positive species Staphylococcus aureus, Bacillus subtilis and the yeast Candida albicans. A major component of the smoke with strong antimicrobial activity (0.13-0.5 mg/ml) was isolated which we have named (-)-genifuranal. Structure elucidation using 2D-NMR and derivatisation demonstrated genifuranal to be 5,6-dihydro-4H-cyclopenta[c]furan-4-ylacetaldehyde. Genifuranal is not observed in the leaves before heating, but is produced in the smoking or heating process and is thought to derive from hydrolysis and rearrangement of geniposidic acid or a related glycoside. Only geographically specific specimens of Eremophila longifolia produced (-)-genifuranal, which strongly supports previous hypothesised geographical variation in traditional usage, reflective of phytochemical variation.

CONCLUSION

It would appear that genifuranal is the medicinal principal involved in traditional use of Eremophila longifolia when smoking modalities are used. Topical treatments traditionally produced by lipophilic extraction into animal fats are not likely to have had genifuranal present, as the mechanism for its formation requires heat.

Antibacterial serrulatane diterpenes from the Australian native plant Eremophila microtheca

Chemical investigations of the aerial parts of the Australian plant Eremophila microtheca resulted in the isolation of three serrulatane diterpenoids, 3-acetoxy-7,8-dihydroxyserrulat-14-en-19-oic acid (1), 3,7,8-trihydroxyserrulat-14-en-19-oic acid (2) and 3,19-diacetoxy-8-hydroxyserrulat-14-ene (3) as well as the previously reported compounds verbascoside (4) and jaceosidin (5). Acetylation and methylation of the major serrulatane diterpenoid 2 afforded 3,8-diacetoxy-7-hydroxyserrulat-14-en-19-oic acid (6) and 3,7,8-trihydroxyserrulat-14-en-19-oic acid methyl ester (7), respectively. The antibacterial activity of 1-7 was assessed against a panel of Gram-positive and Gram-negative bacterial isolates. All of the serrulatane compounds exhibited moderate activity against Streptococcus pyogenes (ATCC 12344) with minimum inhibitory concentrations (MICs) ranging from 64-128 μg/mL. Serrulatane 1 demonstrated activity against all Gram-positive bacterial strains (MICs 64-128 μg/mL) except for Enterococcus faecalis and Enterococcus faecium. This is the first report of natural products from E. microtheca.

The genus Eremophila (Scrophulariaceae): an ethnobotanical, biological and phytochemical review

Objectives

Eremophila (Scrophulariaceae) is an endemic Australian genus with 214 species, which is commonly known as Fuchsia bush, Emu bush or Poverty bush. Plants of this genus played an important role for the Australian Aborigines who used them widely for medicinal and ceremonial purposes. Many studies have been carried out on many species of this genus and have generated immense data about the chemical composition and corresponding biological activity of extracts and isolated secondary metabolites.

Key findings

Thorough phytochemical investigations of different Eremophila species have resulted in the isolation of more than 200 secondary metabolites of different classes with diterpenes as major constituents. Biological studies and traditional clinical practice demonstrated that Eremophila and its bioactive compounds possess various pharmacological properties. Plants were employed especially as a cardiotonic drug and also as potent anti-inflammatory, antimicrobial and antiviral agents.

Summary

Further investigations are required to explore other Eremophila species, to evaluate the different biological activities of either their extracts or the isolated compounds and the possible underlying modes of action.

Distribution of iridiod glucosides and anti-oxidant compounds in Spathodea campanulata parts

The antioxidant principles isolated from the various parts of the plant are verminoside (leaf, stem bark and flowers; EC(50) = 2.04 µg/ml), Specioside (flowers; EC(50) = 17.44 µg/ml), Kampeferol diglucoside (leaf; EC(50) = 8.87 µg/ml) and Caffeic acid (leaf and fruits). The non anti-oxidant components isolated in the study include ajugol (stem bark and fruits) and phytol (leaf).

Mitchellenes A-E, cyclic sesquiterpenes from the Australian plant Eremophila mitchellii

Chemical investigations of the Australian plant Eremophila mitchellii resulted in the isolation of the novel tetracyclic sesquiterpene lactones mitchellenes A-C (1-3), the new sesquiterpene acids mitchellenes D and E (4 and 5), and the previously reported natural products 14-hydroxy-6,12-muuroloadien-15-oic acid (6), casticin, and centaureidin. The chemical structures of all compounds were determined by extensive 1D/2D NMR and MS data analysis. Mitchellenes A-C are the first tetracyclic sesquiterpene lactones to be reported; a biosynthetic pathway is proposed for these unique secondary metabolites.

Exploring the anthelmintic properties of Australian native shrubs with respect to their potential role in livestock grazing systems

We measured in vitro anthelmintic activity in extracts from 85 species of Australian native shrub, with a view to identifying species able to provide a degree of worm control in grazing systems. Approximately 40% of the species showed significant activity in inhibiting development of Haemonchus contortus larvae. The most active extracts showed IC50 values of 60-300 microg/ml. Pre-incubation with polyvinylpolypyrrolidine removed the activity from some extracts, implicating tannins as the bioactive agent, while in other cases the pre-incubation had no effect, indicating the presence of other anthelmintic compounds. Plant reproductive maturity (onset of flowering or fruiting) was associated with increasing anthelmintic activity in some species. Variability was observed between plants of the same species growing in different environments, while variation between individual plants of the same species within a single field suggests the existence of distinct chemotypes. Significant activity against adult H. contortus worms in vitro was also demonstrated in a limited number of extracts tested against this life stage. Our study indicates that there is potential for Australian native shrubs to play an anthelmintic role in grazing systems, and highlights some plant biology factors which will need to be considered in order to maximize any anthelmintic effects.

Bactericidal and cyclooxygenase inhibitory diterpenes from Eremophila sturtii

Two serrulatane diterpenes, 3,8-dihydroxyserrulatic acid (1) and serrulatic acid (2), have been isolated from Eremophila sturtii through bioassay-guided fractionation. These compounds inhibit the inflammation pathway enzymes cyclooxygenase 1 and 2, and exhibit bactericidal activity against Staphylococcus aureus.

Interesting biological activities from plants traditionally used by Native Australians

Four plants routinely used for medicinal purposes by Native Australians were screened for various biological activities. Methanol extracts of Eremophila maculata, Acacia auriculoformis and Acacia bivenosa exhibited antibiotic effects, while Eremophila alternifolia yielded an extract that induced significant changes to the heart activity of spontaneously hypertensive rats. We report on these biological activities.

Pharmacological effects of Eugenia uniflora (Myrtaceae) aqueous crude extract on rat's heart

The effect of aqueous crude extract (ACE) of Eugenia uniflora L. (Myrtaceae) was studied on rat's perfused ventricles. This plant is used in South American traditional medicine as an antihypertensive and we already demonstrated previously its hypotensive properties. In this paper, maximal left intraventriclular pressure (P) of rat's hearts beating at 0.2 Hz firstly increased to 162.1+/-11.1% of basal value during 1-3 min of perfusing ACE 0.6%. Maximum rate of contraction (+P) also increased to duplicating +P/P ratio. Both types of effect were significantly decreased by either propranolol 0.35 microM, and pre-treatment with reserpine (5 mg/kg), suggesting that they were caused by a compound that releases cathecolamines with beta-adrenergic action. Nevertheless, after 20 min of perfusing ACE, ventricles decreased P to about 50% of their basal value, suggesting a negative-inotropic compound present in the extract. The perfusion of 1.2% ACE decreased P in a pressure-[Ca](o) curve (0.5-2 mM) in a non-competitive manner, suggesting that an irreversible Ca-blocking compound is also present in the extract. In summary, E. uniflora ACE has a dual effect on the heart related to its hypotensive action and is probably responsible for the therapeutic or adverse effects in patients under cardiac risk.

Pharmacological effects of lavandulifolioside from Leonurus cardiaca

Lavandulifolioside was detected for the first time in Leonurus cardiaca var. vulgaris [Moench] Briquet (Lamiaceae). The isolation was performed from the butanolic extract of the aerial parts and the identification by NMR and MS. The pharmacological properties of lavandulifolioside consist of significant negative chronotropism, prolongation of the P-Q, Q-T intervals and QRS complex, and decrease of blood pressure. Contrary to the butanolic extract lavandulifolioside did not reduce the spontaneous locomotor activity. In conclusion, the pharmacological pattern of lavandulifolioside did not explain the pharmacological effects of L. cardiaca L. alone.

Lantana camara L. (Verbenaceae)

Lantana camara L. is regarded both as a notorious weed and a popular ornamental garden plant and has found various uses in folk medicine in many parts of the world. Some taxa of the widely variable L. camara complex are toxic to small ruminants and this effect has been associated with the types and relative amounts of some triterpene ester metabolites. However, L. camara also produces a number of metabolites in good yields and some have been shown to possess useful biological activities. All these aspects are considered in this review to allow an evaluation of the potential for utilisation of the large biomass of Lantana available. The phytochemistry of other members of the Lantana genus is included.

Inhibition of platelet aggregation and 5-HT release by extracts of Australian plants used traditionally as headache treatments

To identify potential migraine therapeutics, extracts of eighteen plants were screened to detect plant constituents affecting ADP induced platelet aggregation and [14C]5-hydroxytryptamine (5-HT) release. Extracts of the seven plants exhibiting significant inhibition of platelet function were reanalysed in the presence of polyvinyl pyrrolidone (PVP) to remove polyphenolic tannins that precipitate proteins. Two of these extracts no longer exhibited inhibition of platelet activity after removal of tannins. However, extracts of Crataegus monogyna, Ipomoea pes-caprae, Eremophila freelingii, Eremophila longifolia, and Asteromyrtus symphyocarpa still potently inhibited ADP induced human platelet [14C]5-HT release in vitro, with levels ranging from 62 to 95% inhibition. I. pes-caprae, and C. monogyna also caused significant inhibition of ADP induced platelet aggregation. All of these plants have been previously used as traditional headache treatments, except for C. monogyna which is used primarily for protective effects on the cardiovascular system. Further studies elucidating the compounds that are responsible for these anti-platelet effects are needed to determine their exact mechanism of action.

Mechanism of action of verbascoside on the isolated rat heart: increases in level of prostacyclin

The mechanism of the positive cardioactive effects induced by verbascoside in the Lagendorff rat heart has been investigated. Isolated rat hearts treated with alpha- or beta-adrenergic agents did not show significant reduction of the positive chronotropism, inotropism and increased coronary perfusion rate mediated by verbascoside. A significant increase in prostacyclin levels (142%) observed following the administration of verbascoside suggests that prostacyclin stimulates formation of cAMP which induces the cardioactivity associated with verbascoside.