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-ß-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.

The Biological Effects of Forsythia Leaves Containing the Cyclic AMP Phosphodiesterase 4 Inhibitor Phillyrin.

Forsythia fruit (Forsythia suspensa Vahl (Oleaceae)) is a common component of Kampo medicines for treating the common cold, influenza, and allergies. The main polyphenolic compounds in the leaves of F. suspensa are pinoresinol ß-d-glucoside, phillyrin and forsythiaside, and their levels are higher in the leaves of the plant than in the fruit. It is known that polyphenolic compounds stimulate lipid catabolism in the liver and suppress dyslipidemia, thereby attenuating diet-induced obesity and polyphenolic anti-oxidants might attenuate obesity in animals consuming high-fat diets. Recently, phillyrin was reported as a novel cyclic AMP phosphodiesterase 4 (PDE4) inhibitor derived from forsythia fruit. It was expected that the leaves of F. suspensa might display anti-obesity effects and serve as a health food material. In this review, we summarized our studies on the biological effects of forsythia leaves containing phillyrin and other polyphenolic compounds, particularly against obesity, atopic dermatitis, and influenza A virus infection, and its potential as a phytoestrogen.

Oral administration of Eucommia ulmoides Oliv. leaves extract protects against atherosclerosis by improving macrophage function in ApoE knockout mice.

Eucommia leaf extract (ELE) is a traditional Chinese herbal medicine. We investigated the effect of ELE on the development of atherosclerosis and changes in peritoneal macrophage function in apolipoprotein E knockout (ApoE-/- ) mice. At 8 weeks of age, ApoE-/- mice were randomly divided into three groups that were fed a high-fat diet blended with 0% (control), 5% or 10% ELE for a period of 7 weeks. The 10% ELE dose caused an approximately 36% reduction in atherosclerotic lesions, as estimated by oil red O staining. Real-time PCR analysis showed that the 1-week treatment with ELE reduced mRNA levels of Tnf-alpha, Il-1, and Mif in peritoneal macrophages isolated from the ApoE-/- mice. Furthermore, a 1-week treatment with the 10% ELE diet significantly reduced migration and adhesion functions in peritoneal macrophages. These results suggest that a 10% ELE diet reduces atherosclerotic lesions and modulates macrophage function by reducing cytokine expression. PRACTICAL APPLICATION: Eucommia leaf extract (ELE) is a traditional Chinese herbal medicine that reduces atherosclerotic lesions and suppresses inflammatory cytokines expression.

The Restorative Effects of Eucommia ulmoides Oliver Leaf Extract on Vascular Function in Spontaneously Hypertensive Rats.

Eucommia ulmoides Oliv. leaf is a traditional Chinese antihypertensive and antidiabetic medicine. We examined the effects of chronic Eucommia leaf extract (ELE) administration on artery function and morphology in spontaneously hypertensive rats (SHRs). ELE was orally administered via normal diet ad libitum to six-week-old male SHRs at a concentration of 5% for seven weeks. Acetylcholine (ACh)-induced endothelium-dependent relaxation, sodium nitroprusside (SNP)-induced endothelium-independent relaxation, plasma nitric oxide (NO) levels, and media thickness were assessed. ELE significantly improved ACh-induced aortic endothelium-dependent relaxation but did not affect SNP-induced endothelium-independent relaxation in the SHRs, as compared to the animals receiving normal diet. Plasma NO levels and media thickness were significantly increased and decreased, respectively, in the ELE-treated SHRs. Therefore, long-term ELE administration may effectively improve vascular function by increasing plasma NO levels and bioavailability, and by preventing vascular hypertrophy in the SHR aorta.

Plantago lanceolata L. leaves prevent obesity in C57BL/6 J mice fed a high-fat diet.

The highly abundant and widely dispersed plant Plantago lanceolata L. (narrow leaf or English plantain) has been used for culinary and medicinal purposes since ancient times. Here, we investigated the anti-obesity effects of P. lanceolata leaf powder (shortly PL) when fed to male C57BL/6 J mice. Addition of PL to a high-fat diet did not affect food intake but significantly reduced food efficiency, suppressed body weight gain and visceral fat accumulation, and reduced serum free-fatty acid and glucose levels. PL-fed mice exhibited marked increases in HSL, Adrd3 and Cpt2 mRNA levels, and significant decreases in Fas transcripts in epididymal white adipose tissue (WAT). These findings suggest that dietary PL exerts anti-obesity effects by stimulating metabolism throughout visceral fat tissue by activating lipolysis, accelerating fatty acid ß-oxidation and suppressing fatty acid synthase in WAT. To our knowledge, this is the first demonstration of anti-obesity substances derived from a Plantago species.

Chronic administration of Eucommia leaf stimulates metabolic function of rats across several organs.

Eucommia bark (Eucommia ulmoides Oliver) has been used as an herbal medicine, and more recently, the plant's leaves have been widely used to prepare tea which may have anti-obesity properties. We used a metabolic syndrome-like rat model, produced by feeding a 35% high-fat diet (HFD), to examine potential anti-obesity and anti-metabolic syndrome effects and mechanisms of chronic administration of Eucommia leaf as an extract or green leaf powder. Eighty rats were studied for 3 months in ten groups. Both forms of Eucommia leaves minimised increases in body weight and visceral fat in a dose-dependent fashion. Increases in plasma levels of TAG and NEFA, and insulin resistance secondary to HFD were lessened by both forms of Eucommia leaf. Concomitantly, an increase in plasma adiponectin levels and suppression of plasma resistin and TNF-α levels were confirmed. Real-time PCR studies showed that both forms of Eucommia leaf enhanced metabolic function across several organs, including diminishing ATP production (white adipose tissue), accelerating ß-oxidation (liver) and increasing the use of ketone bodies/glucose (skeletal muscle), all of which may exert anti-obesity effects under HFD conditions. These findings suggest that chronic administration of either form of Eucommia leaves stimulates the metabolic function in rats across several organs. The anti-obesity and anti-metabolic syndrome activity in this rat model may be maintained through secretion and regulation of adipocytokines that depend on the accumulation of visceral fat to improve insulin resistance or hyperlipaemia.

Quantification of a broad spectrum of lignans in cereals, oilseeds, and nuts.

Twenty-four plant lignans were analyzed by high-performance liquid chromatography-tandem mass spectrometry in bran extracts of 16 cereal species, in four nut species, and in two oilseed species (sesame seeds and linseeds). Eighteen of these were lignans previously unidentified in these species, and of these, 16 were identified in the analyzed samples. Four different extraction methods were applied as follows: alkaline extraction, mild acid extraction, a combination of alkaline and mild acid extraction, or accelerated solvent extraction. The extraction method was of great importance for the lignan yield. 7-Hydroxymatairesinol, which has not previously been detected in cereals because of destructive extraction methods, was the dominant lignan in wheat, triticale, oat, barley, millet, corn bran, and amaranth whole grain. Syringaresinol was the other dominant cereal lignan. Wheat and rye bran had the highest lignan content of all cereals; however, linseeds and sesame seeds were by far the most lignan-rich of the studied species.

A novel in vitro endothelium-dependent vascular relaxant effect of Apocynum venetum leaf extract.

1. In the present study, a novel in vitro vascular relaxant effect of Apocynum venetum leaf extract (AVLE; also called 'Luobuma'), obtained from a traditional Chinese medicinal herb with known antihypertensive effects, is reported in isometric contraction studies of rat aorta and superior mesenteric artery. At low concentrations (0.3-10 microg/mL), AVLE had no effect on the resting tension of either blood vessel and caused relaxation in agonist-precontracted vessels with functionally intact endothelium. 2. We demonstrated pharmacologically that the AVLE-induced vasorelaxation was mediated selectively by the endothelial cells in both blood vessels. Using NG-nitro-L-arginine methyl ester (L-NAME) and a low concentration of KCl (15 mmol/L), we also demonstrated that AVLE acted by releasing endothelium-derived relaxation factors; nitric oxide (NO) in the rat aorta and NO plus endothelium-derived hyperpolarizing factor in the rat mesenteric artery. 3. The vascular relaxation following brief exposure to AVLE appeared to persist even after subsequent prolonged washout; this was manifested as an attenuated contraction to subsequent application of phenylephrine (PE) compared with the PE-induced contraction after exposure to carbachol (CCh) and subsequent similar washout. The addition of L-NAME at this point in the absence of AVLE totally restored the contraction to PE, suggesting that enzymatic generation of endothelial NO persisted even after brief exposure to AVLE. 4. Unlike the endothelium-dependent NO-mediated relaxation induced by CCh, which is mediated by endothelial muscarinic receptors (and inhibited by atropine), the relaxation induced by AVLE was not inhibited by atropine and, thus, was not mediated by muscarinic receptors. However, similar to CCh-induced relaxation, AVLE-induced relaxation was associated with the activation of K+ channels. 5. These results provide a strong scientific basis for the folk use of AVLE decoction for antihypertensive therapy in traditional Chinese medicine.

[Studies on antihypertensive effect of Luobuma (Apocynum venetum L.) leaf extract (3)].

To clarify the mechanisms underlying the antihypertensive effect of Luobuma (Apocynum venetum L. (Apocynaceae)) leaf extract (LLE), we investigated the vasodilator effect of LLE in the rat mesenteric vascular bed, which plays an important role in changes in peripheral resistance and thus the regulation of blood pressure. In the perfused mesenteric vascular bed with active tone and intact endothelium, perfusion of LLE (0.1 ng to 100 mg/ml for 15 min) caused dose-dependent vasodilation, which was abolished by chemical removal of the endothelial layer with perfusion of sodium deoxycholate, but not by N(G)-nitro-L-arginine-methyl ester (L-NAME), a competitive inhibitor of nitric oxide (NO), which instead increased the effect. The LLE-induced vasodilation was partially inhibited by high K(+)-containing Krebs solution and tetraethylammonium (a K(+) channel blocker) and completely by the combination of L-NAME and high K(+)-Krebs solution. However, atropine (a muscarinic acetylcholine receptor antagonist) did not affect the vasodilation. These results suggest that the vasodilation induced by LLE is endothelium-dependent and mediated by endothelium-derived hyperpolarizing factor, which involves the activation of K(+)-channels. The higher concentrations of LLE may enhance NO production/release to cause vasodilation.

Apocynum venetum extract does not induce CYP3A and P-glycoprotein in rats.

We investigated the effect of Apocynum venetum L. extract (AV) on the activity of cytochrome P450 (CYP) 3A and P-glycoprotein (P-gp). The plasma concentration of nifedipine (NF), which is a substrate for CYP3A, did not change after oral administration with AV (3.3 mg/kg). Also, AV (3.3 and 33 mg/kg) did not affect the intestinal absorption of NF. In the rats treated with multiple administrations (15 mg/kg/d) of St. John's wort extract (SJW) for 2 weeks, the plasma concentration of NF after oral administration was significantly decreased. On the other hand, there was no significant differences in the pharmacokinetic parameters of NF between AV-treated (3.3 mg/kg/d) and none-treated rats. Furthermore, the intestinal absorption of methylprednisolone, which is a substrate for P-gp, was not affected by AV treatment for 2 weeks. These results suggest that, unlike SJW, the recommended dose of AV (3.3 mg/kg/d) would not influence hepatic CYP3A and intestinal P-gp in rats.

Vascular effects of Siberian ginseng (Eleutherococcus senticosus): endothelium-dependent NO- and EDHF-mediated relaxation depending on vessel size.

Siberian ginseng (SG) has been widely and historically consumed as a health food product for the improvement of self well-being, but whether vascular relaxation may contribute to such a therapeutic health effect has not been studied. We therefore investigated the vasorelaxant effect of the aqueous extract of the roots of SG (Eleutherococcus senticosus Maxim) using several in vitro vascular rings prepared from dog carotid artery, rat aorta and rat mesenteric artery. SG extract (0.04-0.8 mg/ml) caused concentration-dependent relaxation in dog carotid arterial rings pre-contracted with 100 microM phenylephrine (PE), and the relaxation was primarily endothelium-dependent. Treatment with 100 microM L-NOARG (a nitric oxide synthase inhibitor) either prevented or totally reverted SG-induced relaxation, suggesting that the endothelium-dependent relaxation was mediated by NO. Similar endothelium-dependent vascular relaxant responses were also obtained with rat aortic and mesenteric arterial rings, except that it occurred over a relatively higher concentration range of SG (0.5-2.0 mg/ml). When tested in the presence of 300 microM L-NAME, the vasorelaxant effect of SG was inhibited totally in rat aorta but only partially in rat mesenteric artery. The relaxation to SG that was insensitive to L-NAME in rat mesenteric arterial rings was eliminated when the rings (both proximal and distal ends) were pre-treated with a combination of 300 microM L-NAME and 15 mM KCl indicating the involvement of endothelium-derived hyperpolarizing factor (EDHF). This vasorelaxant response of the SG extract was inhibited partially by atropine (1 microM), completely by TEA (5 mM), but not by indomethacin (1 microM) or propranolol (10 microM). SG up to 2 mg/ml had no effect on KCl-induced contraction in any of the vascular rings studied. When compared with carbachol-induced (CCh) relaxation, SG resembles CCh in that the sensitivity to L-NAME inhibition is dependent on vascular size, i.e. aorta >proximal end of mesenteric artery >distal end of mesenteric artery. However, SG exhibited different potencies to relaxation while CCh showed similar potency (EC(50) of about 0.2 microM) in all three vascular segments. In conclusion, we have demonstrated that the vascular effect of SG is endothelium-dependent and mediated by NO and/or EDHF depending on the vessel size. Other vasorelaxation pathways, such as inhibition of K(+)-channels and activation of muscarinic receptors, may also be involved.

Endothelium-dependent vascular relaxation induced by Eucommia ulmoides Oliv. bark extract is mediated by NO and EDHF in small vessels.

The vasorelaxant effects of the aqueous extract prepared from the bark of the Chinese medicinal herb, Eucommia ulmoides Oliv. (also referred to as Tu-Chung or Du-Zhong), which is a common active ingredient in traditional antihypertensive herbal prescriptions in China, have recently been characterized in rat aorta and dog carotid artery. The vasorelaxant effect of eucommia bark extract on these large elastic arteries was found to be entirely endothelium-dependent and nitric oxide (NO)-mediated. Since smaller muscular arteries play a more dominant role in the change of peripheral resistance and thus the regulation of blood pressure, we have now compared the relaxant effects of eucommia bark extract using aorta and the proximal as well as the distal ends of the superior mesenteric arteries from the rat, with a specific objective to investigate whether smaller muscular arteries also elicit endothelium-dependent vascular relaxation (EDVR) in response to eucommia bark extract. We have also determined whether the EDVR, if indeed occurring in the mesenteric arteries, is mediated entirely by NO, or whether it also involves endothelium-derived hyperpolarizing factor (EDHF). We found that all three types of vessel preparations elicit EDVR in response to the eucommia bark extract concentration-dependently in a similar manner to the relaxant responses to carbachol (CCh). Although the NO synthase inhibitor L-NAME totally abolished the EDVR in aorta, it only partial abolished EDVR in mesenteric arteries isolated from each end, the distal end being more resistant to L-NAME. However, the residual L-NAME-resistant relaxation of the rat mesenteric arteries could be further inhibited by preincubation of the vessels with the combination of L-NAME and 15-20 mM KCl (KCl itself at this low concentration caused little or no contraction). Therefore, the EDVR induced by the eucommia extract and CCh in aorta is mediated entirely by NO, and that in mesenteric arteries by NO as well as EDHF, with the EDHF component (inhibited by KCl) larger in the smaller distal end of the rat mesenteric artery. Results of our study offer a plausible mechanistic basis for the vasorelaxing action of Eucommia ulmoides Oliv., which may account for its well-documented antihypertensive action.

Long-term effects of an Apocynum venetum extract on brain monoamine levels and beta-AR density in rats.

The present study was designed to get further insight into the mode of antidepressant action of an extract prepared of the leaves of Apocynum venetum L. (AV). To evaluate biochemical changes, we used a high-performance liquid chromatography system to examine the effects of short-term (2 weeks) and long-term (8 weeks) administration of imipramine (15 mg/kg po) and an AV-extract (15, 60 and 250 mg/kg) on regional levels of serotonin (5-HT), norepinephrine (NE), dopamine (DA) and their metabolites in the rat hypothalamus, striatum and hippocampus. Pronounced changes in 5-HT, NE and DA levels were detected mainly after 8 weeks of daily imipramine treatment. Similar to imipramine, AV-extract reduced NE and DA concentrations after 8 weeks, whereas it failed to affect 5-HT levels. We speculate that the decrease in NE levels after chronic AV treatment might be based partly on the subsensitivity of presynaptic alpha(2)-receptors. In addition to the determination of central monoamine concentrations, quantitative radioligand receptor-binding studies were used to examine the effects of long-term administration of imipramine and AV-extract on beta-adrenergic binding in rat frontal cortex. [125I]CYP binding to beta-adrenergic receptors was found to be decreased after 8 weeks treatment with imipramine, whereas AV-extract had no effect on beta-receptor binding.

Endothelium-dependent vasorelaxant effects of the aqueous extracts of the Eucommia ulmoides Oliv. leaf and bark: implications on their antihypertensive action.

The vascular effects of three extract preparations from the Chinese medicinal herb, Eucommia ulmoides Oliv., which is historically an active ingredient commonly used in antihypertensive herbal prescriptions in China, were investigated with isometric contraction using isolated rat aortic and dog carotid rings. Both aqueous extracts isolated from eucommia leaf (L) and bark (B) concentration dependently caused endothelium-dependent relaxation in vessels precontracted with 1 microM phenylephrine (PE), but the methanol extract of the leaf (M) had no effect. Vessels precontracted with KCl and de-endothelialized vessels precontracted with PE were not affected by B or L. The endothelium-dependent relaxation evoked by B and L was either abolished or substantially inhibited by NG-nitro-L-arginine methyl ester (L-NAME) and methylene blue (MB), indicating the involvement of the nitric oxide (NO) synthase pathway in the vasorelaxant action of B and L. The relaxation to the aqueous extract of eucommia bark was not inhibited with 1 microM atropine, but was inhibited by 3-5 mM tetraethylammonium (TEA) and 3 mM 4-aminopyridine. This suggests that the endothelium-dependent, NO-mediated relaxation evoked by the aqueous eucommia extracts was not mediated via the activation of endothelium muscarinic receptors and may involve the activation of K+ -channels. Results in this study have provided the first evidence on the in vitro vasorelaxant action of E. ulmoides Oliv. that forms the pharmacological basis for its well-documented antihypertensive action.

Effect of Acanthopanax senticosus Harms on biogenic monoamine levels in the rat brain.

The extract of the stem bark of Acanthopanax senticosus Harms (ASH) is known to have healing and protective effects on stress-induced disturbance of mental status. We have analysed whether a single or chronic (2 week) administration of ASH can affect concentrations of noradrenaline (NA), dopamine (DA) and their metabolites in the normal rat brain. A single p.o. administration of ASH elevated the NA and DA levels in the whole brain of rats in a dose-dependent manner. A single or 2 week administration of ASH (500 mg/kg) showed a marked increase in the DA level only in the striatum. However, NA levels were increased by a single dose of ASH in a wide range of brain regions such as the cortex, hypothalamus, striatum, hippocampus, substantia nigra and pons. When administered for 2 weeks no increase in NA levels was seen in these brain regions, except for an increase in the frontal cortex and anterior hypothalamus. The present results suggest that ASH may act by regulating NA and DA levels in specific brain regions related to stress response and Parkinson's disease.

[The plant origins of herbal medicines and their quality evaluation].

The caulis (stem and leaf) of Trachelospermum jasminoides (Lindl.) Lem. (Apocynaceae) is listed as the plant origin of Luoshiteng in the Chinese Pharmacopeia. However, preparations from the caulis of Ficus pumila L. (Moraceae) or Psychotria serpens L. (Rubiaceae) are distributed on the Chinese market. The fruit of Forsythia suspensa Vahl (Oleaceae) is listed as the plant origin of Forsythia Fruit in the Chinese Pharmacopeia, although the fruits of two Forsythia species, F. suspensa and F. viridissima Lindley, are listed as the plant origins in the Japanese Pharmacopeia, and fruits of three Forsythia species, F. viridissima, F. koreana Nakai, and F. suspensa, are listed in the Korean Pharmacopeia. The whole plant of Plantago asiatica L. (Plantaginaceae) is listed as the plant origin of Plantago Herb in the Japanese Phamacopeia, but the whole plants of two Plantago species, P. asiatica and P. depressa Wild, are listed as the plant origins in the Chinese Pharmacopeia. The leaves of two Plantago species, P. lanceolata L. and P. major L., are distributed as Plantain on the European market. Each of these herbal medicines is reviewed based on the differences in plant origins and their quality evaluation from the viewpoints of the morphological properties, chemical components, and biological activities, respectively.