A novel mode of stimulating platelet formation activity in megakaryocytes with peanut skin extract.

We report in this study novel biochemical activities of peanut skin extract (PEXT) on thrombocytopoiesis. Peanut skin, derived from Arachis hypogaea L., is a traditional Chinese medicine that is used to treat chronic hemorrhage. We have shown that oral administration of PEXT increases the peripheral platelet levels in mice. Recently, we reported a liquid culture system that is useful for investigating megakaryocytopoiesis and thrombocytopoiesis from human CD34+ cells. In this liquid culture system, PEXT was shown to enhance the formation of CD41+/DAPI- cells (platelets), but had no effect on the formation of CD41+/DAPI+ cells (megakaryocytes) or on the DNA content. Furthermore, PEXT selectively stimulated proplatelet formation from cultured mature megakaryocytes and phorbol 12-myristate 13 acetate (PMA)-induced formation of platelet-like particles from Meg01 cells. Despite having no influence on the formation of megakaryocyte colony forming units (CFUs), PEXT increased the size of megakaryocytes during their development from CD34+ cells. PEXT showed no effect on the GATA-1 and NF-E2 mRNA levels, which are known to play an important role in thrombocytopoiesis and, based on the results of a pMARE-Luc (pGL3-MARE-luciferase) assay, had no influence on NF-E2 activation in Meg01 cells. These results suggest that PEXT accelerates proplatelet formation from megakaryocytes but does not influence the development of hematopoietic stem cells into megakaryocytes.

Kaempferol from the leaves of Apocynum venetum possesses anxiolytic activities in the elevated plus maze test in mice.

The present work evaluated the anxiolytic activity of an aqueous extract of Apocynum venetum L. (Apocynaceae) and bioguided its fractionation using the elevated plus maze (EPM) in mice as a model of anxiety. A single treatment of AV extract markedly increased the percentage time spent on the open arms of the EPM in two distinct concentration ranges of 22.5-30 and 100-125 mg/kg p.o., respectively, indicating a putative anxiolytic-like activity. Fractions showing anxiolytic effects in concentrations equal to 30 or 125 mg/kg of whole extract were antagonized using the benzodiazepine antagonist flumazenil (3 mg/kg i.p.) or the 5-HT(1A) receptor antagonist WAY-100635 (0.5 mg/kg i.p.). All active fractions in a concentration equal to 125 mg/kg were effectively blocked by the benzodiazepine antagonist flumazenil, while the anxiolytic activities of fractions in the lower dose equivalent to 30 mg/kg of whole extract were inhibited by the 5-HT(1A) receptor antagonist WAY-100635. Through further separation of AV fractions it was possible to isolate and characterize the flavonol kaempferol which showed an anxiolytic-like activity in concentrations from 0.02 to 1.0 mg/kg p.o. The anxiolytic activity of kaempferol was partially antagonized by concomitant administration of flumazenil, but not by WAY-100635. In conclusion, our study clearly demonstrates that AV extract possesses anxiolytic-like activity and that at least one of its flavonoids, kaempferol, can elicit the same kind of neuropharmacological activity.

Constituents from leaves of Apocynum venetum L.

An analysis using HPLC-MS revealed that an extract from dried leaves of Apocynum venetum L. contained more than 15 kinds of phenolic constituents. Two malonated flavonol glycosides were further isolated, and their structures were determined to be quercetin 3-O-(6''-O-malonyl)-beta-D-glucoside (1) and quercetin 3-O-(6''-O-malonyl)-beta-D-galactoside (2) by NMR spectroscopic analysis. This is the first report describing the isolation of these malonated flavonol glycosides from A. venetum L. Both glycosides showed strong scavenging activity against 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical.

Anti-anxiety effects of Apocynum venetum L. in the elevated plus maze test.

The purpose of this study was to characterize the putative anxiolytic-like activity of an ethanolic extract prepared from the leaves of Apocynum venetum (AV) using the elevated plus maze (EPM) in mice. Male C75BL/6 mice were either treated orally with the AV extract or the positive controls diazepam and buspirone, respectively, 1h before behavioral evaluation in the EPM. A single treatment of AV extract markedly increased the percentage time spent on and the number of entries into the open arms of the EPM in doses of 30 and 125 mg/kg p.o., respectively. This effect was comparable to that of the benzodiazepine diazepam (1.5 mg/kg p.o.) and the 5-HT(1A) agonist buspirone (10 mg/kg p.o.). The effects of AV in 125 mg/kg were effectively antagonized by the benzodiazepine antagonist flumazenil (3 mg/kg i.p.). However, the effects of AV extract could only partially be blocked by the unspecific 5-HT(1A) receptor antagonist WAY-100635 (0.5 mg/kg i.p.). Neither diazepam and buspirone nor the AV extract produced any overt behavioral change or motor dysfunction in the open field test. These results indicate that AV extract is an effective anxiolytic agent, and suggest that the anxiolytic-like activities of this plant are mainly mediated via the GABAergic system.

Antidepressant effect of extracts from Ginkgo biloba leaves in behavioral models.

Extracts of Ginkgo biloba (EGB) are a complex product prepared from green leaves of the Ginkgo biloba tree. In the present study, the antidepressant effect of EGB was examined using two behavioral models, the forced swimming test (FST) in rats and tail suspension test (TST) in mice. EGB significantly reduced immobility time in the FST at a dosage of 10 and 50 mg/kg body weight after repeated oral treatment for 14 d, although no change of motor dysfunction was observed with the same dosage in the open field test. These results indicate that EGB might possess an antidepressant activity. In addition, EGB markedly shortened immobility time in the TST after acute inter-peritoneal treatment at a dosage of 50 and 100 mg/kg body weight. The present study clearly demonstrated that EGB exerts an antidepressant effect in these two behavioral models.

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.

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.

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.

A new ent-clerodane diterpene from the aerial parts of Baccharis gaudichaudiana.

A new ent-clerodane diterpene, named bacchariol (1) was isolated from the aerial parts of Baccharis gaudichaudiana DC. (Compositae), together with known ent-clerodane diterpenes (2, 3), eight known flavonoids (4-11) and 3, 5-dicaffeoylquinic acid (12). Their structures were determined by spectroscopic analyses. Flavonoids (7, 8, 11) and 12 showed moderate scavenging activities toward 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radicals.

Effects of polyphenolic anthrone derivatives, resistomycin and hypercin, on apoptosis in human megakaryoblastic leukemia CMK-7 cell line.

A tetrahydroxyanthrone derivative, resistomycin, was isolated from the culture broth of Streptomyces sulphureus and a similar polyphenolic dianthraquinone, hypericin, was isolated from an extract of Hypericum perforatum L. as modulators for apoptosis. Resistomycin inhibited apoptosis induced by actinomycin D (AD) with or without acceleration by colcemid (CL) in human megakaryoblastic leukemia CMK-7 cells, IC50 for inhibition against AD-induced apoptosis was about 0.5 microM and IC50 for inhibition against AD plus CL-induced apoptosis was about 1 microM. CL alone induced weak apoptosis in cells, which was enhanced by resistomycin. Hypericin did not inhibit AD-induced apoptosis and slightly enhanced CL-induced apoptosis. Emodin, corresponding to 1 of 2 anthraquinone units in hypericin, did not show any effect on this apoptotic system. AD-induced apoptosis was inhibited by the antioxidative flavonoid, luteolin (IC50 45 microM), and a protein kinase C (PKC) inhibitor, staurosporine (IC50 1.5 microM), but these compounds did not affect the CL-induced apoptosis. Hypericin and resistomycin scavenged superoxide anion radicals at the same rate as luteolin. PKC in CMK-7 cells was inhibited by hypericin and luteolin, but not significantly inhibited by resistomycin. This result suggests that the inhibition of AD-induced apoptosis by resistomycin is at least partly correlated with its antioxidative activity, and that the enhancement of CL-induced apoptosis by this compound depends upon the lack of PKC inhibitory activity. Though the mechanism is not clear, the enhancement of the CL-induced apoptosis might be hindered by PKC inhibition in the case of hypericin and luteolin.