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.

Cardiotonic effect of Apocynum venetum L. extracts on isolated guinea pig atrium.

The effects on guinea-pig heart muscle of extracts of Apocynum venetum L. leaf, root, stem, old stem and Venetron--a polyphenol-rich extract of leaves--were studied by recording the mechanical activity and heart rate of isolated right atria. Cymarin--a cardiac glycoside--was also determined in A. venetum extracts by LC-MS/MS analysis. All extracts examined here showed a weak cardiotonic effect, i.e., induced a contractile response of the isolated atria and increased the pulse at a concentration of 1 mg/mL, which was not inhibited by propranolol (1 microM)-a beta-adrenoceptor blocker. The cymarin content in extracts of A. venetum was ranked as follows: old stem >> stem > root > leaf >> Venetron. Since the cardiotonic effects of A. venetum extracts did not reflect the cymarin content, a possible mechanism other than that of cardiac glycosides was investigated. The inhibitory effects on phosphodiesterase 3 (PDE3) were studied in a cell-free enzyme assay; all extracts of various parts of A. venetum inhibited PDE purified from human platelets. These results suggest that PDE3 inhibition may contribute to the cardiotonic effects of A. venetum extracts.

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.