Anti-thrombotic effects of higenamine.

The anti-platelet and anti-thrombotic effects of higenamine, a benzyltetrahydroisoquinoline alkaloid of the roots of Aconitum japonicum (Ranunculaceae), were investigated. The degree of platelet aggregation was measured with platelet rich plasma (PRP). An acute thrombotic condition was induced in mice by the injection of the mixture of collagen and epinephrine. The thrombus formation was induced inside the arterio-venous shunt tube installed between an abdominal aorta and the renal vein of rats. Higenamine showed inhibitory activities to both human and rat platelet aggregation induced by ADP, collagen and epinephrine. It was more inhibitory to epinephrine induced aggregation (IC(50); 19 and 7.2 microM to human and rat platelets respectively) than ADP- or collagen-induced aggregation. The anti-thrombotic effects of higenamine were also observed in both mouse acute thrombosis model and rat arterio-venous shunt (AV-shunt) models. The oral administration of higenamine (50 or 100 mg/kg) increased the recovery rates from the acute thrombotic challenge in mice and lowered the weight of thrombus formed inside the AV-shunt tube in rats.

Inhibitors of nitric oxide synthesis and TNF-alpha expression from Magnolia obovata in activated macrophages.

Nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) are the major mediators produced in activated macrophages which contribute to the circulatory failure associated with septic shock. An activity-guided fractionation of an MeOH extract of stem bark of Magnolia obovata afforded two inhibitors of NO production in lipopolysaccharides (LPS)-activated macrophages by the suppression of i-NOS expression. Their structures were elucidated by spectroscopic methods to be magnolol and honokiol with IC50 values of 16.8 and 6.4 microM, respectively. They also inhibited the production of TNF-alpha in LPS-activated macrophages. Thus, these compounds may be possible candidates for the development of new drugs to treat endotoxemia accompanied by the overproduction of NO and TNF-alpha.

Inhibitory effects of higenamine on dopamine content in PC12 cells.

The inhibitory effects of (+/-)-higenamine, a benzylisoquinoline alkaloid, on dopamine biosynthesis in PC12 cells were investigated. Higenamine decreased the intracellular dopamine content dose-dependently and showed 55.2% inhibition of dopamine content in PC12 cells at a concentration of 20 microM with 24 h incubation. The IC50 value of higenamine was 18.2 microM. Dopamine content was lowered and reached minimal level at 12-24 h after exposure to higenamine. In this condition, tyrosine hydroxylase, the rate-limiting enzyme of catecholamine biosynthesis, was also inhibited by the treatment of higenamine in PC12 cells (21.9% inhibition at 20 microM). Higenamine at 20 microM lowered the intracellular Ca2+ concentration by 33.1% inhibition relative to control in PC12 cells. These results suggest that the inhibition of tyrosine hydroxylase activity by higenamine might partially contribute to the decrease in dopamine content in PC12 cells.

Antiplatelet and antithrombotic effects of a combination of ticlopidine and ginkgo biloba ext (EGb 761).

The antiplatelet and antithrombotic effects of the oral combination treatment of ticlopidine and Ginkgo biloba extract (EGb 761) were studied in normal and thrombosis-induced rats. The ex vivo inhibitory effect on ADP-induced platelet aggregation of a small dose of ticlopidine (50 mg/kg/day) in combination with EGb 761 (40 mg/kg/day) was comparable to a larger dose of only ticlopidine (200 mg/kg/day). Bleeding time was also prolonged by 150%. Thrombus weight was also consistently decreased by a combination of ticlopidine and EGb 761 in an arterio-venous shunt model at two doses of ticlopidine (50 mg/kg) plus EGb 761 (20 mg/kg) and ticlopidine (50 mg/kg) plus EGb 761 (40 mg/kg). A combinatory treatment in acute thrombosis model in mice also showed a higher recovery than a single treatment.

Isolation of 3-O-(4'-hydroxybenzyl)-beta-sitosterol and 4-[4'-(4"-hydroxybenzyloxy)benzyloxy]benzyl methyl ether from fresh tubers of Gastrodia elata.

Two new 4-hydroxybenzyl alcohol derivatives (1 and 2) were isolated from the methanol extract obtained from fresh tubers of Gastrodia elata together with 4-hydroxybenzyl methyl ether, 4-hydroxybenzyl alcohol, bis(4-hydroxyphenyl)methane, 4-hydroxybenzaldehyde, beta-sitosterol and palmitic acid. 1 and 2 were identified as 3-O-(4'-hydroxybenzyl)-beta-sitosterol and 4-[4'-(4"-hydroxybenzyloxy)benzyloxy]benzyl methyl ether, respectively, according to the spectroscopic data.

Potential inhibitors of platelet aggregation from plant sources, V. Anthraquinones from seeds of Cassia obtusifolia and related compounds.

Three anthraquinone glycosides, gluco-obtusifolin [11], gluco-chryso-obtusin [15], and gluco-aurantioobtusin [13], were found to be platelet anti-aggregatory constituents of seeds of Cassia obtusifolia. Various other anthraquinone analogues were also tested, and their structure-activity relationships are discussed.

Potential inhibitors of platelet aggregation from plant sources, III.

3,4-Dihydroxybenzoic acid (DBA) was isolated from Acanthopanax senticosus as an antiplatelet aggregatory substance. This paper also reports the results of the investigations on the structural activity relationships among the various dihydroxybenzoic acid derivatives against rat platelet aggregations induced by ADP (adenosine 5'-diphosphate), AA (arachidonic acid), or collagen.

Modified smear method for screening potential inhibitors of platelet aggregation from plant sources.

The smear method developed by Velaskar and Chitre was modified to allow the massive screening of plant extracts and/or fractions for platelet antiaggregating activity. Aspirin and papaverine, known inhibitors of platelet aggregation, were tested by the modified method and showed comparable results with previously reported data. Fifty-four fractions prepared from eighteen plant species were screened for their inhibitory effects on adenosine 5'-diphosphate, arachidonic acid, or collagen-induced rat platelet aggregation. The results suggest that plants could be a potential source of inhibitors of platelet aggregation.