5-HT2A/C receptors mediate the antipsychotic-like effects of alstonine.

The purpose of this study was to determine the effects of alstonine, an indole alkaloid with putative antipsychotic effects, on working memory by using the step-down inhibitory avoidance paradigm and MK801-induced working memory deficits in mice. Additionally, the role of serotonin 5-HT2A/C receptors in the effects of alstonine on mouse models associated with positive (MK801-induced hyperlocomotion), negative (MK801-induced social interaction deficit), and cognitive (MK801-induced working memory deficit) schizophrenia symptoms was examined. Treatment with alstonine was able to prevent MK801-induced working memory deficit, indicating its potential benefit for cognitive deficits now seen as a core symptom in the disease. Corroborating previously reported data, alstonine was also effective in counteracting MK801-induced hyperlocomotion and social interaction deficit. Ritanserin, a 5-HT2A/C receptor antagonist, prevented alstonine's effects on these three behavioral parameters. This study presents additional evidence that 5-HT2A/C receptors are central to the antipsychotic-like effects of alstonine, consistently seen in mouse models relevant to the three dimensions of schizophrenia symptoms.

Constituents of Peucedanum zenkeri seeds and their antimicrobial effects.

The methanol extract of Peucedanum zenkeri L. seeds showed antimicrobial activity which is concentrated in the n-hexane fraction. Bioactivity-guided chromatographic fractionation of the seeds of P. zenkeri led to the isolation and characterization of five major coumarins, umbelliprenin, imperatorin, bergapten, isopimpinellin and byakangelicin, as well as two minor coumarins, 7-methoxy coumarin and 5-hydroxy-8-methoxy psoralen. Amongst the isolated compounds only imperatorin, bergapten and isopimpinellin were found to possess anti-microbial activity.

Biological activity of saponins from two Dracaena species.

Many species of the west African "soap tree" Dracaena are used in traditional medicine for the treatment of a variety of diseases. In continuation of our search for anti-infective agents from plants implicated in traditional medicine, we evaluated the biological activities of saponins from extracts of Dracaena mannii and Dracaena arborea by using a battery of test systems such as radiorespirometry, Cytosensor bioautography, and agar dilution methods and molluscicidal tests. Bioassay-directed fractionation of the methanol extracts of seed pulp using a combination of chromatographic techniques, gel filtration, droplet countercurrent chromatography (DCCC), and low-pressure liquid chromatography (Lobar), led to the isolation and characterization of spiroconazole A, a pennogenin triglycoside [3 beta-O-[(alpha-L-rhamnopyranosyl(1-->2), alpha-L-rhamnopyranosyl(1-->3)-beta-D-glucopyranosyl]-17 alpha-hydroxyl-spirost-5-ene] (Fig. 1). As the active constituent, spiroconazole A exhibited pronounced antileishmanial, antimalarial, and molluscicidal activities. This paper also reports on the fungistatic, fungicidal and bacteriostatic activity of spiroconazole A against 17 species of fungi and 4 of bacteria.

Hypoglycaemic activity of dioscoretine from tubers of Dioscorea dumetorum in normal and alloxan diabetic rabbits.

Dioscoretine isolated from the aqueous fraction of the methanol extract of Dioscorea dumetorum tubers when administered intra-peritoneally to normal and alloxan diabetic rabbits produces significant hypoglycaemic effects at a dose of 20 mg/kg. The fasting blood sugar in normoglycaemic rabbits was reduced from 112 mg/100 ml to 55 mg/100 ml after 4 hours. In alloxan diabetic rabbits, the blood sugar was lowered from 520 mg/100 ml to 286 mg/100 ml at the same time interval. The aqueous fraction of the methanol extract produced comparable effects at 100 mg/kg. The chloroform fraction of the same extract raised the fasting blood sugar of normal rabbits to 196 mg/100 ml after 6 h. The acute toxicity studies gave LD50 values of 1.4 g/kg for the aqueous fraction and 0.58 g/kg for dioscoretine when tested on mice. The hypoglycaemic effects were compared to those of tolbutamide.

Antidiabetic and aldose reductase activities of biflavanones of Garcinia kola.

Kolaviron, a mixture of C-3/C-8 linked biflavonoids obtained from Garcinia kola produces significant hypoglycaemic effects when administered intraperitoneally to normal and alloxan diabetic rabbits at a dose of 100 mg kg-1. The fasting blood sugar in normoglycaemic rabbits was reduced from 115 mg/100 mL to 65 mg/100 mL after 4 h. In alloxan diabetic rabbits, the blood sugar was lowered from 506 mg/100 mL to 285 mg/100 mL at 12 h. The hypoglycaemic effects have been compared with those of tolbutamide. Kolaviron inhibited rat lens aldose reductase (RLAR) activity, with an IC50 value of 5.4 x 10(-6). The significance of these findings in the potential use of kolaviron as an antidiabetic agent is discussed.

Evaluation of the antihepatotoxic activity of the biflavonoids of Garcinia kola seed.

Seeds of Garcinia kola enjoy a folk reputation in Africa as a poison antidote. Their antihepatotoxic properties have been evaluated using four experimental toxins, namely carbon tetrachloride, galactosamine, alpha-amanitin and phalloidin. Kolaviron, a fraction of the defatted ethanol extract, and two biflavones of Garcinia kola seeds (GB1 and GB2) significantly modified the action of all these hepatotoxins. At 100 mg/kg orally, the test substances reduced thiopental-induced sleep in CCl4-poisoned rats. The microsomal enzyme levels in the serum of mice poisoned with phalloidin were significantly protected by treatment with Garcinia extractives. The probable mechanism of the antihepatotoxic action is briefly discussed.

Gastrointestinal studies of Pyrenacantha staudtii leaf extracts.

The main constituents of the ethanol extract of Pyrenacantha staudtii leaves were identified to be triterpenoid saponins and orally this extract was shown to protect rats from developing gastric ulcers induced by various experimental models: drugs (indomethacin, serotonin), cold-restraint stress and Shay rat. The protection was shown to be dose-dependent in the case of indomethacin-induced ulcers. The mechanisms by which the triterpenoids of P. staudtii may exhibit anti-ulcer activities are discussed.