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Ethnobiological and chemical investigations of selected Amazonian plants

University of British Columbia

The ethnobotanical literature of Amazonian South America has been surveyed, compiled and organized. This information allowed the identification of certain taxonomic groups and plants with specific uses which seem promising for further research. The use of Justicia pectoralis as an additive to hallucinogenic Virola based snuffs has been investigated. No alkaloidal compounds could be detected in the plant and the pharmacological effects of an extract on mice were not indicative of the presence of strongly psychoactive constituents. Nor did the J. pectoralis extracts have any inhibitory or synergistic effect upon the responses of mice to 5-methoxy-N,N-dimethyltryptamine, the psychoactive constituent of Virola bark. Extracts of the plant caused the relaxation of smooth muscle and this activity was shown to result from the presence of coumarin and umbelliferone. Betaine, which was also present, was observed to elicit smooth muscle contraction at high concentrations. Strong inhibitory activity of the extract towards four dermatophytic fungi was observed and may explain the use of the plant in the treatment of certain infections. Coumarin was shown to be wholly responsible for the aroma. The possibility that the hypnotic effects of coumarin may play a role in its use as a snuff constituent is considered. The use of Virola elongata as both an hallucinogenicsnuff and an arrow poison was examined. Extracts of the bark were evaluated for their effects on mouse behavior. A non-alkaloidal fraction caused a reduction in spontaneous motor activity in mice while the alkaloidal fraction from the same amount of plant material had no significant effect. The non-alkaloidal fraction was examined and some of its biological activity was attributed to the presence of polyphenolic compounds. Eleven compounds were isolated from the non-polar part of this extract. In addition to β-sitosterol, two isomeric stilbenes, two neolignans, four bis-tetrahydrofuran lignans and two tetrahydrofuran lignans, were identified. The bis-tetrahydrofuran lignans were shown to reduce spontaneous motor activity and isolation induced aggression in mice. The possibility that they are at least partly responsible for the use of Virola elongata as an arrow poison is raised. Thirty-four species of Amazonian Euphorbiaceae were screened for inhibitory activity towards Escherichia coli, Staphylococcus aureus, two yeasts, four dermatophytic fungi, two animal viruses, tumour formation in potato discs and toxicity to brine shrimp. A large proportion of the extracts were active against S. aureus, the dermatophytes, at least one of the viruses, the potato tumours and the brine shrimp. The biological activities observed are discussed with respect to the use of certain species in Amazonian ethnomedicine. The antiviral activity of one of the plants screened, a species of Amanoa was examined. The inhibitory activity towards infection by murine cytomegalovirus was found toresult from the presence of a single compound, identified as the lignan, α- ( - )-peltatin. At low doses(10 ng/ml for two hours), this compound prevented the replication of viruses in already infected cells. It's activity was observed to be very similar to that of another naturally occurring lignan, podophyllotoxin. Lignans of a variety of structural types were examined for antiviral activity but anti-murine cytomegalovirus activity of compounds other than the podophyllotoxin type was not observed.

Text

2010-06-12

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http://hdl.handle.net/2429/25616

Biology

University of British Columbia

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