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Chemistry rooted in cultural knowledge : unearthing the links between antimicrobial properties and traditional knowledge in food and medicinal plant resources of the Secwepemc (Shuswap) Aboriginal Nation Bannister, Kelly Patricia

Abstract

The role of phytochemicals as ecological mediators of interrelationships between humans and plants was explored. Specifically, antimicrobial properties of plants were examined in the context of traditional plant use as food and/or medicine by the Secwepemc (Shuswap) Aboriginal peoples of south central British Columbia. The research was conducted in collaboration with the Secwepemc Cultural Education Society (Kamloops) as part of a larger ethnobotanical research program. The first component of the study involved the screening for antimicrobial activities in vitro of sixty-eight plant species used by the Secwepemc to treat microbial-based conditions. Extracts of eighty-eight percent of plant species examined had antibacterial activity, seventy-five percent had antifungal activity and twenty-five percent had antiviral activity. Based on the screening results and additional ethnobotanical information, Balsamorhiza sagittata (Pursh) Nutt. (Asteraceae), commonly called balsamroot, was selected for further characterisation. In the second part of the study, the phytochemistry of aerial and underground parts of balsamroot was examined within the cultural context of traditional plant preparation and use as food and medicine. The effect of differential heat-processing for food and medicine on antimicrobial compounds in roots was assessed. A biologically active compound known to occur in roots (thiophene E) was used as a ’marker’ to compare the bioactivity and localisation of antimicrobial compounds in pitcooked roots (prepared as food) with boiled roots (prepared as medicine). Only the edible portion of roots was devoid of antimicrobial activity. Bioactivity-guided isolation lead to the purification and identification of a known phytosterone (16R, 23R-dihydroxycycloartenone) and an unreported phytosterol (16R, 23R-dihydroxycycloartenol) from roots. The effect on antimicrobial compounds of drying leaves for medicine also was measured. Three antimicrobial compounds were present in fresh leaves but absent in dried leaves. One of these was purified; using spectroscopic techniques its structure was determined as a previously unreported sesquiterpene lactone (guaianolide), designated 2-deoxy-pumilin-8-O-acetate. The cultural relevance of the findings was discussed in terms of the antimicrobial activity, potential allergenicity and localisation to glandular trichomes of sesquiterpene lactones. The integration of phytochemical data and Secwepemc cultural knowledge of balsamroot underscored the sophistication in Secwepemc botanical knowledge. It served also as an instructive case for the third component of this study, which moved beyond chemistry to raise and discuss some important ethical and legal issues concerned with research involving the cultural knowledge and traditional resources of Aboriginal peoples. The main issues discussed were associated with research obligations, direct and indirect impacts of research, and the dissemination and control of knowledge in ethnobotanical and related investigations.

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