Há uma base biológica na seleção de plantas medicinais? Uma avaliação a partir de sistemas médicos locais

Abstract

This thesis aims to understand the relationship between the taste of medicinal plants and their selection to compose local pharmacopoeias. For this, we use two ways of investigation: 1) evaluate whether the perception of taste influences the selection of medicinal plants to treat a set of specific diseases and whether the acceptability of tastes varies according to each type of taste present in medicinal plants; 2) to assess whether the biological basis of chemosensory perception of bitter taste influences characteristics of medical systems, specifically the attribution of the social role of a local specialist, the habit of being an experimenter of new medicinal plants and knowledge about plants with taste. We collected data from residents over 18 years of age in five communities located in the Catimbau National Park. We recorded knowledge about medicinal plants using free lists and the attributes of taste, acceptability of taste and therapeutic targets through semi-structured interviews. Local experts were identified through local validation and experimenters were asked two objective questions. The biological basis was measured using a threshold test to identify bitter taste, using solutions with increasing concentrations of phenylthiocarbamide. We found that plants with a bitter and “travoso” taste are used to treat a set of specific diseases, corroborating the evidence in the literature. However, the associations were distinct between the five communities studied, indicating that the association between the taste of the plant and the therapeutic purpose is likely to depend more on cultural factors than other aspects. Plants with a sweet taste have greater acceptability while bitter plants have less acceptability of taste. Probably, psychophysiological and cultural mechanisms influence the acceptability of bitter or disgusting tastes, favoring the ingestion of plants with this type of taste. We found that sensitivity in the perception of bitter taste does not influence the attribution of the social role of local specialists or the habit of experimenting new medicinal plants. This sensitivity is also not associated with knowledge about medicinal plants with taste. This biological basis probably played a fundamental role in the beginning of the use of medicinal plants by the human species, but it does not influence the relationship between taste and plant selection in current pharmacopoeias. Future studies could seek to understand whether the chemosensory perception of taste influences the selection of plants by sedentary and semi-sedentary populations, since these communities usually deal with environments that vary in time and space.