Medical Ethnobotany with the Zoque People of Southern Mexico and Herbal Neuropsychopharmacology in Mesoamerica

Mesoamerica (MA) is one of the bioculturally most diverse areas of the world. Research on the neurological activities of mind-altering organic substances from Mexico was fundamental in the emergence of ethnopharmacology as a scientific discipline and provided key insights into the functioning of the human brain. Further, there is historical evidence for a sophisticated medical system in pre-Columbian MA. This notwithstanding, the herbal pharmacopoeia of Mexico contains just 27 native plant species and the information on the herbal drugs used for alleviating mental and neurological disorders has never been systematically reviewed. This thesis thus aims at enhancing the scientific understanding of herbal medicine in MA, focussing on ethnomedical and ethnopharmacological aspects related to the CNS. Chapter 1 of this thesis describes the results of 13 months of fieldwork with the Zoque of Chiapas and Oaxaca. A total of 544 medicinal plant species have been documented and the ethnomedical systems are compared in the light of the differing degrees of acculturation. The 2nd chapter deals with the issue of translating culturally-defined (emic) concepts of disease and treatment to scientific (etic) terms, which facilitates the communication and cross-cultural comparison of research results. We present individual recommendations on how to classify diseases, illnesses, and remedies, depending on the research focus – ethnomedical, cross-cultural, or bioprospecting. Chapter 3 experimentally investigates the correlations between chemosensory properties, humoral qualities, and therapeutic uses of medicinal plants with a Zoque testing panel. Correlations between the drugs’ humoral qualities and the other parameters result particularly significant. Humoral concepts are thus shown to act as an important cultural filter linking the empirically perceived presence of secondary metabolites in plants to their disease-specific application. The findings have implications for culturally appropriate drug development and healthcare strategies. Chapter 4 aims at reconstructing the development and diffusion of medicinal plant knowledge in MA. A database was compiled containing 2188 botanical taxa used medicinally by the five linguistic groups most closely associated with major civilizatory periods in MA. Linguistic analysis indicates that especially Mayan and Mixe-Zoquean cultural groups were instrumental in developing and diffusing herbal medicine in MA. Given a relatively coherent set of health beliefs and a large number of shared medicinal taxa, Mesoamerican Traditional Medicine merits enhanced recognition from both researchers and legislators. Chapter 5 presents an overview of the 1324 botanical species used in MA for illnesses and diseases with a pronounced association with the nervous system. The neuropsychopharmacological data available on 308 species from the 58 cross-culturally most salient genera are systematically reviewed. Further, the most frequently reported mental and psychosomatic folk illnesses are described. The quantitative nature of this review facilitates the prioritization of taxa for future research and establishes a much-needed framework of evidence for practitioners and legislators. In Chapter 6 we experimentally investigate the activities of three flavones (acacetin, diosmetin, and luteolin) from the herbal drug Agastache mexicana on mice in the elevated plus-maze. All three flavone aglycones showed significant anxiolytic-like effects. The combined treatment with all three flavones resulted in an enhanced anxiolytic effect similar to diazepam. While the difference between individual and combined flavone treatment is not statistically significant, the results suggest a synergistic interaction between the flavonoids present in A. mexicana. Studies on human subjects are recommended in order to provide a more reliable evidence-base to users of this herbal drug.