Medical Ethnobotany of the Isthmus-Sierra Zapotecs (Oaxaca, Mexico) and Biological-Phytochemical Investigation of Selected Medicinal Plants

Abstract

The Zapotec inhabitants of the Isthmus' Sierra of Tehuantepec in Oaxaca (Mexico) live in a tropical area of great botanical diversity. In daily subsistence and in response to illness, plants still play a major role. Healer, midwives, and herbalists use more than 445 different plant species belonging to 110 different botanical families during empirical therapies and ritual healing sessions.For the present ethnobotanical and phytochemical study the indigenous uses of medicinal plants and the healing specialists' way of reasoning in medicinal matters were ocumented during a 17-month stay in the field. 3,611 medicinal uses were documented and sets of 445 voucher specimens have been deposited in several herbaria. The Zapotec employ binary forms, usually opposing systems, of classifying illnesses (e.g. hot-cold, sweet-sour, wet-dry). This dichotomy is dominant, but also doctrines of signatures, and taste and smell properties were used to classify plants and illnesses. The Zapotecs gather plants for healing purposes from six indigenous ecological zones which are defined by their respective distance to the community and by the way they are managed. These ecological data are valuable concerning sustainable resource management of the tropical vegetation.In a quantitative approach, the epidemiologically most important plants were evaluated. ermatological illnesses and gastrointestinal complaints are the most frequent medical problems in this region. In a second part of the study, extracts of eleven plant species were prepared and subjected to biological assays for the evaluation of antimicrobial, antifungal, cytotoxic/antitumoral, anti-inflammatory, immunomodulatory, and antisecretory activity. Several activities have been evaluated corroborating the alleged properties as described in traditional medicine and additional information on the plants was obtained. Also, a chemical screening on thin-layer chromatography (TLC} and with spray reagents has been conducted. Begonia herac/eifo/ia Schltdl. & Cham. (Begoniaceae) showed antibacterial and cytotoxic/antitumor activity in the screening corroborating the medicinal use of this plant among the Zapotec healers. With different chromatographic methods, (VLC, MPLC, HPLC, TLC), six cucurbitacins, three sterols, a sterol glycoside, five fatty acids, and an oligosaccharide have been isolated. Structure elucidation was conducted mainly by spectrometric methods (DCl-MS, El-MS, FAB-MS) and 1 Dand 2D-NMR techniques (COSY, HMBC, HMQC, ROESY, TOCSY).Three of the isolated cucurbitacins showed varying cytotoxic/antitumoral activity, while three were inactive. These selective activities may be due to specific structural features of the respective compounds. Research on traditionally used medicinal plants f rom tropical countries shows great promise in the search for new drugs in the treatment of local and global medicinal problems. In case of successful results, it should never be forgotten that the primary selection has been based on empirical indigenous criteria applied over centuries. Solutions to the "intellectual property rights" problems must be found soon, since it is necessary to carry on the important search for natural products which are valuable tor medicine.