Mexican herbal medicines

Aside from tomatl and corn, many other plants widely used in Europe and North America are in fact based on traditional knowledge of the Aztecs and other Mexican indigenous groups. Aguacatl (or avocado) and chilli are just two of the many examples. Medicinal plants are an important element of indigenous medical systems in Mexico as well as in many other countries. These resources are usually regarded as part of a culture’s ‘traditional’ knowledge. Today one finds such plants on Mexican markets and many people in rural and urban areas regularly use herbal medicines.

Picture 1: Medicinal herbs on sale in a Mexican market

Ethnobotany and Ethnopharmacology investigate the relationship between humans and plants in all its complexity. Ethnobotanists live with the members of a community, share their everyday life and, of course, respect the cultures which host them. They have a responsibility both to the scientific community but maybe even more importantly also to the indigenous cultures. A complex set of methods are used which are derived from the social and cultural sciences (including the taking of detailed field notes, quantitative assessments of reported uses, cognitive and symbolic analyses of plant usage) and the natural sciences (collection of plant samples - voucher specimens, that allow for precise determination of the plant species). Ethnobotanical studies have a multitude of theoretical and applied interests and in fact only very few are in any way directly linked with projects in the area of drug discovery. Therefore, the role of the ethnobotanist is not only in the search for new drugs but also as someone who acts as a spokesperson for indigenous interests and helps that such knowledge can still be used by future generations (Heinrich 2009).

The other major early source is the ‘Historia Natural de Nueva España’ by Francisco Hernandez. He - the personal physician to Philip II of Spain- was sent to Mexico and between 1571- 1577 gathered information on plants, animals and minerals of the New World. The complete work was never published and the original manuscript was destroyed during a fire at the Escorial palace. Abridged and amended versions have been published among others by Reccho and by Francisco Ximenez. There are only two important sources on the medicinal plants in 17th and 18th century New Spain: Juan de Esteyneffer’s and Fray Juan de Navarro’s works. The Florilegio medicinal was written by a Jesuit priest Johannes Steinhoffer, which was known as Juan de Esteyneffer in Mexico (Anzures y Bolanos 1978).

Picture 5: one edition of the Hernández work

One of the most famous examples of a drug development project driven by traditional knowledge is the discovery of psilocybin and derivates from the hallucinogenic mushroom Psilocybe, which for centuries has been used by the Mazatec Indians in Oaxaca, Mexico. This drug development project of the 1940’s and 1950’s was only possible thanks to the collaboration of two ethnobotanists and two chemists. R.G. Wasson (1898 –1986) had been trained as a journalist and in literature studies. He later worked in a bank and most notably thanks to his wife Valentina Pavlovna Guercken (1901 – 1958) he became interested in ethnobotany. This brought him in contact with the US-American ethnobotanist Richard Evans Schultes (1916 – 2001), who while doing his PhD dissertation in the Mazatec region learned about the use of hallucinogenic mushrooms commonly known by the Aztec name as teonanacatl. While continuing to work they devoted much of their spare time to the study of these ‘enthogens’. R.G. Wasson ultimately became the first ‘outsider’ to participate in a night-long Velada in the Mazatec community of Huautla de Jimenez. These experiences were publicized very widely and the in 1957 they were even reported in detail in the US-magazine Life.

Picture 7: hallucinogenic mushrooms

For example, the potential of novel anti-diabetic medications is enormous. In Mexico alone a total of 306 species have records of a popular use in the treatment of this syndrome. Opuntia spp. (cactus pears or prickly pears Cactaceae) are an essential element of Mesoamerican botanical history. For centuries the Aztecs and many other Mexican indigenous groups have used ripe fruits and the nopales (or nopalitos, tender cladodes) both as a food and a medicine. Ill-defined extracts from Opuntia species are now widely available over the internet as a treatment for diabetes and related metabolic disorders and chemically and pharmacological characterised extracts are currently under development.

Picture 9: nopalitos

An exciting example of research driven by traditional knowledge is the discovery of a new drug and its target which may help to control pain. This is technically called a receptor (the transient receptor potential vanilloid type 1 protein -TRPV1). This example shows the close links between modern biochemistry and the local and traditional use of a plant. These channels were originally cloned while searching for a molecular target of the pungent compound capsaicin from Mexican hot chilli (spicy varieties of Capsicum annum L. and C. frutescens L.) and the phorboid resiniferatoxin from species of the genus Euphorbia. Of course, chilli and paprika have a long tradition of use in Meso- and South American cultures, famously as a spice, but also as a medicine including for chronic inflammatory conditions. C. annuum (which often is less pungent than C. frutescens) originated from Mesoamerica and C. frutescens from the western Amazonian region or Bolivia, but today both are part of a universal culture and is generally considered an integral part of, for example, the medical and culinary traditions on the Indian subcontinent and it is a typical Balkan (Hungarian) spice.

Picture 11: 19th. century illustration of Euphorbia resinifera

In chemical and pharmacological terns the development of Capsicum spp. is linked to another botanically unrelated, traditional medicinal plant - Euphorbia resinifera Berg (Euphorbiaceae), a large, leafless cactus-like perennial and a native of the Anti-Atlas Mountains of Morocco, which yields Euphorbium. Probably it is King Juba II of Mauretania (50 BC - 23 AD) and his physician Euphorbius who discovered the medicinal potential of the resin. Euphorbium has had a medical history of more than 2000 years. This makes resiniferatoxin (RTX) one of the most ancient drugs still in use today (Appendino et al 2008). Some of its uses, like its application on nerves to suppress chronic pain or on dental cavities to mitigate tooth ache, can be linked directly to the biochemical studies discussed below. The pharmacological interest in this species goes back to the discovery that its key constituent resiniferatoxin has effects on the TRP channel similar to capsacin and this links the history of the drug development of these two botanical drugs (for a review see Heinrich 2009). The example shows how intrinsically linked such development projects are and, of course, they are complex research and development processes.

Picture 13: Euphorbia resinifera

Thus, Aztec knowledge is now part of complex global network of information and may well result in further benefits to humankind.br
The other lesser known and sadly only poorly studied aspect of this is the use of such information in local developmental projects. Information on how to treat oneself with home remedies has been disseminated in México since the time of Juan de Esteyneffer and today local botanic gardens, books and also the internet are used to disseminate such information. Not all medicinal plants are safe and some are even highly toxic. A range of Aristolochia (birthwort) species are utilised in Mexico and Central America but from research on Chinese and European Aristolochia species it is well known that these species contain toxic compounds (aristolochic acids), which cause nephropaties and kidney cancer.

Picture 15: Mexican markets abound with plants, flowers, herbs - and medicines...

In conclusion, Mexico has given the world some of the most widely used food plants and in today’s world, there is a constant and fast exchange of information. Scientists and all of us have the responsibility to make such information available in such a way that it can be used in helping those who need it most; sadly this includes the Modern Aztecs and other indigenous groups in Mexico.
(Emphasis added)

Picture 17: herbal remedies

Picture sources:-
• Pix 1, 6, 10 and 18: courtesy Prof Michael Heinrich
• Pic 2, from faculty.ksu.edu.sa/75032/default.aspx
• Pic 3, from www.hsl.unc.edu/Services/Tutorials/ DrugInformation/pharmacognosy.htm
• Pic 4, from the Badianus Manuscript (‘An Aztec Herbal of 1552’), now in the Vatican Library, scanned from our own copy of ‘The Badianus Manuscript (Codex Barberini, Latin 241), John Hopkins Press, Baltimore, 1940
• Pic 5, from booksellers’ websites
• Pix 7, 8, 9, 11, 13, 14: from Wikipedia
• Pic 12 Image from the Florentine Codex scanned from our copy of the Club Internacional del Libro 3-volume facsimile edition, Madrid, 1994
• Pix 15, 16, 19: photos by Ian Mursell/Mexicolore
• Pic 17: photo by Titus Alexander/Mexicolore

Picture 19: Mexican chillis - Wow!