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Professor Michael Heinrich

Mexican herbal medicines

This article has generously been written specially for us by Michael Heinrich, Head of Centre and Professor, Centre for Pharmacognosy and Phytotherapy, The School of Pharmacy, University of London, and a world expert on research into the medicinal plants used today by indigenous groups of Mesoamerica.

Picture 1: Medicinal herbs on sale in a Mexican market
Picture 1: Medicinal herbs on sale in a Mexican market (Click on image to enlarge)

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.

Plant-derived medical drugs from all over the world are at the centre of a discipline - pharmacognosy - which is both interested in pure compounds used as pharmaceuticals and in complex mixtures from plants (plant extracts) used as phytopharmaceuticals and derived from medicinal plants (botanical drugs). Plants have yielded many important medicines in the past and research groups all over the world (but only a few in the UK) look to discover new lead compounds or complex extracts for future drug development. This requires biological testing of plant extracts and isolation of their active components, as well as toxicological, pharmacokinetic and ultimately clinical studies. Very often clinical studies are also conducted. Overall, this is a very long, time-consuming and generally very expensive process of uncertain outcome. Europe has for many years profited from the exchange with other continents and many of the pure natural products and some of the phytotherapeutic preparations used today are derived from plants used in indigenous cultures.

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).

Picture 4: The Badianus Manuscript
Picture 4: The Badianus Manuscript

So, what is known about the classical and modern Aztecs? An interesting historical example from 16th century Mexico is an herbal written in Nahuatl by the Aztec healer Martin de la Cruz from Tezcoco, who was at the Colegio de Santa Cruz in Tlatelolco. It was translated into Latin by Juan Badiano and given to the King of Spain Carlos I in 1552. It includes numerous colour illustrations of medicinal plants (see picture, right). Today it is possible to identify many of these plant species and, in fact many are still used today.

Picture 5: one edition of the Hernández work
Picture 5: one edition of the Hernández work

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).

However, ethnopharmacology is also concerned with the medicinal plant use of modern populations as my research group has done in studies with Mexican and Central American indigenous groups (Aguilar et al 1994, Argueta 1994, Leonti et al. 2001, Heinrich et al 1998). All Mexican indigenous groups widely use medicinal plants and Aguilar et al. (1994) and Argueta (1994) summarise some of these data. Such data can, on the one hand, be used to develop new ideas for medicines [or as pharmacists call it a (medicinal) drug] or in a variety of ways to further the autochthonous development of such medicines.

Picture 7: hallucinogenic mushrooms
Picture 7: hallucinogenic mushrooms

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 8: Psilocybe mushrooms
Picture 8: Psilocybe mushrooms

Their research received great attention in the media and while no new drug was developed based on the compounds from Psilocybe, the example serves as an example of how such drug discovery programmes may work. Also, while during the 1960’s and 1970’s there was considerable interest in hallucinogenic drugs, today more research focuses, for example on cancer and on chronic diseases including diabetes and arthritis.

Picture 9: nopalitos
Picture 9: nopalitos

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.

Seven other species from Mexico – Cecropia obtusifolia Bertol. (Cecropiaceae), Equisetum myriochaetum Schlecht & Cham, (Equisetaceae), Acosmium panamense (Benth.) Yacolev (Fabaceae), Cucurbita ficifolia Bouché (Cucurbitaceae), {Agarista mexicana (Hemsl.) Judd. (Ericaeae), Brickellia veronicaefolia (Kunth) A. Gray (Asteraceae), Parmentiera aculeata (Kunth), Seem (Bignoniaceae) – have been studied in some detail, too, but have not yet resulted in useable, licensed drugs or nutraceuticals (Andrade Cetto and Heinrich 2005). With the fast increase in the rate in diabetes in México such research will benefit both people in Mexico and abroad.

Picture 11: 19th. century illustration of Euphorbia resinifera
Picture 11: 19th. century illustration of Euphorbia resinifera

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 12: Chilli seller, Florentine Codex Book X
Picture 12: Chilli seller, Florentine Codex Book X (Click on image to enlarge)

Multiple medical uses were recorded during the Aztec period, including uses for dental problems, infections of the ear and various types of wounds as well as digestive problems. Consequently, chillies were also an important element of tribute requested by the Aztec rulers. During the colonial period these uses continued and developed further. Now records of chilli’s use as an aphrodisiac appeared. More recently uses as a rubefacient to locally stimulate blood circulation became a central use of C. frutescens (Solis 1986).

Picture 13: Euphorbia resinifera
Picture 13: Euphorbia resinifera (Click on image to enlarge)

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 14: King Juba II
Picture 14: King Juba II

The ‘Western’ use of such information has come under increasing scrutiny and the national and indigenous rights on these resources have become acknowledged by most academic and industrial researchers (Secretariat of the Convention on Biological Diversity 2001). Central are the questions who owns this information and who receives benefits from it. It is now generally accepted that if research from a plant which is used locally in one area results in economic benefits (normally for a company) the people in the region of origin should receive some sort of financial recompensation. These developments result in a considerable challenge to ethnobotanists and ethnopharmacologists and increase their responsibilities. Simultaneously the need for basic scientific investigations on medicinal plants using in indigenous medical systems becomes ever more relevant. The public availability of the results of research into medicinal plants is essential for further developing and ‘upgrading’ indigenous and traditional medicine (Heinrich 2009), but one needs to consider how this can best be achieved.

Picture 15: Mexican markets abound with plants, flowers, herbs - and medicines...
Picture 15: Mexican markets abound with plants, flowers, herbs - and medicines... (Click on image to enlarge)

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 16: Traditional herbal medicines on sale in a Mexican market
Picture 16: Traditional herbal medicines on sale in a Mexican market (Click on image to enlarge)

The Popoluca of Veracruz, for example, utilise six Aristolochia species (esp. A. ovalifolia and A. asclepiadifolia) against stomach-ache and colic (Leonti et al 2001). The Nahua (Modern Aztecs) of the Sierra de Zongolica boil parts of the stem of guaco ( Aristolochia sp.) to prepare a tea to treat ‘hard pains in the body’ and snakebites. Similar uses are also known from the Isthmus-Sierra Zapotec. While these plants may have beneficial effects in terms of treating these illnesses, most importantly the chronic or continuous use is likely to have serious health risks. This example highlights the benefits of research on medicinal plants and how phytochemical and pharmacological information can be used to guide health care.

Picture 17: herbal remedies
Picture 17: herbal remedies (Click on image to enlarge)

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 18: Traditional medicines/remedies on sale in Mexico today
Picture 18: Traditional medicines/remedies on sale in Mexico today (Click on image to enlarge)

REFERENCES:-
• Aguilar, A, Camacho, J.R, Chino, S., Jáquez, P., López, M.E. (1994) Herbario Medicinal del Instituto Mexicano del Seguro Social. México, D.F. Instiuto Mexicano del Seguro Social (IMSS).
• Andrade-Cetto, A. and M. Heinrich (2005) Mexican plants with hypoglycaemic effect used in the treatment of diabetes. Journal of Ethnopharmacology 99 (3): 325-348.
• Anzures y Bolanos, Maria del Carmen (eda.) (1978). Juan de Esteyneffer: Florilegio Medicinal. Academia Nacional de Medicina, México D.F. 974 pp.
• Appendino, G. A. Minassi, A. Pagani, A. Ech-Chahad The role of natural products in the ligand deorphanization of TRP. channels. Curr. Pharm. Design, 2008, 14, 000-000 1.
• Argueta, V.A., coordinador. (1994) Atlas de las plantas de la medicina tradicional Mexicana. México, DF. Instituto Nacional Indigenista. 3 vols.
• Cruz, Martin de la and Juan Badiano (1991) [orig. 1552] Libellus Medicinalibus Indorum Herbis. Fondo de la Cultura Economica/ Instituto Mexicano del Seguro Social. México D.F. 2 vols. 64 folios y 258 pp.
• Heinrich, M. 2009) Ethnopharmacology and drug development. Invited MS for Comprehensive Natural Products Chemistry II (EDITORS-IN-CHIEF: Lewis N. Mander, Australia and Hung-Wen (Ben) Liu, USA Volume 6: Discovery, Development and Modification of Bioactivity. Volume Editor: Robert Verpoorte invited review in press.
• Heinrich, M., A. Ankli, B. Frei, C. Weimann and O. Sticher (1998) Medicinal plants in Mexico: Healers’ consensus and cultural importance. Social Science and Medicine 47: 1863-1875.
• Leonti, M., H. Vibrans, O. Sticher and M. Heinrich* (2001) Ethnopharmacology of the Popoluca, Mexico: An evaluation. Journal of Pharmacy and Pharmacology 53: 1653 - 1669.br
• Long-Solis J. (1986) “Capsicum y cultura. La historia del Chilli.” Fondo de Cultura Económica, México, D.F.
• Secretariat of the Convention on Biological Diversity. “Handbook of the Convention on Biological Diversity”. Earthscan, London. 2001. ISBN 0-85383 737 7.
• Weimann, C. and M. Heinrich (1997) Indigenous medicinal plants in Mexico: The example of the Nahua (Sierra de Zonglicia). Botanica Acta 110: 62-72.

Picture 19: Mexican chillis - Wow!
Picture 19: Mexican chillis - Wow! (Click on image to enlarge)

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

Learn more about the Badianus Manuscript
‘Mexicans turn to Aztec remedies’ (Financial Times article)
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Here's what others have said:

Mexicolore replies: Hard to believe! For starters, take a trip to the big Mercado de Sonora market in the eastern part of Mexico City. You’ll find loads of stalls selling herbal medicines to ordinary folk...
Mexicolore replies: We should explain that we don’t stock any plants or herbal extracts of any kind! We’re purely an educational service... Sorry to disappoint!