Ethnobotany

The rich untapped flora that human societies have been using for their many needs must be investigated for the purpose of developing new sources of proteins, fats, starches, alkaloids, therapeutic agents, and pharmacodynamic compounds. Much of our present knowledge of plant resources has its origins in indigenous cultures . . .The rich plant lore has been passed on by word of mouth and by tradition from generation to generation in different parts of the world. . . It is to uncover these hidden and secret uses of the flora that ethnobotany has become an important part of our investigation.

-Richard Evan Schultes and Siri von Reis, 1995

Ethnobotany: Evolution of a Discipline

Throughout history, mankind has utilized plants as a primary source of food, medicine, and shelter. This tradition continues today. In 2001, the World Health Organization estimated that 85% of the world’s population was directly dependent on plant-based medicines (Cox and Heinrich, 2001). In contrast with most other organisms, plants have the ability to undergo a process of secondary metabolism, in which unique compounds are produced for the purposes of defense, pollinator attraction, and coloration, among others. Examples of these important secondary metabolites usually fall within the following natural product classes: alkaloids, non-protein amino acids, cyanogenic glycosides, coumarins, glucosinolates, monoterpenes, sesquiterpene lactones, diterpenoids, saponins, liminoids, carotenoids, phenols, flavonoids, and quinones (Dewick, 2001).

These same compounds, which serve important roles in plant survival, are also useful in mammalian systems. For example, upon entry into the human body and an environment of physiological pH, the very structure of alkaloid compounds takes on a quaternary form, through which the compound can interact with human receptors – inhibiting or stimulating activity of the targeted site. This may have a medicinal, or even a toxic, effect on the body. For example, the alkaloid strychnine acts as a glycine mimic, binding to glycine receptor sites in the spinal chord, and exhibiting a toxic effect. On the other hand, the alkaloid atropine can exert a medicinal anticholinergic effect by competing with acetylcholine for the muscarinic receptor site in the parasympathetic nervous system (Dewick, 2001).

Some notable plant-derived drugs still in use today include vincristine (Catharanthus roseus (L.) G. Don; Apocyanaceae), physostigmine (Physostigma venenosum Balf. f.; Fabaceae), pilocarpine (Pilocarpus jaborandi Holmes; Rutaceae), reserpine (Rauvolfia serpentina (L.) Benth. ex Kurz ; Apocyanaceae), and digitalis (Digitalis purpurea L.; Scophulariaceae) (Cox and Balick, 1994; Cox and Heinrich, 2001; Dewick, 2001; Solomon, 2004). Today, the search for new drugs coming from vascular plants continues with particular focus on plants exhibiting antimicrobial, anti-cancer, and antiviral effects. The need for new, structurally unique antimicrobials is of utmost importance in this era of widespread microbial resistance to existing therapies (Levy, 2002; Smith and Coast, 2002; Walsh, 2003).

Many plants that are used for their antimicrobial activity contain polyphenolic compounds, which commonly act as antiviral agents, or essential oils, which often act as antiseptics (Heinrich et al., 2004). One of the best known antimicrobial plants is garlic, Allium sativum L., Liliaceae. Garlic contains a wealth of sulphur compounds, glycosides, and monoterpenoids. These sulphur compounds have shown remarkable in vitro antibacterial, antiviral, and antifungal activity (Blumenthal et al., 2000; Heinrich et al., 2004; Srinivasan et al., 2001; Zenner et al., 2003).

Another well known plant with broad-spectrum antimicrobial activity is the tea tree, Melaleuca alternifolia Cheel., Myrtaceae. The monoterpenoids present in tea tree oil have demonstrated activity against a broad spectrum of microorganisms, including Staphylococcus aureus, Escherichia coli, Candida albicans, Leishmania major, and Trypanosoma brucei (Heinrich et al., 2004).

Secondary metabolites, or natural products, manufactured by plants as a means of defense against herbivory or microbial infection, have demonstrated potent activity against human pathogens. Yet, less than 0.5 % of the more than 265,000 flowering species that exist on earth have been exhaustively studied for their chemical composition and medicinal potential (Cox and Balick, 1994). It is certain that a wealth of novel structures wait to be studied, and likely that some of these will, in fact, exhibit potential for medicinal applications.

On this site, I have included links to publications, websites, and peer-reviewed journals relevant to the study of ethnobotany. My personal research interest focuses on the study of medicinal plant products with antimicrobial activities - particularly against multidrug-resistant isolates of Staphylococcus aureus. In addition to bioassay work, an extensive portion of my doctoral research will include a field study in south Italy regarding the application of medicinal plants to the skin. For more details regarding this ongoing project, see Research.

References Cited:

Blumenthal, M., Goldberg, A., Brinckmann, J., 2000. Herbal Medicine. Expanded Commission E Monographs, American Botanical Council. Integrative Medicine Communications, Newton, MA, pp. 519. Cox, P.A., Balick, M.J., 1994. The ethnobotanical approach to drug discovery. Scientific American 270 (1), 82-87. Cox, P.A., Heinrich, M., 2001. Ethnobotanical drug discovery: uncertainty or promise? Pharmaceutical News 8 (3), 55-59.Dewick, P.M., 2001. Medicinal Natural Products. Second Edition. John Wiley & Sons, Ltd., Chichester, England.Heinrich, M., Barnes, J., Gibbons, S., Williamson, E.M., 2004. Fundamentals of Pharmacognosy and Phytotherapy. Churchill Livingstone, London.Levy, S.B., 2002. The Antibiotic Paradox: How the Misuse of Antibiotics Destroys their Curative Powers. 2nd Edition. Perseus Publishing, Cambridge, MA.Smith, R.D., Coast, J., 2002. Antimicrobial resistance: a global response. Bulletin of the World Health Organization 80, 126-133.Solomon, J., 2004. Missouri Botanical Garden Vascular Tropicos, http://mobot.mobot.org/W3T/Search/vast.html, Missouri Botanical Garden, St. Louis.Srinivasan, D., Nathan, S., Suresh, T., Permalsamy, P.L., 2001. Antimicrobial activity of certain Indian medicinal plants used in folkloric medicine. Journal of Ethnopharmacology 74, 217-220.Walsh, C., 2003. Antibiotics. Actions, Origins, Resistance. ASM Press, Washington, D.C.Zenner, L., Callait, M.P., Granier, C., Chauve, C., 2003. In vitro effect of essential oils from Cinnamomum aromaticum, Citrus limon and Allium sativum on two intestinal flagellates of poultry, Tetratrichomonas gallinarum and Histomonas meleagridis. Parasite 10, 153-157.