Losing nature's medicine cabinet

Jeremy Hance
mongabay.com
October 04, 2010



An interview with Dr. Christopher N. Herndon.

In all the discussions of saving the world's biodiversity from extinction, one point is often and surprisingly forgotten: the importance of the world's species in providing humankind with a multitude of life-saving medicines so far, as well as the certainty that more vital medications are out there if only we save the unheralded animals and plants that contain cures unknown. Already, species have provided humankind everything from quinine to aspirin, from morphine to numerous cancer and HIV-fighting drugs.

"As the ethnobotanist Dr. Mark Plotkin commented, the history of medicine can be written in terms of its reliance on and utilization of natural products," physician Christopher Herndon told mongabay.com. Herndon is co-author of a recent paper in the journal Biotropica, which calls for policy-makers and the public to recognize how biodiversity underpins not only ecosystems, but medicine.


Christopher Herndon with Eñepa healer and family in Venezuela. Photo courtesy of Christopher Herndon.
"Our dependence today on nature for health has not diminished as significantly as commonly presumed. Over the past quarter century, more than half of all pharmaceuticals brought to market were directly derived from or modeled after compounds from other species," Herndon explains.

However, the ecosystems that have yielded some of the world's most important and promising drugs—such as rainforests and coral reefs—are also among the most endangered. Researchers worry that in face of ocean acidification and warming temperatures connected to climate change, few coral reefs will outlive the century. Meanwhile, the world's rainforests continue to vanish at astounding rate, estimated at 80,000 acres (32,300 hectares) every day due to commercial agriculture, livestock, logging, slash-and-burn farming, and massive development projects.

In face of such destruction, Herndon says it's truly difficult to know how many species have been tested for medicinal properties, or for that matter how many have already been lost forever.

"Scientists generally estimate that less than one percent of all species has been fully examined for medical potential. We are only just beginning to appreciate the staggering biodiversity of our planet. A significant portion remains to be discovered by mankind."

Making conservation even trickier, most of nature's medicine cabinet is not stored in big charismatic mammals, such as tigers and elephants, but among the unsung heroes of world's ecosystems: plants, fungi, and invertebrates.

"The organisms that offer the greatest hope to ameliorate human suffering are rarely the most charismatic or cuddly. Unlikely to be profiled in a wall calendar anytime soon, they are often toxic or inhabit the extraordinary microcosms that exist below the limits of the naked eye and the scope of appreciation for many. To save their medical potential, we need to preserve entire ecosystems—we simply cannot predict which species and in what ways they will yield medical breakthroughs," Herndon says.

So, why has everyone—policy-makers, conservationists, doctors, and drug-companies included—failed to recognize this hugely compelling reason to preserve the world's ecosystems?

"Generally speaking, there is a prevailing misconception that biotechnology and synthetic chemistry has somehow supplanted our dependence on the natural world. The potential of nature has not diminished—arguably, it has only enhanced as we gain the technological tools to more efficiently access and utilize its potential for our benefit," Herndon says.

Herndon spoke to mongabay.com in an October interview about the connection between biodiversity and medicine, including amazing past discoveries, vital species and ecosystems, and why society continues to undervalue nature's medicine cabinet.



AN INTERVIEW WITH CHRISTOPHER HERNDON



Mongabay: When people think of animals and plants, they usually don't think of health. How is biodiversity connected to human health? What are some examples?


Strange plant on Mount Kenya. Photo by: Rhett A. Butler.
Christopher Herndon: People have been using species from nature as medicine since the dawn of history. Medicinal plants dating from over 60,000 years ago have been found in an Iraqi cave site. A fur strap found on the wrist of the 5,000 year-old Ice Man from the Alps contained threaded fragments of a birch fungus species known to have antimicrobial properties.

As the ethnobotanist Dr. Mark Plotkin commented, the history of medicine can be written in terms of its reliance on and utilization of natural products. The examples are innumerable—from aspirin to morphine to lovastatin. Our dependence today on nature for health has not diminished as significantly as commonly presumed. Over the past quarter century, more than half of all pharmaceuticals brought to market were directly derived from or modeled after compounds from other species. Globally, the World Health Organization estimates that in many developing countries as much as 80% of the population relies on traditional therapeutics sourced from nature.

More broadly, environmental health is a major determinant of our well-being. One cannot think of the harsh medical realities in Haiti without appreciating that 97% of the half-island country is deforested and much of the land eroded away. The border between Haiti and the adjacent Dominican Republic can be viewed from satellite as an abrupt transition from brown to green. Human diseases are exacerbated through ecologic disturbance. As we encroach into ecosystems, we acquire pathogens from other species. These are not trivial or esoteric diseases—HIV, for example, is the greatest pandemic of the modern era.

Mongabay: Approximately what percentage of known species has been tested for medicinal value?

Christopher Herndon: It is difficult to precisely quantify. Scientists generally estimate that less than one percent of all species has been fully examined for medical potential. We are only just beginning to appreciate the staggering biodiversity of our planet. A significant portion remains to be discovered by mankind.

Mongabay: Besides rainforests, what other ecosystems have yielded important medicines?


Herndon evaluating a sick child with local Eñepa healer in Venezuela. Photo courtesy of: Christopher Herndon.
Christopher Herndon: Tropical rainforests are probably the most celebrated ecosystem as a repository of new medicines. Although comprising only 6% of the earth's land surface, they contain over half of its terrestrial biodiversity. Pharmaceuticals have been developed from species from a diversity of ecosystems. The synthesis of AZT, the first effective treatment for HIV, was guided by compounds isolated from a Caribbean sponge. Taxol was discovered from temperate forests in the Pacific Northwest of the United States. Digitalis was discovered from an English garden plant. Any ecosystem can contain species that may contribute to health and biomedical science.

Mongabay: Why does preserving future medicines mean saving some of the world's less popular species?

Christopher Herndon: The organisms that offer the greatest hope to ameliorate human suffering are rarely the most charismatic or cuddly. Unlikely to be profiled in a wall calendar anytime soon, they are often toxic or inhabit the extraordinary microcosms that exist below the limits of the naked eye and the scope of appreciation for many. To save their medical potential, we need to preserve entire ecosystems—we simply cannot predict which species and in what ways they will yield medical breakthroughs. Who would have guessed that the salivary venom of the gila monster would lead to an FDA-approved treatment for diabetes? Or that the sting of a Arabian desert scorpion would contain a toxin that selectively binds cells of an aggressive form of brain cancer that is largely refractory to therapy? The natural world is out there for our discovery if only we have the wisdom to not discard it.

Mankind's need to develop new medicines is not a quixotic quest but rather a timeless struggle. Speaking as a physician, there are few conditions in medicine for which we are overburdened with too many safe, highly efficacious and inexpensive treatments. It is common need for which all of humanity can directly and tangibly share in its benefit. Although a large portion of the population of the developing world—regions containing the greatest extent of our planet's terrestrial biodiversity—may not be able to access a novel and expensive cancer therapy, they can benefit from pharmaceuticals that target their extensive disease burdens. A contemporary example is artemisinin—a medication derived from a Chinese herb and the most effective treatment for malaria that exists. In 2001, artemisinin-based therapies were adopted by the World Health Organization as the first-line agent in its global fight against malaria.

Mongabay: Why do you think the connection between biodiversity and health is underappreciated? In other words, why are drug companies, cancer non-profits, and physician associations not up in arms over the loss of ecosystems and our future medicines?

Researchers worry that the Great Barrier Reef in Australia may not survive the century. Photo by: Rhett A. Butler.
Christopher Herndon: In medical school, there is little emphasis on how treatments were developed or discovered. How many internists are aware that the groundbreaking blood pressure medicine captopril, one of the best-selling drugs of all time, was developed through the study of the venom of a Brazilian viper? I would like to think practitioners would be more prudent with antibiotic use if they better appreciated the perspective that these miracle drugs—the vast majority of which are derived from nature—are the product of millions of years of evolutionary selection. It is of grave concern that we are burning through them within a timeframe of decades—not even a blink of an eye on an evolutionary scale.

Generally speaking, there is a prevailing misconception that biotechnology and synthetic chemistry has somehow supplanted our dependence on the natural world. The potential of nature has not diminished—arguably, it has only enhanced as we gain the technologic tools to more efficiently access and utilize its potential for our benefit.

Several recent op-ed pieces have lamented the lack of therapies resulting from the sequencing of the human genome. This should not have been surprising—at least in the short term. The Human Genome Project and our ever-deepening understanding of molecular biology are extraordinary achievements that advance a foundation of science. There exists, however, a wide gap between knowledge and therapeutics that enhance lives. Nature has designed and tested novel and highly effective bioactive compounds for 3.5 billion years. Many of the natural compounds that have changed medicine could never have been conceived even today by the most imaginative synthetic chemists. The natural world is an endowment fundamentally worth protecting.



Citation: Christopher Herndon and Rhett Butler. Significance of Biodiversity to Health. Biotropica. 42(5): 558–560 2010 10.1111/j.1744-7429.2010.00672.x.







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CITATION:
Jeremy Hance
mongabay.com (October 04, 2010).

Losing nature's medicine cabinet.

http://news.mongabay.com/2010/1004-hance_herndon.html