Chemical Education Today
Reports from Other Journals
Nature: Environmental Problems and New Hope for the Treatment of Malaria by Sabine Heinhorst and Gordon C. Cannon
Future Trouble for the Arctic Tundra? A column for the Earth Day 2005 issue of the Journal (see also http://www.epa.gov/earthday/; accessed Dec 2004) would be remiss if it did not address the effects of global climate change on man and nature. Scientists have been investigating direct and indirect effects of warming trends in Earth’s climate on ecosystems throughout the globe. Among these, northern tundras are predicted to be particularly vulnerable because of the expected magnitude of temperature increases at high latitudes. Rising temperatures are thought to increase the rate of organic soil material decomposition and release of nutrients, which in turn stimulates plant growth. Mack and colleagues from the University of Florida, the Univer-
sity of Alaska and from the Woods Hole Marine Biological Laboratory have simulated these effects on nutrient availability by fertilizing a test site in the Alaskan tundra and following carbon stored in plant matter and retained in soil over a more than 20-year time span (2004, 431, September 23, 440–443; see also the News and Views feature, 2004, 431, September 23, 401–407). Fertilization, as expected, increased biomass production, mainly as fast-growing woody shrubs. Interestingly, sub-surface (>5 cm depth) soil carbon retention decreased to an extent that the ecosystem incurred a net carbon loss of 2 kg carbon per m2 over 20 years. Although it is not known what caused this unexpected effect, the authors offer as a possibility increased microbial decomposition of organic matter in the deeper soil layers,
photo: Courtesy of Ted Schuur, Univ. of FL
Figure 3. The Alaskan Tundra north of Kotzebue along the Noatak River in the Baird Mountains. Figure 1. The Arctic Tundra. On the right is undisturbed tundra; the left portion shows shrubs growing on a fertilized experimental plot.
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Figure 4. Another view of the Alaskan Tundra north of Kotzebue along the Noatak River in the Baird Mountains.
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photos: John Pearce
Figure 2. The Alaskan Tundra seen from the Denali Highway between Cantwell and Paxon.
Chemical Education Today
which leads to subsequent loss of inorganic or soluble organic carbon. While the experiments conducted by Mack and colleagues do not directly test the effects of an increase in temperature on above- and below-ground carbon storage, the results of their study provide plenty of food for thought. With an estimated one third of Earth’s soil carbon stored in the Arctic tundras, these northern ecosystems are important reservoirs of bound carbon. If their soil carbon is released mostly as CO2 in response to increasing temperatures and nutrient availability, the phenomenon observed by Mack et al. could contribute significantly to atmospheric carbon dioxide levels and has the potential to magnify global warming.
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Trouble from Fire in Southeast Asia Trouble for Earth’s environment is also brewing at the equator. During the Suharto regime, large portions of the peat swamps in the Kalimantan region of Borneo were clear-cut and a system of drainage canals was installed. Kalimantan was supposed to become Indonesia’s new rice bowl as part of the Mega Rice Project, a vision that did not materialize. The News Feature by Peter Aldhous (2004, 432, November 11, 144–147) describes the devastation these drastic changes of the environment have brought to the indigenous people and the wildlife (notably the Orang Utan) of that region of Southeast Asia. The very thick peat stacks proved too acidic for rice cultivation. Moreover, when no longer water-logged during the dry season, the peat regularly catches fire and continues to smolder, releasing large quantities of smoke into the atmosphere that amount to 13–40% of the CO2 emitted annually around the globe from burned fossil fuels. In addition to its impact on global climate, the smog generated by the Kalimantan fires greatly reduced visibility and affected transportation, in addition to creating serious respiratory problems among the inhabitants. We experienced the putrid haze that extended across large areas of Southeast Asia in 1997 first hand, while attending a meeting in Singapore. The sun was hidden by the smog throughout our stay, and our throats became irritated as soon as we ventured outside. Several environmental groups from different countries are currently attempting to reverse the damage and to restore the Kalimantan peat swamps by building dams and by replanting the forest. Their efforts have met with mixed success and their outcome, to a large extent, will depend on the post-Suharto political climate in Indonesia. Breakthrough in Antimalarial Drug Synthesis The final paragraph of this column focuses on malaria, a human disease that is endemic in many developing countries. A series of articles (2004, 430, August 19, 923–945) covers a variety of social, political and scientific topics related to the malaria problem. A major hurdle impeding eradication of the disease is the emerging resistance of the malaria-causing parasite Plasmodium falsiparum to many antimalarial drugs. Notable exceptions are the semisynthetic derivatives of artemisinin, a product of a wormwood species that is well known as a fever-reducing Chinese herbal mediwww.JCE.DivCHED.org
Figure 5. Artemisinin, the natural product from Artemisia annua (sweet wormwood) that is used in traditional Chinese medicine to reduce fever. Structure courtesy H.-J. Schanz.
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Figure 6. New antimalarial candidate drug OZ277; on left of the endoperoxide bridge is the adamantane moiety. Hanging off the six-membered ring to the right is the polar moiety that increases the compound’s water solubility and biological half life. Structure courtesy H.-J. Schanz.
cine. These potent antimalarial compounds are believed to act through reduction of heme and the subsequent free radical-initiated damage to key proteins that are necessary for the survival of the malaria parasite. The compounds’ key structural feature is an endoperoxide bridge, which is essential for their antimalarial properties but poses a formidable challenge for the synthetic chemist and has hampered attempts to synthesize novel structurally similar antimalarial drugs. A multinational team of researchers from academia and from the pharmaceutical industry has tackled the challenge of developing potent new antimalarial drugs that are suitable for use in developing countries as part of the nonprofit Medicines for Malaria Venture at http://www.mmv.org/pages/ page_main.htm (accessed Dec 2004). The researchers have succeeded in synthesizing novel compounds with superior antimalarial properties that hold promise for human applications (Vennerstrom et al., 2004, 430, August 19, 900–904). The researchers stabilized trioxolanes with bulky adamantane groups and obtained potent antimalarial, albeit poorly water-soluble, products. Systematic approaches to increasing the polarity and predicted in vivo lifetime of these compounds without compromising their antimalarial properties led to the development of candidate trioxolane OZ277 (Figure 6) that, according to the accompanying News and Views article (pp 838–839), is currently undergoing its first clinical trials. Note 1. Figures 2, 3, and 4 courtesy John Pearce, wildlife biologist at the Alaska Science Center, Anchorage, AK; http:// www.absc.usgs.gov/ (accessed Dec 2004).
Sabine Heinhorst and Gordon C. Cannon are in the Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, MS 39406-5043; email:
[email protected] and
[email protected].
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