REPORT pubs.acs.org/jchemeduc
Research Advances: Using Chemistry To Repel Pests, Improve Flavor, and Offer New Treatments Angela G. King* Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109, United States ABSTRACT: Chemists worldwide are applying basic chemical principles in news ways. This research and the resulting gain in understanding can impact our health, diet, and comfort. KEYWORDS: First-Year Undergraduate/General, General Public, High School/Introductory Chemistry, Second-Year Undergraduate, Upper-Division Undergraduate, Biochemistry, Chemoinformatics, Environmental Chemistry, Organic Chemistry, Bioanalytical Chemistry FEATURE: Reports from Other Journals
’ SHOO, FLY! CATNIP OIL REPELS BLOODSUCKING FLIES Catnip, the plant that attracts domestic cats like an irresistible force, has proven 99% effective in repelling the blood-sucking flies that attack horses and cows, causing $2 billion in annual loses to the cattle industry.1 Junwei Zhu and colleagues note that stable flies, Stomoxys calcitrans (L.), not only inflict painful bites, but also transmit multiple diseases. Cattle harried by these bloodsuckers may produce less meat and milk, have trouble reproducing, and develop diseases that can be fatal. All traditional methods for controlling stable flies, even heavy applications of powerful insecticides, have proven less than effective. The scientists thus turned to catnip oil, already known to repel more than a dozen families of insects, including house flies, mosquitoes, and cockroaches. Electroantennograms showed that catnip oil and Z, E- and E, Z-nepetalactone (Figure 1), which together make up greater than 90% of catnip oil, all elicited significant antennal responses from both male and female stable flies and showed repellant activity in an olfactometer study. To field test the oil as a repellant, scientists made pellets of catnip oil, soy, and paraffin wax, and spread them in a cattle feedlot. Within minutes, the pellets shooed the flies away, with the repellent action lasting for about 3 h (Figure 2). Pellets without catnip oil, in contrast, had no effect. The scientists now are working on making the repellent action last longer, which they say is the key to putting catnip to use in protecting livestock both in feedlots and pastures. This approach to stable fly management affords the benefits of being environmentally
nonpersistant and having low mammalian toxicity and this is justifying its use in a push-pull pest control strategy. In documented success stories for such strategies, a repellant, or “push” agent, in this case catnip oil, is paired with a “pull” component, which attracts the pests to other areas where they are concentrated for elimination. Figure 1 shows the structure for 1-octen-3-ol, a lead for the attractant for the stable fly system, which scientists hope to bring to fruition after addressing the longevity of catnip oil’s repellency (see Figure 3). Additional information on this research project is available online.2 Readers interested in insect bioassays may find resources on electroantennograms,3,4 construction of an olfactometer,5 or related research on why some hosts get bitten by flies more than others6 interesting. This research falls in the interdisciplinary field of chemical ecology, which was eloquently introduced in this Journal in 19837 and John Byers maintains an excellent Internet resource for those wanting to learn more about the field.8 Research Advances has previously reported on research projects involving honey bee and cockroach pheromones.9,10
’ PACKING MORE FLAVOR INTO MODERN PORK Perhaps you cannot make a silk purse out of a sow’s ear, but scientists are reporting progress in pulling off the same trick with the notoriously bland flavor of pork. They are reporting new insights into the biochemical differences in the meat of an Italian swine renowned for its good flavor since the ancient Roman Empire and the modern “Large White” or Yorkshire hog, whose roots date back barely 125 years.11 Lello Zolla and colleagues note that modern lean pork’s reputation as bland and tasteless has fostered new interest in heritage breeds. Among them are the Casertana, which produces more fat but has been heralded for its good flavor for thousands of years. One of the ultimate goals of that research is production of lean but more flavorful pork. In the new study, the scientists focused proteomics and microarray approaches on the mechanism that converts genetic
Figure 1. Z, E-nepetalactone (left) and E, Z-nepetalactone (middle), the main components of catnip oil, have been shown to repel stable flies while 1-octen-3-ol (right) is attractive to the flies. Structures provided by A. King. Copyright r 2011 American Chemical Society and Division of Chemical Education, Inc.
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Figure 2. Mean number of adult stable flies observed landing on catnip oil-treated areas and the untreated control areas of cattle feeding lots. The means for each sample time with different letters are significantly different at the level of p < 0.05 ANOVA, separated by the Scheffe test. Reprinted with permission from ref 1. Copyright 2010 American Chemical Society.
Figure 3. Catnip oil volatiles (analytes) recovered by solid phase extraction (5 min atmospheric sampling) in feedlot areas after treatment with a waxpellet formulation of catnip oil. Means with different letters are significantly different at the level of p < 0.05 ANOVA, separated by the Scheffe test. Reprinted with permission from ref 1. Copyright 2010 American Chemical Society.
information in DNA into proteins and the actual proteins present in the longissimus lumborum muscle of Casertana and Large White pigs. That muscle appears in the supermarket as pork chops, pork tenderloin, and pork ribs. The researchers identified biochemical mechanisms involved in the Large White’s ability to
produce more meat than fat, and the corresponding mechanisms that enable the Casertana to produce more fat (Figure 4). Large White pigs clearly showed a tendency to muscular growth, with all overexpressed proteins belonging to protein groups that make up the fiber and sarcoplasmic reticulum. In addition, Large White 533
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Figure 4. 2-DE of longissimus lumborum extracts from Large White and Casertana pig breeds. IEF pH range is 3-10, 12% T, 3% C Acrylamide. Gels have been stained with colloidal Coomassie. Each gel image has been elaborated with Progenesis SameSpots (Nonlinear Dynamics, New Castle, U.K.) and represent an average of 30 gels (3 technical replicate for 10 biological replicate samples), upon background subtraction. Reprinted with permission from ref 11. Copyright 2010 American Chemical Society.
pigs appear to be geared for lipid mobilization and oxidation, which reduces fat accumulation. Casertana pigs appear to rely on glycolitic enzymes when fed the same diet as the Large Whites. The findings are a step toward developing new pig breeds with a more desirable combination of both leanness and flavor not seen in current pork products, the study suggests. This Journal has previously published materials to help instructors incorporate tandem mass spectrometry (MS/MS), an important tool for proteomic studies such as this, into their classrooms.12
Figure 5. 3,4-Diaminopyridine (1) was the model compound for development of leading small molecule Kþ channel inhibitors for symptomatic relief of botulinum neurotoxin (2) and (3). Structures provided by A. King.
’ MULTIPLE SCLEROSIS DRUG SERVES AS MODEL FOR POTENTIAL DRUGS TO TREAT BOTULISM POISONING Botulinum neurotoxins (BoNT) are etiological agents that cause botulism, a disease that displays flaccid paralysis in humans owing to a peripheral neuromuscular blockade due to inhibition of acetylcholine release of neuromuscular junctions. BoNT are classified as bioterrorism agents because they are easy to make and have a lethal potency of 1 ng/kg, which means BoNT are 10,000 times deadlier than cyanide and some of the most poisonous substances known to humans. Currently no pharmacological treatments for BoNT exist. Kim D. Janda and colleagues explain that the lack of any approved drug treatment for botulism poisoning leaves a major gap in defenses against bioterrorism and biological warfare. People exposed to botulism toxin develop paralysis, cannot breathe, and may require months of treatment on respirators. “The numbers of medical care units capable of providing supportive care for recovery in the event of a bioterrorism incident would be limited”, they note. Janda’s team is now reporting that variants of a drug (1, Figure 5) already approved for treating multiple sclerosis show promise as a long-sought treatment for victims of bioterrorist attack with BoNT.13 The potential drugs also could be useful in treating other forms of botulism poisoning, as well as Alzheimer’s disease, multiple sclerosis, and myasthenia gravis, according to the research team. The scientists knew that the multiple sclerosis drug diaminopyridine (1) showed promise for working inside nerve cells to counteract the effects of botulism toxin by blocking voltagedependent Kþ channels. However, diaminopyridine itself had
Table 1. Apparent Toxicitya at 10 pM BoNT/Ab 0 μM, %
30 μM, %
100 μM, %
330 μM, %
100
—
—
—
1 (3,4-DAP)
—
99
9
6
2
—
99
10
9
3
—
99
20
8
Control
a
Apparent toxicity is the percent of toxicity (as measured by paralysis time) of tissues exposed to 10 pM BoNT/A, e.g., 10% toxicity is equivalent to the toxicity of a 1 pM BoNT/A dose. b Reprinted with permission from ref 13. Copyright 2010 American Chemical Society.
disadvantages, including its ability to pass through the bloodbrain barrier (BBB) and have toxic effects on brain tissue. The scientists modified the molecular structure of 1 to produce two new substances (2 and 3) that showed great potential as botulism treatments in mice that had been paralyzed by the toxin (Figure 5). All three compounds become equivalent to each other with respect to therapeutic value when their apparent toxicity is compared (Table 1). Compounds 2 and 3 were both shown to block Kþ channels and reverse symptoms from BoNTinduced paralysis in a mouse phrenic nerve-hemidiaphram assay. Compound 2 was found to be as effective as the “gold standard”, 3,4-diaminopyridne, in rescuing BoNT-poisoned mice in a mouse lethality assay. Pharmokinetic experiments showed that 2 did not effectively penetrate the BBB, which is a step toward resolving neurotoxicity issues associated with other treatments. More information on this and other research in Janda’s lab can be found online.14 534
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’ AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected].
’ REFERENCES (1) Zhu, J.; Dunlap, C.; Behle, R.; Berkebile, D.; Wienhold, B. Repellency of a Wax-Based Catnip-Oil Formulation against Stable Flies. J. Agric. Food Chem. 2010, 58, 12320–12326. (2) McGinnis, L. United States Department of Agriculture, Agricultural Research Service: News & Events—Developing Attractants, Repellants for a Cattle Pest. http://www.ars.usda.gov/is/pr/2009/090731. htm (accessed Feb 2011). (3) Tony Purcell Research Group Home Page. http://www.biochemistry.unimelb.edu.au/research/res_purcell.html (accessed Feb 2011). (4) Perez, P.; Rozas, R. J. Chem. Educ. 1987, 64, 356–358. (5) Omrania, S. M.; Vatandoost, H.; Oshaghi, M. A.; Shokri, F.; Guerin, P. M.; Yaghoobi Ershadi, M. R.; Rassi, Y.; Tirgari, S. J. Vector Borne Dis.. 2010, 47 (1), 17-25. http://www.ncbi.nlm.nih.gov/ pubmed/20231769 (accessed Feb 2011). (6) UK Biotechnology and Biological Sciences Research Council, Rothamsted Research Institute, Science Snapshots: Biting Back at the Flies. http://www.rothamsted.ac.uk/Research/Centres/Content.php? Section=ForThePublic&Page=Flies (accessed Feb 2011). (7) Wood, W. J. Chem. Educ. 1983, 60, 531–539. (8) Byers, J. Chemical Ecology of Insects Web Site Home Page. http://www.chemical-ecology.net/ (accessed Feb 2011). (9) King, A. J. Chem. Educ. 2005, 82, 810–814. (10) King, A. J. Chem. Educ. 2005, 82, 1274–1278. (11) Murgiano, L.; D’Alessandro, A.; Egidi, M.; Crisa, A.; Prosperini, G.; Timperio, A.; Valentini, A.; Zolla, L. Proteomics and Transcriptomics Investigation on longissimus Muscles in Large White and Casertana Pig Breeds. J. Proteome Res. 2010, 9, 6450–6466. (12) Arnquist, I.; Beussman, D. J. Chem. Educ. 2009, 86, 966–968. (13) Mayorov, A.; Willis, B.; Di Mola, A.; Adler, D.; Borgia, J.; Jackson, O.; Wang, J.; Luo, Y.; Tang, L.; Knapp, R.; Natarajan, C.; Goodnough, M. C.; Zilberberg, N.; Simpson, L. L.; Janda, K. D. Symptomatic Relief of Botulinum Neurotoxin/A Intoxication with Aminopyridines: A New Twist on an Old Molecule. ACS Chem. Biol. 2010, 5, 1183–1191. (14) Home Page of the Janda Group at the Scripps Research Institute, the Skaggs Institute for Chemical Biology. http://www. scripps.edu/chem/janda/ (accessed Feb 2011).
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