IT'S ELEMENTAL!
ANTIMONY NINA ULRICH, UNIVERSITY OF HANNOVER, GERMANY
A
NTIMONY IS ONE OF THE LEAST
famous chemical elements. If you ask someone on the street about it, you'll be met with a blank stare. Not like the response you would get if you mentioned everyday elements such as oxygen or elements famous for their toxicity such as arsenic. Even a chemist might respond: "Well, antimony it's just like arsenic. Toxic, you know Its chemical properties are quite similar, fifth main group. But less useful, except maybe for some alloys." That was also my point of view when I started antimony speciation analysis 10 years ago. But I quickly realized that this element has been part of history for a long time and has many important functions in the pres-
A F F L I C T E D A young Sudanese boy with visceral leishmaniasis.
ent. In the future, there could be even more applications, especially in the medical field. Antimony's use is first documented by the ancient Egyptians. They loved the beautiful colors of compounds like the bright orange antimony sulfide, especially for cosmetic purposes. But even in that period, antimony was taken as medicine for different fevers and skin irritations, as old papyri show And medicine stayed one of the main fields for antimony application (besides alchemy). In the 13th century, Roger Bacon described several of its properties, and in the 17th century, Theodor Kerckring wrote the first monograph of a 126
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chemical element about antimony In addition, antimony is part of the canon of homeopathy and has been widely applied in the past few centuries. Back in the early-20th century, antimony was discovered to be extremely useful in the therapy of tropical diseases, especially leishmaniasis. This is a deadly parasitic infection; there are millions of people at risk and, according to the ^Jforld Health Organization, an estimated 2 million cases occur every year. In some areas of South America, leishmaniasis is endemic and its cutaneous form is simply viewed as a children's disease. The more severe form, visceral leishmaniasis, however, leads to fever and massive enlargement of the intestines, liver, and spleen and, sadly when untreated it has a mortality rate of 98%. The vector is a small insect, a sand fly that lives in human houses, and the reservoir contains not only humans but also many kinds of mammals and even some reptiles like crocodiles. Therefore, it is nearly impossible to exterminate the disease.
of metals and metalloids. Ideally the conformation of the chemical compounds can directly be determined. Although there are numerous problems—for example, the stability of the compounds, the low concentrations of the species, and insufficient separation—much progress has been made in the past few years. It has been possible to differentiate between trivalent and pentavalent antimony in cell samples. In addition, the formation of chemical bindings
ANTIMONY AT A GLANCE Name: From the Greek anti and monos, not alone. The symbol is from the Latin stibium, mark. Atomic mass: 121.76. History: Antimony was recognized in compounds by ancient civilizations and was known as a metal at the beginning of the 17th century. Occurrence: Found in many minerals. Appearance: Bluish white, solid metal. Behavior: Antimony is highly toxic. Uses: Addition of antimony to alloys increases the hardness and mechanical strength of lead and other metals.
between organic compounds in the cells, such as enzymes or proteins, and antimony has been observed. Although the mechanism of antimony The chemical analysis led to these retoxicity to the parasite remained unclear, sults for the biological processes: The penseveral therapeutic agents have been develtavalent antimony is reduced in the oped. In the earlyyears, mainly trivalent anamastigote cells to the trivalent oxidation timony had been applied, which showed a state. Afterward, the trivalent antimony nice ability to kill the parasite but unfortutakes effect on the parasite. The antimonately also to kill the human host. So the anny resistance of some strains of the leishtimony was switched to the pentavalent oxmaniasis parasite is possibly caused by the idation state in the 1950s, resulting in much inability of these cells to effect the reduclower toxicity Nowadays, mainly sodium tion, thereby interrupting the chemical restibogluconate (pentostam) and meglumine actions. In addition, some cell antimonite (glucantime) are used. groups show a reduced antimoIn the past decade, health ofny uptake or accelerated antificials noted that the disease was mony excretion. becoming resistant to antimony treatment. That led to increased Speciation analysis in combiefforts for the development of nation with biomedical experinew therapeutic agents and the ments has helped explain much understanding of their mode of about the biochemistry of antiaction. New techniques—both mony in leishmaniasis. But much CELEBRATING on the biomedical and on the more research is needed before C&EN'S 80TH chemical side—were developed the mode of action of antimony ANNIVERSARY for cell samples. Scientists sucin the parasite is fully understood. ceeded in cultivating the parasite This knowledge then might be cells, the amastigotes, on media, giving the used as a basis for the development of new opportunity for direct investigation of antherapeutic agents that are more toxic to timony toxicity on them. the parasites and cause fewer side effects. Meanwhile, in analytical chemistry, adNina Ulrich is a professor of inorganic chemvances were being made in the field of speistry at the Institute of Inorganic Chemistry, ciation analysis, which deals with different University ofHannover, Germany. oxidation states and the chemical bindings HTTP://WWW.CEN-0NLINE.ORG
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