Synthesis of tetraethyl pyrophosphate (TEPP): from physician Abbot and pharmacist Riegel to chemist Nylen.

Tetraethyl pyrophosphate (TEPP) made history not only as the first man-made organophosphate cholinesterase inhibitor but also as a most successful commercial product traded under a good number of names. The substance was first synthesized by a Russian chemist, Wladimir Petrovich Moshnin, while studying in Paris as an eleve (student) of Wurtz. The synthesis was soon thereafter repeated and reported to the Academy of Sciences by Philippe de Clermont, another student of Wurtz, who acknowledged the earlier work of Moshnin. Holmstedt in his chapter dealing with the beginnings of organophosphate chemistry in Koelle's Textbook Cholinesterases and Anticholinesterase Agents concluded his remarks by noting that after the initial synthesis by Moshnin and de Clermont, over the years, a good half-a-dozen of other pharmacists and chemists also managed the feat (of synthesizing TEPP). This led to my attempts at identifying those involved in the synthesis of TEPP. The compiled list turned out to be quite long: Abbot (1879), Riegel (1896), Cavalier (1906), Rosenheim A, Stadler & Jacobsohn (1906), Rosenheim & Pritze (1908), Balareff (1914), Nylen (1930), Arbusow & Arbusow (1931), Schrader (1938), Woodstock (1946) and Toy (1948). This report while summarizing the synthetic approach used in obtaining TEPP by the respective scientists mainly attempts to shed light on the life of the less known pharmacists and chemists involved in the synthesis of TEPP. The focus is on the pre-industrial synthesis period ending with Nylen largely because details on the Arbusow family, as well as on Schrader and Toy are fairly well known or have recently been described.

Pharmacists Adolf Schall and Ernst Ratzlaff and the synthesis of tabun-like compounds: a brief history.

The history of the synthesis of organophosphate inhibitors of cholinesterase starting with the synthesis of tetraethyl-pyrophosphate by Moschnin(e) and de Clermont and leading to the recognition about half a century later of the toxicity of the phosphor ester by Lange and von Krueger has been told in great detail previously. An almost parallel history -described originally by Bo Holmstedt--exists for organophosphonate inhibitors of cholinesterase starting with the synthesis (1898) in Rostock of diethylamido-ethoxy-phosphoryl-cyanide by the pharmacist Adolph Schall (1870-1957), a graduate student of August Michaelis (1847-1916), the re-examination of the chemical structure of the Schall compound (1903) by Michaelis, recognition (1937) of the toxicity of class by Gerhard Schrader (1903-1990) and confirmation (1951) of the structure by Bo Holmstedt (1919-2002). This short report attempts to shed some light on the life of the pharmacists and chemists involved in the synthesis of the first P-CN organophosphonate inhibitor of cholinesterase, focusing on the two less known pharmacists, the graduate students of Professor Michaelis Adolph Schall and Ernst Ratzlaff (1870-1948).

The history of acetylcholinesterase inhibitors in the treatment of myasthenia gravis.

The beneficial effects of acetylcholinesterase inhibitors for the treatment of myasthenia gravis (MG) was a major discovery that came about through one young physician putting together a string of previous observations. To understand how this discovery came to light, we must first go back to earlier times when men hunted by bow-and-arrow to capture their prey. The substance used to poison the prey was eventually was identified as curare. Centuries later, a connection was made between the physiological effects of curare and a disease entity with no known pathological mechanism or treatment, myasthenia gravis. In 1935, house officer Dr. Mary Walker was the first physician to try physostigmine in the treatment of MG, which had previously been used to treat curare poisoning. What she saw was a dramatic improvement in the symptoms experienced in patients with MG, and thus became the first documented case of use of physostigmine, an acetylcholinesterase inhibitor, in the treatment of MG. This article is a summary of the history of the use of acetylcholinesterase inhibitors in the treatment of myasthenia gravis. This article is part of the special issue entitled 'Acetylcholinesterase Inhibitors: From Bench to Bedside to Battlefield'.

Toxicity of phosphor esters: Willy Lange (1900-1976) and Gerda von Krueger (1907-after 1970).

In 1851 Williamson serendipitously discovered a new and efficient way to produce ethers using ethyl iodide and potassium salts. Based on this new synthetic approach, the Frenchman Philippe de Clermont and the Muscovite Wladimir Moschnin, both élèves of Adolphe Wurtz in his Paris School of Chemistry, achieved the synthesis of the first ester of pyrophosphoric acid (TEPP). de Clermont "tasted" the new compound and although TEPP is a potent cholinesterase inhibitor he failed to recognize its toxicity. Almost a century later, in 1932, Willy Lange (1900-1976) and his graduate student Gerda v. Krueger (1907-after 1970) described the toxicity of organophosphonates. While the classic paper of the two "Uber Ester der Monofluorphosphorsäure." is cited by almost everybody working in the field, little is known about Lange and almost nothing about v. Krueger. This brief communication attempts to shed some light on the life of both.

Acetylcholinesterase inhibitors (nerve agents) as weapons of mass destruction: History, mechanisms of action, and medical countermeasures.

Nerve agents are organophosphorus acetylcholinesterase inhibitors. Acute exposure to nerve agents can cause rapid death. In this review, we summarize the history of nerve agent development and use in warfare, the mechanisms by which these agents cause death or long-term brain damage, and the treatments for preventing death or long-term morbidity. The G-series nerve agents, tabun, sarin, soman, ethyl sarin, and cyclosarin, were developed by the Nazis. VX, the best-known of the V-series agents, was synthesized in the 1950's by a British scientist. Little is known about the development of the novichoks (the "A-series") by the former Soviet Union. Nerve agents were used for the first time in the battlefield by the Iraqi government in the Iran-Iraq War, in the 1980s. The Chemical Weapons Convention, in 1993, banned all chemical weapons production and use, yet, sarin was subsequently used in terrorist attacks in Japan and, recently, in the war in Syria. Pyridostigmine has been used as a prophylactic treatment, and bioscavengers are presently investigated as a better alternative. Atropine, along with an oxime, can prevent rapid death from the nerve agent-induced peripheral cholinergic crisis. Treatment with diazepam or midazolam for the cessation of nerve agent-induced status epilepticus cannot protect against brain damage, and, therefore, these benzodiazepines should be replaced by novel anticonvulsants and neuroprotectants. The AMPA/GluK1 receptor antagonist LY293558 (tezampanel) has shown superior antiseizure and neuroprotective efficacy against soman, particularly when administered in combination with caramiphen, an antagonist of muscarinic and NMDA receptors. This article is part of the special issue entitled 'Acetylcholinesterase Inhibitors: From Bench to Bedside to Battlefield'.

The synthesis of phosphor ethers: who was Franz Anton Voegeli?

The synthesis of the first organophosphate cholinesterase inhibitor (tetraethyl pyrophosphate, TEPP) is credited to the French organic chemist Philippe de Clermont (1831-1921) and to the Russian chemist Wladimir P. Moshnin from Moscow, both working in the laboratories of Adolphe Wurtz in Paris. In his publications de Clermont describes however not only the TEPP synthesis but also that of the related compound triethyl phosphate (TEP). TEP was previously synthesized by the Swiss chemist Franz Anton Voegeli (1825-1874), working in the laboratory of Gustav Magnus in Berlin. While TEPP is a potent organophosphate cholinesterase inhibitor with an IC50 in the low nanomolar range, TEP has no anticholinesterase activity up to millimolar concentrations. Therefore de Clermont and Moschnin are indeed the fathers of the first organophosphate cholinesterase inhibitor (TEPP), but are not entitled to claim paternity of the first compound in the class of phosphoric acid esters (TEP), an honor which belongs to Franz Anton Voegeli.

Dr Lazar Remen (1907-74): a forgotten pioneer in the treatment of myasthenia gravis.

Dr Lazar Remen (1907-74) was the first, in 1932, to describe the beneficial effect of prostigmine on a myasthenia gravis patient. His observation actually preceeded by two years Mary Broadfoot Walker's (1888-1974) paper, which is considered to be the landmark article on this association.

Alzheimer's disease drugs: an application of the hormetic dose-response model.

This article provides an evaluation of the dose-response features of drugs that are intended to improve memory, some of which have been used in the treatment of Alzheimer's disease (AD). A common feature of these drugs is that they act via an inverted U-shaped dose response, consistent with the hormetic dose response model. This article assesses historical foundations that lead to the development of AD drugs, their dose-response features and how the quantitative features of such dose responses affected drug discovery and development, and the successes and possible failures of such agents in preclinical and clinical settings. This story begins about 150 years ago with the discovery of an active agent in the Calabar bean plant called physostigmine, its unfolding medical applications, and its implications for dose-response relationships, memory enhancement, and improved drug discovery activities. The article also demonstrates the occurrence of U-shaped dose responses for memory with numerous endogenous agonists including neurosteroids, various peptides (e.g., vasopressin, CCK-8, neuropeptide Y), and other agents (e.g., epinephrine, antagonists for platelet activity factor and nicotinic receptors), supporting the generalizability of the hormetic biphasic dose response. Finally, the significance of the U-shaped dose response is critical for successful clinical application, since it defines the therapeutic window.

The history of cholinesterase inhibitors: who was Moschnin(e)?

The synthesis of the first organophosphate cholinesterase inhibitor (tetraethyl pyrophosphate, TEPP) is often credited to the French organic chemist Philippe de Clermont, working in the laboratories of Adolphe Wurtz in Paris. The two de Clermont's publications dealing with TEPP clearly state however that the first synthesis of TEPP was achieved by another student of Wurtz, named Moschnine. While de Clermont is well known, nobody really knows who Moschnine was. This brief communication attempts to give an overview about the life and achievements of the Russian chemist Wladimir Petrovich Moshnin from Moscow.

Mary Broadfoot Walker: 83 years since a historical discovery.

Mary Broadfoot Walker was a Scottish physician who, in 1935, described in great detail the effect of an anticholinesterase drug (physostigmine) on the signs and symptoms of myasthenia gravis. An original five-minutes movie is available online and the skepticism of her contemporary British medical doctors is understandable when the drastic effect of the treatment is shown in this movie. What Mary Walker taught us, more than eight decades ago, about myasthenia gravis continues to be the basis of a pharmacological diagnostic test and treatment of this disease.

Monoamine oxidase: isoforms and inhibitors in Parkinson's disease and depressive illness.

A few years after the foundation of the British Pharmacological Society, monoamine oxidase (MAO) was recognized as an enzyme of crucial interest to pharmacologists because it catalyzed the major inactivation pathway for the catecholamine neurotransmitters, noradrenaline, adrenaline and dopamine (and, later, 5-hydroxytryptamine, as well). Within the next decade, the therapeutic value of inhibitors of MAO in the treatment of depressive illness was established. Although this first clinical use exposed serious side effects, pharmacological interest in, and investigation of, MAO continued, resulting in the characterization of two isoforms, MAO-A and -B, and isoform-selective inhibitors. Selective inhibitors of MAO-B have found a therapeutic role in the treatment of Parkinson's disease and further developments have provided reversible inhibitors of MAO-A, which offer antidepressant activity without the serious side effects of the earlier inhibitors. Clinical observation and subsequent pharmacological analysis have also generated the concept of neuroprotection, reflecting the possibility of slowing, halting and maybe reversing, neurodegeneration in Parkinson's or Alzheimer's diseases. Increased levels of oxidative stress in the brain may be critical for the initiation and progress of neurodegeneration and selective inhibition of brain MAO could contribute importantly to lowering such stress. There are complex interactions between free iron levels in brain and MAO, which may have practical outcomes for depressive disorders. These aspects of MAO and its inhibition and some indication of how this important area of pharmacology and therapeutics might develop in the future are summarized in this review.

The early toxicology of physostigmine: a tale of beans, great men and egos.

Mid-19th century European visitors to Old Calabar, an eastern province of Nigeria, could not avoid becoming aware of native belief in the power of the seeds of a local plant to determine whether individuals were innocent or guilty of some serious misdemeanour. The seeds were those of a previously unknown legume and soon referred to as the ordeal bean of Old Calabar. Their administration was known locally as 'chop nut'. Missionaries who arrived in Calabar in 1846 estimated that chop nut caused some 120 deaths annually and documented the course of poisoning. The latter information and samples of the beans rapidly found their way to Scotland, the home of the missionaries' parent church, explaining why the early toxicology of physostigmine, quantitatively the most important of three active alkaloids in the beans, has such strong Scottish, predominantly Edinburgh, associations. However, it was 1855 before the first of many medical scientists, Robert Christison, a toxicologist of repute, investigated the effects of the beans to the extent of eating part of one himself and documenting the moderate, if not severe, consequences. A further 6 years were to pass before Balfour's comprehensive botanical description of the bean plant appeared. It was he who named it Physostigma venenosum. It was not so long until the next event, one that sparked more intensive and international interest in the beans. In 1863 a young Edinburgh ophthalmologist, Argyll Robertson, published a paper announcing the arrival of the first agent that constricted the pupil of the eye. The drug was an extract of Calabar beans and Argyll Robertson openly admitted that he had been alerted to its unusual property by his physician friend, Thomas Fraser. A minor flood of contributions on the ophthalmic uses of bean extracts followed in the medical press in the next few months; those on their systemic toxicity were fewer. Fraser's MD thesis, submitted to the University of Edinburgh in 1862 and clearly pre-dating Argyll Robertson's involvement with the beans, became generally available a few weeks after the appearance of Argyll Robertson's paper and was the first to address in detail the features of systemic administration of extracts of the beans. A major problem facing all early researchers of the beans was that of deciding how best to extract their active principle, a task made all the more difficult because bioassays were the only means of determining if the toxin was being tracked. The stability of extracts was an inevitable issue and the active principle finally became known as physostigma or physostigmine, after the botanical name of the parent plant. The features of physostigmine toxicity were soon exhaustively documented, both in animals and humans. How they were mediated was another matter altogether. Fraser maintained that muscular paralysis, the cardinal feature, was the result of depression of the spinal cord and was generally, but far from unanimously, supported. Of those who had reservations, Harley was the most prominent. He concluded that paralysis was secondary to effects on the motor nerve endings and, in so doing, came nearest to present-day knowledge at a time when acetylcholine, cholinesterases and cholinesterase inhibitors were not even imagined. Differences of opinion on the mode of action of the beans were to be expected and it is hardly surprising that they were not resolved. No standard formulation of physostigmine was available so the potency of those used would have varied from one investigator to another, the range of animals experimented upon was large while the number used by any researcher was commonly in single figures, more readily available cold-blooded creatures seemed less sensitive to physostigmine toxicity than warm-blooded ones and only Fraser determinedly pursued an answer; in general, the others made one foray into bean research then turned their attentions elsewhere. The same problems would beset other aspects of bean research. While Fraser did not get as close to the mode of action of physostigmine as Harley, he reigns supreme when it comes to antagonism between physostigmine and atropine. By this time, the 1870s had dawned and although the concept of antagonism between therapeutic agents was not new, it had little, if any, reliable scientific foundation. This was about to change; antagonism was becoming exciting and rational. Fraser's firm belief that physostigmine and atropine were mutually antagonistic at a physiological level was contrary to the conventional wisdom of his contemporaries. This alone would earn him a place in history but his contribution goes much, much further. Unlike any other at the time, he investigated it with scientific rigour, experimenting on only one species, ensuring as best he could the animals were the same weight, adjusting the doses of drugs he gave them for bodyweight, determining the minimum lethal dose of each drug before assessing their antagonistic effects, adopting a single, incontrovertible endpoint for efficacy and carrying out sufficient numbers of experiments to appear convincing in a later era where the statistical power of studies is all-important. To crown it all, he presented his results graphically. Fraser never claimed to have discovered the antagonism between physostigmine and atropine. Bartholow in 1873 did, based on work done in 1869. But his data hardly justify it. If anyone can reasonably claim this particular scientific crown it is an ophthalmologist, Niemetschek, working in Prague in 1864. His colleague in the same discipline, Kleinwächter, was faced with treating a young man with atropine intoxication. Knowing of the contrary actions of the two drugs on the pupil, Niemetschek suggested that Calabar bean extract might be useful. Kleinwächter had the courage to take the advice and his patient improved dramatically. Clearly, this evidence is nothing more than anecdotal, but the ophthalmologists were correct and, to the present day, physostigmine has had an intermittent role in the management of anticholinergic poisoning. The converse, giving atropine to treat poisoning with cholinesterase inhibitors, of which physostigmine was the first, has endured more consistently and remains standard practice today. It is salutary to realise that the doses and dosage frequency of atropine together with the endpoints that define they are adequate were formulated by Fraser and others a century and a half ago.

Neurosciences and research on chemical weapons of mass destruction in Nazi Germany.

As a side-product of industrial research, new chemical nerve agents (Tabun, Sarin, Soman) superior to those available to the Allied Forces were discovered in Nazi Germany. These agents were never used by Germany, even though they were produced at a large scale. This article explores the toxicological and physiological research into the mechanisms of action of these novel nerve agents, and the emergence of military research objectives in neurophysiological and neurotoxicological research. Recently declassified Allied military intelligence files document secret nerve agent research, leading to intensified research on anticholinesterase agents in the peripheral and the central nervous system. The article discusses the involvement of IG Farben scientists, educational, medical and military institutions, and of Nobel Prize laureate Richard Kuhn, director of the Kaiser Wilhelm Institute for Medical Research.

Contemporary opinions about Mary Walker: a shy pioneer of therapeutic neurology.

OBJECTIVE: To contribute to a better understanding of a poorly appreciated pioneer of therapeutic neurology, Mary Broadfoot Walker, MD. BACKGROUND: At a time when the treatment of myasthenia gravis (MG) was "a source of discouragement to the patient and a cause of nightmare for the physician," Mary Walker demonstrated that temporary relief of myasthenic symptoms could be produced by subcutaneous injection of physostigmine or neostigmine (Prostigmin; Roche, Basel, Switzerland). She also pioneered the concept of a circulating factor as the etiology of myasthenia and was the first to report hypokalemia in familial periodic paralysis. Throughout her career she was dependent on her salaried jobs as a medical officer in several large London hospitals and was thus forced to turn down an offer of an honorary staff position with research beds. DESIGN/METHODS: Previously unpublished material written by persons who lived at the same time as Mary Walker is incorporated with the published record into an account of Mary Walker's accomplishments as assessed by her contemporaries. RESULTS: 1) Although Mary Walker's 1934 report on physostigmine for MG was ignored by most of those in clinical medicine at the time, those responsible for the financing of British medical research vainly hoped that it could be used as an example of the practical outcome of basic research. 2) Her 1935 demonstration of the beneficial effect of neostigmine (Prostigmin) was greeted with general skepticism because of the rapidity with which the patient's symptoms of myasthenic weakness improved, but she was soon vindicated by published confirmatory reports from several contemporaries. 3) Her 1938 demonstrations of what came to be known as "the Mary Walker effect" may have helped her reputation because subsequent published opinions of her contributions were generally favorable, although some people continue to disparage her even today. CONCLUSION: Mary Walker, with her brief case reports and her frequent demonstrations, not only offered symptomatic treatment for MG that has stood the test of time, but also provided the most convincing evidence at the time that the neuromuscular junction was the focus of the disease.

Research on cholinesterases in the Soviet Union and Russia: a historical perspective.

Research on cholinesterases and effects of their inhibition in the USSR and Russia since 1930-1940s till present is exposed in historical aspects. The first physiological and toxicological effects of cholinesterase inhibition were reported by Alexander Ginetsinsky during World War II, when academic institutions were evacuated from Leningrad to Kazan. The main scientific schools that initiated research on chemistry, enzymology and physiology of cholinesterases and their inhibitors were leaded by Alexandr and Boris Arbuzovs, Victor Rozengart, Viktor Yakovlev, Michael Michelson, Martin Kabachnik, Mikhail Voronkov, Ivan Knunyants, Alexandr Bretskin and others. They investigated the main physiological effects of cholinesterase inhibitors, and analyzed the catalytic mechanisms of cholinesterases and related enzymes. Their contributions are landmarks in the history of cholinesterase research. At the present time revival of research on cholinesterases in different universities and institutes is vivid, in particular at the Moscow State University, research institutes of Russian Academy of Sciences and Kazan Scientific Center.

Anticholinesterase insecticide retrospective.

The anticholinesterase (antiChE) organophosphorus (OP) and methylcarbamate (MC) insecticides have been used very effectively as contact and systemic plant protectants for seven decades. About 90 of these compounds are still in use - the largest number for any insecticide chemotype or mode of action. In both insects and mammals, AChE inhibition and acetylcholine accumulation leads to excitation and death. The cholinergic system of insects is located centrally (where it is protected from ionized OPs and MCs) but not at the neuromuscular junction. Structural differences between insect and mammalian AChE are also evident in their genomics, amino acid sequences and active site conformations. Species selectivity is determined in part by inhibitor and target site specificity. Pest population selection with OPs and MCs has resulted in a multitude of modified AChEs of altered inhibitor specificity some conferring insecticide resistance and others enhancing sensitivity. Much of the success of antiChE insecticides results from a suitable balance of bioactivation and detoxification by families of CYP450 oxidases, hydrolases, glutathione S-transferases and others. Known inhibitors for these enzymes block detoxification and enhance potency which is particularly important in resistant strains. The current market for OPs and MCs of 19% of worldwide insecticide sales is only half of that of 10 years ago for several reasons: there have been no major new compounds for 30 years; resistance has eroded their effectiveness; human toxicity problems are still encountered; the patents have expired reducing the incentive to update registration packages; alternative chemotypes or control methods have been developed. Despite this decline, they still play a major role in pest control and the increasing knowledge on their target sites and metabolism may make it possible to redesign the inhibitors for insensitive AChEs and to target new sites in the cholinergic system. The OPs and MCs are down but not out.