The French chemist and pharmacist Pierre-Jean Robiquet (1780–1840) made major strides in analytical chemistry in the early 19th century. In addition to recognizing the connection between protein and amino acids, he identified the chemical components of everyday substances ranging from caffeine to mustard seed to strychnine.
Pierre-Jean Robiquet was the first to isolate an amino acid, thereby discovering one of the fundamental building blocks of proteins, and he determined the chemical composition of numerous substances in common use today. Through his investigations, he isolated the painkiller codeine and the stimulant caffeine, working independently of colleagues who were pursuing these studies concurrently. Beyond these firsts, Robiquet was notable for the range and imagination of his scientific activities. His inquiring mind compelled him to the laboratory, where he investigated the properties of dyes and what made them work; studied the chemical basis of aromas; worked to isolate chemical compounds in bitter almonds, mustard seeds, and other foods; and investigated the properties of useful poisons such as strychnine and cantharides. Robiquet's work was important not only in the realm of pure chemistry but in the development of France's chemical and pharmaceutical industries.
Robiquet was born in Rennes, France, on January 13, 1780; coming of age during the violent epoch defined by the French Revolution was to shape his life significantly. His father, Jean-François Robiquet, was a printer who, as a social conservative (Girondin), became ensnared in the Jacobin-Girondin controversy of 1793, was condemned by Jacobin activists, and arrested. Robiquet attended a free, church-affiliated school whose staff of clergy likewise ran afoul of the Jacobin proto-communist revolutionaries, with the result that the school was closed down. After studying architecture briefly, he was taken in by family friends and apprenticed to a carpenter. Another relative managed to find him an apprenticeship in the more lucrative trade of pharmacy, and for a year he worked in a pharmacy owned by a man named Clary. In 1795, Robiquet advanced in his new career when he was employed by the pharmacy of the French Navy, which had been crippled by the revolution's penchant for beheading aristocratic officers.
Robiquet rejoined his family in Rennes after his father's release from prison, working his way through a classical education. He supported himself by performing pharmacist duties for the French Army of the West, a force then engaged in pacifying the civil war in western France. In 1796, when the revolutionary force was reconfigured by the First French Republic, the 16-year-old returned to Paris for another set of pharmacy courses, at one point studying under eminent chemist Antoine François, a colleague of Antoine Lavoisier (1743–1794). This course so impressed Robiquet that he decided to pursue a career as a chemist. With his father's help, he got a job in a chemical lab owned by Fourcroy and another prominent chemist, Louis Nicolas Vauquelin. Still in his teens, he now participated in cuttingedge research on the composition of urinary tract deposits.
A registered pharmacist at Paris's École Polytechnique after 1808, Robiquet became a lecturer in chemistry in 1811. That same year, by decree of Emperor Napoleon Bonaparte, he was appointed assistant professor of pharmaceuticals at the city's Faculté de Pharmacie, and he became full professor in 1814. At that point, he was given an assistant, Pierre-Joseph Pelletier (1788–1842), who would draw on Robiquet's work in future collaborations with other chemists at the Faculté de Pharmacie.
Between 1805 and 1835, Robiquet published more than 60 scientific papers on an impressive variety of subjects. Some of his early research, on vegetable dyes and mineral pigments, had practical results—his discoveries improved manufacturing processes in the French dye industry—but it also oriented him toward pure analytical chemistry as he tried to isolate the components that gave plants the ability to impart a color that could affix itself to cloth. Some of his research focused on the madder root (rubia tinctorum), which only one other scientist had tried to break down to its constituent parts. Robiquet succeeded in isolating the coloring agent, which he called alizarin.
Robiquet also investigated the pharmaceutical properties of cantharides, an extract from a beetle that was known as Spanish fly. While cantharides was famed for its aphrodisiac qualities, Robiquet was primarily interested in its capacity for irritating the skin and producing blisters. Another area of his interest was the investigation of aromas—the specific substances that gave an orange flower a particular scent when water distilled from that flower had no scent. Robiquet discovered that, for many plants, such odor-causing agents developed only through combination with other chemical substances.
In other experiments, Robiquet analyzed foods such as bitter almonds, mustard seeds, black and white pepper, and asparagus. Breaking them down and processing them by boiling, evaporation, and separation of the resulting liquids and solids, he extracted their essences—the substances that gave them their essential flavors—and studied how these essences interacted with water when a food was cooked. His first important paper, published in 1806, was based on his work with Vauquelin and dealt with their discovery of the amino acid asparagine.
In experiments performed in 1822 and 1831, together with the chemist Antoine Boutron-Charlard, Robiquet processed bitter almond extracts with various substances, including ammonia, and closely observed the results. The seeds of Prunus dulcis var. amara contain a recessive gene that produces a bitter-tasting seed. Isolating the essential oil of these bitter nuts, Robiquet and BoutronCharlard isolated an enzyme they named amygdalin. The basis of laetrile, which was promoted as a cancer treatment beginning in the early 1950s, amygdalin contains a component that can be released as the toxic substance cyanide.
Robiquet's analyses of discrete foodstuffs generated detailed and specific results that surpassed those achieved by earlier chemists, and his work alerted scientists to the existence of amino acids, fundamental building blocks of organic matter. Asparagine was the first amino acid ever identified; amygdalin is a derivative of another amino acid, phenylalanine. German scientists Friedrich Wöhler (1800–1882) and Justus von Liebig (1803–1883) would build on Robiquet's research and their discoveries of the compounds benzamide and benzoin would be important stepping stones in the development of modern organic chemistry.
Using similar methods to those he developed during his research on foods, Robiquet isolated caffeine, the stimulant component of coffee, in an experiment he described to the Paris Society of Pharmacy in 1821. Three other scientists, Friedlieb Ferdinand Runge (1795–1867), and the team of Pelletier and Joseph Bienaimé Caventou (1795–1877), independently discovered caffeine at almost the same time.
In 1817 Robiquet followed a line of study begun by Jean-François Derosne (1774-1855) and Friedrich Wilhelm Sertürner (1782–1841) in isolating the active ingredient of the opium poppy, Papaver somniferum. Derosne had produced a white salt from raw opium that he named narceine, and Sertürner provided a fresh interpretation, deducing that this crystalline distillate, which he called morphia, could only be effective in combination with meconic acid. Robiquet substantiated Derosne's work and built on it, doing his own experiments on narcotine (another opium distillate) and morphia (morphine) while overseeing the work of other scientists under the direction of the Société de Pharmacie.
In 1830, together with an assistant, J.B. Berthemont, Robiquet was validating the ongoing work involving opium when he recognized the uniqueness of a byproduct of morphine extraction. He called this substance codeine, which also had psychotropic effects. Discussing this new opiate, a rival to morphine, Robiquet wrote in a medical journal (as quoted by Jaime Wisniak in Educación Química) that, “Dr. Kunckel, to whom I have provided with a small sample, is convinced that (codeine) has a very strong action on the spinal chord and that does not paralyse the back parts (as morphine does). It approximates very much the action that opium has on animal economy.” Codeine remains a central component of modern pain management.
Complete Dictionary of Scientific Biography, Volume 11, Scribner's, 2008.
Weinberg, Bennett Alan, and Bonnie K. Bealer, The World of Caffeine: The Science and Culture of the World's Most Popular Drug, Psychology Press, 2001.
Educación Química, Volume 24, Supplement 1, March 2013, Jaime Wisniak, “Pierre-Jean Robiquet,” pp. 139–149.
World of Chemicals, http://www.worldofchemicals.com/119/chemistry-articles/pierre-jean-robiquet-discoverer-ofasparagine-alizarin-dye.html (January 24, 2018), “PierreJean Robiquet: Discoverer of Asparagine and Alizarin Dye.” □