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International Year of Chemistry

Flavors and perfumes

Sweet, bitter and smelly compounds are the main characters in the story

MARIANA ZANETTIPerfume elevates the mood, seduces and, according to some, reaches the gods. The sweetness brings energy to the palate and generates fuels that enable a substantial part of Brazil’s fleet of motorized vehicles to move. The bitter causes aversion, but also dependence, and therefore generates wars. In a series of talks with a Rio de Janeiro accent, Vitor Ferreira, from Fluminense Federal University (UFF), along with Claudia Rezende and Angelo da Cunha Pinto, both from the Federal University of Rio de Janeiro (UFRJ), covered the chemical history of these flavors and odors on August 3, during the fifth meeting of the cycle of conferences organized by FAPESP and by the Brazilian Chemistry Society, which is celebrating the International Year of Chemistry.

A room at the congress, full of sighing women, as they smelled the perfume of Napoleon Bonaparte well into the twenty-first century. Do not doubt what you have just read: it does concern the French emperor and the congress took place almost 200 years after his death. The person who recounted the scene was Claudia Rezende, who was present. Although incongruent, the reaction to the perfume calls attention to the use of fragrances for the purpose of seduction. Napoleon, according to the researcher, was a major encourager of the production of perfume and glass flasks. Using the recently found recipe, Osmotheque, a perfume museum in Versailles, France, has reconstituted the eau-de-cologne produced by perfumist Jean-Marie Farina for the monarch, towards the end of the latter’s life.

However, seduction is not the sole purpose of fragrances. Long ago, aromatic substances were used in personal care. “In Ancient Egypt a fragrance was used for each part of the body,” said Claudia. Records from Ancient Rome also include flasks and the description of aromas. According to the speaker, the greatest shock of the perfumed Romans in the face of the invasions of the Barbarians must have been the sight and rancid smell of the fat-smeared Vikings, this being necessary to assuage the cold of the Scandinavian lands and seas. “The use of aromas was so substantial that it caused an imbalance in the balance of trade,” as a result of the importing myrrh and frankincense, she narrated.

Myrrh and frankincense (incense) were, indeed, two of the gifts that the Magi took to Jesus, according to the Bible, which shows the inclination of religion toward using scents. “It’s a volatile material that, it is believed, might help to communicate with the gods,” explained the chemists from UFRJ. This use, common among the Assyrians, Persians and Ancient Greeks, could reach the sophistication of assigning specific scents, such as sandalwood or cinnamon, to each one of the divinities.

Furthermore, one cannot set aside the medicinal properties of perfume, which precede, by far, today’s fashionable aromatherapy. In Ancient Greece, around 330 B.C., Theophrastus studied the use of plants for healing purposes. In the fourteenth century, when the bubonic plague decimated Europe, those who were better off tried to protect themselves by carrying herb extracts in bags in front of their mouth and nose. According to Claudia, it was thought that the streets’ fetid odor of disease and death (the miasmas) were the means of transmission.

As from the Renaissance, a wealthier aristocracy emerged and aromas reached the table in the form of meats seasoned with pepper, cinnamon, cloves, ginger and sugar, and in desserts perfumed with roses, orange blossom and carnations.

Technology and knowhow on how to take possession of natural perfumes also varied over the course of time. From the use of aromatic plants directly, to today’s more precise chemistry, extraction techniques have been used, as described in the book Perfume: The story of a murderer, by Patrick Suskind (and in the film of the same name). “The film is a lesson in perfumery,” Claudia sums up. During the enfleurage, often used in the past, the flowers (or women, in this terrifying work of fiction) were wrapped in odorless fat that absorbed the volatile substances, later extracted with ethanol. Distilling too has always played an important part in the process of making alcohol-based perfumes.

Eduardo CesarVitor Ferreira, Claudia Rezende and Angelo da Cunha PintoEduardo Cesar

As from the nineteenth century, it became possible to identify and isolate aromatic molecules. During this time, famous perfumes appeared, such as those by Guerlain, Hermès and Roger Gallet. In Brazil,  pharmacies were beginning to appear, such as Imperial Drogaria and Pharmacia de Granado & Cia. To this day, the latter continues to make antiseptic powder and soaps, among other products. Another icon of Brazilian perfumery is Phebo soap, manufactured as from 1924 by Portuguese that migrated from the Southeast to the North in search of an aroma similar to one found in certain British products. The main raw material was the Brazilian rosewood, a tree from the Amazon region that is also a key ingredient in the mythical Chanel no. 5 perfume created in 1921.

At this time, the study of molecules was the beginning of the path toward producing fragrances on an industrial scale. The Croatian chemist Leopold Ruzicka was a pioneer in the field and caused him to become a Nobel prize laureate. In 1926, he elucidated the structure of muskone, a substance extracted from musk deer 20 years earlier and often used in perfumery.

Claudia also presented some of the historical path of menthol, a flavoring widely used in foods and cosmetics. Up to World War II, the production of wild mint (Mentha arvensis) was controlled by China and by Japan. However, given the difficulties brought on by the war, immigrants started growing the plant in Brazil. By 1973, they reached a peak of 6,300 tons a year. In products in which something refreshing is  desirable , it is menthol : candy, chewing gum, toothpaste, soups, shaving creams and even cigarettes – in this case, to reduce the impact of  smoke on the throat. For many of the uses it was necessary to modify the molecular structure, in order to eliminate side effects such as prolonged stinging of the eyes after putting after-shave lotion on the face. “Much of the chemical development of menthol came from the tobacco industry,” the researcher explained. Today, part of this substance in the world is synthetic.

Notwithstanding the progress of chemical manipulation, Claudia still feels a like the master perfumist in Perfume: waving a hankie to detect the substances that make up an aroma. A lot of the research, she states, still depends on sharp noses: “It’s an empirical science, though it has a sophisticated scientific arsenal,” she summed up.

Bitterness
The story of the bitter flavor told by Angelo da Cunha Pinto is also rich is empiricism. The oldest known medical text consists of recipes carved in cuneiform writing from ancient Sumer, in Asia, around 2200 BC. From the potions of the sorcerous gods of mythology,”natural product chemists with a lot of laboratory expertise,” to the manufacturers of present day drugs, the plants that produce alkaloid substances have been tried in several ways.

They have even given rise to wars such as the Opium War, between China and England, in the nineteenth century. What led to this war was the delicate poppy, grown in Thailand, Laos and Myanmar, from which opium is extracted. The substance was used primarily as medication, but smoking it became a habit in China because of the prohibition of tobacco consumption. And the supplier was the British Empire, which led to a trade dispute.

However, besides being involved in war and dependence, opium is a precious alkaloid in medicine. One of its byproducts is morphine, the painkiller that gave rise to the hypodermic syringe, first used in 1853 in the Crimean War. Many old drugs contained opium in their formulations, such as the paregoric elixir, used to cure diarrhea until the 1970’s, and codeine-based cough medicines.

Cocaine, the star of the “war in Rio de Janeiro,” in the words of Cunha Pinto, was synthesized in 1857 by the German citizen Albert Niemann, being often used in teas, elixirs, wines and even toothache pastilles. “From wine and tonics it moved into drugs,” lamented the speaker.

Besides these examples, there are a lot of plants that produce natural alkaloids that are used in various ways by peoples from around the world and throughout all historical periods, such as quinine to fight malaria, mandrake as a fortifier and aphrodisiac, and ayahuasca, a beverage made from the yage liana and chacruna leaves, used in rituals such as the those of the santo daime cult.

Sugar
Also using nature as a starting point, Vitor Ferreira took a dive into advanced chemistry. Showing to the FAPESP auditorium audience a little bag of sugar and another of artificial sweetener, such as one finds in coffee shops and restaurants, he stressed the difference in size between them. Artificial sweeteners, he explained, are far sweeter than natural saccharose: 600 times, in the case of sucralose. However, sugar does much more than merely sweeten life.

“Even sweeter than sweetness is the potential of carbohydrates for chemical products,” joked the speaker. The same sugar that the body seeks as a source of energy also gives rise to biofuels,  which several countries are betting on as the solution to achieve a balance between transport needs and the problem of emitting pollutants. The large-scale production of biofuels based on a series of substances is real progress but, according to Ferreira, it is far from being a new thing. “The [German engineer Rudolf] Diesel himself, when he invented the diesel engine, ran it on peanut oil.”

Now, the manufacturing of several sugar-based products, such as foods and chemical raw materials, is progressing in that it is achieving cleaner and more sustainable synthesis, giving rise to the so-called green chemistry. “In 2020, green chemistry is expected to generate US$307 billion,” he stated. There is no shortage of raw material: 95% of the biomass produced by nature, i.e., some 200 billion tons a day, consists of carbohydrates. Man only uses about 5% of this.

As part of a veritable parade of molecules, such as maltose, chitin and cellulose, Ferreira showed how sugar-based building blocks generate an endless number of products, including aroma fixing agents in soft drinks, biodegradable plastics and surgical sutures. “The chemistry of saccharose is so important that it even has a name: sucrochemistry.” Furthermore, its importance should grow as oil becomes scarcer, provided there is enough investment in research. “We have to learn to make everything that we make with oil with this biomass,” he warned. According to him, alternative sources, such as solar power and wind power, might help to solve energy problems, but fine chemistry will depend on carbohydrates and,  in the economics of this type of chemistry, Brazil should stand out.

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