Veilchenduft, ectopic olfactory receptors and endogenous volatile compounds: Who was Paul Krüger (1859-1916)?

The pharmacist and chemist Ferdinand Tiemann (1848-1899) having succeeded in the synthesis of vanillin, is considered to be the father of Geschmackstoff-Chemie (flavor chemistry). Tiemann, together with Paul Krüger (1859-1916) and then with Friedrich-Wilhelm Semmler (1860-1931), developed a method to obtain with a good yield Veilchenduft (violet scent); they condensed citral with di-methyl-ketone (acetone) thus generating an intermediate which upon exposure to an acidic environment cyclizes to ionone. By doing so the fragrance chemistry was born. Ionone (the compound responsible for the violet scent) was produced on an industrial scale at the factory of Wilhelm Haarmann (1847-1931) in Holzminden, factory renamed 1876 Haarmann & Reimer, after Karl Reimer (1845-1881) joined the group of owners. While a number of chemists and pharmacists were involved in the synthesis of Ionone (Veilchenduft; violet scent) and irone (iris scent), with few exceptions, their biographies are pretty well documented. In contrast, very little transpired about Dr. Paul Krüger, who spent some seven years trying to iron out the difficulties of ionone synthesis. The purpose of this short contribution is to shed some light on the life and work of Paul Krüger while providing an overview on the status of ionone pharmacology and to highlight the historical significance of ionone synthesis.

Cleopatra: from turpentine and juniper to ionone and irone.

Cleopatra VII (69-30 BC), the last Ptolemaic ruler of Egypt, is probably best known for her love affairs with Julius Caesar (100-44 BC) and Marcus Antonius (83-30 BC). Rightly or wrongly she became the epitome of shrewd seduction, leading brave Roman commanders on a path to debauchery and destruction. Among the seductive strategies attributed to her is the ingestion of small amounts of turpentine [the resin of the terebinth tree (Pistacia terebinthus)] or of derived oil (Oleum terebinthinae) with the purpose of conferring to her urine a more pleasant scent reminding of violets. Turpentine components are metabolized among other compounds to ionones and irones, which - renally excreted - are responsible for the flowery scent. Having obviously worked with great generals, the strategy is said to have been embraced for everyday use by many affluent Roman women. Complicating the issue somewhat is the fact that juniper berries (Fructus juniperi) and derived oil (Oleum juniperi) containing many of the same terpenoids as turpentine have a similar effect on urine. The purpose of this contribution is to briefly review the pharmacology of turpentine and juniper derived compounds assumed to be responsible for altering the scent of urine and to examine the origin and veracity of the mentioned habit. While the effect of ingested turpentine on the scent of urine is well documented our attempts at identifying Greek or Latin authors mentioning its intentional use for this explicit purpose (by Cleopatra or anybody else) failed.