November 23, 1935

Sulfanilamide

Pasteur researchers report sulfanilamide's antibacterial activity

By a later account, the decisive test happened because four infected mice were left over and Bovet suggested trying the plain colourless fragment of the dyes.

A two-page report, 23 November 1935

A two-page communication associated with the Société de Biologie session of 23 November 1935 reported the activity of p-aminophenylsulfonamide — sulfanilamide, laboratory code 1162F — against experimental streptococcal infections in mice and rabbits.

The authors were Jacques Tréfouël, Thérèse Tréfouël, Federico Nitti and Daniel Bovet, working in Ernest Fourneau's medicinal-chemistry laboratory at the Institut Pasteur in Paris. Older citations nearly erase Thérèse Tréfouël by listing her only as "Mme J. Tréfouël."

They reported a tolerated dose of 1,000 mg/kg without observed harmful effects.

The colour was never the point

They found that the simple, colourless sulfanilamide molecule protected infected animals with activity comparable to the more complex azo dye Prontosil.

Their structural argument suggested that Prontosil-like dyes were split in the body to release sulfanilamide. That antibacterial activity did not depend on the colored dye structure opened the way to systematic development of sulfonamide drugs — and undercut the commercial advantage of Prontosil's patented structure.

Direct detection of sulfanilamide in blood and urine after Prontosil administration came later, from A. T. Fuller in 1937.

A report date, not a eureka date

The 23 November date is well supported as the date of the Société de Biologie session or issue associated with the communication, which ran to two pages at 756–758 of volume 120.

It is not securely documented as the calendar day on which the decisive laboratory experiment occurred, so it should be read as the report date.

The finding was also not the first synthesis of sulfanilamide: Paul Gelmo had made the compound decades earlier without recognising any antibacterial use.

Sources

Researched 23 Aug 2026 7 sources 2 audit passes Traditional date

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

Traditional date. This date is the conventional one, not one fixed by a contemporary record.

What the sources leave uncertain

November 23 is well supported as the date of the Société de Biologie session or issue associated with the two-page communication.
It is not securely documented as the calendar day on which the decisive laboratory experiment occurred. The event should therefore be presented as the report or communication date, not a precisely dated eureka moment.
The 1935 work inferred that Prontosil was cleaved to an active sulfanilamide component; Fuller directly demonstrated sulfanilamide in the blood and urine after Prontosil administration in 1937.