Rachel Fuller Brown

Rachel Fuller Brown (1898–1980) was an American chemist working in the laboratory of the New York State Department of Health in Albany. With the microbiologist Elizabeth Lee Hazen she described, in 1951, fungicidin — an antibiotic produced by a soil actinomycete, known today as nystatin.

Her contribution concerned the part that is easily dropped from the short version of the story. Hazen established that a given culture halted fungal growth — Brown had to answer the question of what exactly was doing it. That means extraction, fractionation, crystallisation and testing the activity of each fraction separately — and then establishing that the culture contains two different active substances, one of them suitable for use in people and the other too toxic.

Separating them was the precondition for everything that followed. Without a purified substance you cannot set a dose, test toxicity or patent a compound. A microbiological discovery without the chemistry remains the observation that "something in this culture works".

Brown and Hazen described nystatin under its final name in 1960 in the Annals of the New York Academy of Sciences, a journal of their own state. It is worth noting that both appear together on both publications — joint authorship by a microbiologist and a chemist is, in this story, not a formality but a description of how the work was actually done.

The chemistry behind nystatin proved far from trivial. The compound belongs to the polyenes — large, fragile molecules that are hard to purify without destroying them and that dissolve poorly in water. Establishing the conditions under which the substance keeps its activity was the precondition for turning it into a medicine rather than a reagent.

The mechanism was understood later: nystatin binds ergosterol, a sterol present in fungal membranes and absent from human ones, and makes the cell membrane leak. That single chemical difference between two eukaryotes still underpins most antifungal drugs — and explains why finding them took so long.

The method is recorded in the patent

US patent 2,797,183 names Elizabeth Lee Hazen and Rachel Fuller Brown as joint inventors and Research Corporation as assignee; it was filed on 7 January 1952 and granted on 25 June 1957. Its claims expose Brown’s chemical part of the work: Streptomyces noursei growth was separated from the culture medium, the fungistatic substance extracted from the mycelium with a lower alcohol or ketone, then recovered and purified through repeated dissolution and precipitation. The document covers surface culture and aerated submerged culture that could be scaled using established antibiotic-production equipment.

A patent is neither a clinical paper nor evidence that Brown worked alone. It is a primary record of how a biological observation became a repeatable process for producing and purifying nystatin. The profile should place its flow diagram beside the Hazen–Brown paper: one document asks “does it work?”, while the other records “how can it be made?”.