THE ISOLATION OF p-AMINOBENZOIC ACID FROM YEAST

The present investigation is primarily concerned with the isolation of p-aminobenzoic acid from yeast. The presence of this substance in yeast was adumbrated by Woods (1) who made the important discovery that. this aromatic amino acid possesses the unique propcity of antagonizing the bsctcriostat~ic action of sulfanilamidt? and that the component. of yeast extracts which exerts a similar antisulfanilamide action has properties consonant with those of p-aminobenzoic acid. Subsequently Rubbo and Gillespie (2), utilizing a procedure involving the benzoylation of a suitably prepared yeast extract, succeeded in isolating from 30 kilos of yeast 2 mg. of p-benzoylaminobenzoic acid whose identity was established only by its melting point. Determinations of the antisulfanilamide activity of yeast extracts conducted by Woods (1) indicate that if such activity is due solely to p-aminobenzoic acid the concentration of this substance in yeast must be very considerably greater than that indicated by the isolation mentioned above. In agreement with this we have found upon calorimetric analysis that commercial pressed bakers’ yeast contains a quantity of dia,zotizable aromatic amine equivalent to approximately 0.5 mg. per cent when calculated as p-aminobenzoic acid. In consequence it appeared desirable to undertake the present, investigation in order to establish definitely the nature of the aromatic amine present in yeast and to gain a more precise estimate of the quantity of p-aminobenzoic acid present. At the outset it appeared that the isolation procedure might be materially facilitated by starting with a commercial yeast extract of the type used as a source of the vitamin B complex. Subse-