Studies on pigmentation of Serratia marcescens. I. Spectral and paper chromatographic properties of prodigiosin

The red pigment of Serratia marcescens, prodigiosin, has interested chemists because it has been reported to be the only naturally occurring tripyrrylmethene and as such its biosynthesis might be related to porphyrin biosynthesis (Hubbard and Rimington, 1950). Wrede and Hettche (1929) extracted the pigment from S. marcescens using a procedure involving sodium hydroxide treatment. By degrading the alkali-extracted pigment, Wrede and Rothhaas (1934) defined the structure of prodigiosin as a tripyr-rylmethene, a single compound. Hubbard and Rimington (1950) extracted prodigiosin by means of acid and alkali and compared the spectral properties of the pigment to a synthetic tripyr-rylmethene. Since the spectral properties of the two substances were similar, these authors con-cluded that the tripyrrylmethene structure of prodigiosin was probably correct, and implied that the pigment was a single substance. How-ever, Weiss (1949) showed that prodigiosin ex-tracted by a mild organic solvent, n-butyl alcohol, separated into several bands when chromato-graphed on columns of magnesium oxide or a mixture of calcium carbonate and celite. This fact suggested that Hubbard and Rimington (1950) might have dealt with a mixture of pig-ments which they assumed to be a single sub-stance. Since Weiss (1949) indicated the mixed nature of extracted prodigiosin, we felt further study of mildly extracted prodigiosin was war-ranted. Unfortunately, n-butyl alcohol extraction did not give satisfactory results in our hands. As a consequence we have developed a different method for pigment extraction and for the sepa-l This investigation was supported by researc