Soluble browning reaction pigments of aged Burley tobacco. I. The nondialyzable fraction

Abstract
A dark-brown pigment, identified as an iron-protein-chlorogenic acid-rutin complex, was isolated by precipitation with acetic acid from the soluble nondialyzable fraction of aged Burley tobacco in an amount corresponding to 0.32% of dry leaf weight. Identification was made by paper chromatography of the products of hydrolysis and potassium hydroxide fusion. The acetic acid-insoluble pigment, an acetic acid-soluble brown pigment of similar qualitative composition, and a polysaccharide comprised the total acetone-precipitated nondialyzable fraction. Identification of the natural pigment confirms previous in vitro conclusions regarding the participation of chlorogenic acid and rutin in the browning of air-cured tobacco.