Chlorogenic Acid of Lettuce Seeds

Abstract

THE high concentration of chlorogenic acid in lettuce seed has not previously been reported. Fig. 1 compares the ultra-violet absorption spectrum of a methanol solution of chlorogenic acid, 0.02 gm./l., with that of a methanol extract of 1 gm. of lettuce seed made up to 1 litre. The lettuce seed had been extracted continuously with methanol for 16 hr. in a Soxhlet apparatus. Paper chromatography of the extract showed the predominant fluorescent component to be chlorogenic acid. Several other fluorescent components which after elution show the same ultra-violet absorption spectra as chlorogenic acid are also present on the chromatograms. These are probably isomers of chlorogenic acid, but could be other depsides of caffeic acid. Caffeic acid itself is not a major component. Assuming that the compounds which have the same absorption spectrum as chlorogenic acid are isomers and have the same molecular extinction coefficient at 330 mμ, 2 per cent of the weight of the dry seed is chlorogenic acid and its isomers.