Identification of oxidized chlorophylls and metallochlorophyllic complexes of copper in table olives (cv. Gordal) with green staining alteration

Abstract

In Spanish green table olives showing the alteration known as green staining, new chlorophyll derivatives have been identified: the copper complexes of 31,32-didehydrorhodochlorin-15-glyoxylic acid-173-phytyl ester a and b (Cu-15-glyoxylic acid pheophytins a and b), and 31,32-didehydro-151-hydroxy-151-hydroxyrhodochlorin-15-acefic acid δ-lactone-152-methyl-173-phytyl ester a and b (Cu-151-OH-lactone-pheophytins a and b). These compounds were isolated by normal phase thin-layer chromatography and identified from their UV-visible and mass spectra and by co-chromatography with authentic standards. The chromatographic and spectroscopic characteristics and the molecular mass for a new allomerized chlorophyll derivative and its copper complex are reported. The corresponding molecular structure according to the molecular mass has been proposed. The characterization of the latter compounds enables their possible detection in processed fruits and vegetables. The present work gathers new advances in the study of the color alteration in table olives and this is the first time that copper complexes of oxidized chlorophylls are detected in foodstuffs.