Pigments in Vegetables

Preparation of chlorophylls and pheophytins by isocratic liquid chromatography.

Revue bibliographique sur les techniques d'extraction, les proprietes spectroscopiques et l'analyse chromatographique des chlorophylles des fruits et legumes et sur leur alteration au cours de la senescence et des processus de transformation ou de conservation

Chlorophylls in foods

Tosylation and acylation of cellulose were performed under mild reaction conditions using imidazolium based ionic liquids (ILs) as solvents. The non-degradative nature, lower viscosity, as well as higher solubility of cellulose in [amim]Cl encouraged us to carry out the reactions in this media. The reactions described here were optimised for this particular solvent in order to obtain different cellulose derivatives with high yields, homogeneity and degree of substitution (DS). Two reagents employed for the in situ activation of carboxylic acids were N,N′-carbonyldiimidazole (CDI) and 1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride (EDCI). Final products were characterised by solution and solid-state NMR techniques.

Tosylation and acylation of cellulose in 1-allyl-3-methylimidazolium chloride

The assembly kinetics of a pigment-binding membrane protein, the light-harvesting chlorophyll a/b complex of green plants, have been determined in vitro. Time-resolved fluorescence spectroscopy, with millisecond time resolution, has been used to monitor changes in both protein and chlorophyll (Chl) fluorescence, as well as in energy transfer from Chl b to Chl a, during complex assembly. Three reaction steps could be resolved after rapid, stopped-flow, mixing of the apoprotein (light-harvesting Chl a/b protein, LHCP) and pigments, solubilized in sodium dodecyl sulfate (SDS) and octyl glucoside (OG), respectively. A fast step in the range of 10 ms was detected regardless of whether the reaction mixture contained pigments or protein, or both, and is interpreted as being connected with the formation of mixed SDS and OG detergent micelles. Two further steps were resolved:  one with a time constant of about 1 min and another, slow step with a time constant of several minutes. Both of these were dependent on the...

Assembly of light-harvesting chlorophyll a/b complex in vitro. Time-resolved fluorescence measurements.

Powdered sugar column chromatographic separation and isolation of chlorophyll were studied. A wet column was employed using a Pharmacia R25 chromatographic tube connected, through a UV monitor, to a fraction collector. Chlorophyll extracted from spinach leaves with acetone was selectively precipitated with dioxane and water, and then was washed with 80% (v/v) aqueous methanol. Use of the further purified chlorophyll as a starting material for chromatographic separation and isolation of chlorophyll, made column chromatographic procedures become extremely effective and easier. Thin-layer chromatographic and high-performance liquid chromatographic tests revealed that chlorophyll preparations in this study did not contain any other photosynthetic pigments and their degradation products.

Masahiko Yoshiura

Papers

An Improved Method Fòr Extraction, Partial Purification, Separation and Isolation of Chlorophyll from Spinach Leaves