Association of hydrophilic derivatives of chlorophyll a in ethanol–water and ethanol–water–solubilizer systems

Abstract

Electronic absorption spectroscopy and fluorescence spectroscopy were used to study conditions for the formation of associates of amphiphilic phorbins and chlorins in an ethanol–water system. The conditions and degree of disaggregation in the presence of solubilizing additives of nonionic surfactants (Tween 80) and biocompatible polymers (polyethylene glycol and polyvinylpyrrolidone) were also investigated. The propensity of the macroheterocycles based on chlorophyll a to association in water-alcoholic solutions decreases on going from covalently bound dimeric structures to monomeric ones, on going from phorbins to chlorins and on accumulating hydrophilic glycol or positively charged alkylammonium fragments in the molecule. Among the considered solubilizers, the nonionic surfactant Tween 80 emerged as the most efficient means for destroying chlorin associates in water–alcohol solutions with a high content of water.