Comprehensive two-dimensional liquid chromatography to characterize polyphenols from sargassum muticum brown algae

Abstract

Sargassum muticumis a brown algae widely distributed along the European Atlantic coast. This species is well-known for possessing a special class of polyphenols that are typical from brown algae, phlorotannins. These compounds are complex polymers of phloroglucinol units that can be attached through different linkages and to a variety of degrees of polymerization, which brings about a greatly complex natural mixture. Moreover, they have been described to possess several important bioactivities including, most-notably, antioxidant activity. Due to the great similarity among components as well as to the high number of closely related different structures that can be naturally found, the analysis of these components is quite difficult. We have already developed an analytical strategy based on the use of comprehensive two-dimensional liquid chromatography (LC × LC) to separate and identify these complex components in algae. In the present contribution, that method is further optimized and applied to the analysis of phlorotannins from different Sargassum muticum samples harvested at five different geographical locations from Portugal to Norway. An experimental design was applied to select the best extraction conditions (including extraction temperature and extraction solvent mixture) to obtain these components using pressurized liquid extraction. The attained extracts were characterized in terms of total phenols content, total phlorotannins amount and antioxidant activity. The obtained results show that environmental growing conditions significantly affect the chemical composition of the extracts obtained. Besides, LC × LC is demonstrated as a useful technique to obtain chemical patterns to compare among different samples.