Synthesis and characterisation of novel astaxanthin metal complexes

Abstract

Astaxanthin is produced in a wide range of organisms, its extractability from the native Irish brown crab (Cancer pagurus) was carried out using glacial acetic acid. The extractable natural astaxanthin yield is quantified using High performance liquid chromatography. In this research the possibility of yielding extractable astaxanthin from crustacean waste was examined to provide a natural source of the xanthophyll. Astaxanthin is popular in demand by the nutraceutical market due to its high radical scavenging activity. The question stands does this ability withstand the biochemical reactions undergone following ingestion. In order to assimilate these reactions examination of complex formation with transition metal salt were carried out a three temperatures of 20°C, 37 °C and 78 °C. Complexation with copper chloride proved successful at a higher activation energy (78 °C) as significant changes were confirmed in electronic spectra and cyclic voltammograms. Cobalt chloride proved unsuccessful in the formation of complexes with astaxanthin as no changes were observed apart from a stabilisation effect in cyclic voltammograms providing a two electron oxidation transfer. Astaxanthin is a natural powerful antioxidant but the involvement of the radical scavenging sites in biochemical reactions can hinder or improve it effects as proven in this research the metal chlorides exhibit a stabilisation effect on the molecules antioxidant activity but also changed the aggregation of the molecule when complexed with copper chloride at a higher temperature causing a more tight H-type packing. These effects require further examination before marketing this molecule as a nutraceutical as these reactions may negate it intake.