Anthocyanin dye conjugated with Hippospongia communis marine demosponge skeleton and its antiradical activity

Abstract

A study was made of the adsorption of anthocyanin dye onto spongin-based marine demosponge skeletons of the species Hippospongia communis. The influence of time, dye concentration, ionic strength, pH and temperature on adsorption efficiency was assessed. Adsorption kinetics was analyzed using pseudo-first and pseudo-second-order models, and the pseudo-second-order model was found to represent the experimental data satisfactorily. The adsorption mechanism was verified based on Langmuir and Freundlich isotherms and the adsorption capacity (qm) reached 1413.9 mg/g. The developed sponge-hybrid materials were thoroughly analyzed using Fourier transform infrared spectroscopy (FTIR), cross polarization magic angle spinning nuclear magnetic resonance (13C CP MAS NMR), thermogravimetric (TG), elemental analysis (EA) and optical and scanning electron microscopy (SEM). The antioxidant activity of the studied materials was also tested by estimating the ability of the dye–biopolymer system to scavenge the stable 2,2'-diphenyl-1-picrylhydrazyl free radical (DPPH•). Anthocyanins were adsorbed on the sponge skeleton with high efficiency, and the resulting hybrid material was able to remove up to 95% of free radicals from solution.