Synthesis, characterization and potential application of hydrophobically modified carrageenan derivatives as pharmaceutical excipients.

New amphiphilic derivatives of kappa-carrageenan (KC) were synthesized by hydrophobic modification with octyl chloride. Two different methods based on microwave and conventional heating were used. All KC derivatives (KCRs) were characterized by different techniques. The FT-IR and 1HNMR studies demonstrated that the octyl groups were effectively grafted onto KC backbone and confirmed that the derivative KCRMM, obtained by microwave heating, presented a higher degree of substitution (DS = 0.77) compared to KCRCM (0.45). The amphiphilic character investigation also revealed that KCRMM exhibited a lower critical aggregation concentration (CAC) value of 0.13% w/v than KCRCM (0.15%). Furthermore, KCRs greatly improved the stability of oil/water emulsions as the droplet size decreased with increasing DS. Unlike the conventional heating method, novel derivatives with a higher DS, greater amphiphilic character, and an improved emulsifying power were obtained by microwave-assisted synthesis. These derivatives could potentially be used in food, cosmetics, or as excipients in pharmaceutics.