Quantification of 3,6-anhydro-galactose in red seaweed polysaccharides and their potential skin-whitening activity

This study determined the composition of the monosaccharide, 3, 6-anhydrogalactose (AnGal), in red algae and explored the potential whitening activity of the extract. Using gas chromatography-mass spectrometry (GC-MS), the AnGal composition of six different species of red seaweed (Porphyra haitanensis, Gracilaria chouae, Gracilaria blodgettii, Gracilaria lemaneiformis, Eucheuma galetinae, and Gelidium amansii) was successfully analyzed, revealing molar ratios ranging from 1.0:1.0 to 1.0:3.1 of AnGal and galactose (Gal), respectively. Employing the tyrosinase inhibition assay, the skin-whitening effect of AnGal red seaweed polysaccharides was determined. Polysaccharides from P. haitanensis, G. chouae, and G. blodgettii as well as their degradation products showed higher tyrosinase inhibitory activity (inhibition rates 24.2-26.8%). These results suggest that the GC-MS approach could conveniently be used in quality control or for the quantitative determination of AnGal and Gal in red seaweed polysaccharides as well as exploring their potential application in cosmetic and functional food products. The findings here exhibited that red seaweed polysaccharides and their degradation products were potential ingredients for cosmeceutical industries.