Structural characterization and anti-pigmentation of a novel heteropolysaccharide from Gracilaria lemaneiformis via α-MSH/MC1R pathway

[Display omitted] •A novel heteropolysaccharide (GLHP) isolated from Gracilaria lemaneiformis was mainly composed of galactose and glucosamine, consisting of a backbone of → 4)-α-D-Glcp-(1 → 4)-α-D-Glcp-(1 → 4)-β-D-Galp-(1 → 6)-α-D-Glcp-(1 → 6)-α-D-Glcp-(1 → units.•GLHP significantly inhibited the effect of hyperpigmentation in UVA-stimulated melanoma cells and keratinocyte cells.•GLHP significantly reduced the melanin contents in zebrafish tail models.•GLHP blocked the α-MSH/MC1R signaling pathway to inhibit the melanogenesis. Gracilaria lemaneiformis, a commercially edible red alga, is rich in polysaccharide. In this study, we investigated the structural characteristics and anti-pigmentation activities of a novel heteropolysaccharide (GLHP) isolated from Gracilaria lemaneiformis. The structure of GLHP was characterized using gel chromatography (GCP), FT-IR and NMR spectroscopy, while anti-pigmentation activity was evaluated using HaCaT, A375, B16F10 cells and zebrafish models. The results indicated that the molecular weight of GLHP was 47,600 Da and it was mainly composed of galactose (62.08%) and glucosamine (14.72%). The backbone of GLHP was identified to be → 4)-α-D-Glcp-(1 → 4)-α-D-Glcp-(1 → 4)-β-D-Galp-(1 → 6)-α-D-Glcp-(1 → 6)-α-D-Glcp-(1 →. Additionally, GLHP via α-Melanocyte-Stimulating Hormone (α-MSH)/Melanocortin 1 receptor (MC1R) pathway inhibited the tyrosinase activity and the melanogenesis in UVA-stimulated melanoma cells, and suppressed the migration of MLANA in UVA-induced A375 and HaCaT cells. Furthermore, it upregulated the melanin contents in zebrafish tails. In conclusion, these results suggested GLHP could be used in cosmetics as a novel anti-pigmentation agent.