Isolation, Structural Elucidation, and Anti-Melanogenic Activity of a Novel Pectic Polysaccharide From Alhagi camelorum Fisch

Hyperpigmentation disorders motivate the search for structurally defined and effective natural depigmenting agents from plant-derived polysaccharides. The present study characterized the structural features and evaluated the anti-melanogenic activity of ACP-II-1, a novel pectic polysaccharide isolated from Alhagi camelorum Fisch. ACP-II-1 had a molecular weight of 26.145 kDa and contained GalA, Rha, Gal, Ara, GlcA, and Xyl at respective molar proportions of 0.798, 0.072, 0.053, 0.052, 0.016, and 0.009. Integrated monosaccharide, methylation, FT-IR, and NMR analyses indicated a GalA-rich structure dominated by homogalacturonan (HG)-type →4)-α-D-GalpA-(1→ sequences, with less abundant branched rhamnogalacturonan-I (RG-I)-type motifs and heterogeneous neutral side-chain motifs. In forskolin-stimulated B16F10 cells, ACP-II-1 significantly lowered melanin content and cellular tyrosinase activity; it also decreased pigmentation and tyrosinase activity in zebrafish. These effects in B16F10 cells coincided with lower MITF, TYR, TRP-1, and TRP-2 protein levels, together with altered readouts associated with GSK-3β/β-catenin, PKA/CREB, and p38/JNK signaling. Collectively, these findings support the anti-melanogenic potential of ACP-II-1 and warrant further validation in mammalian and human-relevant skin models, together with comprehensive safety evaluation.