Anti-Melanogenesis Effect of Polysaccharide from Saussurea involucrata on Forskolin-Induced Melanogenesis in B16F10 Melanoma Cells.

As one of the prominent medicinal plants listed in the Chinese pharmacopoeia (2020), Saussurea involucrata (Kar. et Kir.) Sch.-Bip was demonstrated to possess various therapeutic effects. In our recent research, we extracted the polysaccharides from S. involucrata (SIP) at optimal conditions and conducted further structure elucidation on the main fraction as well as the confirmation of its possible anti-inflammatory activity. Hence, in this work, we assessed the in vitro antioxidant activity and anti-melanogenesis effects of the crude SIP in forskolin-induced B16F10 melanoma cells. The results show that SIP possessed strong antioxidant activity and was effective in concentration-dependently decreasing melanin formation and inhibiting tyrosinase activity in forskolin-induced B16F10 cells. Based on these results, the inhibitory mechanism of melanogenesis was investigated by measuring Tyrosinase (TYR), Tyrosinase related protein-1 (TRP-1), Tyrosinase related protein-2 (TRP-2), Microphthalmia-associated transcription factor (MITF), cAMP-response element binding protein (CREB), mitogen-activated protein kinases (MAPK) signaling protein members, and ß-catenin degradation in forskolin-induced B16F10 cells. The anti-melanogenesis response of SIP might be attributed to the regulation of c-Jun N-terminal kinase (JNK) phosphorylation and ß-catenin degradation pathways. These results suggest that polysaccharides from S. involucrata possess a strong anti-melanogenic effect, and thus could be used as a high-value natural material for skin whitening in cosmeceutical industries.

Isolation, structure elucidation, and biological activity of polysaccharides from Saussurea involucrata.

The optimum extraction condition for the Saussurea involucrata polysaccharide (SIP) was determined to be a temperature of 80 °C, time 2 h, and a liquid-solid ratio of 30 mL/g with a yield of 11.37 %. An acidic homogenous polysaccharide, namely SIP-II was isolated from Saussurea involucrate through anion exchange and gel permeation column chromatography. The structure of the SIP-II was elucidated through the combination of HPLC, GC-MS, IC, peroxide oxidation, smith degradation, methylation, NMR analysis, it was mainly composed of arabinose, rhamnose, galactose, galacturonic acid, and glucose with the molar ratio of 19.85:20.30: 27.12:11.95:8.69 with a molecular weight of 237,570 Da. The glycosidic linkages of SIP-II mainly composed of →1)-α-L-Rhap-(2→, T-Araf, →1)-ß-D-GalpA-(4→, →1)-ß-D-Galp-(3,6→, →1)-ß-D-Galp-(6→, →1)-α-L-Rhap-(2,4→, T-Galp, and →1)-α-L-Araf-(5→. Meanwhile, the structures were characterized through extensive analysis of UV, FT-IR, SEM-EDX, CD, XRD, and TG. SIP-II possessed a remarkable anti-inflammatory activity by effectively inhibiting the expression of pro-inflammatory cytokines and inflammation-related mediators in LPS-stimulated RAW264.7 macrophages, and the anti-inflammatory response of SIP-II might be attributed to the regulation of the NF-κB, MAPK and JAK/STAT pathways. The results showed that polysaccharides from Saussurea involucrate could be a potential ingredient in the functional food and pharmaceutical industry.