Extraction process, structural features, and bioactivity validation of Dendrobium officinale polysaccharides

To optimize the extraction-purification process of Dendrobium officinale polysaccharides (DOPs) and characterize the fine structures of two homogeneous fractions (DOP-1, DOP-2), as well as to evaluate their anti-photoaging activity on HFF cells.

An integrated process including petroleum ether defatting, cellulase hydrolysis, water extraction-ethanol precipitation, trypsin-Sevag deproteinization, activated carbon decolorization, and dialysis was used. DOP-1 and DOP-2 were separated by DEAE-52 and Sephadex G-100 chromatography. Their structures were analyzed by FT-IR, methylation-GC/MS, NMR, and SEM. Anti-photoaging effects were assessed via CCK-8, SA-β-Gal staining, and qPCR of TGF-β/Smad pathway genes.

The optimized process increased crude polysaccharide yield from 30.34% to 35.03% and polysaccharide content from 31.23% to 49.34%. DOP-1 (Mn 989 Da, PDI 1.15) was a linear oligosaccharide composed of →4)-β-D-Manp (72.32%) and →4)-β-D-Glcp (23.78%) in an alternating pattern. DOP-2 (Mn 2970 Da, PDI 1.67) was a branched polysaccharide with a backbone of →6)-α-D-Glcp (58.06%) and branches at →2,6)-Manp and →4,6)-Glcp. Both DOP-1 and DOP-2 (62.5 μg/mL) protected HFF cells from UVA-induced photoaging, upregulated TGF-β1, Smad3, Smad4, and Collagen I, and downregulated Smad7 and MMP-1, with DOP-2 showing dose-dependent effects.

The optimized process enables efficient preparation of DOPs. DOP-1 and DOP-2 possess distinct structural features and exert anti-photoaging effects via regulation of the TGF-β/Smad signaling pathway.