Structural characterization of three acidic polysaccharides from Opuntia dillenii Haw. fruits and their protective effect against hydrogen peroxide-induced oxidative stress in Huh-7 cells

Three novel acidic polysaccharide fractions (OFPP-1, OFPP-2, OFPP-3) with different molecular weights (803.7, 555.1 and 414.5 kDa) were isolated from the peeled Opuntia dillenii Haw. fruits by alkali -extraction, graded alcohol precipitation and column chromatography. Structural analysis indicated that OFPPs were pectic polysaccharides consisting of rhamnose, arabinose and galactose residues. The backbone of OFPP-1 consisted of a repeating unit -> 6- alpha - D -Gal p A-(1 -> 2)- alpha - L -Rha p -(1 -> with T- alpha - D -Gal p A-(1 -> 6)- alpha - D -Gal p A-(1 -> 4)- alpha - D -Glc p -(1 ->, T- beta - D -Xyl p -(1 -> 6)- alpha - D -Gal p A-(1 -> 4)- alpha - D -Glc p -(1 -> or T- alpha - D -Gal p A-(1 -> 3)- alpha - L -Ara f -(1 -> as the side chains. The backbone of OFPP-2 consisted of a disaccharide repeating unit -> 2)- alpha - L -Rha p - (1 -> 4)- beta - D -Gal p A-(1 -> with T- beta - L -Ara f -(1 -> as the branches substituted at the O-4 position of -> 2,4)- alpha - L - Rha p -(1 ->. Whereas the backbone of OFPP-3 was -> 2,4)- alpha - L -Rha p -(1 -> 2)- alpha - L -Rha p -(1 -> 3)- beta - L -Ara f -(1 -> or -> 2,4)- alpha - L -Rha p -(1 -> 2)- alpha - L -Rha p -(1 -> 4)- beta - D -Gal p A-(1 ->, which was branched at the O-4 position of -> 2,4)- alpha - L -Rha p -(1 ->. Moreover, these three polysaccharide fractions could protect Huh -7 cells against H 2 O 2 - induced oxidative stress to different extents by decreasing the MDA content and increasing the SOD, CAT, GSH-Px activities and the GSH level in the Huh -7 cells. These results suggest that OFPPs have the potential to be used as natural antioxidants. (c) 2024 Beijing Academy of Food Sciences. Publishing services by Tsinghua University Press. This is an open access article under the CC BY -NC -ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).