Copra meal and guar gum β-manno-oligosaccharides inhibit glycation of human serum albumin: Mechanistic insights using multi-spectroscopic and bioinformatic analysis

We investigated the inhibitory effects of β-MOS derived from guar gum (GG-β-MOS) and copra meal (CM-β-MOS)
using GH26 endo-mannanase on AGEs formation using a glucose-human serum albumin (HSA) in vitro model.
β-MOS were found to be an effective anti-glycating agent by acting on all the stages (early, intermediate, and
late) of glycation, evident by reduced formation of fructosamine, carbonyl, and dicarbonyl compounds, specific
fluorescent AGEs, thiol oxidation products and increased free lysine and arginine contents. CM-β-MOS (IC₅₀
~134.0 μg/ml) exhibited stronger AGEs inhibition than GG-β-MOS (IC₅₀ ~285.4 μg/ml) and was more potent in
trapping methylglyoxal. Biophysical studies suggested that β-MOS protected the microenvironment around the
hydrophobic regions, prevented changes in the tertiary structure, restored α-helical content, and reduced the
amyloid aggregates in glycated HSA. CM-β-MOS maximally suppressed the formation of cross-linked structures in
GHSA and was more effective than GG-β-MOS in preventing GHSA aggregation. The β-MOS-HSA complexation
process was spontaneous and thermodynamically favourable. CM-β-MOS-HSA complex was more stable (higher
quenching and binding constant) than GG-β-MOS-HSA. LC-MS/MS studies demonstrated that β-MOS reduced
glycation sites, decreased the degree of substitution per peptide in glycated peptides, and altered the location of
glycation. Molecular docking suggested mannotriose (M3) had a strong affinity and lower binding energy ( 5.96
kcal/mol) for HSA. M3 interacted with amino acid residues spanning domains I (Site IB) and III (Sudlow site II) of
HSA via hydrogen bonding, van der Waals forces, carbon‑hydrogen, and alkyl interactions. MD studies
corroborated that the HSA-M3 complex was stable, less flexible and more compact.