Structural Features and Anti-Inflammatory Activity of a Low-Molecular-Weight Oligosaccharide Fraction from Lotus Bee Pollen

A novel low-molecular-weight water-soluble oligosaccharide fraction (LBPP-1) was prepared from lotus bee pollen via microwave-assisted extraction, followed by Sevag deproteinization and diethylaminoethyl (DEAE)-cellulose-52 chromatography purification. Ion chromatography (IC) indicated a glucose-rich composition (84.6 mol% glucose), with minor amounts of arabinose, glucosamine, and galactose. Fourier transform-infrared spectroscopy (FT-IR), methylation analysis, and 1H nuclear magnetic resonance (NMR) collectively supported the assignment of LBPP-1 as a glucan-rich, structurally heterogeneous oligosaccharide fraction containing candidate →4)-Glcp-rich domains and minor arabinose/galactose-related linkages. However, the marked difference between the IC composition and the sugar-type distribution estimated from PMAA peak areas limits quantitative interpretation of the residue proportions and branching architecture. Furthermore, in vitro biological assays demonstrated that LBPP-1 significantly attenuated lipopolysaccharide (LPS)-induced inflammatory responses in RAW264.7 macrophages. It effectively reduced the secretion of nitric oxide (NO) and the levels of inducible nitric oxide synthase (iNOS), interleukin (IL)-6, and tumor necrosis factor (TNF)-α in RAW264.7 macrophages. Reverse transcription–quantitative polymerase chain reaction (RT-qPCR) analysis further revealed that LBPP-1 selectively suppressed the mRNA expression of cyclooxygenase-2 (COX-2), IL-1β, IL-6, iNOS, and transforming growth factor (TGF)-β1. These findings collectively suggest that LBPP-1, as a bioactive carbohydrate fraction derived from lotus bee pollen, holds promise as a natural functional food ingredient for managing inflammation-related conditions.