Synthesis and functional analysis of polysaccharide-Fe (III) complexes from Lilium davidii var. willmottiae: a step toward bioavailable iron supplements

Lilium polysaccharides (LLP) exhibited various biological activities. However, the low bioavailability of polysaccharides limits their effectiveness in practical applications. To enhance their functionality and bioavailability, polysaccharides from Lanzhou lily (Lilium davidii var. willmottiae (E.H. Wilson) Raffill) bulbs were purified and chemically synthesized into polysaccharide-Fe (III) complexes in this study. Then, the structural characterization, physicochemical properties, thermal stability and digestibility of LLP-Fe (III) were systematically evaluated to assess its potential as an iron supplement. Results showed that LLP-Fe (III) had a higher molecular weight than LLP, with a monosaccharide composition dominated by mannose and glucose at a molar ratio of 1:1.23. LLP-Fe (III) was also revealed to have significantly enhanced thermal stability. FT-IR analysis confirmed the chelation between Fe (III) and carboxyl and hydroxyl groups in LLP through stable Fe−OOH bonds. Scanning electron microscopy displayed a dense morphology with smooth and small particles in LLP-Fe (III). Furthermore, in vivo simulated digestion tests indicated superior gastrointestinal stability and acid tolerance of LLP-Fe (III). These findings suggested that the polysaccharide-Fe (III) complexes hold promise as a novel iron supplement with potential health benefits.