Dynamic distribution of label-free polysaccharides after intestinal lymphatic absorption

The weak detection of trace amounts of absorbed polysaccharides in biological samples has limited our knowledge of their oral pharmacokinetics, hindering the clinical translation of natural polysaccharides into functional foods and natural medicines. This study established a highly sensitive oligosaccharide marker-based LC-MS strategy to map RAP-released structural signals after intestinal lymphatic absorption, using Radix Astragali polysaccharide (RAP) as an example. The method achieved a 10 ng/mL limit of detection (LOD) and was validated using matrix-matched calibration curves prepared in biological tissue/serum matrices, together with repeatability, intra-/inter-day precision, sensitivity, and accuracy evaluations. The method revealed dynamic RAP-derived marker signals: signals in Peyer's patches (PPs) peaked at 2 h post-oral dosing, appeared in mesenteric and inguinal lymph nodes at 4 h, and were detected in cervical and axillary lymph nodes at 6 h; RAP-derived signals were also observed in major organs by 2 h. DiGalA was detectable in the liver without prior hydrolysis at 6 h, suggesting possible hepatic processing of RAP-derived structures, and DiGalA persisted in the kidney. These findings offer new insights into natural polysaccharides' pharmacokinetics via intestinal lymphatic absorption. The method has application potential for pharmacokinetic and mechanistic studies of structurally characterized GalA-containing polysaccharides when enzyme-accessible and matrix-specific marker signals are available.