A novel method to quantify Dendrobium officinale polysaccharides in biological samples via 99mTc-labelling and radioHPGPC analysis

Natural polysaccharides are attracting increasing attention due to their excellent pharmacological properties and low toxicity. However, the clinical translation of these biomacromolecules has been hindered by a lack of pharmacokinetic studies. Polysaccharide labelling presents a promising method for performing pharmacokinetic investigations on polysaccharides. The combination of radioisotopic labelling and high-performance gel permeation chromatography (HPGPC) has not yet been applied to the detection of polysaccharides in biological samples. Here, Dendrobium officinale polysaccharides (DOP) were selected as model polysaccharides. DOP and radiolabelling of DOP ( 99m TC-DTPA-DOP) were prepared and characterized. Then, HPGPC with a radio-HPLC flow detector (radioHPGPC) was used to analyse 99m TC-DTPA-DOP in biological samples for the first time. The detection method was demonstrated to exhibit good linearity (R 2  > 0.997), sensitivity (LLOD <100 nCi, and 62.99 ng/mL for the Conc of DOP), specificity, and recovery rate (>90 %). The blood concentration and distribution in major organs after oral and intravenous administration were studied. The results showed that the bioavailability of DOP was 2.68 %. This method is superior to γ counting or liquid scintillation counting because radioHPGPC could not only eliminate the impact of free 99m Tc and quantity the DOP tracer but also qualitatively analyse the metabolism during absorption and distribution. This study provides detailed pharmacokinetic profiles of DOP and a practical method for labelling and pharmacokinetic studies of other polysaccharides with high molecular weight.