Quantum dots combined with a fluorescence-linked immunosorbent assay for detecting the metabolic balance of DT-13 excretion in rats

Saponin monomer 13 of the dwarf lilyturf tuber (DT-13) is a steroidal saponin component isolated from the tuber of Liriope muscari (Decne.) Bailey that exhibits multiple pharmacological activities. We used a liquid chromatography-tandem mass spectrometry method and MetaboLynx XS software to investigate the metabolites of DT-13 in vivo and obtained potential metabolites and changes in functional groups during the formation of metabolites from the substrate. The main metabolites obtained had the ruscogenin (RUS) backbone structure. We also report a competitive fluorescence-linked immunosorbent assay (FLISA) based on monoclonal antibodies (MABS) conjugated with quantum dots (QDs) for rapid and sensitive quantitative analysis of DT-13 and its metabolite levels in biological samples. Using this method, the DT-13 levels detected in rat urine and feces displayed a good linear relationship within the corresponding linear ranges. The DT-13 recovery rate ranged from 85.28 to 101.40%, with a relative standard deviation of 2.96-9.26%. The method was successfully applied to study the distribution of DT-13 excretion in rats after oral administration. DT-13 was primarily excreted in the urine after metabolism. This study provides a new tool for pharmacokinetic studies of DT-13 and other active substances for which the analysis efficacy does not match the bioavailability or that are difficult to study using isotope labeling. (C) 2020 Published by Elsevier B.V.