Seiichi Sakamoto

Introduction Glycyrrhizin (GLY) and sennoside A (SA) are characteristic bioactive marker compounds of the Kampo medicine Daiokanzoto. Their accurate detection in blends of Rhei rhizoma and Glycyrrhizae radix of several species (4:1 or 4:2) is essential for quality control and to ensure therapeutic efficacy. A rapid, efficient assay can significantly facilitate their detection. Objective To establish a rapid qualitative assay for GLY and SA detection, a lateral flow immunoassay (LFA) was developed using specific monoclonal antibody (mAb) nanoparticles. Methodology This assay harnesses the competitive binding of mAb nanoparticles to the immobilized analytes on test strips and free analytes in the samples. Two conjugates for detecting GLY and SA, GLY–bovine serum albumin and SA–human serum albumin, were separately immobilized on the test zones of LFA strips. The detection mechanism is reliant on the visual detection of color changes in the test zones. Results When GLY and SA were present in samples, they contended with the immobilized conjugates on the strip to bind with the mAb nanoparticles and produced distinct color patterns in the test zones. The limits of detection of the assay for GLY and SA were both 3.13 μg/mL. The capability of the LFA was substantiated using plant samples and Daiokanzoto, and its alignment with indirect competitive ELISA results was confirmed. Conclusion The introduced LFA is a groundbreaking procedure that offers a rapid, straightforward, and sensitive method for simultaneously detecting GLY and SA in Daiokanzoto samples. It is instrumental in ensuring product quality.