Lateal Flow Immunoassay for Sensitive and Rapid Detection of Methylisomiroestrol in <i>Pueraria candollei</i> Using Monoclonal Antibody

Methylisomiroestrol is a novel chromene compound with moderate estrogenic activity and an important biomarker for quality control in Pueraria candollei. The indirect competitive enzyme-linked immunosorbent assay (icELISA) provides high sensitivity, complexity, time consumption, and difficulty for practical fields. This study aimed to develop a rapid qualitative detection for methylisomiroestrol in P. candollei using monoclonal antibodies as lateral flow immunoassay (LFIA). The LFIA was developed and evaluated for sensitivity, cross-reactivity, and application to plant samples. Methylisomiroestrol (0.12-62.5 ng/mL) was used to determine the limit of detection (LOD). Cross-reactivity was assessed with related compounds such as chromenes and isoflavonoids. The developed method was applied to detect methylisomiroestrol in P. candollei samples and compared to icELISA. The LFIA showed 31.25 ng/mL for the LOD of methylisomiroestrol within 15 min. Cross-reactivity revealed interactions with related chromenes including isomiroestrol (8.89%), miroestrol (4.22%), and deoxymiroestrol (3.08%) and isoflavonoid compounds (< 0.6%). The application to P. candollei samples showed consistency results with the icELISA method that confirmed the qualitative detection of methylisomiroestrol in both root and stem materials. The developed LFIA provided a simple, quick, and easy-to-use method for the qualitative detection of methylisomiroestrol for quality control. However, further improvement toward semiquantitative analysis would increase the method's utility for comprehensive herbal medicine standardization.