Quantification of methylisomiroestrol, a phytoestrogen of Pueraria candollei, by enzyme-linked immunosorbent assay in comparison with high-performance liquid chromatography

Abstract Pueraria candollei is a phytoestrogen-rich herb used to treat estrogen deficiency disorders; however, quality control of P. candollei-related health products is required for consistency of clinical outcomes. Estrogenically active (+)-7-O-methylisomiroestrol could be a potential chemical marker that facilitates the prediction of the overall estrogenic activity of P. candollei. The analytical performance of ELISA using newly produced monoclonal antibodies against methylisomiroestrol was compared with HPLC analysis. The developed indirect competitive ELISA (icELISA) was highly sensitive to methylisomiroestrol for detection, with an LOQ of 2.9 ng/mL, whereas the LOQ was 1.15 µg/mL by HPLC. The results from method validation indicated acceptable precision (1.71 - 6.37% and 0.13 - 2.40%) and accuracy (99.23 -102.54% and 96.84 - 101.88%) of the methylisomiroestrol analysis using icELISA and HPLC. These methods were effectively applied for the determination of the methylisomiroestrol content in P. candollei samples. Apart from the plant tubers, the stem was observed as a source of methylisomiroestrol. The developed ELISA was more effective than HPLC in detecting a small quantity of methylisomiroestrol in the plant samples [0.23 × 10-3% (w/w) to 0.628 × 10-3% (w/w) dry weight]. Therefore, the ELISA could be a useful tool for the standardization of P. candollei, which is the crucial step to improve the quality of plant-derived products.