A lateral flow colloidal gold-based immunoassay for rapid detection of miroestrol in samples of White Kwao Krua, a phytoestrogen-rich plant

White Kwao Krua (WKK)-derived products have been used worldwide as dietary supplements to relieve climacteric symptoms in menopausal women. Miroestrol is a unique chromene found in WKK tuberous roots that corresponds to the estrogenic activity of WKK. However, miroestrol naturally accumulates at low levels in WKK samples, which are difficult to detect. The development of a rapid and sensitive assay to detect miroestrol in numerous products derived from this plant would be a practical and useful method to guarantee the quality of raw materials. To allow rapid and easy qualitative detection of miroestrol, a lateral flow immunoassay (LFIA) using a colloidal gold-labeled monoclonal antibody (mAb) against miroestrol was developed. The qualitative LFIA was based on the competition of free miroestrol in the sample and immobilized miroestrol-conjugated proteins on the strip for a limited number of antibodies in the detection reagent. Anti-miroestrol mAb was colored by colloidal gold labels and used as the detection reagent in LFIA. Anti-mouse immunoglobulin G was used to indicate the functioning of the LFIA system. The detection limit of the LFIA was 0.156 μg of miroestrol. The LFIA was applied to determine the miroestrol content in WKK samples and products. The result was compared with the validated enzyme-linked immunosorbent assay (ELISA) and demonstrated a correlative outcome. This study shows that the developed LFIA is practical and suitable for detecting small amounts of miroestrol in WKK samples. This qualitative assay is more rapid in screening miroestrol in WKK samples (within 10 min) than conventional methods (ELISA and HPLC).