Rapid detection of aflatoxin B1 in medicinal materials of radix and rhizome by gold immunochromatographic assay.

A rapid screening of the most toxic aflatoxin B1 (AFB1) in medicinal materials of radix and rhizome was performed by an immune chromatography method for the first time. The colloidal gold immunochromatographic strip was prepared after optimization of the conjugation of gold particles with monoclonal antibody, the test line and the control line. Under optimized conditions, the detection limit of the constructed test strip was as low as 0.1 ng mL-1 and the total analysis was conducted within 15 min by naked eyes. Four kinds of medicinal materials (Gastrodia elata, Poria cocos, Bletilla striata and Radix Angelicae Dahuricae) were investigated by the strip. Various complex matrixes pay a significant influence on the feasibility and effectiveness of the strip screening in medicinal materials. Aiming to the characteristics of selected medicinal materials, the screening was successfully proceeded with extraction by 70% methanol-water as well as three-fold dilution in Gastrodia elata and Radix Angelicae Dahuricae, 70% methanol-PBS as well as four-fold dilution in Poria cocos., and 60% methanol-water as well as four-fold dilution in Bletilla striata. Among the collected 40 samples, one was found to be positive of AFB1 with level above 5 μg kg-1. The result was in a good agreement with those obtained from LC-MS/MS determination (6.12 μg kg-1). The gold immunochromatographic strip was demonstrated as a rapid, cost-effective, reliable and on-site screening technique for mycotoxins in starch and polysaccharides-rich herbal medicines.