The naturally occurring pentacyclic triterpenoid compounds ursolic acid (UA) and oleanolic acid (OA) are commonly found together in various fruits and find broad applications in pharmaceuticals, cosmetics, food and agricultural fields. In this study, a sensitive and practical icELISA method was developed based on a monoclonal antibody (mAb) YC23-101, with a median inhibitory concentration (IC 50 ) of 15.56 ng/mL and a linear range of 5.26 to 54.1 ng/mL. The limits of detection (LOD) ranges from 0.98-5.11 ng/mL in fruit matrices and the recoveries were 94.03-112.21% with coefficients of variation below 5.73%. Cross-reactivity analysis showed that mAb YC23-101 could also specifically recognize OA with similar sensitivity to UA, indicating feasibility for the simultaneously quantification of UA and OA in fruits. The developed icELISA was applied to several fruits, and the results showed good correlation with that of HPLC. Molecular docking analysis predicted equal binding energy of UA and OA to the mAb with hydrophobic interactions playing a predominant role. All these findings demonstrated that this icELISA is reliable, sensitive, and suitable for the high-throughput quantification of total UA and OA content in fruits composition analysis.
A specific polyclonal antibody was prepared based on a new hapten with stable structure. Based on this, an indirect competitive enzyme-linked immunosorbent assay (icELISA) was established for determination of tylosin residues in food and environmental samples. The experimental conditions were optimized as follows: the coating antigen and antibody were respectively diluted by 6000 times and 2000 times, and the competitive reaction time was 40 min. Under the optimized conditions, the method showed a detection limit of 0.07 ng mL −1 , an IC 50 of 1.39 ng mL −1 and a linear range of 0.17–11.0 ng mL −1 . The recoveries of spiked raw milk and water samples were ranged from 78.4% to 105.6%, with the RSDs of less than 15%. Good correlation between icELISA and HPLC method was obtained for spiked samples ( R 2 = 0.97). This method was suitable for the determination of tylosin residues in milk and water samples.
危险品化学品经营许可证（带存储）