This study developed an analytical method to determine pyrrolizidine alkaloids (PAs) in teas using liquid chromatography–tandem mass spectrometry combined with rapid-easy extraction. PAs were extracted with 40 mL of 0.05 M sulfuric acid in 50% methanol solution and cleaned up using Oasis MCX SPE cartridges. Chromatographic separation of 21 PAs was conducted on an X-Bridge C18 column with gradient elution. According to the AOAC official analysis methods, the developed method was verified to establish linearity, limits of detection, limits of quantification, accuracy, inter-day precision, and intra-day precision for each PA. Overall, the method showed excellent repeatability, sensitivity, and reproducibility. The verified method was applied to tea samples, including maté, lemon balm, fennel, hibiscus, chrysanthemum, lavender, oolong tea, chamomile, rooibos, peppermint, mix tea, black, and green tea. One of the main advantages of the method developed in this study is that it allows complete separation of lycopsamine and intermedine peaks. Therefore, the method could be used to monitor PAs in teas.

Auxin-binding protein 57 (ABP 57 ), a soluble auxin-binding protein, acts as a receptor to activate plasma membrane (PM) H ? -ATPase. Here, we report the cloning of abp57 and the biochemical characterization of its protein expressed in E. coli. The analysis of internal amino acid sequences of ABP 57 purified from rice shoots enabled us to search for the corresponding gene in protein DB of NCBI. Further BLAST analysis showed that rice has four abp57-like genes and maize has at least one homolog. Interestingly, Arabidopsis seems to have no homolog. Recombinant ABP 57 expressed in E. coli caused the activation of PM H ? -ATPase regardless of the existence of IAA. Scatchard analysis showed that the recombinant protein has relatively low affinity to IAA as compared to natural ABP 57 . These results collectively support the notion that the cloned gene is responsible for ABP 57 .

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