Rapid characterization of caged xanthones in the resin of Garcinia hanburyi using multiple mass spectrometric scanning modes: the importance of biosynthetic knowledge based prediction.

Although the anticancer activities of the resin of Garcinia hanburyi have been well demonstrated, the chemical composition of this medicinal plant is still not fully understood. In this study, a highly effective qualitative method was developed for rapidly profiling the target and non-target caged xanthones in the resin of G. hanburyi. This method mainly involves three steps as follows: (1) prediction of the possible unknown caged xanthones in the resin of G. hanburyi according to the structure characters of the known ones and some well established biosynthetic knowledge; (2) structure classification according to the diagnostic fragment ions (DFIs) of the known caged Garcinia xanthones; (3) detection and characterization of the target and non-target caged xanthones in the resin of G. hanburyi using multiple mass spectrometric (MS) scanning modes. By use of such procedures, mass spectrometric data can be used for confirming the rationally predicted chemical structure rather than sophisticated and time-consumed de novo structure elucidation of a completely unknown component. Finally, a total of 34 caged xanthones including 18 likely new ones from the resin of G. hanburyi were rapidly detected and characterized within one working day.

Development of a method for the detection of beta-lactamases in milk samples.

With the rapid growth of the dairy industry and the establishment of strict antimicrobial residue limits in the People's Republic of China's (PRC) milk supply, a beta-lactamase product known as "antimicrobial destroyer" was introduced into dairy production without regulatory review. We developed a method for detecting this product in milk samples based on a modified cylinder plate method. The presence of beta-lactamase is defined as a difference between the inhibitory zones of the test samples (supplemented with 25 microg/mL sulbactam plus 0.5 microg/mL penicillin G) and control samples (supplemented only with 0.5 microg/mL penicillin G) > or = 3 mm. Using this method, 77 individually packaged milk samples were randomly collected from 5 retail stores in 3 cities over a 4-month period (May to August 2006). Of the 77 samples, 49 were found to be beta-lactamase-positive. In 2 undiluted milk samples showing extremely high beta-lactamase activity, 25 microg/mL sulbactam could not inhibit penicillin G activity. Because there is a lack of safety data on beta-lactamases in milk products, these data indicated a potentially serious safety concern for the dairy industry in the PRC.