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Two similar Dracocephalum species, namely, Dracocephalum tanguticum Maxim and Dracocephalum moldavica L, are commonly used as ethnic medicines in China. Here we describe a strategy of combining high-performance liquid chromatography with quadrupole time-of-flight mass spectrometry, as well as fingerprints and chemometrics for characterization and discrimination of chemical constituents on the two herbs. A total of 49 compounds including 33 flavonoids, 5 phenylethanol glycosides, 1 coumarin glycoside, 8 organic acids, and 2 other types of compounds were unambiguously or tentatively identified from the two Dracocephalum species. Among the compounds identified, 26 were characterized for the first time and 4 compounds, rosmarinic acid (7), salvianolic acid B (10), luteoloside (22), diosmetin-7-O-glucoside (28), were inferred as common constituents for the two herbs. Flavonoids featured in these two Dracocephalum species while their types presented significant differences. Acacetin (45) and acacetin glycosides (acatetin-7-O-glucuronide (30), acacetin-7-O-(6"-O-malonyl) glucoside (33), buddleoside (34), tilianin (35), and agastachoside (42)) were detected only in D. moldavica, which can be used to discriminate two herbal medicines. In addition, six characteristic constitutes in D. tanguticum were simultaneously quantified. Moreover, the induced chemometrics methods including similarity analysis and hierarchical clustering analysis were successfully applied for origin discrimination and quality evaluation of D. tanguticum and D. moldavica.

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Short-chain aliphatic amines are a class of hazardous impurities in drug substances. A simple method, involving derivatization followed by high-performance liquid chromatography with diode array detection, has been developed for residue determination of eight aliphatic amines simultaneously in drug substances. Different halonitrobenzenes derivatization reagents were systematically compared. As a result, 1-fluoro-2-nitro-4-(trifluoromethyl)benzene was selected since the derivatization effectively shifted the absorption wavelength to the visible region (400-450 nm), where most drug substances, impurities and even the derivatization reagent absorb very weakly. Due to the redshift effect, interference was minimized and adequately low limits of quantitation were reached (0.24-0.80 nmol/mL). Moreover, the derivatization reaction was readily carried out in dimethyl sulfoxide at room temperature for 1 h using N,N-diisopropylethylamine as catalyst to achieve the highest yield. Without any pre-treatment, the derivatives were analyzed by high-performance liquid chromatography with diode array detection. The high stability of the derivatives within 24 h at room temperature (RSD<1.04%) further facilitated the simultaneous preparation and consecutive analysis of quantities of samples. Finally, the proposed method was successfully applied for residue determination of eight aliphatic amines simultaneously in eight drug substance samples. This study could be helpful for the routine analysis and residue control of aliphatic amines in drug substances.