Identification of Sinomenine from Sinomenium actum and Its Simultaneous Quantitation by GC–MS and Non-Aqueous CE

Identification of alkaloid constituents from Fangchi species using pH control liquid-liquid extraction and liquid chromatography coupled to quadrupole time-of-flight mass spectrometry

RATIONALE

Fangchi (F.) species from four different origins have been widely used to treat or prevent diseases, and their main constitutes are several types of alkaloids. Identification of alkaloids in F. species is a necessary step to understand the therapeutic properties of each different origin, but this has not yet been fully performed.

METHODS

Several types of alkaloids were extracted from F. species using ultrasonication with 70% CH(3)OH and the extract was partitioned at pH 2 and 12 to enrich alkaloid constituents and to remove interferences. The separation of alkaloids in the Fangchi extract was performed on a C18 column using gradient elution and their tandem mass spectra were obtained by quadrupole time-of-flight tandem mass spectrometry (QTOF-MS/MS) to perform accurate mass measurements of fragment ions for the alkaloid constituents.

RESULTS

Several types of alkaloids were successfully separated and identified by LC/ESI-MS/MS. The structural assignment of individual alkaloids was performed based on convergence of MS/MS spectral data, pH partitioning behavior, LC retention behavior, and accurate mass measurements. The pH partition of the extract provided structural information about unknown alkaloids extracted from Fangchi species. A total of 28 compounds were identified and tentatively characterized, and of these 10 alkaloids were reported for the first time in the investigated F. species.

CONCLUSIONS

The chemical profiling of alkaloids in F. species with different origins was performed for the first time and provided diagnostic ions for diverse alkaloids in F. species. Marker compounds were suggested based on the 28 characterized compounds for quality evaluation and the differentiation of Fangchi species with four different origins.

Analysis of active alkaloids in the Menispermaceae family by nonaqueous capillary electrophoresis-ion trap mass spectrometry

A nonaqueous CE-IT MS with a nanospray ionization interface method was developed for the identification and quantification of tetrandrine (TET), fangchinoline (FAN), and sinomenine (SIN) using berberine as internal standard. The TET, FAN, and SIN standard solutions were directly infused into IT-MS for collecting MS(1-3) spectra. The major fragment ions of analytes were confirmed and possible main cleavage pathways of fragment ions were studied. A bare fused-silica capillary was used for separation of the analytes. A sheath liquid (50% aqueous methanol containing 0.2% acetic acid) to the capillary effluent with a nanoelectrospray ionization interface was added. Separation buffer comprised 80 mM solution of ammonium acetate, in a mixture of 70% methanol, 20% ACN, and 10% water, which also contained 1% acetic acid. The CE-MS method was validated for linearity, sensitivity, accuracy, and precision, and then used to determine the content of the above components. The detection limits of TET, FAN, and SIN are 0.05, 0.08, and 0.15 μg/mL, respectively. The precision was no more than 4.67% and the mean recovery of the analytes were 95.36-99.24%. This method was successfully applied to determine TET, FAN, and SIN in real samples radix Stephaniae tetrandrae and rhizomes of Menispermum dauricum.