Rapid analysis of Callicarpa L. using direct spray ionization mass spectrometry

Abstract

Direct spray such as leaf spray and paper spray ionization mass spectrometry (MS) is a powerful type of ambient MS for phytochemical analysis. In this paper, direct spray MS methods to rapidly distinguish and analyze five species of Callicarpa L. have been developed. To distinguish species, leaf spray MS was employed to directly analyze leaves. A small triangular leaf sample was wetted with 15μL of spray solvent and a high DC voltage was then simply applied to the wet leaf sample, which was positioned in front of the inlet of a mass spectrometer to produce electrospray ionization. The MS signals of phenylpropanoid glycosides, i.e. forsythiaside B, poliumoside, verbascoside in leaves could be sensitively detected. The content characteristics of the phenylpropanoid glycosides in five species including Callicarpae kwangtungensis Folium, Callicarpae macrophyllae Folium, Callicarpa nudiflora Folium, Callicarpae formosanae Folium, Callicarpa longissima Folium could be used to distinguish them, then the mass spectra of the Callicarpa L. samples were analyzed using principal component analysis(PCA) or partial least squares-discriminant analysis(PLS-DA).For the rapid semi-quantitative analysis, of phenylpropanoid glycosides in leaves, paper spray MS was employed to determine phenylpropanoid glycosides in the extracts of Callicarpa L. leaves. Ginsenoside Rg1 was selected as an internal standard (I.S.). The calibration curves were constructed through ratios of target ion abundance to I.S. ion abundance vs. concentration of targets. The linearity range was 8–250μg/mL (R2=0.9947) for forsythiaside B, 9–280μg/mL (R2=0.9939) for verbascoside, and 9–260μg/mL (R2=0.9917) for poliumoside, respectively. The limit of detection (LOD) was 1μg/mL, 0.5μg/mL and 1μg/mL for forsythiaside B, verbascoside, and poliumoside, respectively.