Screening for cytotoxic chemical constituents from Justicia procumbens by HPLC–DAD–ESI–MS and NMR

BACKGROUND The Acanthaceae family is an important source of therapeutic drugs and ethno medicines. There are many famous medicinal plants from this family, such as Andrographis paniculata, Baphicacanthus cusia, and Dicliptera chinensis. Justicia procumbens (J. procumbens) is widely distributed in tropical and sub-tropical of the world. It has long been used in traditional Chinese medicine for cancer. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed the ethyl acetate extract of J. procumbens had a cytotoxic activity. Therefore, qualitative and quantitative analysis of the chemical constituents in the ethyl acetate extract was important for understanding its pharmacological mechanism. RESULTS A high-performance liquid chromatography with diode array detection coupled to electrospray ionisation quadrupole time-of-flight tandem mass spectrometry procedure was established. Eleven dibenzylbutanes and four arylnaphthalenes were confirmed by HPLC-DAD-ESI-QTOF-MS analysis. A novel dibenzylbutane (5-methoxy-4,4'-di-O-methylsecolariciresinol-9'-monoacetate) and seven isomers of arylnaphthalene were isolated and characterized by NMR and QTOF-MS. Compounds 1, 2, and 13 were detected for the first time. The content of six lignans were determinated in the ethyl acetate extract. CONCLUSIONS This study showed that the cytotoxic activity assay of J. procumbens could be mainly attributed to the constituents of lignans. The bioactivity of the ethyl acetate extract and determined compounds support the traditional use of this plant in cancer. These chemical constituents may be developed as novel therapeutics.