Prioritization of the Secondary Metabolites for the Rapid Annotation Based on Liquid Chromatography-High Resolution Mass Spectrometry Assessment: Varanasine and Schroffanone from Murraya paniculata and Cytotoxic Evaluation.

Abstract

The liquid chromatography-high resolution mass spectrometry (LC-HRMS) technique enables the detection of phytochemicals present in the extracts. LC-HRMS-generated mass list showed abundant compounds of interest, artifacts, and primary metabolites. The identification of a secondary metabolite of interest within the extract is very challenging. We hypothesized that identifying the "new metabolite" in the whole metabolome is more challenging than identifying it within the class of metabolites. The proposed prioritization strategy focused on the elimination of unknown and prioritizing the known class of secondary metabolites to identify new metabolites. The prioritization strategy demonstrated on Murraya paniculata for the identification of new metabolites. LC-HRMS-generated information is used as a filter to target the secondary metabolite and the new metabolites. This strategy successfully annotated the new coumarin and coumarin alkaloids from the mass list of 1448 metabolites. Varanasine (3), schroffanone (4), schroffanene (5), and O-methylmurraol (9) are new compounds, and coumarin (1, 2, and 6-8) are known. Varanasine (3) is the first naturally occurring 7-aminocoumarin with additional N-formyl functionality. The isolates were screened for cytotoxicity against the panel of cancer cell lines. Varanasine (3) and minumicrollin (6) showed significant cytotoxicity and apoptosis-inducing potential. The immunoblot analysis confirmed inhibition of apoptotic protein PARP-1 and caspase-3 expression by 3 and 6.