Metabolomic and proteomic signature of Gloriosa superba leaves treated with mercuric chloride and phenylalanine, a precursor of colchicine alkaloid

Gloriosa superba is a tropical, medicinally important plant used in the treatment of gout, rheumatism, and other ailments. It produces pharmaceutically important alkaloids like colchicine, gloriosine, thiocolchicoside and others. In the present study, gas chromatography (GC)-mass spectrometry (MS) method has been deployed for the identification of low abundance phytochemicals in mercuric chloride (elicitor)-treated leaves. The analysis revealed nearly 500 molecules including 15 key secondary metabolites like estragole, N-methylloline (alkaloid), aphidocolin, 3-hydroxykynurenine, octyl salicylate, butibufen, anonaine (aporhine alkaloid), bolasterone, austricin, bolandione, octahydrocoumarin, jacaranone, bonducellin, quinacridone, and β-carotene that may have medicinal importance. Liquid chromatography-mass spectrometry (LC-MS) analysis of leaf proteome in the control and phenylalanine (a precursor of colchicine)-treated tissues revealed a total of 982 and 937 proteins respectively. In precursor-treated tissues, 364 differentially expressed proteins were noticed besides others. Key proteins involved in shikimate/chorismate pathway such as phenylalanine ammonia-lyase, chalcone-flavone isomerase (associated with flavonoid biosynthesis), chalcone synthase (involved in the synthesis of bioactive compounds in plants), chorismate synthetase, chorismate mutase, tryptophan synthase, and medium chain triglyceride protein were detected. Importantly, detection of nearly 154 proteins with unknown functions may hold key and play a role in colchicine biosynthetic pathway. These studies suggest that while metabolomic studies help to detect new secondary plant products, proteomic studies assist us in identifying key enzymes implicated in the biosynthetic pathway of alkaloids in G. superba.