Chemical characterization of plant materials and development of analytical methodologies for metabolite determination

Abstract

Plants synthesize a huge number of metabolites, involved in essential life functions (primary metabolites) or in particular defense, signaling and development roles (secondary metabolites). Plant metabolome remains for a large part uncharacterized, due to the high variability among species. The investigations of this rich variety of plant metabolites have been improved in the 20th century with the development of new analytical techniques, which permitted the identification of low-abundant molecules and their structural characterization. In this study we present different approaches for the characterization of the chemical composition of plant materials. Taking advantage from the use of HRMS technology, we developed both quantitative and qualitative methods, in order to obtain a comprehensive profiling of metabolites. In the first research chapter we describe a study of wild and transgenic Nicotiana Langsdorfii plants, exposed to different abiotic stresses. These plants have been traditionally used for genetic and physiologic studies. The plants were modified by the insertion of the Rol C gene, from Agrobacterium rhizogenes, and of the rat glucocorticoid receptor (GR). The aim of this study was the investigation of the metabolic changes associated with the genetic modifications and stress exposition, in order to highlight eventual advantages deriving from the inserted genes and to better understand the effects of abiotic stresses. In the second study we considered two different species of the Glycyrrhiza genus, G. Glabra and G. Uralensis, commonly used for the production of licorice. The characterization of the two G. Glabra varieties, glandulifera and typica, was also carried out. The application of the metabolomic method aimed to the characterization of the chemical composition of each species, which is directly involved in the quality of the derived products. The third study report the analysis of the fruits of Coffea Canephora and Coffea Arabica, the most cultivated species for the production of coffee beans. The different parts of the fruits (perisperm, endosperm, pulp) were collected separately in two different harvest seasons. The metabolomic analysis was performed by integration of two analytical approaches: the use of HPLC-HRMS for the detection of secondary metabolites and the use of GC-TOF for the identification of primary metabolites. This work showed the potential of the integration of different approaches in analytical chemistry, contributing to the comprehension of plant stress response and suggesting some possible application of the genetic modifications tested. Moreover we provide useful information about licorice and coffee, demonstrating the potential of metabolomic methodology as a tool in the food characterization and quality assurance. The metabolomic analyses also permit to suggest a few biosynthetic pathway regulations involved in stress response and ripening process. The study represents a good starting point for future works in the field of foodomics and of system biology, highlighting original findings, not reported before, which should be better investigated.