oa The sidra tree: Profiling of proteins and small molecules using high resolution accurate mass protocols

Representing the Qatar Foundation (QF) Logo, the Sidra tree (Ziziphus spina-christi -ZSC) is native to Qatar and grows wild in harsh and arid conditions. It serves as a symbol of perseverance, nourishment, solidarity, determination and perfection, encompassing the vision and mission of QF. Previous phytochemical investigation of the ZSC leaves and fruits has revealed a whole host of saponins, flavonoids and antioxidants present in both water and solvent crude extracts of components of the organism. These studies have not only demonstrated the presence of key potentially bioactive components but also the utility of these extracts as antimicrobial, antidiarrheal and antidiabetic agents. In the current study, both the profiling of proteins and characterization of small molecules in the leaves, fruits and seeds of the Sidra tree was undertaken using high-throughput protocols. Following pulverization under liquid nitrogen, proteins were extracted into aqueous buffer then precipitated using cold acetone with the supernatant reserved for further characterization of small molecules. Using HRAM MS and MS/MS. Protein profiling experiments were performed using Gelfree systems for mass separation of proteins into 12 fractions; these were later trypsin-digested for MS/MS analysis on the Orbitrap Elite system using CID (collision-induced dissociation) and HCD (High-energy collision dissociation) activation protocols. Peptides produce spectrum containing b- and y-ions permitting amino acid sequencing of these peptides; protein identification was subsequently achieved using SEQUEST and PEAKS Studio database search and de novo interpretation. This approach produced the first investigation of the proteome of the Sidra tree. Identification of small molecule bioactive components was achieved through high resolution accurate mass determination of the elemental composition and MS/MS high resolution confirmation of the compound structure. A dereplication mass list was configured citing components that have been identified elsewhere as well as the potential components that may be further confirmed through MSn analysis. This study reports many newly identified potentially bioactive compounds.