Combining high-speed countercurrent chromatography three-phase solvent system with electrospray ionization-mass spectrometry and nuclear magnetic resonance to profile the unconventional food plant Syzygium malaccense

Syzygium malaccense (L.) Merr. & L.M. Perry is a native tree to Malaysia, but also occurs in other tropical regions of the world, including Brazil. The increasing interest in the consumption of its leaves motivated the investigation of compounds of the plant. Metabolite profiling of S. malaccense leaves was achieved by high-speed countercurrent chromatography (HSCCC) fractionation coupled off-line to electrospray massspectrometry (ESI-MS) detection and nuclear magnetic resonance (NMR) analysis. The ethanolic leaf extract was submitted to HSCCC using a three-phase solvent system (TPSS) composed by n -hexane - ethyl acetate - acetonitrile - H 2 O (2:1:1:1, v/v). The stepwise gradient elution was employed due to the extract's chemical complexity. HSCCC fractions were further analyzed by ESI-MS/MS using a flow injection experiment and by NMR acquiring 1 H, HSQC and HMBC spectra. MS based dereplication was achieved by comparing acquired data to those available in public and commercial databases. Results were also correlated to previously isolated compounds described for the Syzygium genus. This process led to the annotation of 90 compounds. The NMR data provided structural confirmation and substitution patterns for some of them. Extract chemical composition is characterized by having flavonoids, benzoic acids, hydroxycinnamic acids, quinic acids, hydrolizable tannins, fatty acids, anacardic acids and others primary metabolites. Most of these compounds were described for the first time in the plant. This approach greatly facilitates phytochemical analysis and could be applied to improve metabolite discovery in other studies.

Automated summary

The chemical composition of Syzygium malaccense leaves was analyzed using HSCCC fractionation coupled with ESI-MS and NMR techniques, resulting in the annotation of 90 compounds, most of which were described for the first time in the plant. NMR data provided structural confirmation and substitution patterns, enriching the understanding of compounds in Syzygium malaccense.