Metabolomic Study on the Halophyte Suaeda salsa in the Yellow River Delta

Plant metabolomics has been well established and applied across multiple fields including medicine, biotechnology, and environmental sciences in the post-genomic era. The Chenopodiaceae C-3 halophyte Suaeda salsa is the most important plant species in the vegetation of saline soil and even intertidal zone in the Yellow River Delta, which is economically consumed as food, widely used as a bioindicator of environmental stresses (salinity, drought, and pollution) and typically applied for the phyto-remediation of degraded wetland. However, no global studies have been focused on the metabolic profile of this halophyte which is widely applied in environment related research areas. In metabolomics, the first crucial step is the preparation of plant samples. In this work, several strategies of metabolite extraction from this C-3 halophytes S. salsa were evaluated and the metabolic profile was characterized by NMRbased metabolomics. Multiple replicates of plant tissues (approx. 250 mg whole fresh weight of leaves and stems) were homogenized by a high throughput automated Precellys 24 bead-based homogenizer and then extracted using the following solvent systems of varying polarities:methanol, water, methanol/water, methanol/chloroform/water, and acetonitrile. The hydrophilic metabolites were analyzed using one-dimensional proton NMR spectroscopy, and the subsequent NMR spectra were evaluated by principal components analysis (PCA). Each extraction protocol revealed unique metabolic profile from S. salsa. Overall, the quality of each extraction protocol was assessed based on the yield, reproducibility, ease, and speed, and we concluded that the solvent of methanol/water was preferable for the metabolite extraction due to its highest reproducibility, ease, and speed, and considerably high yield. Validation of methanol/ water (1:1) solvent also showed a high degree of reproducibility with technical variation being considerably lower than biological variation in S. salsa samples. This demonstrated the quality and robustness of the methanol/water extraction method for NMRbased metabolomics studies.