Green Synthesized of Sulfur Nanoparticles and Its Application on Lettuce Plants Metabolic Profiling

This study aims to green synthesis of sulfur nanoparticles (SNPs) and investigation on its effects at different doses on metabolic profiling of lettuce plants. Whereas previous works only focused on effects of SNPs on growth and stress tolerance of exposed plants, the current work investigates on impact of SNPs on metabolite profiling of plants. SNPs were synthesized via Cinnamomum zeylanicum barks extract and sodium thiosulfate. In order to characterization of SNPs, scanning electron microscopy (SEM), TGA/DTA, and FT-IR techniques were used. The lettuce seeds were pretreated with different concentrations of sulfur nanoparticles (0, 0.001, 0.01, 1, and 10 mg/ml). The leaves of obtained seedlings have been harvested after 6 weeks and subjected for extraction using methanol and then the extracts were analyzed using GC–MS. A MANOVA method, as least squares-discriminant analysis (PLS-DA), was used in order to discriminate between treatment and control groups and changed metabolites have been estimated using HMDB online database. The changed metabolic pathways were estimated using with MetaboAnalyst software, as well. SEM and TEM analyses confirmed highly crystalline pure SNPs with uniform shape and an average particle size range of 43 to 61 nm with average size of 50.33 nm. Results also showed the significant changes in some sugars, amino acids, fatty acids, carboxylic acids, alkanes, and antioxidants levels of lettuce plants treated with different doses of SNPs. PLS-DA analysis indicated that the lettuce group treated with 10 mg/ml of SNP was separated from other groups with different metabolite levels. Some metabolic pathways such as aromatic amino acid biosynthesis, citric acid, and glyoxalate-dicarboxylate pathways exhibited high impact in treated plants than others. It was concluded that the use of C. zeylanicum barks extract can be a rapid and eco-friendly method for SNPs synthesis. On the other hand, although SNPs at high concentration (10 mg/ml) displayed high toxicity on lettuce plants metabolism, but its lower concentration may cause a significant increase in some metabolite levels and made the plants capable to tolerate against environmental stress. Also, applying the appropriate concentration of SNPs (1 mg/ml) can alter metabolic processes and improve the nutritional value of lettuce.