Metabolomic analysis of Salvia hispanica seeds using NMR spectroscopy and multivariate data analysis

The metabolic profile of the seeds of seven Chia (Salvia hispanica L.) populations, three commercial (two black, and one white) and four early flowering genotypes (G3, G8, G17, W13.1), was investigated by NMR spectroscopy. The research aimed at evaluating the chemical composition of the different genotypes both from a qualitative point of view, through the identification of the major classes of organic compounds by NMR analysis, and from a quantitative point of view, through the integration of NMR spectra followed by Principal Component Analysis and chemometrics. Results showed that apolar organic extracts were mainly composed of mono- and polyunsaturated fatty acids, such as α-linolenic acid, while polar organic extracts contained the sugars glucose, raffinose and sucrose as the main metabolites, together with caffeoyl derivatives, flavonoids, organic acids, and free amino acids. Tashinone I and 15,16 dihydro Tanshinone I were detected in Chia seeds for the first time. Chemometric results showed significant differences in the metabolic fingerprinting of the different populations, with the content of most of the detected metabolites showing higher variation in the seeds of early flowering genotypes compared to commercial seeds. In particular, black genotypes are richest in carbohydrates comparing to the early flowering and white genotypes. The analysis was also extended to two black samples grown in Basilicata (Southern Italy) to evaluate the effect of agronomic management, such as fertilization with mineral nitrogen, on the metabolite composition. The obtained data indicated that the effect of mineral nitrogen supply positively affected the content of aliphatic free amino acids, and negatively that of the main carbohydrates and flavonoids, while the pools of caffeoyl derivatives, organic and fatty acids remained almost unaffected.