Unraveling Compositional Study, Chemometric Analysis, and Cell-Based Antioxidant Potential of Selective High Nutraceutical Value Amaranth Cultivars Using a GC-MS and NMR-Based Metabolomics Approach

Abstract

Amaranthus (family Amaranthaceae) is a potentially nutritious pseudocereal also known as a functional food owing to its high nutritional quality grains especially rich in essential amino acids. Emerging study, however, unambiguously indicates that apart from essential nutrients like protein, other phytochemicals present in amaranth seeds provide excellent health benefits. Squalene is one such phytonutrient found in Amaranthus seeds, which is also its largest vegetal source. In this research work, GC-MS and NMR spectroscopy-based metabolomics have been utilized for the compositional analysis of Amaranthus seeds coupled with a multivariate data set. Investigation of nonpolar and polar seed extracts of six different cultivars of amaranth identified 47 primary and secondary metabolites. One-way ANOVA showed significant quantitative metabolic variations in different cultivars of amaranth. Multivariate principal component analysis of both the GC-MS and NMR analyzed data broadly classified in two groups showed significant variations in the polar (lysine, arginine, GABA, and myoinositol) and nonpolar (squalene, tryptophan, and alkylated phenols, which are potential nutraceutical agents) metabolites. The squalene content estimated using HPLC varied significantly (1.61 to 4.72 mg g-1 seed dry weight) among six different cultivars. Positive correlations were found among the cellular antioxidant activity and squalene content. Cultivar AM-3 having the maximum squalene content showed the highest antioxidant activity evaluated on the cellular level over human embryonic kidney cells, clearly revealing potent intercellular reactive oxygen species scavenging capacity and strong membrane lipid peroxidation inhibition potential. Oxidative stress markers such as MDA, SOD, GSH, and CAT levels in cells further corroborated the research work. The study also indicated high concentrations of lysine (80.49 mg g-1 dry seeds) in AM-2, squalene (0.47% by weight) in AM-3, and 2,4-di-tert-butyl phenol (18.64% peak area) and myoinositol (79.07 mg g-1 dry seeds) in AM-5. This novel comparative metabolomic study successfully profiles the nutrient composition of amaranth cultivars and provides the opportunity for the development of nutraceuticals and natural antioxidants from this functional food.