The recent study aimed to investigate the composition of monosaccharides and their derivatives in the leaves of vegetable species Amaranthus tricolor L. cv. ‘Valentina’ of different ages, as well as, their vital role in enhancing the adaptive potential of the plant. Forty-eight monosaccharides and 28 of their derivatives have been identified in the composition of amaranth leaves of different ages. The maximum number of hydrophilic carbohydrate metabolites clustered in the young leaf. However, in older leaves, the number of water soluble metabolites showed similarities to that of the soluble in ethyl alcohol. Along with the general carbohydrate metabolites, the old leaves also contained specific monosaccharides, such as, lixopyranose, glucose, sorbose, mannobiose, cellobiose, and monosaccharide derivatives, i.e., methyl galactoside, glucopyranosiduronic and glucuronic acids, and alcohol erythritol. However, in Amaranthus tricolor L., the young leaf is characterized by arabinofuranose and carbohydrate derivatives, i.e., alpha-ketogluconic, arabinohexane, glucaric, galactaric, xylonic-D, lactone acids, and alcohol pentatriol. The leaves of different ages’ composition showed polyhydric alcohols (glycerin, ribitol, and myo-inositol). It also showed osmoprotective and antioxidant properties.