Amaranth (Amaranthus spp.) is an important food crop source of nutrients and bioactive compounds. Different species of amaranth showed considerable phenotypic variations and could possess diverse nutritional properties. The presented study strove to determine the diversity of amaranth collection for morphological and biochemical traits and their antioxidant potential for developing new cultivars adapted to the environmental conditions of Central Russia. The selected 16 amaranth accessions had high variability in morphological and biochemical traits. With red-colored leaves, amaranthine content ranged from 0.319^a to 2.031^f mg/g fresh weight (FW). The water-soluble antioxidant content ranged from 0.425^a to 1.439^h mg of gallic acid equivalent (GAE)/g FW. In amaranth accessions, the phenolic compound content in leaves varied from 2.700^a to 4.825^g mg GAE/g FW. In the amaranth collection, the total chlorophyll content ranged from 0.9946^a to 3.5467^j mg/g, and carotenoids from 0.2196^a to 0.8289ⁱ mg/g. A strong positive correlation (P ≤ 0.05) was evident between total chlorophyll and carotenoid contents (r≈0.90), plant height and inflorescence length (r≈0.79), and inflorescence length and seed weight harvested per plant (r≈0.76).

In summary, when evaluating the antioxidant levels in various samples, the Valentina cultivar, characterized by red leaves, appeared to have the highest amaranthine concentration. Both Valentina and Fakel cultivars exhibited the maximum overall antioxidant capacity. Additionally, the Valentina and Duimovochka cultivars emerged as the top accumulators of polyphenols. These findings highlight the significant antioxidant potential present in these specific cultivars.

Keywords: Amaranth (Amaranthus spp.), agricultural traits, antioxidant content, amaranthine, phenolic compounds, photosynthetic pigments

Key findings: In the latest study, the 16 Amaranth accessions belonging to eight species succeeded in evaluation for morphological and biochemical parameters. Based on the investigations, the different accessions identified are recommendable for breeding and developing new, improved amaranth cultivars and preferable sources of phytopigments and antioxidants at the seedling stage.