Soluble sugar contents, total phenolic, and antioxidant capacity in a diverse set of Amaranthaceae accessions

Thirty-Five Amaranthaceae accessions from seven species collected from the Germplasm Resources Information Network, USDA-ARS and then grown in a greenhouse in the USA were analyzed for their soluble sugars, total phenolic, and antioxidant capacity. The sugar contents were analyzed using high-performance liquid chromatography (HPLC). The sucrose, glucose, and fructose were found the pure sugars of the amaranth accessions with sucrose was the predominant. But wide ranges of variations were observed among the accessions. The sucrose contents ranged from 2.50-131.20 mg.100 g-¹ DW (average 42.46 mg.100 g-¹ DW). The glucose and fructose contents ranged 2.60-66.64 (average 23.47 mg.100 g-¹ DW) and 0.60-34.60 (average 13.28 mg.100 g-¹ DW). A significant positive correction found between total sugar contents and sucrose (r= 0.944), glucose (r= 0.797) and fructose (r= 0.792). Total phenolic (TP) contents were measured using the Folin-Ciocalteu reagent and was expressed as mg Tannic acid equivalents per gram of plant material on the dry basis (mg TAE. g-¹). The Trolox equivalents antioxidant capacity (TEAC) based on the DPPH free radical scavenging ability of the extract was expressed as milligram Trolox equivalents per gram of plant material on the dry basis (mg TEAC. g-¹). Variability among accessions was greater for TP contents (CV 44.81%); individuals ranged nearly ninefold from 1.39 to12.37 mg TAE. g-¹ on a dry weight basis. Variation among accessions was also evident for TAEC values (CV 20.43%) and individually ranged nearly threefold from 0.17 to 0.44 mg TAEC. g-¹ on a dry weight basis. There were significant differences (P> 0.005) for TP and TAEC while compared among the seven species. The highest TP content was observed in C. argentea (7.69 mg TAE.g-¹) followed by A. hypochondriacus (6.98 mg TAE.g-¹), and the TEAC was found highest in A. blitum and A. hypochondriacus (0.36 mg TEAC.g-¹) followed by A. caudatus (0.35 mg TEAC.g-¹). However, TP and TEAC values were not significantly correlated (r= 0.430). The significant difference among accessions regarding soluble sugar contents, total phenolic, and antioxidant capacity showed their potentiality to use the accessions for further breeding programs.