Determination of nutritional composition, enzyme inhibitory activity and antioxidant activity of pretreated, dehydrated Amaranthus viridis L. Leaves

Abstract

Amaranthus viridis L., belongs to the family Amaranthaceae is a perennial edible plant, and traditionally used for medicinal treatments in South Asia. Despite the significant uses of the plant, availability of scientific data on plant's biological efficiency is lacking in the scientific domain. There is a higher potential and demand for dehydrated value-added products from the local and international market. Hence, the objective of the research was to determine the impact of pretreatments and dehydration on nutritional composition, phytochemical profile, antioxidant activity, and enzyme inhibitory activity of A.viridis leaves. Magnesium oxide 0.1% (w/v), sodium bicarbonate 0.1% (w/v) and potassium metabisulphite 0.5% (w/v) were selected as the best pretreatment based on the experiments. The pretreated leaves were steam blanched (5 min), followed by dehydration at 60 ± 1°C for 12 hours. Protein (21.90 ± 1.01%db), fat (3.70 ± 0.02%db), fiber (5.90 ± 0.05%db), ash (11.30 ± 0.12%db) and carbohydrate (49.24 ± 0.08%db) were determined. Data was statistically analyzed using one-way analysis of variance (ANOVA) test at a 95% confidence level (p < 0.05). A qualitative phytochemical analysis was conducted. The total phenolic content, 5.89 ± 0.30 mg in Gallic acid equivalents per 1g was determined in pretreated, dehydrated powder. FRAP, DPPH radical scavenging activity and ferrous ion chelating activity of the methanolic extract were 20.22 ± 0.45 mg Trolox equivalents, 1.68 ± 0.07 mg in Trolox equivalents and 3.83 ± 0.06 mg EDTA equivalents per 1g of pretreated dehydrated leaf powder, respectively. Methanolic extract (500 μg/mL) showed inhibitory activity of 25.30 ± 0.60% on 5-lipoxygenase, 30.80 ± 0.50% on alpha-amylase and 25.60 ± 0.40% on alpha-glucosidase. Inhibitory activity was not detected against lipase, acetylcholine esterase and butyrylcholinesterase enzymes. In conclusion, pretreated, dehydrated, A. viridis leaves are recommended as a health beneficial food ingredient.