Evaluation of the Polyphenolic, Nutritive and Biological Activities of the Acetone, Methanol and Water Extracts of Amaranthus asper~!2009-06-16~!2010-02-02~!2010-04-14~!

Abstract

The nutritional, phytochemical, antioxidant and antibacterial activities of the acetone, methanol and water extracts of the leaves of Amaranthus asper were investigated using standard analytical methods in order to assess the numerous potential of the plant leaves. The proximate analysis showed that the leaves of this plant contained moisture, ash, crude protein, crude lipid, crude fibre, energy and carbohydrate. Elemental analysis in mg/100 g (DW) indicated that the leaves contained sodium (0.0373), potassium (2.872), calcium (2.504), Magnesium (0.569), Iron (419), Zinc (26), phosphorus (0.177), Copper (18), Manganese (91), and Nitrogen (1.78). The chemical composition in mg/100 g (DW) for alkaloid, saponins, and phytate were 0.3, 7.0 and 9.25 respectively. Comparing the nutrient and chemical constituents with recommended dietary allowance (RDA) values, the results reveal that the leaves contain an appreciable amount of nutrients, minerals, and phytochemicals and low levels of toxicants. At 1mg/ml, the acetone extract caused 98.2% ABTS radical scavenging inhibition while the methanol, water and BHT caused inhibition at 95.4, 97.1 and 99.3% respectively. The result for DPPH scavenging activity was close to that of ABTS. The plant was also rich in the different polyphenols analyzed in this study. The ferrous reducing antioxidant power (FRAP) values for acetone extract (1084.9) is much higher than that of methanol (143.5), water (42.4), BHT (63.5), and catechin (972.02) but lower than those of ascorbic acid (1632.1) and quercetin (3107.3). The methanol extract has antibacterial activity against all the Gram-positive organisms used in this study. This study has to some extent validated the need for the use of the leaves of Amaranthus asper for nutritional and medicinal purposes.