Total polyphenol content and antioxidant capacity of cowpea effect of variet and locality

Leguminous seeds belong to plant foods which are generally rich in phenolic compounds. Cowpea seeds are a major source of plant proteins and vitamins for man, feed for animals. Polyphenolic compounds are secondary metabolites of amino acids present in many plant species, including legume. Their content depends on various factors, such as cultivar, pedoclimatic and cultivation conditions. The influence of cultivar, locality on the total polyphenols (TPC) and antioxidant activity (TAC) of Cowpea seeds was studied. Cowpea cultivars were cultivated under different climatic conditions in Iraq Republic. The main objective of the present work was to consider the changes of total polyphenols content in dependence on variety and to evaluate an antioxidant potential of three Cowpea varieties (white, light brown and red color) in different localities of Erbil City in Kurdistan Region Iraq and to evaluate the content of bioactive compounds (polyphenolics) in legumes commonly utilized in the human diet in Iraq, to compare their antioxidant capacity and to evaluate the influence of grown locality on observed parameters. Total polyphenols were determined by the Lachman´s method and expressed as mg of Gallic acid equivalent per kg dry matter. Total antioxidant capacity was measured by the Brand-Williams method using a compound DPPH (2,2-diphenyl-1-picrylhydrazyl). Analysis of variance indicated significant differences (p0.05) among locality and color for phenolic contents and antioxidant capacity. The various varieties of white color cowpea had significant influence on TPC and TAC and affected by locality too. From tested seeds the highest polyphenol content was measured in red color (802.323 ±15.937 - 825.700 ±8.494 mg.kg-1 GAE). The lowest value was in white color (480.195 ±15.286 - 721.952 ±25.004 mg.kg-1GAE).The similar trend was observed at values of TAC. The highest TAC value was determined in red color (28.709 ±15.937 - 34.777 ±8.494% DPPH). The lowest value was in white color (6.065 ±0.836% - 9.578 ±0.884% DPPH). The various varieties had significant influence on TPC and TAC according to used statistical analyses. Correlation between the phenolic contents and antioxidant activity was significantly positive (r = 0.783645). Our results confirmed that legumes can be a good source of bioactive compounds in the human nutrition