Total phenolic content and antioxidant activity in eight cowpea ( Vigna unguiculata) genotypes

Abstract

Cowpea is considered as one of the underutilized legumes which is rich in secondary metabolites. These metabolites can be detected during the plant growth and the contents increase especially after the plants are stressed both abiotic and biotic. This study aimed to determine total phenolic and flavonoid contents as well as antioxidant activity in seeds of eight cowpea genotypes. Two extraction solvents (70% acetone and 70% acidified acetone) were used to extract the secondary metabolites in those cowpea genotypes. Total flavonoid contents of those genotypes extracted in 70% acetone and 70% acidified acetone were in the range from 7.28 to 10.90 mg CE/g and 7.84 to 11.58 mg CE/g, whereas total phenolic contents were from 15.20 to 19.99 mg GAE/g and 15.03 to 21.15 mg GAE/g. Inhibition percentages of antioxidant activity were in the range from 46.90 % to 59.46 % and 50.71 % to 63.81 % for 70% acetone and 70% acidified acetone, respectively. Both solvents were effective to extract those secondary metabolites. Flavonoid and phenolic contents of MLGU 0239 were the highest among other genotypes, which were 11.58 mg CE/g and 21.15 GAE/g and antioxidant activity was 63.81 % inhibition after being extracted with 70% acidified acetone. This study observed the variation of the secondary metabolites among eight cowpea genotypes with different seed coat colours.