Extraction Treatments Affect Total Flavonoid and Phenolic Contents of Cowpea (Vigna Unguiculata L. Walp.)

Abstract

Plant secondary metabolites exist during normal plant growth. The production increases remarkably when the plants are challenged by environmental stress. Quantification of these metabolites is affected by extraction solvents and preparation treatments. This study aims to select extraction solvents and treatments which are able to extract high total flavonoid and phenolic contents in cowpea seeds. Acetone at concentrations of 70-80% produced higher total flavonoid and phenolic contents of 10.37-11.93 mg CE/g and 18.20 – 20.20 mg GAE/g in two cowpea cultivars. Antioxidant activities were in the range from 115.9 to 126.1 umol TE/g. Extraction of cowpea seeds using 70% acidified acetone produced a similar amount of total phenolic contents to those of 70-80% acetone. Traditional extraction treatments of shaking and maceration extracted a similar amount of the secondary metabolites. These simple extraction methods, therefore, could be suggested to extract flavonoid and phenolic contents as well as antioxidant activity in cowpea where access to modern types of equipment is limited.