Effects of some experimental parameters on the activity of cowpea alpha-amylase inhibitors.

alpha-amylase inhibitor activity in seeds of cowpea (Vigna unguiculata L Walp), a legume widely consumed in subtropical areas, was studied. The effects on the in vitro inhibitor assay of some experimental parameters, such as pH, time of enzyme-inhibitor incubation, reaction temperature, ionic strength of the buffer, extraction procedure and dehulling were investigated. Maximum inhibitor activity was obtained by carrying out the assay at neutral pH and 30°C. An incubation period of 20 min between the enzyme and seed extract was essential before substrate addition. The presence of additional calcium ions in the reaction buffer increased enzyme inhibition. The comparison between amylase inhibitor activity of whole and dehulled seeds has shown that coats strongly affect the inhibitor assay.