Folic acid conjugase from plasma. III. Use of the enzyme in the estimation of folate activity in foods.

A convenient method for the estimation of food folates using human plasma as a source of folic acid conjugase has been standardized. Bovine, goat and dog plasma could not be used for the purpose because of low enzyme activity and slow reaction rates. Human plasma conjugase released food folates from conjugated forms over a pH range of 4.5 to 6.0. The food folate values obtained by employing rat liver and chicken pancreas conjugase closely agreed with the values obtained by using human plasma conjugase. The advantages in using human plasma as a source of conjugase were (1) easy availability (2) non-essentiality of preliminary processing (3) stability of the enzyme on storing plasma in cold (4) low enzyme blank folate activity and (5) low amount of plasma needed for assay. Using this method, folic acid activity of some common Indian foods of plant and animal origin has been estimated. There were wide variations in the folate activity of different classes of foods. In general legumes and green leafy vegetables were found to be rich in folate activity.