Quick screening of maize kernels for provitamin A content

Improving the micronutrient content of foods by bio-fortification is one of the strategies to alleviate micronutrient deficiencies. One of the target crops being bred for increased provitamin A content is maize. In order to estimate the success of these activities, we developed a quick screening method that allows distinction between low, medium and high levels of provitamin A carotenoids in maize by semi-quantitative analysis. Carotenoids in 13 lines of maize were extracted with acetone/hexane and carotenes and monohydroxy carotenoids were separated on a de-activated alumina column. The two fractions were quantified separately by absorption at 450 nm. Regression lines were constructed between the spectrophotometrically determined carotenoids in the fractions and the amount of retinol equivalents (RE) determined by HPLC in the full extract. Total carotene (μg/100 g)=7.62 RE+176; r = 0.97 , P < 0.01 ; SEE=10 RE/100 g. Total monohydroxy carotenoids (μg/100 g)=15.36 RE+374; r = 0.86 , P < 0.01 ; SEE=12 RE/100 g. The method described allows fast screening of maize kernels on levels of pro-vitamin A without the need of a full HPLC analysis of all samples, and hence reduces the cost of analyses.