The present invention relates to a process for converting commercially available lutein and/or lutein esters from extracts of marigold flower petals to (3R)-β-cryptoxanthin (major) and (3R,6′R)-α-cryptoxanthin (minor) in ratios ranging from 95:5 to 98:2 in a one-pot reaction at room temperature. Because the entire process can be carried out by employing safe and environmentally friendly food-grade reagents, the resulting mixture of these carotenoids is suitable for human consumption as a dietary supplement.