University System of Maryland

Yufa Liu

Frederick Khachik

Holly Showalter

The present invention relates to a process for converting lutein and/or lutein esters to (3R)-&#x3b2;-cryptoxanthin and (3R,6'R)-&#x3b1;-cryptoxanthin, suitable for human consumption as dietary supplements, by employing safe and environmentally friendly reagents. (3R)-&#x3b2;-Cryptoxanthin and (3R,6&#x2032;R)-&#x3b1;-cryptoxanthin are two rare food carotenoids that are not commercially available and the former exhibits vitamin A activity. In the first synthetic step, commercially available lutein and/or lutein esters are transformed into a mixture of dehydration products of lutein (anhydroluteins) in the presence of a catalytic amount of an acid. The resulting anhydroluteins are then converted to (3R)-&#x3b2;-cryptoxanthin (major product) and (3R,6&#x2032;R)-&#x3b1;-cryptoxanthin (minor product) by heterogeneous catalytic hydrogenation employing transition elements of group VIII (Pt, Pd, Rh supported on alumina or carbon) in a variety of organic solvents under atmospheric pressure of hydrogen and at temperatures ranging from &#x2212;15&#xb0; C. to 40&#xb0; C. Among these catalysts, Pt supported on alumina at 40&#xb0; C. in ethyl acetate provides the best yield of (3R)-&#x3b2;-cryptoxanthin and (3R,6&#x2032;R)-&#x3b1;-cryptoxanthin. Several homogeneous catalysts can also promote the regioselective hydrogenation of anhydroluteins to a mixture of (3R)-&#x3b2;-cryptoxanthin and (3R,6&#x2032;R)-&#x3b1;-cryptoxanthin in low to moderate yields. The catalysts may be transition metal complexes such as palladium acetylacetonate, Rh(PhP)Cl (Wilkinson's catalyst), [(CH)P[CH][CHN]IrPF6(Crabtree catalyst), or [CH][(MePhP)]IrPF6. Among these, Wilkinson catalyst converts anhydroluteins to (3R)-&#x3b2;-cryptoxanthin and (3R,6&#x2032;R)-&#x3b1;-cryptoxanthin in nearly quantitative yield. A novel feature of this invention is the regioselective hydrogenation of anhydroluteins while the highly conjugated polyene chain of these carotenoids remains intact.

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West Des Moines, IA, United States of America

Yufa Liu