Green leaf carotenoids mainly composed of lutein and β-carotene were studied regarding their its biochemical and physicochemical properties from new stand points in research. This review conains the following contents; 1) Compositions of leaf carotenoids vary by season and temperature effects this phenomenon. 2) Lutein was isolated from spinach leaves as a crystal. 3) Lutein inhibits spinach lipoxygenase activity, and the addition of a small amount of vegetable oil to feed grasses will keep their yellowish color. 4) Lutein disperses in aqueous systems, for example, protein solution, surfactant solution, dilute acetone aq. solution, to make chiral molecular aggregates. This phenomenon suggests some probabilities, for example, an electron conductor in chloroplast or a biotip for a light switch. 5) When lutein is used together with carotene, human leukemia cells differentiate more clearly than by a single addition of carotene. This means that lutein has a synergistic activity for carotene in control of cancers. 6) Behaviors of absorption of absorption and metabolism in the intestine were examined with both hens and quails as carotenoid-accumulating animals and rats as non-accumulators. The former accumulate lutein in the body, while in the latter lutein is missing after absorption. 7) β-Carotene cleavage enzyme and retinal reductase were studied in vitro regarding revised assay methods and some enzymatic properties. 8) A new method of separating palm carotene from crude palm oil was developed for the palm edible oil industry.
absoption and metabolism of carotenoids