Content of an eye-protective nutrient lutein in sweetpotato leaves

The content of lutein, an eye-protective nutrient, in 'Suioh' leaves grown in the field, ranged from 31.5 mg to 42.6 mg/100 g fresh weight, and the average content was 36.8 mg/100 g fresh weight. The lutein contents in stems and petioles were much lower than in the leaves. The average content in 'Suioh' leaves was higher than that of Ipomoea aquatica leaves (11.9 mg/100g fresh weight) and exceeded that in other fruits and vegetables listed in a carotenoid database of 120 fruits and vegetables. Lutein content in 13 cultivars or breeding lines repeatedly harvested from a nursery bed tended to decline gradually throughout the growing season while showing cultivar differences. The average content from these cultivars or lines progressively decreased from 21.8 to 10.0 mg/100 g fresh weight, while the content in 'Suioh' leaves decreased from 25.7 to 12.9 mg/100 g. Lutein content correlated highly with levels of beta-carotene, another carotenoid that provides eye-protective nutrients, and chlorophyll b and a. These results suggest that sweetpotato leaves would be suitable for use as a vegetable which can help prevent or mitigate eye diseases, and that cultivar selection and harvesting time are important considerations to achieve higher lutein content in the leaves.