%0 PDF %T The Role of Antioxidants in Enhancing the Vitamin A Value of Plant Foods in Child Nutrition. %A Muzhingi, Tawanda. %8 2017-04-14 %R http://localhost/files/xg94j240h %X Abstract: Vitamin A deficiency is a public health problem among children aged 6-36 months old in Zimbabwe. The children are vitamin A deficient partly because the complementary diets are starchy white gruels, devoid of vitamin A or provitamin A carotenoids. Green leafy vegetables of Brassica oleracea family such as kale are rich in provitamin A carotenoids. Despite the widespread consumption of kale, it is not a common complementary food. A kale complementary food cooked with peanut butter is not only nutrient and energy dense, but may also increase the bioavailability of &beta-carotene. Kale is consumed as relish to staple maize porridge. Therefore, it is important to also optimize the vitamin A value of maize based complementary foods. Our previous studies show that &alpha-tocopherol, an antioxidant found abundantly in maize promotes the exclusive central cleavage of &beta-carotene by the BCMO1 enzyme to vitamin A. However, the genetic variation of vitamin E and antioxidants in biofortified yellow maize and their effects on BCMO1 enzyme is unknown. Currently, there is also a lack of information on the genetic characterization of carotenoids in Brassica oleracea green vegetables consumed in Zimbabwe, and human studies showing their vitamin A value. The primary objective of this thesis was to demonstrate that kale and biofortified maize can improve the vitamin A value of complementary foods in Zimbabwe. The following studies were pursued to address the primary objective. The first study determined the genetic variation of carotenoids, vitamin E and phenolic compounds in biofortified maize. HPLC analysis of 20 genotypes of biofortified maize showed &beta-cryptoxanthin and &beta-carotene as the main provitamin A carotenoids. Biofortified maize was also high in vitamin E, γ-oryzanol, ferulic acid and p-coumaric acid. Our study showed that genotype was a significant determinant of provitamin A carotenoids and vitamin E variation in maize (p<0.01). The second study characterized carotenoid profiles of brassica oleracea var. acephala vegetables varieties commonly consumed in Zimbabwe. HPLC analysis showed significant differences in the lutein and &beta-carotene contents among the six brassica oleracea vegetables varieties (p<0.05). Our study showed that the Zimbabwean brassica oleracea var. acephala vegetables are a very good source of provitamin A carotenoids. Our third study determined the effect of antioxidants on the enzymatic cleavage of &beta-carotene in vitro. Extracts of kale and biofortified maize were incubated with rat intestinal mucosal homogenate for an hour at 37°C. This study showed that vitamin E and γ-oryzanol promote central cleavage of &beta-carotene to form vitamin A. The fourth study determined the effect of peanut butter on the bioconversion of deuterium labeled kale [2H9] &beta-carotene to vitamin A. Preschool children were randomly assigned to ingest 1 mg [13C10] retinyl acetate reference dose and 50 g cooked kale (1.5 mg &beta-carotene) with either 33 g peanut butter (PBG) or 16 g lard (LG) on d1. Serum samples were analyzed by NCI-GC/MS for the enrichments of labeled [2H] retinol from kale [2H9] &beta-carotene and [13C10] retinol from reference dose. The area under the curve (AUCs) of molar retinol enrichments at days 1, 2, 3, 6, 15, and 21 after the labeled doses showed the calculated conversion factors of kale &beta-carotene to vitamin A to be 13.4 ± 3.1 and 11.0 ± 3.9 to 1 by weight for LG and PBG respectively. This showed that kale is a good source of vitamin A. In summary, our research studies showed that kale and biofortified maize can improve the vitamin A value of complementary diets of children aged 6-59 months who are vulnerable to vitamin A deficiency.; Thesis (Ph.D.)--Tufts University, 2014.; Submitted to the Dept. of Biochemical and Molecular Nutrition.; Advisor: Guangwen Tang.; Committee: Odilia Bermudez, Kyung-Jin Yeum, and Andrew Siwela.; Keywords: Nutrition, Chemistry, and Food science. %[ 2022-10-11 %~ Tufts Digital Library %W Institution