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The provitamin A carotenoid β-carotene is an attractive candidate for the prevention of cancer. Indeed, abundant evidence suggests that β-carotene inhibits carcinogenesis. β-Carotene is thought to inhibit carcinogenesis by scavenging free radicals involved in tumor formation. However, there is no direct evidence that β-carotene traps radicals under conditions where it inhibits carcinogenesis. The overall objective of this dissertation research was to identify β-carotene oxidation products from β-carotene antioxidant reactions in model systems. Identification of such products will enable the direct measurement of β-carotene antioxidant activity in systems where it inhibits neoplastic transformation. In hexane solution, β-carotene was oxidized by peroxyl radicals to 5,6-epoxy-β, β-carotene, 15,15'-epoxy-β, β-carotene, a previously unreported product, and several unidentified polar products. Studies on the kinetics of product formation suggested that polar products are formed by both epoxide-dependent and -independent pathways. Because β-carotene may be localized within lipid bilayers in vivo, peroxyl radical oxidation of β-carotene in model membranes was examined. In soy phosphatidylcholine liposomes, β-carotene was oxidized by peroxyl radicals to the 5,6-epoxide and to unidentified polar products. β-Carotene antioxidant activity in the liposome system was the same at 15 torr and 160 torr O₂ and decreased at 760 torr O₂. These results suggest that β-carotene provides equal antioxidant protection in all tissues in vivo. The relative rates of product formation and β-carotene oxidation at different pO₂ suggested that β-carotene antioxidant activity is governed by the relative proportions of β-carotene radical trapping and autoxidation reactions, which do not contribute to radical trapping. Therefore, the loss of β-carotene antioxidant action at 760 torr O₂ may result from an increase in β-carotene oxidation by autoxidation pathways. The 5,6-epoxide was formed during both antioxidant reactions and autoxidation reactions and may be marker for the peroxyl radical oxidation of β-carotene. Attempts to study β-carotene antioxidant reactions in biological membranes were only partially successful. In vitro incorporation of β-carotene into microsomes was attempted by several methods. However, these efforts resulted in only modest β-carotene antioxidant activity in microsomes. These studies provide a basic understanding of β-carotene antioxidant chemistry in model systems. Their results will enable further investigation of β-carotene antioxidant action in biological systems.

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Beta-carotene presence or absence in muskmelon is controlled by two genes, green flesh gf and white flesh wf. In its dominant form the wf gene is responsible for orange flesh color; however, the epistatic interactions of gf and wf can create three flesh colors: orange, white and green. Two F2 populations, consisting of 77 greenhouse grown and 117 field grown plants, from the cross of ‘Sunrise’ (white fleshed) by ‘TAM Uvalde’ (orange fleshed), were used to examine the relationships of beta-carotene content, flesh color, and flesh color intensity. Bulk segregent analysis was used with RAPD markers to identify molecular markers associated with high beta-carotene content. Flesh color and flesh color intensity both had significant relationships with beta-carotene content. A significant correlation between total soluble solids and beta-carotene content was also found. Molecular markers were identified in both F2 populations and all significant, associated markers from ‘TAM Uvalde’ were linked with WF. A single QTL was also found to be linked with the WF locus. The identified QTL can be used to screen potential breeding lines for high beta-carotene. It was also confirmed that the visual ratings of flesh color intensity can be reliably used to select high beta-carotene content melons.

Genetic transformation is a useful tool to incorporate novel genes, potentially allowing sexual incompatibility and interspecific barriers to be circumvented. The purpose of this study was to improve beta-carotene levels in melon fruits by transferring a phytoene synthase (PSY) gene. At present, there are not sufficient regeneration and transformation studies reported on two commercially important melon types - western shipper cantaloupe and honeydew. To establish a high efficiency shoot regeneration system, we evaluated three types of explants in our elite breeding lines. A shoot tip with a hypocotyl and cotyledon fragments, regenerated shoots whereas a shoot tip with a hypocotyl without cotyledon, did not produce regenerants. Murashige & Skoog (MS) basal medium with 1 mg 1⁻¹ benzyladenine (BA), 0.26 mg 1⁻¹ abscisic acid (ABA) and 0.8 mg 1⁻¹ indole-3-acetic acid (IAA) was the best for regeneration from cotyledon explants in cantaloupe 'F39'. MS basal medium with 1 mg 1⁻¹ BA and 0.26 mg 1⁻¹ ABA was chosen for honeydew '150' to solve a curving-up problem of explants. Fifty to sixty percent of regenerants were found to be polyploids. To establish a reliable Agrobacterium-mediated transformation protocol, kanamycin sensitivity as well as Timentin[trademark] and Clavamox® were evaluated. Kanamycin 200 and 150 mg 1⁻¹ were chosen as the threshold levels for 'F39' and '150' respectively. No significant differences were found between Timentin[trademark] and Clavamox® in 'F39'; however, Clavamox® reduced the incidence of vitrification and increased the frequency of shoot elongation in '150'. A. tumefaciens strain EHA105, harboring pCNL56 carrying nptII and gusA genes, was used to establish a transformation protocol. The transformation efficiency was 0.3% from 'F39' and 0.5% from '150'. We introduced a watermelon PSY-C gene under the control of a fruit-specific promoter of a polygalacturonase gene into '150'. All the transgenic plants were tetraploids based on flow cytometry assays. Up to 32-fold of beta-carotene was elevated in the rind tissue of transgenic honeydew including phytoene increase. This is a very promising result for a further investigation to increase beta-carotene level in flesh tissue using the PSY-C gene with an appropriate promoter.

The object of this study is to determine the intake (in food) and output (in feces) of vitamin A and carotene of several groups of college women living in the Home Management House.

Vitamin A deficiency is recognized as a major health concern worldwide, especially in developing countries. Sweet potatoes are a cash crop that is abundantly grown and available, providing an excellent source of the carotenoid, beta-carotene. Carotenoids are precursors to vitamin A (retinol). Three sweet potato cookie products were developed: glutenree, wheat-containing, and glutenree with extra sweet potato. Products were evaluated by adults and pre-school aged children based on appearance, aroma, texture, flavor, and overall acceptability. Results showed that overall the children liked both the glutenree and wheat-containing cookies (p<0.05). Adults preferred (p<0.05) the glutenree with extra sweet potato and the wheat-containing products. The glutenree cookie contained 10.1 parts per million of beta-carotene as determined by high-performance liquid chromatography.

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