Browsing by Subject "vicine"

Faba bean (Vicia faba L.) is an annual herbaceous cool-season food legume widely cultivated worldwide, especially for its high seed protein content. However, its major limitation in being used as food and feed, is the presence of antinutritional factors in its seeds, especially vicine and convicine (VC), two related compounds, which may be harmful to livestock and G6PD-deficient humans. To remove VC, the most sustainable method is breeding for low-VC faba bean cultivars. To improve the efficiency and speed of breeding programs, breeders use marker-assisted selection (MAS). The identification of genes responsible for VC content allows the development of reliable DNA markers and a better understanding of the molecular basis of this trait. The major-effect QTL controlling VC content named “VC1”, was identified in faba bean chromosome 1, and a few minor-effect QTLs were detected in previous studies. Hence, a total of 165 RILs from the cross Mélodie/2 (low-VC) x ILB 938/2 (high-VC) were genotyped and evaluated for VC content. Composite interval mapping was run on R/qtl software with accurate phenotypic data associated with a high-density SNP-based genetic map. Results revealed two minor-effect QTLs in addition to VC1. One was on chromosome 4 and had about 15% effect on convicine content. The other was on chromosome 5 and had 15% effect on vicine and total VC content. This research also reports candidate genes for the newly detected minor-effect QTLs through comparative genomics with the Medicago truncatula genome. Hypotheses were proposed on the role of these candidate genes on the VC biosynthetic pathway or transportation into the embryo beans for further testing.

Divicine and isouramil are the causative agents of favism. The stability of divicine is of vital importance in faba bean detoxification. The literature review of this thesis focused on the hydrolysis of vicine to divicine, the oxidation processes of divicine and its stability studies. The main aims of this thesis were to produce divicine using the hydrolysis of vicine with ?-glucosidase, and study the effects of nitrogen/air atmosphere, reducing agent, pH and temperature on the stability of divicine. The identities of other compounds observed in vicine hydrolysis were also to be investigated. In addition, convicine was also hydrolyzed in the extracts and pure convicine fractions. Vicine and convicine were co-extracted from dehulled faba bean flour and were separated with preparative HPLC-MS. The extracts and the pure vicine and convicine fractions were hydrolyzed with ?-glucosidase to yield divicine and isouramil. The identities of the compounds formed during vicine fraction hydrolysis were studied by MS. In the following stability studies, the pure vicine fractions were hydrolyzed with ?-glucosidase under nitrogen and in the presence of (+)-sodium L-ascorbate. Moreover, the fractions were firstly hydrolyzed under air, next, the formed divicine was incubated at pH 3.0 or 5.0 at 20 or 37 ºC. An analytical HPLC method was used to study the changes during hydrolysis and stability tests. It was found that higher ?-glucosidase concentration and longer incubation period resulted in higher hydrolysis degrees of vicine and convicine. Further, vicine was hydrolyzed more rapidly at pH 3.0 than 5.0. Vicine was hydrolyzed to divicine. Divicine further generated two compounds, named compound 1 and compound 2 in this thesis. Their corresponding retention times and absorption maxima were: 2.15 min, 282 nm; 1.79 min, 262 nm; and 1.94 min, 210 nm. Compound 1 was directly generated from divicine. It was possibly oxidized divicine, but its characterization with MS failed in this study. Compound 1 decomposed to compound 2 at pH 5.0 at 20 ºC, but at pH 3.0 at 20 ºC, divicine might directly decompose to compound 2. Only one compound (named compound 3) was formed during convicine hydrolysis, and its retention time and absorption maximum were 2.50 min and 280 nm. Divicine and compounds 1, 2, and 3 were not stable, they finally decomposed to non-UV absorbing substances. Divicine was more stable under nitrogen than under air, and in the presence of (+)-sodium L-ascorbate than without its presence. Divicine decomposed similarly at pH 3.0 and 5.0 at 37 ºC, but at 20 ºC, divicine was more stable at pH 5.0. At both pH values, the stability of divicine was increased at 20 ºC compared with 37 ºC.

Faba bean (Vicia faba L.) also known as broad bean is an ancient pulse, grown since Neolithic times. It is an excellent source of protein, energy and fibre to humans and animals. Recently in Finland, faba bean has featured heavily in meat replacements, meant for vegan consumers. Faba bean can also be grown further north, than soybean (Glycine max (L.) Merr.), making it a possible domestic plant protein source for Finns. The problem with faba bean is that the beans contain various anti-nutritional compounds. The major ones are vicine and convicine (v-c), located in the cotyledons of the beans, which means that dehulling the seeds does not remove them. V-c can cause favism in humans with G6PD gene mutation this is a disease where red blood cells are destroyed, in worst cases resulting in blood transfusions and death. V-c is also an anti-feedant to livestock and can among other things cause increase in mortality in poultry. Normal v-c content of faba bean is around 1%. There are low v-c faba beans that contain only 5-15% of the original v-c. Markers for this trait have been found, but gene controlling for this trait is not known yet. The synthesis pathway of the v-c is not known. There is a new hypothesis by Dr Fernando Geu Flores of The University of Copenhagen, where the v-c synthesis is an off shoot of another biosynthetic pathway. An experiment was done where RNA of two populations (one low v-c and other high) were compared to each other. The samples were taken during the seed filling period, which is thought to be when v-c is synthesized. Kernel, testa, pod and leaf tissues were collected and RNA of those extracted. Only kernel and testa samples were sequenced. This thesis focuses on the testa results. Results showed differences between the populations. Considering the new hypothesis, the results showed some differences in the beginning of the suspected pathway, with the high v-c population having a 4.97 fold increase compared to the low v-c population. Other differences were also noted, which may cast light on other steps in the pathway.