Fluorescent pigments: new perspectives in betalain research and applications. Food Res Int 38(8-9):879-884
ABSTRACT Betaxanthins are natural water-soluble yellow pigments found in plants of the order Caryophyllales. The fluorescence of five of these compounds, derived from the amines, tyramine and dopamine, and from the amino acids, methionine sulphoxide, glutamic acid and aspartic acid, was detected and characterized for the first time. Fluorescence in betacyanins, the violet counterpartner of betaxanthins was not detected.We report here not only the fluorescent properties of the betaxanthins but also a new method for determining the pigment content in complex samples by HPLC using a fluorescence detector for the first time. The method was successfully applied to the analysis of the betaxanthins present in Mirabilis jalapa (Nyctaginaceae) flowers. Our findings concerning fluorescence may open up new possibilities for the detection of betaxanthins, improve existent HPLC protocols and represent a new field for biochemical investigations.
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- "There are two major types of betalains, the red-purple betacyanins and the yellow/orange betaxanthins, both of which accumulate in the vacuole. The betaxanthins also emit green autofluorescence, which is not seen with the betacyanins [9-11]. While the production of flavonoids and carotenoids has been extensively studied and metabolically engineered in a variety of species, betalain biosynthesis has yet to be fully characterised [1,2]. "
ABSTRACT: Carotenoids and anthocyanins are the predominant non-chlorophyll pigments in plants. However, certain families within the order Caryophyllales produce another class of pigments, the betalains, instead of anthocyanins. The occurrence of betalains and anthocyanins is mutually exclusive. Betalains are divided into two classes, the betaxanthins and betacyanins, which produce yellow to orange or violet colours, respectively. In this article we show betalain production in species that normally produce anthocyanins, through a combination of genetic modification and substrate feeding. The biolistic introduction of DNA constructs for transient overexpression of two different dihydroxyphenylalanine (DOPA) dioxygenases (DODs), and feeding of DOD substrate (L-DOPA), was sufficient to induce betalain production in cell cultures of Solanum tuberosum (potato) and petals of Antirrhinum majus. HPLC analysis showed both betaxanthins and betacyanins were produced. Multi-cell foci with yellow, orange and/or red colours occurred, with either a fungal DOD (from Amanita muscaria) or a plant DOD (from Portulaca grandiflora), and the yellow/orange foci showed green autofluorescence characteristic of betaxanthins. Stably transformed Arabidopsis thaliana (arabidopsis) lines containing 35S: AmDOD produced yellow colouration in flowers and orange-red colouration in seedlings when fed L-DOPA. These tissues also showed green autofluorescence. HPLC analysis of the transgenic seedlings fed L-DOPA confirmed betaxanthin production. The fact that the introduction of DOD along with a supply of its substrate (L-DOPA) was sufficient to induce betacyanin production reveals the presence of a background enzyme, possibly a tyrosinase, that can convert L-DOPA to cyclo-DOPA (or dopaxanthin to betacyanin) in at least some anthocyanin-producing plants. The plants also demonstrate that betalains can accumulate in anthocyanin-producing species. Thus, introduction of a DOD and an enzyme capable of converting tyrosine to L-DOPA should be sufficient to confer both betaxanthin and betacyanin production to anthocyanin-producing species. The requirement for few novel biosynthetic steps may have assisted in the evolution of the betalain biosynthetic pathway in the Caryophyllales, and facilitated multiple origins of the pathway in this order and in fungi. The stably transformed 35S: AmDOD arabidopsis plants provide material to study, for the first time, the physiological effects of having both betalains and anthocyanins in the same plant tissues.BMC Plant Biology 03/2012; 12(1):34. DOI:10.1186/1471-2229-12-34 · 3.94 Impact Factor
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ABSTRACT: Protocols for in vitro regeneration and production of in vitro-propagated plants and a transformation system were developed for Mirabilis jalapa (Nyctaginaceae). Among the types of explants and the different media tested, consistent shoot regeneration was obtained only from nodal segments grown in a regeneration medium consisting of Murshashige and Skoog medium supplemented with 2mgl−1 6-benzyladenine, 2mgl−1 zeatin and 1mgl−1 indole acetic acid. Regeneration efficiency was dependent on the type of plant – white or pink flowers – used as the source of explants. Stable transformation was obtained following inoculation of nodal segments with Agrobacterium tumefasciens strain EHA105, which harbours the binary plasmid pAD1339 containing both nptII and gus genes under the control of the 35S promoter. Transformation was confirmed by PCR and Southern blot analysis of genomic DNA from mature regenerated plants. β-Glucuronidase (GUS) activity was observed only in tissues regenerated from in vitro-grown plants and not in tissues originating from greenhouse-grown plants. GUS expression was not uniform in regenerated leaves and showed a chimera pattern.Scientia Horticulturae 02/2007; 111(3):304-309. DOI:10.1016/j.scienta.2006.10.027 · 1.50 Impact Factor
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ABSTRACT: Petit suisse cheese was elaborated with substitution of 30% milk volume for cheese whey retentate (volumetric reduction ratio=5.0) obtained by ultrafiltration (cheese 1) and 100% milk (cheese 2). These were evaluated regarding physicochemical composition: moisture, ash, total solids, lipids, total proteins, acidity in lactic acid and pH. Natural pigments were added to the cheeses: Cabernet Sauvignon (Vitis vinifera L.) grape anthocyanins or (Beta vulgaris L.) beetroot betalains. The cheese samples were maintained at 6±1°C for 40 days in light-impermeable packaging and evaluated regarding pigment stability by determining half-life time and percentage color retention. The results of the physicochemical analyses demonstrated that significant differences occurred between cheeses 1 and 2 regarding total solid content, moisture, protein, lipids and carbohydrates. The half-life time and percentage color retention values obtained for the anthocyanin and betalain extracts added to the cheeses were adequate for the shelf life of this product.Lebensmittel-Wissenschaft und-Technologie 06/2008; 41(5):905-910. DOI:10.1016/j.lwt.2007.05.019 · 2.47 Impact Factor