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Thread: Vitamin A

  1. #1 Vitamin A 
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    Hi,

    Currently I am working on some kind of project for school. The project goes about vitamins and how they work in the body.
    As an experiment I want to look at the influence of preparation (eg. cooking & frying) on the vitamin content of the food.
    In the case of vitamin A this gives some problems.
    When I've prepared a certain type of vegetable, I need to extract the retinol and bta-carotene.
    I think this should be done with petroleum ether, but is this the optimal solvent?
    I also don't really know how to indicate the presence of bta-carotene and retinol. I've searched the internet already, but I didn't find any answer for what indicator or other method I should use to determine the amount of vitamine A and provitamin A in the extract.
    And last question. Given the fact that retinoids and carotenoids are most abundant in chloroplasts, shouldn't I find a way to destroy the membranes of these chloroplasts so the retinoids and carotenoids are more easily extracted? Perhaps I can do this by adding toluene?

    Thanks in advance.


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  3. #2  
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    Hi,

    it would be alot harder than you think to successfully isolate any natural product from its plant parent. Not something I would advocate for a school experiment without proper specialist equipment or training. Not because you will hurt yourself, but beacuse you will be very confused, very quickly.

    Perhaps you might be lucky enough to find an NMR of either material, and if you are fortunate you might be able to get a visible NMR handle with which you could follow the progress of the subject vitamins via an assay.

    Either that, or by running the crude reaction mixture on a HPLC you might be able to assay each of the individual components.

    If you have access to either of these techniques, you may be lucky enough.

    Good luck


    Chemistry is everything!
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  4. #3  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    I remember beta-carotene being relatively easy to isolate from plant extract through, I remember vaguely, way back when in the year 2003, doing it in an introductory organic chem class.

    I probably have the procedure filed away somewhere, but God knows where, probably at my mother's home.
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  5. #4  
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    Is Vitamin A important for our body??
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  6. #5  
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    Indeed it is. Its common name is Retinol, and is found (amongst many other places) in the eyes. It effectively allows us to see. my Biology only goes to Alevel, but I'm sure you can find out more if you want on wikki, or any A level text book.
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  7. #6  
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    Retinol is indeed important for the human body. It has an important function in the retinal rod cells. It is necessary in order to distinct contrast. It also has a role in the differentiation of premature cells into mature cells, especially in mucous tissue. But, as Luka says, wikipedia gives a quite complete and quick overview.

    @Luka:
    I found this article that had a recipe for the extraction of bta-carotene: http://myais.fsktm.um.edu.my/2712/1/...icle4_amin.pdf.
    I gave it a try last week at school, but the results weren't really what I expected.
    I made the extract the way it is described in the article than I used a chromatography column to try and separate the different substances, but there weren't really distinct fractures. When I analyzed the samples with a spectrophotometer (I checked the absorption at 458 nm, because my reference book told me that the absorption peek of carotene was at this wavelength). When I converted the absorptions to concentrations and amount of carotene in one kg of carrots, I had an improbable low value as outcome. According to our measures there was about .30 micro gram of carotene per kilogram carrots, so this cannot be right. I used an attenuation coefficient of 117000, because this was also given in the book I used for reference.
    I don't think HPLC or NMR is an option, given the fact that there aren't really any institutions nearby who might have such a device.
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