• Chemistry 25.04.2011 No Comments
    Molecular Structure of Parietin

    Molecular Structure of Parietin

    While preparing the treebark for the extraction of the Aesculin (see previous entry), I noticed that some lichen, growing on the bark, glowed yellow in ultraviolet light. Under normal light it has an orange color. Some research on Wikipedia revealed the lichen as Xanthoria parietina (Xanthus meaning “yellow” in greek, parietina “on walls”). The fluorescent dye contained in the upper layers of the lichen is Parietin.

    I collected some of the lichen and tried several solvents (Isopropanol, Acetone and Ethanol)  to extract the parietin. All solvents were heated to their respective boiling point to accelerate the process.

    The color of the solution differs between the solvents under visible light as well as under ultraviolet light. The Isopropanol-solution is dark green and fluoresces orange while the Acetone- and Ethanol-solutions have a brighter green and glow yellow.

    Due to this result I tested the influence of different solvents on the color of Aesculin. Here, the effect was not as distinct as with the parietin solutions, but the brightness of the fluorescence differed.

    Aesculine & Parietin Solutions in visible Light

    Aesculine & Parietin Solutions in visible Light

    Aesculin & Parietin Solutions in ultraviolet Light

    Aesculin & Parietin Solutions in ultraviolet Light

    Solutions in the images from left to right:

    1. Aesculin in distilled Water
    2. Aesculin in 75% Isopropanol
    3. Aesculin in Acetone
    4. Aesculin in 96% Ethanol
    5. Parietin in Acetone with 33% Sodium Hydroxide
    6. Parietin in 75% Isopropanol
    7. Parietin in Acetone
    8. Parietin in 96% Ethanol
    Parietin in Isopropanol with NaOH

    Parietin in Isopropanol + NaOH (405nm)

    Interestingly, the effect of the NaOH also depends on the solvent. On the one hand, the color in visible light is either violet/pink (in case of Aceton) or it stays green (in case of Isopropanol). On the other hand, the response to ultraviolet light changes. The Isopropanol solution emits a bright magenta fluorescence when irradiated with  405nm light and a dim orange fluorescence with 350nm Р370nm.
    The Acetone solution shows no fluorescence with 350nm – 370nm and almost none with 405nm.

    Aesculin & Parietin Solution

    Aesculin & Parietin Solution

    To further concentrate and purify the Aesculin and the Parietin, the Isopropanol solutions are slowly evaporated to crystallize the dyes.
    The previous attempt with water solutions failed, due to the many other substances that solved in the water and caused mold to grow.

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  • Chemistry 09.09.2008 No Comments

    In my entry about the slime I mentioned fluorescein as dye. Today I am going to explain how I made it.

    I had some phthalic anhydride and resocinol in an old chemistry set but the resorcinol was quite dirty so I got some new at the pharmacy.

    Most synthesis instructions recommend zincchloride as catalyst but some drops of sulfuric acid work as well. (Sulfuric acid and zincchloride are both hydrophile, which is the needed effect).

    Fluorescein drop in water

    Fluorescein drop in water

    15g phtalic anhydride an 22g resorcinol are ground to a fine powder and placed in a test-tube and heated. I used an alcohol burner but i recommend a hot air gun.

    When the powder melts and turns into a thick, red, honeylike substance stop heating and let it cool down.

    The fluorescein can then be dissolved in a small amount of water resulting in a dark red/brown solution.

    One-two drops of this solution are enough to colour 500ml of water to a bright green.

    The best results are achieved when the coloured water is viewed in sunlight.

    A more detailed synthesis manual can be found at LambdaSyn.

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