Dear Sir. Concerning your issue about what class of compound will a yellow spot on an analytical thin layer chromatography plate possibly be. Chlorophyll A and B are halfway in the final step and lutein the first compound staining yellow. Also there are other compounds stained yellow, I think the following below links may help you in your analysis:
https://en.wikipedia.org/wiki/Thin-layer_chromatography
http://www.chemistry.mcmaster.ca/adronov/resources/Stains_for_Developing_TLC_Plates.pdf
https://www.hindawi.com/journals/bmri/2014/732078/
Thanks
Dear Gloria,
The yellow spot on your TLC can be attributed to no of classes of compounds to name a few there are xanthophylls, carotenoids, xanthones, quinones, flavonoids, anthocyanins etc. The can be segregated based on their solubility and polarity. eg, Carotenoids are soluble in hexane, ether but falvonoids and anthocyanins are not. You can alternatively use a reagent called as NP-PEG Reagent (2-Aminoethyl diphen ylborinate)to derivitize your TLC Plate which will give you a characteristic colour and help in identification of the band. You can alternatively subject the extract to different phytochemical test to identify the class of phytoconstituents
Dear Gloria,
the colour is related to the presence of a conjugated double bond system in molecule. I guess You could find this phenonmenon for different type compounds. I would recommended you to try different phytochemical tests on compound types already found in this plant extract as Galvina Ferreira did. (Thin-Layer Chromatography:
A Laboratory Handbook. (Ed. Egon Stahl), Springer 1969)
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