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Does aminosugars give positive response to test for alkaloids such as tests with Dragendorff's reagent, mayer's reagent, Hager's reagent, Wagner's reagent etc?

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    $\begingroup$ Dragendorff's reagent works for tertiary amines (and some secondary), amino sugars contain primary amines so there is no reaction nor do N-acetylaminosugars $\endgroup$ – Waylander Jul 23 at 18:23
  • $\begingroup$ I saw "aminosugars" but read it as "aminosugaris" and was thinking I don't recognize that dinosaur name, and what's it have to do with alkaloids? Too much with the kids I guess :) $\endgroup$ – CrossRoads Jul 25 at 15:38
  • $\begingroup$ @CrossRoads I dont know about any such Aminosaurus :P :D $\endgroup$ – Always Confused Oct 25 at 4:36
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Most alkaloids are tertiary amines. Almost all tests for alkaloids, reagents of which are are solutions of the salts of heavy metals, are precipitation tests. For example, all of tests with Dragendorff's reagent, Mayer's reagent, Hager's reagent, and Wagner's reagent give color precipitates: The heavy metal atom in the reagent with the nitrogen in the alkaloid would form ion pairs. These ion pairs form an insoluble precipitate. The color of the precipitate depends on reagent, plant species, etc. (Ref.1). Most amino sugars are either primary amines or acetamides, thus, I doubt they'd give precipitates with sought reagents. However, some reagents give false-positive tests for non-nitrogenous extracts indicating the presence of alkaloids. The best example is Dragendorff's spray reagent (Ref.2).

Mean time, some reagents are giving negative results even with alkaloid extracts, e.g., Mayer's reagent (Ref.3). Therefore, my answer is purely opinion based.

References:

  1. Felix G. Coe, Gregory J. Anderson, "Screening of medicinal plants used by the Garífuna of Eastern Nicaragua for bioactive compounds," Journal of Ethnopharmacology 1996, 53(1), 29-50 (https://doi.org/10.1016/0378-8741(96)01424-9).
  2. Abdel‐Azim M. Habib, "False‐positive alkaloid reactions," Journal of Pharmaceutical Sciences 1980, 69(1), 37-43 (https://doi.org/10.1002/jps.2600690111).
  3. J. W. Field, M. Kandiah, "A note on the use of mayer's reagent for the detection of quinine in alkaline urine," Transactions of the Royal Society of Tropical Medicine and Hygiene 1935, 28(4), 385-390 (https://doi.org/10.1016/S0035-9203(35)90133-X).
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    $\begingroup$ If I get scope to do this simple lab tests I'll publish it as answer. Currently aminosugars are not available to me. We have chitin flakes though, that makes technically a different question because chitin is polysaccharide. $\endgroup$ – Always Confused Oct 25 at 4:46
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    $\begingroup$ Thanks for the theoretical insight. $\endgroup$ – Always Confused Oct 25 at 4:48

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