--- title: "Ninhydrin test for amino acids Template | MolDraw" url: https://www.moldraw.com/templates/ninhydrin-test/ description: "Ninhydrin test for amino acids template: Ninhydrin (the hydrate of indane-1,2,3-trione) forms an imine with the amino group; the imine decarboxylates, is…" lang: en publisher: Scidart Academy generated: 2026-11-13 --- [MolDraw](https://www.moldraw.com/) › [Templates](https://www.moldraw.com/templates/) › [Biochemistry](https://www.moldraw.com/templates/biochemistry/) › Ninhydrin test for amino acids [Biochemistry](https://www.moldraw.com/templates/biochemistry/)Premium # Ninhydrin test for amino acids template ![Ninhydrin test for amino acids template: Ninhydrin (the hydrate of indane-1,2,3-trione) forms an imine with the amino group; the imine decarboxylates, is hydrolysed to an aldehyde and 2-aminoindane-1,3-dione, and that amine condenses with a second ninhydrin to give Ruhemann’s purple.](https://www.moldraw.com/templates/ninhydrin-test.webp) [Edit in MolDraw](https://www.moldraw.com/)Download with Pro Premium template. Preview and edit it free in MolDraw; downloading and exporting it is part of [MolDraw Pro](https://www.moldraw.com/pricing). Ninhydrin (the hydrate of indane-1,2,3-trione) forms an imine with the amino group; the imine decarboxylates, is hydrolysed to an aldehyde and 2-aminoindane-1,3-dione, and that amine condenses with a second ninhydrin to give Ruhemann’s purple. ## Mechanism step by step An α-amino acid and two ninhydrin give Ruhemann’s purple, CO₂ and the aldehyde one carbon shorter 1. **Triketone** – Ninhydrin is a hydrate; losing water gives the reactive central C=O 2. **Imine (Schiff base)** – The amino group condenses with the central C=O (arrows as in imine formation) 3. **Decarboxylation** – CO₂ leaves; the electrons end on C2, between two C=O groups 4. **Protonation** – C2 takes a proton: a new imine, now on the side-chain carbon 5. **Hydrolysis** – Water splits the imine: the aldehyde and 2-aminoindane-1,3-dione 6. **Ruhemann’s purple** – The amine condenses with a second triketone; loss of H⁺ gives the conjugated anion ## Key points - Every primary α-amino acid gives the same purple dye (λmax 570 nm), so the colour measures total amino acid: used in amino acid analysers. - The side chain leaves as the aldehyde one carbon shorter (alanine → ethanal), with CO₂ from the carboxyl group. - Proline and hydroxyproline (secondary amines) cannot form Ruhemann’s purple: they give a yellow product (λmax ≈ 440 nm). - Ammonia and other primary amines also react. Ninhydrin spray develops amino acid spots on TLC and latent fingerprints. Drawn with 250 atoms, 12 arrows, 8 shapes – every one editable in MolDraw. ## Sources - [Nelson & Cox, Lehninger Principles of Biochemistry, 8th ed., 2021, ch. 3](https://openlibrary.org/isbn/9781319228002) Textbook - [Berg, Tymoczko, Gatto & Stryer, Biochemistry, 9th ed., 2019](https://openlibrary.org/isbn/9781319114657) Textbook - [Friedman, J. Agric. Food Chem. 2004, 52, 385](https://doi.org/10.1021/jf030490p) Review ## How to use this template 1. Press **Edit in MolDraw**. The template opens on the canvas of the free MolDraw editor. 2. Change anything: move structures, edit atoms and labels, recolour highlights or delete what you do not need. 3. Add your own structures, arrows and text next to it, or combine several templates on one page. 4. Export the drawing as PNG, SVG or PDF for slides, worksheets, theses and papers. ## Frequently asked questions ### Is the Ninhydrin test for amino acids template free? You can preview the Ninhydrin test for amino acids template here and open and edit it in MolDraw for free. Downloading or exporting it is part of MolDraw Pro, together with the other premium templates. ### Can I edit the Ninhydrin test for amino acids template? Yes. It opens as an ordinary MolDraw drawing, so every structure, arrow, label and colour can be changed, and you can add your own content around it. ### Is the chemistry checked? Every structure is checked with RDKit and every curly arrow passes MolDraw’s electron-flow audit. The sources used are listed on this page. ### Are the biochemical pathways drawn with structures? Yes. 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