Inhibition of Cyanogenesis by tannins.
1Department of Ecology and Evolutionary Biology, University of California, Irvine, 92717, Irvine, CA.
Journal of Chemical Ecology
|December 7, 2013
Summary
Tannins in papaya extracts can inhibit cyanide release from cyanogenic glycosides. Removing tannins allows for accurate detection of these plant defense compounds, revealing potential chemical interactions in nature.
Area of Science:
- Biochemistry
- Plant Science
- Chemical Ecology
Background:
- Cyanogenic glycosides are plant defense compounds that release cyanide.
- Initial papaya extracts showed weak cyanide tests, suggesting inhibition.
Purpose of the Study:
- To investigate the cause of inhibited cyanogenesis in Carica papaya extracts.
- To determine the role of polyphenolics, specifically tannins, in this inhibition.
Main Methods:
- Isolation of cyanogenic glycosides from Carica papaya.
- Qualitative and quantitative assays for cyanide release.
- Testing the inhibitory effects of various condensed and hydrolyzable tannins on cyanogenesis.
- Assessing the impact of tannin precipitation on cyanide detection.
Main Results:
- Polyphenolic compounds, particularly tannins, were identified as inhibitors of cyanogenesis.
- Both condensed tannins (from quebracho, wattle, chestnut) and hydrolyzable tannin (tannic acid) significantly inhibited cyanide release.
- Removing tannins from the extracts restored optimal cyanide detection.
Conclusions:
- Negative cyanide tests in plant extracts should be interpreted cautiously due to potential tannin interference.
- Tannins can mask the presence of cyanogenic glycosides, impacting their detection.
- These findings highlight potential ecological synergisms between different plant defensive chemicals.
Related Concept Videos
01:19Phase II Reactions: Miscellaneous Conjugation Reactions
473
Phase II biotransformations are detoxification mechanisms that conjugate xenobiotics with endogenous substances, neutralizing their toxicity.
A key example involves the conjugation of cyanide ions, which impair cellular respiration and alter hemoglobin into non-oxygen-carrying cyanmethemoglobin. To neutralize this threat, a sulfur atom from thiosulphate is transferred to the cyanide ion, catalyzed by the enzyme rhodanese, resulting in an inactive compound called thiocyanate. The production of...
A key example involves the conjugation of cyanide ions, which impair cellular respiration and alter hemoglobin into non-oxygen-carrying cyanmethemoglobin. To neutralize this threat, a sulfur atom from thiosulphate is transferred to the cyanide ion, catalyzed by the enzyme rhodanese, resulting in an inactive compound called thiocyanate. The production of...
473
01:32Aldehydes and Ketones with HCN: Cyanohydrin Formation Overview
3.2K
Cyanohydrins are compounds that contain –CN and –OH groups on the same carbon atom. They are formed by the nucleophilic addition of the cyanide ions to the carbonyl group. Cyanide ions are highly basic and nucleophilic and can be generated from HCN under aqueous conditions. However, since HCN is a weak acid, the number of cyanide ions generated is very small. Hence, a small amount of base or KCN/NaCN is added to HCN to increase the concentration of the cyanide ions in the reaction...
3.2K
00:46Feedback Inhibition
44.1K
Biochemical reactions are occurring constantly in cells, converting starting substances to different products, usually with the help of enzymes that speed the reactions. Without enzymes, it would take far too long for most reactions to occur to be useful to the cell!
44.1K
01:19Oral Hypoglycemic Agents: α-Glucosidase Inhibitors
953
α-glucosidase inhibitors, including acarbose (Precose), miglitol (Glyset), and voglibose (Voglib) (primarily available in Asia), are drugs that control blood sugar levels by delaying the digestion of starch and disaccharides. They achieve this by inhibiting α-glucosidase enzymes in the intestine, which slow the absorption of carbohydrates in the intestine, which in turn leads to a prolonged release of the glucoregulatory hormone GLP-1 from intestinal L-cells.
Acarbose and miglitol are...
Acarbose and miglitol are...
953
01:30Enzyme Inhibition
72.4K
Inhibitors are molecules that reduce enzyme activity by binding to the enzyme. In a normally functioning cell, enzymes are regulated by a variety of inhibitors. Drugs and other toxins can also inhibit enzymes. Some inhibitors bind to the enzyme’s active site, while others inhibit enzymatic activity by binding to other sites on the protein structure.
72.4K
01:10Aldehydes and Ketones with HCN: Cyanohydrin Formation Mechanism
3.7K
Cyanohydrins are formed when cyanide nucleophiles and carbonyl compounds like aldehydes and ketones react. A strong base, the cyanide ion, catalyzes cyanohydrin formation. The ions are generated from HCN under aqueous conditions. Once the cyanide ions are generated, the first step involves the nucleophilic attack of the cyanide ions on the electrophilic carbonyl carbon. This attack shifts the π electrons from the C=O to the oxygen atom forming the alkoxide ion intermediate. The alkoxide...
3.7K