Thiocyanate was used to treat hypertension in the early twentieth century, but it is no longer utilized due to its related toxicity. However, sodium nitroprusside, a metabolite of which is thiocyanate, is still utilized to treat hypertensive crises. Thiocyanate is also used as a preservative in medicine and cosmetics. In biology, thiocyanate serves as a ligand for sulfur donor molecules such as glutathione and cysteine. It has been shown to be an inhibitor of histone deacetylases and DNA methyltransferases. In chemistry, thiocyanate acts as a nucleophile that reacts with various electrophiles to form stable cyanates. Thiocyanate is used in laboratory experiments to inhibit enzymes by blocking active site residues. It can also be used to make fluorescent probes that detect oxygen or hydrogen peroxide. Finally, thiocyanate is used as a reagent for removing amino groups from proteins. Thiocyanate is used in medicine to induce anesthesia by inhibiting acetylcholine receptors on nerve endings. It can also be used as a preservative in medicine and cosmetics. Thiocyanate is used as a food additive in some countries to preserve other foods.