Pharmacognosy

Львівському національному медичному університету

DEPARTMENT OF PHARMACOGNOSY AND BOTANY

ISOTHIOCYANATES

Isothiocyanates comprise the chemical group -N=C=S, formed by substituting sulfur for oxygen in the isocyanate group. Isothiocyanates, such as phenethyl isothiocyanate (PEITC) and sulforaphane, have been shown to inhibit carcinogenesis and tumorigenesis and as such are useful chemopreventive agents against the development and proliferation of cancers. They work on a variety of levels. Most notably, they have been shown to inhibit carcinogenesis through inhibition of cytochrome P450 enzymes, which oxidize compounds such as benzo[a]pyrene and other polycyclic aromatic hydrocarbons (PAHs) into more polar epoxy-diols which can then cause mutation and induce cancer development. Phenethyl isothiocyanate (PEITC) has been shown to induce apoptosis in certain cancer cell lines, and in some cases, is even able to induce apoptosis in cells that are resistant to some currently used chemotherapeutic drugs. For example, in drug resistant leukemia cells which produce the powerful apoptosis inhibitor protein BCl-2. Furthermore, isothiocyanates have been the basis of a drug in development which replaces the sulfur bonds with selenium, with far stronger potency against melanoma.

Allyl isothiocyanate is an organosulfur compound with the formula CH2CHCH2NCS found in mustard oil and is responsible for its pungency. It is used for amino acid sequencing in Edman degradation. This colorless oil is responsible for the pungent taste of mustard, horseradish, and wasabi. It is slightly soluble in water, but well soluble in most organic solvents. Hydrolysis of allyl isothiocyanate gives allyl amine.

 Allyl isothiocyanate comes from the seeds of black mustard (Brassica nigra) or brown Indian mustard (Brassica juncea). When these mustard seeds are broken, the enzyme myrosinase is released and acts on a glucosinolate known as sinigrin to give allyl isothiocyanate.

Allyl isothiocyanate serves the plant as a defense against herbivores; since it is harmful to the plant itself, it is stored in the harmless form of the glucosinolate, separate from the myrosinase enzyme. When an animal chews the plant, the allyl isothiocyanate is released, repelling the animal.

Allyl isothiocyanate can be liberated by dry distillation of the seeds. The product obtained in this fashion is known as volatile oil of mustard and is usually around 92% pure. It is used principally as a flavoring agent in foods. Synthetic allyl isothiocyanate is used as an insecticide, bacteriocide, and nematocide, and is used in certain cases for crop protection.