Diallyl disulfide

Diallyl disulfide is the principal constituent of garlic oil. The compound is biologically active, being both cytotoxic and hepatoprotective depending on dose.

Skin. Applied undiluted to rabbit skin it was irritating. A 1 percent patch test on 31 volunteers was not sensitizing. In garlic-sensitive individuals a 5 percent patch test produced reactions in 18 of 23 cases, but none at 0.5 percent. Photoallergic and systemic contact dermatitis have been reported.

Oral. Acute oral LD50 in mice is 145 mg/kg (male) and 130 mg/kg (female), in rats 260 mg/kg. Acute dermal LD50 in rabbits is 3.6 g/kg.

Cardiovascular. Diallyl disulfide shows strong antiplatelet aggregation activity in vitro.

Liver. Cytotoxic to hepatocytes at 2 mM, but at the low dose of 14.6 mg/kg orally it protected rat liver from carbon tetrachloride damage.

Mutagenicity and cancer. The compound shows dual activity, both inducing and protecting against mutagenesis depending on context. It induces phase II detoxifying enzymes, triggers apoptosis in colorectal, liver, blood, breast and skin cancer cells.

After ip injection in mice, more than 80 percent of the compound concentrates in liver cytosol within two hours. Diallyl disulfide is primarily metabolized to allyl mercaptan and allyl methyl sulfide in rat hepatocytes, and is reduced to diallyl sulfide in the isolated perfused rat liver.

The compound induces phase II detoxifying enzymes such as glutathione S-transferase and glutathione peroxidase, which is the principal mechanism explaining both its hepatoprotective and anticancer activities.

Diallyl disulfide together with diallyl trisulfide accounts for the characteristic aroma and bioactivity of garlic. Sulfide-rich essential oils such as garlic, mustard and onion are rarely used in perfumery or cosmetics due to overpowering odor and irritation risk.