An agent thought to have disinfectant properties and used as an expectorant. (From Martindale, The Extra Pharmacopoeia, 30th ed, p747) Present in Parmesan cheese, tea and soybean. Flavouring ingredient

Guaiacol is a phenolic compound with a methoxy group and is the monomethyl ether of catechol. Guaiacol is readily oxidized by the heme iron of peroxidases including the peroxidase of cyclooxygenase (COX) enzymes. It therefore serves as a reducing co-substrate for COX reactions. Guaiacol is a phenolic natural product first isolated from Guaiac resin and the oxidation of lignin. It is a yellowish aromatic oil that is now commonly derived from guaiacum or wood creosote. It is used medicinally as an expectorant, antiseptic, and local anesthetic. Guaiacol is used in traditional dental pulp sedation, and has the property of inducing cell proliferation; guaiacol is a potent scavenger of reactive oxygen radicals and its radical scavenging activity may be associated with its effect on cell proliferation. Guaiacol is also used in the preparation of synthetic vanillin. Guaiacol is also present in wood smoke, as a product of pyrolysis of lignin. Guaiacol has been found in the urine of patients with neuroblastoma and pheochromocytoma. (A3556, A3559).