Isopropyl m-cresol is extracted from oil of Thymus vulgaris (thyme, of the mint family) by partitioning into alkaline aqueous medium followed by acidification. The crystals obtained from the mother liquor are large and colorless, with a thymelike odor. Thymol is only slightly soluble in water, but it is extremely soluble in alcohols and other organic solvents. Thymol has mild fungicidal properties and is used in alcohol solutions and in dusting powders for the treatment of tinea (ringworm) infections.
4-Allyl-2-methoxyphenol is obtained primarily from clove oil. It is a pale-yellow liquid with a strong aroma of cloves and a pungent taste. Eugenol is only slightly soluble in water but is miscible with alcohol and other organic solvents. Eugenol possesses both local anesthetic and antiseptic activity and can be directly applied on a piece of cotton to relieve toothaches. Eugenol is also used in mouthwashes because of its antiseptic property and pleasant taste. The phenol coefficient of eugenol is 14.4.
Resorcinol m-Dihydroxybenzene (resorcin), or resorcinol, is prepared synthetically. It crystallizes as white needles or as an amorphous powder that is soluble in water and alcohol. Resorcinol is light sensitive and oxidizes readily, so it must be stored in tight, light-resistant containers. It is much less stable in solution, especially at alkaline pH. Resorcinol is only a weak antiseptic (phenol coefficient 0.4). Nevertheless, it is used in 1% to 3% solutions and in ointments and pastes in concentrations of 10% to 20% for the treatment of skin conditions such as ringworm, eczema, psoriasis, and seborrheic dermatitis. In addition to its antiseptic action, resorcinol is a keratolytic agent. This property causes the stratum corneum of the skin to slough, opening the barrier to penetration for antifungal agents.
4-Hexylresorcinol, or "hexylresorcinol," is a white crystalline substance with a faint phenolic odor. When applied to the tongue it produces a sensation of numbness. It is freely soluble in alcohol but only slightly soluble in water (1-20,000 parts). Hexylresorcinol is an effective antiseptic, possessing both bactericidal and fungicidal properties. The phenol coefficient of hexylresorcinol against S. aureus is 98. As is typical for alkylated phenols, hexylresorcinol possesses surfactant properties. The compound also has local anesthetic activity. Hexylresorcinol is formulated into throat lozenges because of its local anesthetic and antiseptic properties. These preparations are probably of little value. Hexylresorcinol (in the concentration in the lozenge) is probably not antiseptic, and the local anesthetic property can anesthetize the larynx, causing temporary laryngitis.
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