Essential oils, found in Listerine mouthwash, contains eucalyptol, menthol, thymol, and methyl salicylate. Important terpenoids derived from monocyclic terpenes are menthol, thymol, carvacrol and many others. Chemical compounds such as ethylene oxide, thymol, and orthophenyl phenol are regularly used. The main compounds of interest in essential oils are thymol, carvacrol, linalool, and "p"-cymene. The plant contains thymol, an antiseptic and fungicide. Racemic menthol can also be formed by hydrogenation of thymol, menthone, or pulegone. Sucrose fermentation produces acid, which converts the colour of bromothymol blue or thymol blue. He prepared thymol, and fennel and lemon oils. The plant contains the chemical compounds thymol, carvacrol and cedrol. Eugenol and thymol were found to possess general anesthetic properties. For prevention of mold growth in aqueous solutions, thymol is sometimes added. This process starts from "m"-cresol which is alkylated with propene to thymol. "Gundelia" contains several essential oils, with large proportions (20-25% each) of thymol and germacrene-D. Regions lacking natural sources of thymol obtain the compound via total synthesis. Thymolphthalein is a related laxative made from thymol.