The Biological Activities of Troponoids and Their Use in Agriculture A Review

Chemical compounds containing the tropone structure (2,4,6-cycloheptatrien-1-one), in their molecule, called troponoids, characterized by a seven-membered ring, are distributed in some plants, bacteria and fungi, although they are relatively rare. ß-Thujaplicin (2-hydroxy-4-isopropyl-2,4,6-cycloheptatrien-1-one), also known as hinokitiol, is a natural compound found in several plants of the Cupressaceae family. Besides hinokitiol, related compounds were identified in Cupressaceae trees. It has been demonstrated that hinokitiol and its derivatives have various biological effects, such as antibacterial, antifungal, insecticidal, antimalarial, antitumor, anti-ischemic, iron chelating and the inhibitory activity against polyphenol oxidase activity. Activity similar to ß-thujaplicin has tropolone and its derivatives, which are not present nature. Due to the high scientific and practical interest, synthetic ß-thujaplicin and other troponoids have been produced for many years. In this review, the major biological effects of troponoids, mostly ß-thujaplicin and tropolone, on tyrosinase and polyphenol oxidase activity, ethylene production, antibacterial, antifungal and insecticidal activities, and biotransformation of ß-thujaplicin by cultured plant cells are presented. Accumulation of ß-thujaplicin and related troponoids has been shown in cell cultures of Cupressus lusitanica and other species of Cupressaceae. The biosynthetic pathway of the troponoids in plants, bacteria and fungi has been also briefly described.