Heterologous expressed human cytochromes are useful tools in synthesis of thymoquinone

Thymoquinone (4) is a phytochemical compound from Nigella sativa. Because of its properties like anti-oxidant, anti-cancer and anti-inflammatory effects this compound is interesting for medicinal use. Due to variable contents of thymoquinone in plants the establishment of a standardized medicine is difficult and an alternative synthesis is required. Aim of this project is the biochemical synthesis of the compound of interest directly starting with p-cymene (1) as a simple and omnipresent terpenoid. Biotransformation of p-cymene, thymol (2) and carvacrol (3) by six human hepatic enzymes, CYP1A1, CYP1A2, CYP2A6, CYP2C9, CYP2D6 and CYP3A4, heterologously expressed in E. coli DH5alpha, was investigated. Mixtures of E. coli whith expressed enzymes where incubated for 2 hrs at 37°C and analyzed by HPLC. Human cytochromes CYP1A2 and CYP2A6 are the most promising enzymes in conversion of p-cymene to thymoquinone with thymol and carvacrol as intermediates. In case of thymol and Carvacrol as substrates thymoquinone is formed directly, although the transformation of thymol is more efficiently than that of carvacrol. In-vitro biotransformation of p-cymene to thymoquinone with heterologous expressed cytochromes could become an interesting alternative to its chemical synthesis.