Title: 1. A novel organofluorine-specific analysis for new fluorometabolite discovery; 2. Towards a structural understanding of the cyanobactin biosynthesis

Presenter: Hai Deng; Marcel Jaspars

University: University of Aberdeen

Time: 9:00-12:00, September 27, 2012

Venue: Room A203, Institute of Microbiology, Chinese Academy of Sciences

Abstract:

Organofluorine compounds are important in medicinal chemistry as fluorination has emerged as a powerful tool to improve the efficacy of drug in development towards biological targets. They have also found extensive use in agrochemicals and in a diversity of areas involving performance organic materials such as liquid crystals for electronic displays. [[i]] Unlike the number of other halogen-containing natural products (X= Cl and Br) in thousands, the naturally occurring fluorometabolites remain extremely rare entities. [[ii]] Considering the advance of sophisticated extraction, isolation and screening methods in natural product discovery, the dearth of fluorometabolites is particularly astonishing. Nature hardly evolves a biochemistry of fluorine. Another reason for fluorometabolite discovery is the lack of a sensitive organofluorine-specific screening methodology capable of screening extract without prior molecular information. 19FNMR is organofluorine-specific, though this method lacks sensitivity. [[iii]] Mass spectrum is sensitive but not suitable for organofluorine detection because, unlike chlorine and bromine, fluorine is monoisotopic without distinct isotopic pattern. As such MS is insufficient to distinct organofluorine compounds from hundreds of organic substances in the extract.

Recently, we pioneered the development of high resolution continuus source molecular absorption spectrometry (HR-CS-MAS) as a novel and sensitive organofluorine–specific analytic tool.[[iv]] As proof of principle, two model aromatic organofluorine compounds, trifluorobenzoic acid (TFBA) and 5-fluoroindol-2-carboxlic acid (FICA), were used to demonstrate the feasibility of using CS-MAS for the organofluorine-specific detection. We also utilized high-performance liquid chromatography (HPLC) coupled with CS-MAS for identification of single organofluorine in the mixture of inorganic fluoride, TFBA and FICA after HPLC fractionation. The limit of detection for TFBA and FICA was determined to be 100 ppb. Here we report mapping the fluorometabolites and identification of a new fluorometabolite from the soil bacterium Streptomyces cattleya using HPLC coupled off-line with CS-MAS and high resolution LC-MS. In this report, we firstly utilized CS-MAS to map the fluorometabolite production in the time course experiments over 14-day cultivation period of S. cattleya. It was then demonstrated that S. cattleya is able to convert inorganic fluoride to organofluorine as low as ~500 ppb through HPLC/CS-MAS analysis. Finally, a trace amount of new organofluorine compound was detected during the screening of the culture broth of S. cattleya. HR-LCESIMS analysis indicated the presence of 5’-fluoro-5’-deoxyadenosine (5’-FDA). Spiked with the synthetic sample, 5’-FDA was further confirmed. This is the second nucleotide fluorometabolite ever discovered. It has been nearly 60 years since the first fluorinated nucleocidine was discovered in the soil bacterium Streptomyces calvus in 1956.[[v]]