Lyophilized extracts from vegetable flours as economical alternative to purified oxygenases for the synthesis of oxylipins

Oxylipins are oxygenated bioactive natural products deriving from the oxidation of polyunsaturated fatty acids (PUFAs) that have attracted increasing interest has for their potent anti-inflammatory activity as well as cancer preventing agents [1]. Considerable synthetic efforts have been devoted to the development of selective processes for the production of single isomers of hydroxy- or epoxy- fatty acids, but in most cases multistep sequences are necessary to control the functionalization of a specific double bond of the polyenic molecules. Lipoxygenases (LOX) are (non-heme) iron-containing enzymes which catalyze the insertion of oxygen into polyunsaturated fatty acids, whereas plant peroxygenases (PXG) contain the heme prosthetic group and use alkyl hydroperoxides to form an oxyferryl specie that is catalytically active in epoxidation of the PUFAs. Since lipoxygenases and peroxygenases are present in a wide variety of plants, particularly legumes and cereals, soybean flour extracts and enzyme-enriched microsomal fractions of oat flour extracts have been proposed as economical alternative to the purified enzymes [2-3]. In spite of their potential in organic synthesis, however, in most cases the reactions with soybean flour and oat flour have been carried out on analytical scale and the products identified by MS-analysis. We decided to investigate the feasibility of preparative reactions in the presence of inexpensive extracts of soybean flour or oat flour using eicosapentaenoic acid (EPA) as test substrate. In this context, we found that the freeze-drying of extracts was advantageous in terms of activity and reproducibility, with a checked stability up to 6 months. The use of lyophilized flour extracts allowed the regio- and steroselective functionalization of EPA and the optimization of reaction and purification conditions led to good yields of isolated products, whose structures were established by 1D- and 2D-NMR experiments. [1] Moro, K; Nagahashi, M; Ramanathan, R; Takabe, K; Wakai T. World J Clin Cases 2016, 4, 155-164. [2] Tu, H.-A. T.; Dobson, E. P.; Henderson, L. C.; Barrow, C. J.; Adcock, J. L. New Biotechnology 2018, 41, 23-33. [3] Piazza, GJ; Foglia, TA ; A Nuñez JAOCS 2001, 78, 589-592.