The transformation of 12 radioactively labeled compounds into 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF), glycosidically bound DMHF, and 2,5-dimethyl-4-methoxy-3(2H)-furanone (DMMF) was investigated in detached ripening strawberry fruits (Fragaria × ananassa) over a 3-day period. Radiochemical analysis of the different fruit parts revealed that major portions of the applied radioactivity (up to 66%) remained in the stems and calyx. Incorporation levels of [2-14C]dihydroxyacetone, d-[1-3H]glucose, d-[U-14C]-glucose, d-[U-14C]glucose 6-phosphate, d-[U-14C]fructose, and d-[U-14C]fructose 1,6-bisphosphate into the total amount of furanone derivatives were 0.022, 0.032, 0.035, 0.147, 0.202, and 0.289% of the radioactivity entering the fruits, respectively. Minor amounts of radioactivity (<0.001%) were detected in the furanone structures after the administration of [1-14C]acetate and [3-14C]pyruvate. l-[1-14C]Fucose, l-[6-3H]fucose, l-[1-3H]rhamnose, l-[U-14C]threonine, l-[U-14C]lactaldehyde, and [2-14C]malonic acid were not transformed into DMHF or a derivative thereof. Keywords: Biosynthesis; carbohydrate metabolism; 2,5-dimethyl-4-hydroxy-3(2H)-furanone; Fragaria × ananassa; Rosaceae

The transformation of S-[methyl-14C]adenosyl-l-methionine (14C-SAM) and [2-(or 5-)methyl-14C]-2,5-dimethyl-4-hydroxy-3(2H)-furanone (14C-1) was investigated in detached ripening strawberry fruits over a three-day period. Radiochemical analysis of the different fruit parts revealed that 46% and 51% of the applied 14C remained in the stems for 14C-SAM and 14C-1, respectively. In samples obtained by solid phase extraction, 1, 2,5-dimethyl-4-methoxy-3(2H)-furanone (2), and glycosidically bound 1 were analyzed by reversed-phase high-performance liquid chromatography. Incorporation of 14C-SAM and 14C-1 into 2 was observed with transformation rates of 0.4% and 0.3% of the applied 14C, respectively. In addition, 0.7% of the applied 14C-1 was recovered as glycosidically bound 1. The data support the conclusions that 14C-SAM is the source of the methyl group in the 4-methoxy compound 2 and that 1 is the precursor of 2 and the glycosides studied. Keywords: 2,5-Dimethyl-4-hydroxy-3(2H)-furanone; 2,5-dimethyl-4-methoxy-3(2H)-furanone; Furaneol; methoxyfuraneol; S-adenosyl-l-methionine; metabolism; strawberry

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