Radiotracer studies on the formation of 2,5-dimethyl-4-hydroxy-3(2H)-furanone in detached ripening strawberry fruits

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 x 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-C-14]dihydroxyacetone, D-[1-H-3]glucose, D-[U-C-14]-glucose, D-[U-C-14]glucose 6-phosphate, D-[U-C-14]fructose, and D-[U-C-14]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-C-14]acetate and [3-C-14]pyruvate. L-[1-C-14]Fucose, L-[6-H-3]fucose, L-[1-H-3]rhamnose, L-[U-C-14]threonine, L-[U-C-14]lactaldehyde, and [2-C-14]malonic acid were not transformed into DMHF or a derivative thereof.