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(2 H )-furanone (DMHF), glycosidically bound DMHF, and 2,5-dimethyl-4-methoxy-3(2 H )-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- 14 C]dihydroxyacetone, d -[1- 3 H]glucose, d -[U- 14 C]-glucose, d -[U- 14 C]glucose 6-phosphate, d -[U- 14 C]fructose, and d -[U- 14 C]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- 14 C]acetate and [3- 14 C]pyruvate. l -[1- 14 C]Fucose, l -[6- 3 H]fucose, l -[1- 3 H]rhamnose, l -[U- 14 C]threonine, l -[U- 14 C]lactaldehyde, and [2- 14 C]malonic acid were not transformed into DMHF or a derivative thereof.