Radiotracer Studies on the Formation of 2,5-Dimethyl-4-hydroxy-3(2H)-furanone in Detached Ripening Strawberry Fruits

Abstract

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

FaQR, Required for the Biosynthesis of the Strawberry Flavor Compound 4-Hydroxy-2,5-Dimethyl-3(2H)-Furanone, Encodes an Enone Oxidoreductase

“…Naturally occurring HDMF was removed by dialysis (exclusion limit, 10 kD) against a phosphate buffer solution, pH 7.0. Standard activity assays consisted of the dialyzed crude strawberry protein extract, D-fructose-1,6-diphosphate, as HDMF precursor (Roscher et al, 1998) and the reducing agent NADH, because the conversion involves a reduction step. After 24 h of incubation, a solid-phase extraction was performed and the products eluted by diethyl ether were analyzed by HPLC-UV (285 nm), HPLC-diode array detection (DAD), and HPLC-mass spectrometry (MS).…”

“…The first indications for the enzymatic formation of HDMF in strawberry fruit were provided by studies demonstrating the correlation of fruit ripening stage and HDMF concentration (Sanz et al, 1995). Incorporation experiments showed that, after the application of 15 different water-soluble, radioactively labeled substances, D-[U-14 C]fructose-1,6-diphosphate had the highest incorporation rate into the furanone structures (Roscher et al, 1998) (Schwab, 1998), and studies with D-[2-2 H]glucose demonstrated the involvement of phosphohexose isomerase in the conversion of D-glucose to the furanones, thus confirming the proposal that D-fructose-6-phosphate is a natural precursor of HDMF and DMMF (Wein et al, 2001). Even though the detailed biogenetic pathway from D-fructose-1,6-diphosphate to HDMF remained unknown, all studies have indicated that HDMF is derived from carbohydrate metabolism.…”

Historical Review on the Identification of Mesifurane, 2,5-Dimethyl-4-methoxy-3(2H)-furanone, and Its Occurrence in Berries and Fruits

“…d -Glucose, d -fructose, d -fructose 6-phosphate, and d -fructose 1,6-diphosphate have been confirmed as intermediates of the precursor pathway of DMHF formation in strawberries. 47−49 It has further been shown that in ripening strawberries, DMHF is a methylation substrate, and S -methyl- 14 C-adenosyl- l -methionine is the methyl donor in the biosynthesis of mesifurane (DMMF). 50 The locus required for the production of mesifurane in strawberry is the Fragaria x ananassa O -methyltransferase gene ( FaOMT ), and the partially purified enzyme has a molar mass of 80 kDa.…”

Formation of 4-Hydroxy-2,5-Dimethyl-3[2H]-Furanone by Zygosaccharomyces rouxii : Identification of an Intermediate

“…D-Xylulose-5-phosphate, D-ribulose-5-phosphate, and D-sedoheptulose-7-phosphate were determined as potential precursors of homofuraneol and norfuraneol (31). Hecquet et al (13) demonstrated that HDMF is produced by Z. rouxii from D-fructose-1,6-bisphosphate (FBP), and results from Roscher et al (30) confirmed FBP as the most effective precursor in ripe strawberry fruits. Z. rouxii produced approximately 80 ppm of HDMF after 11 days of incubation in nutrient solutions containing 10% FBP and 5% D-glucose (carbon source).…”