Biosynthesis of straight-chain ester volatiles in red delicious and granny smith apples using deuterium-labeled precursors.
Biosynthesis of straight-chain ester volatiles by Granny Smith and Red Delicious apples was investigated using deuterium-labeled fatty acids, C-6 aldehydes, and alcohols. Perdeuterated saturated and monounsaturated fatty acids were metabolized to hexyl-d(11), hexanoate-d(11), heptanoate-d(13), and octanoate-d(15) esters, whereas perdeuterated linoleic acid produced only hexyl-d(11) and hexanoate-d(11) esters. Exposure of fruit to vapors of deuterated 3Z-hexenal, 2E-hexenal, and hexanal identified the following biosynthetic processes: (1) isomerization between 3E, 3Z, and 2E-hexenals; (2) reduction to 3E, 3Z, and 2E-hexenyl esters; (3) reduction to hexanol and hexyl esters; (4) oxidation to hexanoic acid and formation of hexanoate esters; (5) beta-oxidation of hexanoic acid leading to butyl and butanoate esters; and (6) alpha-oxidation of hexanoic acid leading to pentyl and pentanoate esters. Unsaturated straight-chain ester volatiles appear to arise only by the lipoxygenase pathway and may be useful indicators of lipoxygenase activity in fruit.
Rowan
D D
DD
Horticulture and Food Research Institute of New Zealand Ltd., Batchelar Research Centre, Private Bag 11030, Palmerston North, New Zealand. DRowan@hort.cri.nz
Allen
J M
JM
Fielder
S
S
Hunt
M B
MB
D002849:Chromatography, Gas / Q000379:methods; D003903:Deuterium; D004952:Esters / Q000378:metabolism*; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000737:chemistry / Q000378:metabolism; D005638:Fruit / Q000737:chemistry*; D014835:Volatilization
D004952:Esters; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D003903:Deuterium