- Determination and isolation of a thioesterase from passion fruit (Passiflora edulis Sims) that hydrolyzes volatile thioesters
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Volatile organosulfur compounds (VOSCs) are high impact aroma chemicals characteristic of tropical fruits which are active as both free thiols and the respective thioesters. Using a simple and sensitive colorimetric enzyme assay, a thioesterase activity toward VOSCs has been identified in ripening purple passion fruit (Passiflora edulis Sims). The assay was based on determining the release of free thiols from 2-methyl-3-furanthiol acetate using Ellman's reagent. The major thioesterase in the fruit was found to be a wall-bound protein in the mesocarp. The extracted enzyme activity was purified 150-fold and shown to be associated with a 43 kDa monomeric serine hydrolase which was selectively labeled with a fluorophosphonate suicide probe. MS-MS sequencing identified the thioesterase as a class 13 glycoside hydrolase, most similar to pectin acetylesterase, an enzyme involved in cell wall modifications in the peel of a number of fruit. Our results suggest that cell wall hydrolases in tropical fruit may have additional useful roles in biotransforming VOSCs.
- Tapp, Edward J.,Cummins, Ian,Brassington, David,Edwards, Robert
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experimental part
p. 6623 - 6630
(2010/04/06)
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- Characterization of the aroma-active compounds in pink guava (Psidium guajava, L.) by application of the aroma extract dilution analysis
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The volatiles present in fresh, pink-fleshed Colombian guavas (Psidium guajava, L.), variety regional rojo, were carefully isolated by solvent extraction followed by solvent-assisted flavor evaporation, and the aroma-active areas in the gas chromatogram were screened by application of the aroma extract dilution analysis. The results of the identification experiments in combination with the FD factors revealed 4-methoxy-2,5-dimethyl-3(2H)-furanone, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 3-sulfanylhexyl acetate, and 3-sulfanyl-1-hexanol followed by 3-hydroxy-4,5-dimethyl-2(5H)-furanone, (Z)-3-hexenal, trans-4,5-epoxy-(E)-2-decenal, cinnamyl alcohol, ethyl butanoate, hexanal, methional, and cinnamyl acetate as important aroma contributors. Enantioselective gas chromatography revealed an enantiomeric distribution close to the racemate in 3-sulfanylhexyl acetate as well as in 3-sulfanyl-1-hexanol. In addition, two fruity smelling diastereomeric methyl 2-hydroxy-3- methylpentanoates were identified as the (R,S)- and the (S,S)-isomers, whereas the (S,R)- and (R,R)-isomers were absent. Seven odorants were identified for the first time in guavas, among them 3-sulfanylhexyl acetate, 3-sulfanyl-1-hexanol, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, frans-4,5-epoxy-(E)-2-decenal, and methional were the most odor-active.
- Steinhaus, Martin,Sinuco, Diana,Polster, Johannes,Osorio, Coralia,Schieberle, Peter
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experimental part
p. 4120 - 4127
(2010/03/31)
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- CHIRALE, SCHWEFELHALTIGE AROMASTOFFE DER GELBEN PASSIONSFRUCHT (PASSIFLORA EDULIS F. FLAVICARPA). DARSTELLUNG DER ENANTIOMEREN UND ABSOLUTE KONFIGURATION
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3-Methylthio-hexane-1-ol and 2-methyl-4-propyl-1,3-oxathiane, chiral S-containing aroma substances of the yellow passion fruit are resolved to enantiomers and absolute configurations are elucidated.
- Heusinger, Georg,Mosandl, Armin
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p. 507 - 510
(2007/10/02)
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