(Methylsulfanyl)alkanoate ester biosynthesis in Actinidia chinensis kiwifruit and changes during cold storage
摘要:
Four 3-(methylsulfanyl)propionate esters, ethyl 3-(methylsulfanyl)prop-2-enoate, two 2-(methylsulfanyl)acetate esters and their possible precursors 2-(methylsulfanyl)ethanol, 3-(methylsulfanyl)propanol and 3-(methylsulfanyl)propanal were quantified from the headspace of Actinidia chinensis 'Hort 16A' kiwifruit pulp by GC-MS-TOF analysis. The majority of these compounds were specific for eating-ripe fruit and their levels increased in parallel with the climacteric rise in ethylene, accumulating towards the very soft end of the eating firmness. No ethylene production could be observed after long-term storage (4-6 months) at 1.5 degrees C and the levels of all methylsulfanyl-volatiles, except methional, declined by 98-100% during that period. This depletion of (methylsulfanyl)alkanoate-esters after prolonged cold storage points towards little flavour impact of these compounds on commercial 'Hort 16A' kiwifruits. However, ethyl 3-(methylsulfanyl)propionate is suggested to be odour active in ripe 'Hort 16A' fruit that has not been stored. Gene expression measured by q-RT PCR of six ripening-specific alcohol acyltransferase (AAT) expressed sequence tags and (methylsulfanyl)alkanoate-ester production of cell-free extracts were also significantly decreased after prolonged cold storage. However, (methylsulfanyl)alkanoate-ester synthesis of cell-free extracts and AAT gene transcript levels could be recovered by ethylene treatment after five months at 1.5 degrees C indicating that the biosynthesis of (methylsulfanyl)alkanoate-esters in 'Hort 16A' kiwifruit is likely to depend on ethylene-regulated AAT-gene expression. That the composition but not the concentration of (methylsulfanyl)alkanoate-esters in fresh fruit could be restored after ethylene treatment suggests that substrate availability might also have an impact on the final levels of these volatiles. (C) 2010 Elsevier Ltd. All rights reserved.
Efficient Synthesis of β‐Alkyl/Arylsulfanyl Carbonyl Compounds by In‐TMSCl‐Promoted Cleavage of Dialkyl/Diaryl Disulfides and Subsequent Michael Addition
作者:Brindaban C. Ranu、Tanmay Mandal
DOI:10.1080/00397910701229859
日期:2007.5
Abstract A convenient and efficient procedure for the synthesis of β‐alkyl/arylsulfanyl carbonyl compounds has been developed by a simple one‐pot reaction of dialkyl/diaryl sulfides with α,β‐unsaturated aldehydes, ketones, carboxylic esters, and nitriles in presence of indium and trimethylsilyl chloride under sonication.
A facile generation of C–S bonds via one-pot, odourless and efficient thia-Michael addition reactions using alkyl, aryl or allyl halides, thiourea and electron-deficient alkenes in wet polyethylene glycol (PEG 200) under mild reaction conditions
An efficient and odourless synthesis of thia-Michael adducts by the reaction of various organic halides (primary, secondary, tertiary, allylic, and benzylic), structurally diverse electron-deficient alkenes (ketones, esters, and acrylonitrile) and thiourea in the presence of sodium carbonate in wet polyethylene glycol (PEG 200) at 30–35 °C has been developed. This protocol is also a highly useful method
Pronounced Catalytic Effect of a Micellar Solution of Sodium Dodecyl Sulfate (SDS) on the Efficient C-S Bond Formation<i>via</i>an Odorless Thia-Michael Addition Reaction through the<i>in situ</i>Generation of<i>S</i>-Alkylisothiouronium Salts
Abstractmagnified imageA pronounced catalytic effect of sodium dodecyl sulfate (SDS) was observed on thein situproduction ofS‐alkylisothiouronium saltsviathe reaction of primary, allyl and benzyl halides with thiourea in SDS droplets .Hydrolysis of the generatedS‐alkylisothiouronium salts in the palisade layer of the droplets produces the corresponding thiol moieties which are immediately added to the electron‐deficient olefins that are present in the micellar core to produce the thia‐Michael adducts. The entire route is an almost odorless process. The yields of the products are good to excellent and the method is applicable to large‐scale operation without any problem.
Characterisation of two alcohol acyltransferases from kiwifruit (Actinidia spp.) reveals distinct substrate preferences
作者:Catrin S. Günther、Christian Chervin、Ken B. Marsh、Richard D. Newcomb、Edwige J.F. Souleyre
DOI:10.1016/j.phytochem.2011.02.026
日期:2011.6
Volatile esters are key compounds of kiwifruit flavour and are formed by alcohol acyltransferases that belong to the BAHD acyltransferase superfamily. Quantitative RT-PCR was used to screen kiwifruit-derived expressed sequence tags with proposed acyltransferase function in order to select ripening-specific sequences and test their involvement in alcohol acylation. The screening criterion was for at least 10-fold increased transcript accumulation in ripe compared with unripe kiwifruit and in response to ethylene. Recombinant expression in yeast revealed alcohol acyltransferase activity for Actinidia-derived AT1, AT16 and the phylogenetically distinct AT9, using various alcohol and acyl-CoA substrates. Functional characterisation of AT16 and AT9 demonstrated striking differences in their substrate preferences and apparent catalytic efficiencies (V-max' K-m(-1)). Thus revealing benzoyl-CoA:alcohol O-acyltransferase activity for AT16 and acetyl-CoA:alcohol O-acyltransferase activity for AT9. Both kiwifruit-derived enzymes displayed higher reaction rates with butanol compared with ethanol, even though ethanol is the main alcohol in ripe fruit. Since ethyl acetate and ethyl benzoate are major esters in ripe kiwifruit, we suggest that fruit characteristic volatile profiles result from a combination of substrate availability and specificity of individual alcohol acyltransferases. (C) 2011 Elsevier Ltd. All rights reserved.
NOVEL AMINO-GROUP-CONTAINING SILOXANES, PROCESSES FOR THEIR PREPARATION AND USE
申请人:EVONIK DEGUSSA GMBH
公开号:US20140309446A1
公开(公告)日:2014-10-16
The invention relates to novel amino-group-containing siloxanes, to their preparation processes and to their use in care formulations for skin, hair and textiles.