Loop-Grafted Old Yellow Enzymes in the Bienzymatic Cascade Reduction of Allylic Alcohols
作者:Sabrina Reich、Bettina M. Nestl、Bernhard Hauer
DOI:10.1002/cbic.201500604
日期:2016.4.1
Rational loop grafting transfers enzyme properties: The reaction activity in the bienzymatic cascade reduction of allylicalcohols was successfully transferred within ene reductases by the rational exchange of two β/α surface loop regions near the entrance of the active site.
Monoterpene glucosides and other constituents from Perilla frutescens
作者:Tomoyuki Fujita、Mitsuru Nakayama
DOI:10.1016/s0031-9422(00)90843-4
日期:1993.12
Abstract Three new monoterpene glucosides named perilloside B-D have been isolated from the fresh leaves of Perillafrutescens. The structures were determined on the basis of spectral and chemical evidence.
Two novel antioxidants (vinyl caffeate and trans-p-menth-8-en-7-yl caffeate) and seven known antioxidants (3,4-dihydroxybenzaldehyde, methyl 3,4-dihydroxy-benzoate, methyl caffeate, 3′,4′,5,7-tetra-hydroxy-flavone, caffeic acid, 6,7-dihydroxycoumarin, and rosmarinic acid) were isolated from Perilla frutescens Britton var. crispa (Thunb.). The redox potentials of the novel isolated antioxidative compounds were comparable to those of known antioxidants. trans-p-menth-8-en-7-yl caffeate was effective to prevent the oxidative degradation of perillaldehyde in the essential oil of P. frutescens.
A study on the regioselective reduction of the conjugate double bond of perillaldehyde is described. The chemical reduction of this substrate was investigated in order to provide a straightforward access to the relevant natural flavour, dihydroperill-aldehyde. The biological reduction of both natural (S)-(-)-perillaldehyde and synthetic (R)-(+)-perillaldehyde was accomplished by means of fermenting baker's yeast. The latter microorganism converted, with different diastereoselectivity, the (S)- and (R)-enantiomers into the corresponding trans and cis saturated alcohols, respectively. The origin of the hydrogen atoms added to the double bond was studied by deuterium labelling experiments and H-2 NMR measurements that clearly demonstrate a different mechanism of the biohydrogenation of the two enantiomeric forms of perillaldehyde. (C) 2004 Elsevier Ltd. All rights reserved.