In-depth understanding of the activation mechanism in asymmetric organocatalysis is of great importance for rational development of highly efficient catalytic systems. In this Article, the mechanism for the direct vinylogous Michael reaction of α,β-unsaturated γ-butyrolactam (Nu) and chalcone (EI) catalyzed by the bifunctional cinchona alkaloid thiourea organocatalyst (Cat) was studied with a combination of experimental (NMR) and theoretical (DFT) approaches, through which a new dual activation pathway was found. The key feature of this new dual activation mechanism (Pathway C) is that one N-H(A) of the thiourea moiety and the N-H of the protonated amine in Cat simultaneously activate Nu, while the other N-H(B) of the thiourea moiety activates EI. Both the NMR measurement and the DFT calculation identified that the interaction of Cat with Nu is stronger than that with EI in the catalyst-substrate complexes. Kinetic studies via variable-temperature NMR measurements indicated that, with the experimental activation energy E(a) of 10.2 kcal/mol, the reaction is all first-order in Nu, EI, and Cat. The DFT calculation further revealed that the C-C bond formation is both the rate-determining and the stereoselectivity-controlling steps. In agreement with the experimental data, the energy barrier for the rate-determining step along Pathway C was calculated as 8.8 kcal/mol. The validity of Pathway C was further evidenced by the calculated enantioselectivity (100% ee) and diastereoselectivity (60:1 dr), which are in excellent match with the experimental data (98% ee and >30:1 dr, respectively). Mechanistic study on the Michael addition of nitromethane to chalcone catalyzed by the Catalyst I further identified the generality of this new dual activation mechanism in cinchona alkaloid thiourea organocatalysis.

The effect of steam flash explosion (SFE), a green processing technology, on the phenolic composition, antioxidant activity and antiproliferation to HepG2 of wheat bran was investigated. Moderate SFE treatment significantly enhanced the total soluble phenolic content of wheat bran. After SFE pretreatment, the free and conjugated ferulic acid content in the wheat bran were significantly increased. Antioxidant activities of SFE treated wheat bran were higher than those untreated wheat bran. The cellular antioxidant and antiproliferative activities of SFE treated wheat bran were also significantly ameliorated. It was suggested that SFE pretreatment could be applied to release the bound phenolic compounds and enhance the antioxidant activities and antiproliferative activities of wheat bran.

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The substitution of CaCl 2 by MgCl 2 was undertaken in Deak's two-step process of separating the soybean 11S and 7S globulins, aiming at higher purities and lower phytic acid (PA) contents of recovered protein fractions. The effects of pH and the addition of NaCl were also evaluated. Compared with CaCl 2 , MgCl 2 reduced the PA content of the 11S-rich fraction by 63-71% but increased that of the 7S-rich fraction by 14-28%, depending on pH. Correspondingly, more Ca 2? was recovered in the 11S-rich fraction, while more Mg 2? co-precipitated with the 7S-rich fraction. NaCl increased the purity of the 11S-rich fraction and reduced its PA content, but the purity of the 7S-rich fraction was reduced by using 50-100 mM NaCl. Lowering pHs from 6.4 and 4.8 to 5.6 and 4.0 in the two precipitation steps increased the yield of both fractions. The optimized fractionating procedure was as follows: the 11S-rich fraction was precipitated at pH 5.8 by using 5 mM MgCl 2, 10 mM NaHSO 3 and 20 mM NaCl, followed by the precipitation of the 7S-rich fraction at pH 4.5. The new method provided both fractions with satisfactory protein yields (22% for 11S and 16% for 7S), purities (88% for 11S and 80% for 7S) and PA contents (0.356% for 11S and 0.882% for 7S).

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