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Abstract: A new resource of biocatalyst for asymmetric reduction of aromatic ketones has been discovered for the first time from a common plant seed, adzuki bean, i.e. Phaseolus angularis (Willd.) W.F. Wight. The study investigated the best methods to prepare the biocatalyst and its ability to reduce ketones. Our results indicated that the biocatalyst from adzuki bean could reduce various aromatic ketones at relatively high concentrations (e.g. 100mM), exhibiting excellent stereoselectivity (>98% e.e.). In addition, it was found that NADPH acts as the reducing cofactor, which can be regenerated by the crude enzyme system itself using glucose as an auxiliary substrate. [Copyright &y& Elsevier]

Abstract: Salidroside is a natural glycoside with pharmacological activities of resisting anoxia, microwave radiation and fatigue, improving oxygen lack, and postponing ageing. In this work, salidroside and other natural glucosides such as cinnamyl O-β-d-glucopyranoside and 4-methoxybenzyl O-β-d-glucopyranoside were efficiently synthesized via an environmentally benign and energy economic process. In the synthetic process, apple seed, easily available from discards of fruit processing factories, was employed as a natural and green catalyst. Moreover, all of the catalyst, solvent and excessive substrate was reused or recycled. The biocatalytic reaction was carried out in a clean and less toxic medium of aqueous tert-butanol and the glucoside produced was selectively removed from reaction mixture by alumina column adsorption, making excessive substrate (aglycon) recyclable for a repeated use in the next batch of reaction. For improvement of the biocatalyst stability, apple seed meal was further cross-linked by glutaraldehyde, yielding a net-like porous structure within which the dissociating proteins were immobilized, resulting in improved permeability of the biocatalyst. After the simple cross-linking treatment, the half-life of apple seed catalyst was significantly improved from 29 days to 51 days. The productivity of the bioreactor in the case of salidroside can reach ca. 1.9gl−1 d−1, affording the product in up to 99.3% purity after refinement. [Copyright &y& Elsevier]

Abstract: A monophasic organic–water system for efficient enzymatic synthesis of β-d-glucopyranoside by reverse hydrolysis was constructed and optimized. p-Nitrobenzyl alcohol (pNBA), selected as a model substrate alcohol, was readily glucosylated with d-glucose through reverse hydrolysis using almond β-d-glucosidase in a monophasic aqueous-organic medium, producing a new glucoside, p-nitrobenzyl β-d-glucopyranoside (pNBG). The effects of different buffers, organic solvents and water contents were investigated. Buffer type and pH affected the initial reaction rate but had little effect on the final yields. The ratio of organic solvent to water plays a crucial role in shifting the reaction equilibrium toward synthesis, but a minimum amount of water is necessary to maintain the enzyme activity. Dioxane, which was previously known as an unsuitable solvent for β-d-glucosidase-catalyzed reactions, was found to be the most appropriate solvent for this synthetic procedure. The reaction equilibrium and enzyme stability in the reaction medium were also investigated. Under the optimal reaction conditions, i.e. 90% dioxane (v/v)+10% buffer (Na2HPO4–KH2PO4, 70mM, pH 6.0) with alcohol-to-glucose molar ratio of 9:1, p-nitrobenzyl β-d-glucopyranoside was produced with a maximum yield (13.3%). [Copyright &y& Elsevier]

Salidroside, a natural glycoside, was enzymatically derived for the first time into novel esters using lipase as biocatalyst. The reaction system of glycoside acylation was optimized, and the effect of solvent nature, concentrations of substrate and biocatalyst, and acyl donors'' structure on the acylation was studied. In the optimal system, various structures of acyl donors, either natural or unnatural, including short alkyl acyl groups, long chain acyl groups and acyl donors with aryl group were connected to molecular backbone of the glycoside, forming various structures of novel glycoside esters. [Copyright &y& Elsevier]