Enzymatic synthesis of an ezetimibe intermediate using carbonyl reductase coupled with glucose dehydrogenase in an aqueous-organic solvent system.

(4S)-3-[(5S)-5-(4-Fluorophenyl)-5-hydroxypentanoyl]-4-phenyl-1,3-oxazolidin-2-one ((S)-ET-5) is an important chiral intermediate in the synthesis of chiral side chain of ezetimibe. Recombinant Escherichia coli expressing carbonyl reductase (CBR) was successfully constructed in this study. The total E. coli biomass and the specific activity of recombinant CBR in 5L fermenter culture were 10.9gDCWL-1 and 14900.3Ug-1DCW, respectively. The dual-enzyme coupled biocatalytic process in an aqueous-organic biphasic solvent system was first constructed using p-xylene as the optimal organic phase under optimized reaction conditions, and 150gL-1 (4S)-3-[5-(4-fluorophenyl)-1,5-dioxophentyl]-4-phenyl-1,3-oxazolidin-2-one (ET-4) was successfully converted to (S)-ET-5 with a conversion of 99.1% and diastereomeric excess of 99% after 24-h, which are the highest values reported to date for the production of (S)-ET-5.

Purification and Immobilization of a Novel Enantioselective Lipase from Tsukamurella tyrosinosolvents for Efficient Resolution of Ethyl 2-(2-oxopyrrolidin-1-yl) Butyrate.

A highly enantioselective lipase from Tsukamurella tyrosinosolvents E105 was purified via ultrasonic extraction, precipitation, and chromatographic steps. The enzyme was purified about 38-fold with the recovery yield of 9 % and was confirmed as a dimer protein consisting of two identical subunits with a molecular mass of 24 kDa. The purified lipase was used to catalyze resolution of racemic ethyl 2-(2-oxopyrrolidin-1-yl) butyrate to (S)-2-(2-oxopyrrolidin-1-yl) butyric acid. The maximum activity of such lipase was obtained at pH 7.5, 35 °C, and the highest relative activity (156.80 %) was observed in the presence of 0.5 mM Co2+. Subsequently, the lipase was encapsulated within a mixture of 3 % sodium alginate and 0.8 % carrageenan, and then cross-linked with 0.6 % glutaraldehyde to enhance its biocatalytic capability and stability. Comparing with 36.9 % product yield and 97.5 % product ee of free lipase, the highest product yield of 46.3 % and ee of 98.5 % for immobilized lipase were achieved with the presence of 20 mM substrate. In addition, the reusability of immobilized lipase was also investigated, which could maintain 63.7 % of its initial conversion yield after seven repeated batch reactions. Thus, the evaluated enantioselective lipase in this work has a good potential for further industrial application.

Enhanced biocatalytic production of L-cysteine by Pseudomonas sp. B-3 with in situ product removal using ion-exchange resin.

Bioconversion of DL-2-amino-Δ(2)-thiazoline-4-carboxylic acid (DL-ATC) catalyzed by whole cells of Pseudomonas sp. was successfully applied for the production of L-cysteine. It was found, however, like most whole-cell biocatalytic processes, the accumulated L-cysteine produced obvious inhibition to the activity of biocatalyst and reduced the yield. To improve L-cysteine productivity, an anion exchange-based in situ product removal (ISPR) approach was developed. Several anion-exchange resins were tested to select a suitable adsorbent used in the bioconversion of DL-ATC for the in situ removal of L-cysteine. The strong basic anion-exchange resin 201 × 7 exhibited the highest adsorption capacity for L-cysteine and low adsorption for DL-ATC, which is a favorable option. With in situ addition of 60 g L(-1) resin 201 × 7, the product inhibition can be reduced significantly and 200 mmol L(-1) of DL-ATC was converted to L-cysteine with 90.4 % of yield and 28.6 mmol L(-1 )h(-1) of volumetric productivity. Compared to the bioconversion without the addition of resin, the volumetric productivity of L-cysteine was improved by 2.27-fold using ISPR method.

Efficient biocatalytic synthesis of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol by a newly isolated Trichoderma asperellum ZJPH0810 using dual cosubstrate: ethanol and glycerol.

(R)-[3,5-bis(trifluoromethyl)phenyl] ethanol is a crucial intermediate for the synthesis of Aprepitant. An efficient biocatalytic process for (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol was developed via the asymmetric reduction of 3,5-bis(trifluoromethyl) acetophenone, catalyzed by whole cells of newly isolated Trichoderma asperellum ZJPH0810 using ethanol and glycerol as dual cosubstrate for cofactor recycling. A fungal strain ZJPH0810, showing asymmetric biocatalytic activity of 3,5-bis(trifluoromethyl) acetophenone to its corresponding (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol, was isolated from a soil sample. Based on its morphological and physiological characteristics and internal transcribed spacer sequence, this isolate was identified as T. asperellum ZJPH0810, which afforded an NADH-dependent (R)-stereospecific carbonyl reductase and was a promising biocatalyst for the synthesis of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol. Some key reaction parameters involved in the bioreduction catalyzed by T. asperellum ZJPH0810 were subsequently optimized. The effectiveness of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol production was significantly enhanced by employing a novel dual cosubstrate-coupled system for cofactor recycling. The established efficient bioreduction system contained 50 mM of 3,5-bis(trifluoromethyl) acetophenone and 60 g l(-1) of resting cells, employing ethanol (6.0 %, v/v) and glycerol (0.5 %, v/v) as dual cosubstrate. The bioreduction was performed in distilled water medium, at 30 °C and 200 rpm. Under the above conditions, a best yield of 93.4 % was obtained, which is nearly a 3.5-fold increase in contrast to no addition of cosubstrate. The ee value of the product reached above 98 %. This biocatalytic process shows great potential in the production of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol, a valuable chiral building block in the pharmaceutical industry.

Asymmetric biocatalytic reduction of 3,5-bis(trifluoromethyl) acetophenone to (1R)-[3,5-bis(trifluoromethyl)phenyl] ethanol using whole cells of newly isolated Leifsonia xyli HS0904.

A novel bacterial strain HS0904 was isolated from a soil sample using 3,5-bis(trifluoromethyl) acetophenone as the sole carbon source. This bacterial isolate can asymmetrically reduce 3,5-bis(trifluoromethyl) acetophenone to (1R)-[3,5-bis(trifluoromethyl)phenyl] ethanol with high enantiometric excess (ee) value. Based on its morphological, physiological characteristics, Biolog, 16S rDNA sequence and phylogenetic analysis, strain HS0904 was identified as Leifsonia xyli HS0904. To our knowledge, this is the first reported case on the species L. xyli exhibited R-stereospecific carbonyl reductase and used for the preparation of chiral (1R)-[3,5-bis(trifluoromethyl)phenyl] ethanol. The optimization of parameters for microbial transformation of 3,5-bis(trifluoromethyl) acetophenone to (1R)-[3,5-bis(trifluoromethyl)phenyl] ethanol catalyzed by whole cells of L. xyli HS0904 was carried out by examining some key factors including buffer pH, reaction temperature, shaking speed, substrate concentration, and reaction time. The obtained optimized conditions for the bioreduction are as follows: buffer pH 8.0, 70 mM of 3,5-bis(trifluoromethyl) acetophenone, 100 g l(-1) of glucose as co-substrate, 200 g l(-1) of resting cells as biocatalyst, reaction for 30 h at 30 °C and 200 rpm. Under above conditions, 99.4% of product ee and best yield of 62% were obtained, respectively. The results indicated that isolate L. xyli HS0904 is a novel potential biocatalyst for the production of (1R)-[3,5-bis(trifluoromethyl)phenyl] ethanol.

[Effect of several penetration enharcers on transdermal permeation and skin accumulation of artemether].

OBJECTIVE: To investigate penetration characteristics of artemether and the effect of different permeation enhancer on transdermal permeation of artemether through rat skin. METHOD: The permeation experiments were performed using rat skin on modified Franz diffusion cells in vitro. The concentrations of artemether in receptor compartment at specified time points were determined by HPLC. RESULT: The permeating ratio through human skin of artemether solution was Js (2.78 +/- 0.78) microg x cm(-2) x h(-1), the quantity of drug penetrated through and accumulated in the skin by the end of the experiment were (69.07 +/- 3.01) microg x cm(-2), (58.93 +/- 3.56) microg x cm(-2) respectively. Four different permeation enhancers can improve the transdermal permeation of artemether. CONCLUSION: Artemether have the potential to be developed to new transdermal preparation.

[Comparison of kinetic behavior in both plasma and tissue after intravenous administration of alpha-asarone in lipid emulsion and aqueous solution in rats and mice].

OBJECTIVE: To compare the pharmacokinetics and tissue distribution of alpha-asarone in lipid emulsion and aqueous solution for injection and study the feasibility of lipid emulsion of alpha-asarone as the parenteral drug delivery system. METHOD: HPLC was used to determine the drug concentration in rat plasma and mice tissues after intravenous (i.v.) administration of lipid emulsion and aqueous solution of alpha-asarone at a single dose (40 mg x kg(-1)), respectively. RESULT: The plasma concentration-time profiles of lipid emulsion and aqueous solution of alpha-asarone after intravenous administration of them are similar and the drug concentration-time data were fitted to a two-compartment open model. The results of tissues distribution showed that distribution contents of alpha-asarone from lipid emulsion and aqueous solution in vivo are similar in lungs but lipid emulsion increased the uptake in livers and spleens, and decreased the uptake in hearts and kidneys for alpha-asarone. CONCLUSION: The plasma concentration-time profiles of alpha-asarone in lipid emulsion and aqueous solution are similar, but lipid emulsion significantly altered the tissue distribution of alpha-asarone, which may be beneficial to decrease its potential toxicity to heart and kidney.

[Transdermal and lymph targeting transfersomes of vincristine].

Vincristine (VCR) is mainly used to treat acute lymphocytic leukemia, Hodgkin and non-Hodgkin lymphoma in clinic with definite therapeutic effect. But the obvious neurotoxicity and local stimulation of which limit its clinic use. In order to increase the lymph targeting to enhance the curative effect and to lower the adverse reaction of VCR, the VCR loaded transfersomes (VCR-T) were prepared with dry-film and ultrasonic dispersing methods, and the corresponding pharmaceutical properties, pharmacokinetical characteristics and the targeting ability were studied. The average particle size of VCR-T prepared was 63 nm with an entrapment ratio of 59%. The in vitro transdermal research with modified Franz cell showed that VCR-T permeated through the skin in accordance with polynomial equation, and with an accumulation permeation percentage of 67.4% up to 12 h. An HPLC method was utilized to determine the pharmacokinetics and tissue distribution of VCR. Compared with the iv injection of VCR solution, the retention time of VCR in blood was extended by 12 times with VCR-T, and the targeting index in rat lymph was increased by 2.75 times. As a result, transfersomes could penetrate the skin and enter into the systemic circulation carrying VCR with good lymph targeting ability, which makes it probably a new lymphtic targeting drug delivery system.