Electron Transfer between Genetically Modified Hansenula polymorpha Yeast Cells and Electrode Surfaces via Os‐complex modified Redox Polymers

Graphite electrodes modified with redox‐polymer‐entrapped yeast cells were investigated with respect to possible electron‐transfer pathways between cytosolic redox enzymes and the electrode surface. Either wild‐type or genetically modified Hansenula polymorpha yeast cells over‐expressing flavocytochrome b2 (FC b₂) were integrated into Os‐complex modified electrodeposition polymers. Upon increasing the L ‐lactate concentration, an increase in the current was only detected in the case of the genetically modified cells. The overexpression of FC b₂ and the related amplification of the FC b₂/L ‐lactate reaction cycle was found to be necessary to provide sufficient charge to the electron‐exchange network in order to facilitate sufficient electrochemical coupling between the cells, via the redox polymer, to the electrode. The close contact of the Os‐complex modified polymer to the cell wall appeared to be a prerequisite for electrically wiring the cytosolic FC b₂/L ‐lactate redox activity and suggests the critical involvement of a plasma membrane redox system. Insights in the functioning of whole‐cell‐based bioelectrochemical systems have to be considered for the successful design of whole‐cell biosensors or microbial biofuel cells.     

Visible‐Light‐Promoted Dearomative Fluoroalkylation of β‐Naphthols through Intermolecular Charge Transfer

The first visible‐light‐promoted dearomative fluoroalkylation of β‐naphthols was realized without the assistance of any transition‐metal catalysts or external photosensitizers. Inexpensive fluoroalkyl iodides were directly used as efficient fluoroalkylation reagents under very mild reaction conditions. The scope of this process was found to be general and broad, and both trifluoromethyl and perfluoroalkyl groups (‐C₄F₉, ‐C₆F₁₃, and ‐C₈F₁₇) were installed in excellent yields. Preliminary mechanistic studies suggest that visible‐light‐promoted intermolecular charge transfer within the naphtholate–fluoroalkyl iodide electron donor–acceptor (EDA) complex induces a single electron transfer in the absence of photocatalysts.     

Electrochemical Determination of L‐Lactate Using Phenylboronic Acid Monolayer‐Modified Electrodes

The surface of a gold (Au) disk electrode was modified with a self‐assembled monomolecular layer of dithiobis(4‐butylamino‐m‐phenylboronic acid) (DTBA‐PBA) to prepare L ‐lactate‐sensitive electrodes. The DTBA‐PBA‐modified electrodes exhibited an attenuated cyclic voltammogram (CV) for the Fe(CN)₆^3? ion in the presence of L ‐lactate, as a result of the formation of phenylboronate ester of L ‐lactate accompanied with the addition of OH^? ion to the boron atom. In other words, the negatively charged DTBA‐PBA monolayer blocked the electrode surface from the access of the Fe(CN)₆^3?/4? ions. Thus, the DTBA‐PBA monolayer‐modified Au electrode can be used for determining L ‐lactate on the basis of the change in redox current of Fe(CN)₆^3?/4? ions. The calibration graph useful for determining 1–30 mM L ‐lactate was obtained.     

Urinary d‐lactate levels reflect renal function in aristolochic acid‐induced nephropathy in mice

Urinary d ‐lactate is highly correlated to diabetic nephropathy – a progressive kidney disease in renal glomeruli. In this study, we used a C3H/3e mouse model to investigate the relationship between urinary d ‐lactate and aristolochic acid nephropathy where the glomerular structure is not affected. The nephropathy was induced using intravenous injections of aristolochic acid at a dosage of 10 mg/kg per day for 5 days and was characterized biochemically and histologically. The urinary excretions of proteins, N‐acetyl‐β‐d ‐glucosaminidase and serum creatinine were determined and connected to histological conventional findings. Urinary d ‐lactate was analyzed using column‐switching high‐performance liquid chromatography with fluorescence detection. The results showed a remarkable increase of urinary markers, including of urinary proteins and N‐acetyl‐β‐d ‐glucosaminidase, and the histological examination confirmed a diagnosis of acute tubule necrosis. The ratio of d ‐lactate to creatinine in the urine of aristolochic acid‐treated mice was approximately 36 times greater than that of the mice in the control group (p < 0.05). The ratios for the two groups of mice were 311.00 ± 71.70 and 8.60 ± 1.80 µmol/mmol creatinine, respectively. These data confirm in vivo that urinary d ‐lactate reflects renal injury conditions in aristolochic acid‐treated mice and may be a marker for the assessment of nephropathy. Copyright © 2013 John Wiley & Sons, Ltd.     

Elevated levels of liver methylglyoxal and d‐lactate in early‐stage hepatitis in rats

Methylglyoxal (MGO) is highly cytotoxic and its levels are elevated in diabetes, nephropathy and atherosclerosis. However, it has never been studied in liver disease. For this reason, we aimed to assess the levels of MGO and its metabolite d ‐lactate in an early hepatitis model. Wistar rats were administered CCl₄ (0.75 mL/kg, i.p.) to induce hepatitis. In either CCl₄‐treated or untreated rats, alanine transaminase and aspartate transaminase levels did not change over the course of the study, indicating that significant liver damage did not occur following CCl₄ treatment. However, the levels of MGO and d ‐lactate were higher in the livers of CCl₄‐treated animals than in untreated animals (MGO: 128.2 ± 18.8 and 248.1 ± 64.9 μg/g protein, p < 0.01; d ‐lactate: 0.860 ± 0.040 and 1.293 ± 0.078 μmol/g protein, respectively p < 0.01). Furthermore, in untreated and treated animals, serum d ‐lactate levels were 57.65 ± 2.59 and 92.16 ± 16.69 μm and urine d ‐lactate levels were 1.060 ± 0.007 and 1.555 ± 0.366 μmol/mg UCr, respectively (p < 0.01). These data show that in this model of early‐stage liver damage, the levels of MGO and its metabolite d ‐lactate are elevated and that d ‐lactate could be useful as a reference marker for the early stage of hepatitis.     

Preparation and Stability Evaluation of Size‐Controllable PDHCA‐β‐CD Nanoparticles as Drug Carrier

A novel biocompatible polymer was prepared by grafting the derivate of β ‐cyclodextrin (6‐SH ‐β ‐CD ) onto poly(3,4‐dihydroxycinnamic acid) (PDHCA ) via Michael addition. PDHCA ‐β ‐CD nanoparticles were prepared by the self‐assembly of amphiphilic PDHCA ‐β ‐CD polymer with N,N ‐dimethylformamide (DMF ) as good solvent and water as poor solvent. The PDHCA ‐β ‐CD nanoparticles were monodispersed with spherical morphology as shown in the scanning electron microscopic (SEM ) images in accord with the result of dynamic light scattering (DLS ) measurement. The size of the nanoparticles could be controlled from 60 to 180 nm by tuning the grafting degree (GD ) of PDHCA ‐β ‐CD polymer and also significantly influenced by the amount of water used during the process. These as‐prepared nanoparticles were stable without any significant change in the particle size after six‐months’ storage and even after being irradiated by UV at λ >280 nm for hours. The formation mechanism of PDHCA ‐β ‐CD nanoparticles was explored. The content of doxorubicin (DOX ) loaded onto the nanoparticles was up to 39% with relatively high loading efficiency (approximately 78.8% of initial DOX introduced was loaded). In vitro release studies suggested that DOX released slowly from PDHCA ‐β ‐CD nanoparticles. These features strongly support the potential of developing PDHCA ‐β ‐CD nanoparticles as carriers for the controlled delivery of drug.     

Poly[tetra‐μ2‐l‐lactato‐indium(III)sodium(I)]

The asymmetric unit of the title compound, [InNa(C₃H₅O₃)₄]_n, consists of one In^III ion, one Na^I ion and four crystallographically independent l ‐lactate monoanions. The coordination of the In^III ion is composed of five carboxylate O and two hydroxy O atoms in a distorted pentagonal–bipyramidal coordination geometry. The Na^I ion is six‐coordinated by four carboxylate O atoms and two hydroxy O atoms from four l ‐lactate ligands in a distorted octahedral geometry. Each In^III ion is coordinated by four surrounding l ‐lactate ligands to form an [In(l ‐lactate)₄]⁻ unit, which is further linked by Na^I ions through Na—O bonds to give a two‐dimensional layered structure. Hydrogen bonds between the hydroxy groups and carboxylate O atoms are observed between neighbouring layers.     

Finely dispersed palladium on silk‐fibroin as an efficient and ligand‐free catalyst for Heck cross‐coupling reaction

A palladium–fibroin complex (Pd/Fib.) was prepared by the addition of sonicated fibroin fiber in water to palladium acetate solution. Pd (OAc)₂ was absorbed by fibroin and reduced with NaBH₄ at room temperature to the Pd(0) nanoparticles. Powder‐X‐ray diffraction, scanning electron microscopy–energy‐dispersive X‐ray spectroscopy, Fourier transform‐infrared, CHN elemental analysis and inductively coupled plasma‐atomic emission spectroscopy were carried out to characterize the Pd/Fib. catalyst. Catalytic activity of this finely dispersed palladium was examined in the Heck coupling reaction. The catalytic coupling of aryl halides (‐Cl, ‐Br, ‐I) and olefins led to the formation of the corresponding coupled products in moderate to high yields under air atmosphere. A variety of substrates, including electron‐rich and electron‐poor aryl halides, were converted smoothly to the targeted products in simple procedure. Heterogeneous supported Pd catalyst can be recycled and reused several times.     

Contrasting Effects of Axial Ligands on Electron‐Transfer Versus Proton‐Coupled Electron‐Transfer Reactions of Nonheme Oxoiron(IV) Complexes

The effects of axial ligands on electron‐transfer and proton‐coupled electron‐transfer reactions of mononuclear nonheme oxoiron(IV) complexes were investigated by using [Fe^IV(O)(tmc)(X)]ⁿ⁺ ( 1 ‐X) with various axial ligands, in which tmc is 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane and X is CH₃CN ( 1 ‐NCCH₃), CF₃COO^? ( 1 ‐OOCCF₃), or N₃^? ( 1 ‐N₃), and ferrocene derivatives as electron donors. As the binding strength of the axial ligands increases, the one‐electron reduction potentials of 1 ‐X (E_red, V vs. saturated calomel electrode (SCE)) are more negatively shifted by the binding of the more electron‐donating axial ligands in the order of 1 ‐NCCH₃ (0.39) > 1 ‐OOCCF₃ (0.13) > 1 ‐N₃ (?0.05 V). Rate constants of electron transfer from ferrocene derivatives to 1 ‐X were analyzed in light of the Marcus theory of electron transfer to determine reorganization energies (λ) of electron transfer. The λ values decrease in the order of 1 ‐NCCH₃ (2.37) > 1 ‐OOCCF₃ (2.12) > 1 ‐N₃ (1.97 eV). Thus, the electron‐transfer reduction becomes less favorable thermodynamically but more favorable kinetically with increasing donor ability of the axial ligands. The net effect of the axial ligands is the deceleration of the electron‐transfer rate in the order of 1 ‐NCCH₃ > 1 ‐OOCCF₃ > 1 ‐N₃. In sharp contrast to this, the rates of the proton‐coupled electron‐transfer reactions of 1 ‐X are markedly accelerated in the presence of an acid in the opposite order: 1 ‐NCCH₃ < 1 ‐OOCCF₃ < 1 ‐N₃. Such contrasting effects of the axial ligands on the electron‐transfer and proton‐coupled electron‐transfer reactions of nonheme oxoiron(IV) complexes are discussed in light of the counterintuitive reactivity patterns observed in the oxo transfer and hydrogen‐atom abstraction reactions by nonheme oxoiron(IV) complexes (Sastri et al. Proc. Natl. Acad. Sci. U.S.A. 2007 , 104, 19 181–19 186).     

Conformational analysis of the disaccharide methyl α‐d‐mannopyranosyl‐(1→3)‐2‐O‐acetyl‐β‐d‐mannopyranoside monohydrate

The crystal structure of methyl α‐d ‐mannopyranosyl‐(1→3)‐2‐O‐acetyl‐β‐d ‐mannopyranoside monohydrate, C₁₅H₂₆O₁₂·H₂O, ( II ), has been determined and the structural parameters for its constituent α‐d ‐mannopyranosyl residue compared with those for methyl α‐d ‐mannopyranoside. Mono‐O‐acetylation appears to promote the crystallization of ( II ), inferred from the difficulty in crystallizing methyl α‐d ‐mannopyranosyl‐(1→3)‐β‐d ‐mannopyranoside despite repeated attempts. The conformational properties of the O‐acetyl side chain in ( II ) are similar to those observed in recent studies of peracetylated mannose‐containing oligosaccharides, having a preferred geometry in which the C2—H2 bond eclipses the C=O bond of the acetyl group. The C2—O2 bond in ( II ) elongates by ～0.02 Å upon O‐acetylation. The phi (?) and psi (ψ) torsion angles that dictate the conformation of the internal O‐glycosidic linkage in ( II ) are similar to those determined recently in aqueous solution by NMR spectroscopy for unacetylated ( II ) using the statistical program MA′AT, with a greater disparity found for ψ (Δ = ～16°) than for ? (Δ = ～6°).     

Chemical synthesis of poly‐γ‐glutamic acid by polycondensation of γ‐glutamic acid dimer: Synthesis and reaction of poly‐γ‐glutamic acid methyl ester

α‐Methyl glutamic acid (L ‐L )‐, (L ‐D )‐, (D ‐L )‐, and (D ‐D )‐γ‐dimers were synthesized from L ‐ and D ‐glutamic acids, and the obtained dimers were subjected to polycondensation with 1‐(3‐dimethylaminopropyl)‐3‐ethylcarbodiimide hydrochloride and 1‐hydroxybenzotriazole hydrate as condensation reagents. Poly‐γ‐glutamic acid (γ‐PGA) methyl ester with the number‐average molecular weights of 5000∼20,000 were obtained by polycondensation in N,N‐dimethylformamide in 44∼91% yields. The polycondensation of (L ‐L )‐ and (D ‐D )‐dimers afforded the polymers with much larger |[α]_D | compared with the corresponding dimers. The polymer could be transformed into γ‐PGA by alkaline hydrolysis or transesterification into α‐benzyl ester followed by hydrogenation. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 732–741, 2001     

Chemical Synthesis of Burkholderia Lipid A Modified with Glycosyl Phosphodiester‐Linked 4‐Amino‐4‐deoxy‐β‐L‐arabinose and Its Immunomodulatory Potential

Modification of the Lipid A phosphates by positively charged appendages is a part of the survival strategy of numerous opportunistic Gram‐negative bacteria. The phosphate groups of the cystic fibrosis adapted Burkholderia Lipid A are abundantly esterified by 4‐amino‐4‐deoxy‐β‐L ‐arabinose (β‐L ‐Ara4N), which imposes resistance to antibiotic treatment and contributes to bacterial virulence. To establish structural features accounting for the unique pro‐inflammatory activity of Burkholderia LPS we have synthesised Lipid A substituted by β‐L ‐Ara4N at the anomeric phosphate and its Ara4N‐free counterpart. The double glycosyl phosphodiester was assembled by triazolyl‐tris‐(pyrrolidinyl)phosphonium‐assisted coupling of the β‐L ‐Ara4N H‐phosphonate to α‐lactol of β(1→6) diglucosamine, pentaacylated with (R)‐(3)‐acyloxyacyl‐ and Alloc‐protected (R)‐(3)‐hydroxyacyl residues. The intermediate 1,1′‐glycosyl‐H‐phosphonate diester was oxidised in anhydrous conditions to provide, after total deprotection, β‐L ‐Ara4N‐substituted Burkholderia Lipid A. The β‐L ‐Ara4N modification significantly enhanced the pro‐inflammatory innate immune signaling of otherwise non‐endotoxic Burkholderia Lipid A.     

cis‐trans Peptide‐Bond Isomerization in α‐Methylproline Derivatives

α‐Methyl‐L ‐proline is an α‐substituted analog of proline that has been previously employed to constrain prolyl peptide bonds in a trans conformation. Here, we revisit the cis‐trans prolyl peptide bond equilibrium in derivatives of α‐methyl‐L ‐proline, such as N‐Boc‐protected α‐methyl‐L ‐proline and the hexapeptide H‐Ala‐Tyr‐αMePro‐Tyr‐Asp‐Val‐OH. In Boc‐α‐methyl‐L ‐proline, we found that both cis and trans conformers were populated, whereas, in the short peptide, only the trans conformer was detected. The energy barrier for the cis‐trans isomerization in Boc‐α‐methyl‐L ‐proline was determined by line‐shape analysis of NMR spectra obtained at different temperatures and found to be 1.24 kcal/mol (at 298 K) higher than the corresponding value for Boc‐L ‐proline. These findings further illuminate the conformationally constraining properties of α‐methyl‐L ‐proline.     

Expression,Purification and Characterization of a Bifunctional α‐L‐Arabinofuranosidase/β‐D‐Xylosidase from Trichoderma Koningii G‐39

A gene of α‐L ‐arabinofuranosidase (Abf) from Trichoderma koningii G‐39 was successfully expressed in Pichia pastoris. The recombinant enzyme was purified to > 90% homogeneity by a cation‐exchanged chromatography. The purified enzyme exhibits both α‐L ‐arabinofuranosidase and β‐D ‐xylosidase (Xyl) activities with p‐nitrophenyl‐α‐L ‐arabionfuranoside (pNPAF) and 2,4‐dinitrophenyl‐β‐D ‐xylopyanoside (2,4‐DNPX) as substrate, respectively. The stability and the catalytic feature of the bifunctional enzyme were characterized. The enzyme was stable for at least 2 h at pH values between 2 and 8.3 at room temperature when assayed for Abf and Xyl activities. Enzyme activity decreased dramatically when the pH exceeded 9.5 or dropped below 1.5. The enzyme lost 35% of Abf activity after incubation at 55 °C for 2 h, but retained 95% of Xyl activity, with 2,4‐DNXP as substrate, under the same conditions. Further investigation of the active site topology of both enzymatic functions was performed with the inhibition study of enzyme activities. The results revealed that methyl‐α‐L ‐arabinofuranoside inhibition is noncompetitive towards 2,4‐DNPX as substrate but competitive towards pNPAF. Based on the thermal stability and the inhibition studies, we suggest that the enzymatic reactions of Abf and Xyl are performed at distinct catalytic sites. The recombinant enzyme possesses both the retaining transarabinofuranosyl and transxylopyranosyl activities, indicating both enzymatic reactions proceed through a two‐step, double displacement mechanism.     

Accumulation of methylglyoxal and d‐lactate in Pb‐induced nephrotoxicity in rats

Lead (Pb) is an environmental pollutant associated with several diseases, such as nephrotoxicity. Methylglyoxal (MG) is a reactive dicarbonyl compound formed during glycolysis and reported to increase in kidney damage. Metformin is used as an MG scavenger in the clinic. In this study, we investigated the mechanism of Pb‐induced renal injury and the effect of metformin on Pb‐induced nephrotoxicity. Eighteen Wistar rats were randomly divided into three groups: control, Pb, and Pb + metformin groups. Pb (250 ppm) was administered in drinking water, and 50 mg/kg of metformin was co‐administered orally. After 28 days, the levels of MG and its metabolite d ‐lactate in urine, serum and renal tissues were examined. The elevation of renal MG (56.86 ± 17.47 vs 36.40 ± 5.69, p < 0.01) and urinary d ‐lactate (0.68 ± 0.28 vs 0.32 ± 0.13, p < 0.01) was observed in Pb‐exposed rats compared with those in control rats. After co‐treatment with metformin, these phenomena were attenuated. In the present study, it was demonstrated for the first time that urinary d ‐lactate might serve as the candidate marker for Pb‐induced nephrotoxicity in the clinic, and metformin might be a new therapeutic candidate for Pb poisoning.     

Convenient synthesis of poly(γ‐benzyl‐L‐glutamate) from activated urethane derivatives of γ‐benzyl‐L‐glutamate

A series of activated urethane‐type derivatives of γ‐benzyl‐L ‐glutamate were synthesized, and their potential as monomers for polypeptide synthesis was investigated. The derivatives of the focus of this work were a series of N‐aryloxycarbonyl‐γ‐benzyl‐L ‐glutamate 1 , of which aryl groups were phenyl, 4‐chlorophenyl, and 4‐nitrophenyl. These urethanes 1 were reactive in polar solvents such as dimethylsulfoxide, N,N‐dimethylformamide (DMF), and N,N‐dimethylacetamide (DMAc), and were efficiently converted into poly(γ‐benzyl‐L ‐glutamate) (poly(BLG)) under mild conditions; at 60 °C without addition of any catalyst. Among the three urethanes, that having 4‐nitrophenoxycarbonyl group 1c was the most reactive to give poly(BLG) efficiently, as was expected from the highly electron deficient nature of the nitrophenoxycarbonyl group. On the other hand, the urethane 1a having phenoxycarbonyl group was also efficiently converted into poly(BLG), in spite of the intrinsically less electrophilicity of the phenoxycarbonyl group. In addition, the successful formation of poly(BLG) by the reaction of 1a favored its diluted concentration (0.1 M) much more than 2.0 M, the optimum initial concentration for 1c . ¹H NMR spectroscopic analyses of the reactions in situ revealed that the predominant pathway from 1 to poly(BLG) involved the intramolecular cyclization of 1 into the corresponding N‐carboxyanhydride, with release of phenol and its successive ring‐opening polymerization with release of carbon dioxide. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2649–2657, 2008     

Tragacanth gum‐based pH‐responsive magnetic hydrogels for “smart” chemo/hyperthermia therapy of solid tumors

The drug delivery performances of pH‐responsive magnetic hydrogels (MHs) composed of tragacanth gum (TG), poly(acrylic acid) (PAA), and Fe₃O₄ nanoparticles (NPs) were investigated in terms of physicochemical as well as biological features. The fabricated drug delivery systems (DDSs) were analyzed using Fourier transform infrared spectroscopy, X‐ray diffraction, vibrating sample magnetometer, scanning electron microscopy, and transmission electron microscopy. The synthesized MHs were loaded with doxorubicin hydrochloride (Dox) as a universal model anti‐cancer drug. The MHs showed excellent Dox loading and encapsulation efficiencies, mainly due to strong hydrogen bonding and electrostatic interaction between the drug and polymeric matrix, as well as porous micro‐structures of the fabricated MHs. The drug‐loaded MHs showed negligible drug release values in physiological condition. In contrast, in cancerous condition (pH 5.0), both MHs exhibited highest drug release values that qualified them as “smart” DDSs. The cytocompatibilities of the MHs as well as the cytotoxicity of the Dox‐loaded MHs were investigated against human epidermoid‐like carcinoma (Hela) cells through MTT assay. In addition, hyperthermia therapy induced by Fe₃O₄ NPs was applied to locally raise temperature inside the Hela cells at 45 ± 3°C to promote cell death. As a result, the Dox‐loaded MHs can be considered as potential DDSs for chemo/hyperthermia therapy of solid tumors.     

Synthesis and ring‐opening (co)polymerization of L‐lysine N‐carboxyanhydrides containing labile side‐chain protective groups

This contribution describes the synthesis and ring‐opening (co)polymerization of several L ‐lysine N‐carboxyanhydrides (NCAs) that contain labile protective groups at the ?‐NH₂ position. Four of the following L ‐lysine NCAs were investigated: N^?‐trifluoroacetyl‐L ‐lysine N‐carboxyanhydride, N^?‐(tert‐butoxycarbonyl)‐L ‐lysine N‐carboxyanhydride, N^?‐(9‐fluorenylmethoxycarbonyl)‐L ‐lysine N‐carboxyanhydride, and N^?‐(6‐nitroveratryloxycarbonyl)‐L ‐lysine N‐carboxyanhydride. In contrast to the harsh conditions that are required for acidolysis of benzyl carbamate moieties, which are usually used to protect the ?‐NH₂ position of L ‐lysine during NCA polymerization, the protective groups of the L ‐lysine NCAs presented here can be removed under mildly acidic or basic conditions or by photolysis. As a consequence, these monomers may allow access to novel peptide hybrid materials that cannot be prepared from ?‐benzyloxycarbonyl‐L ‐lysine N‐carboxyanhydride (Z‐Lys NCA) because of side reactions that accompany the removal of the Z groups. By copolymerization of these L ‐lysine NCAs with labile protective groups, either with each other or with γ‐benzyl‐L ‐glutamate N‐carboxyanhydride or Z‐Lys NCA, orthogonally side‐chain‐protected copolypeptides with number‐average degrees of polymerization ≤20 were obtained. Such copolypeptides, which contain different side‐chain protective groups that can be removed independently, are interesting for the synthesis of complex polypeptide architectures or can be used as scaffolds for the preparation of synthetic antigens or protein mimetics. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1167–1187, 2003     

Huangqiyenins G – J,Four New 9,10‐Secocycloartane (=9,19‐Cyclo‐9,10‐secolanostane) Triterpenoidal Saponins from Astragalus membranaceus Bunge Leaves

Four new 9,10‐secocycloartane (=9,19‐cyclo‐9,10‐secolanostane) triterpenoidal saponins, named huangqiyenins G–J ( 1 – 4 , resp.), were isolated from Astragalus membranaceus Bunge leaves. The acid hydrolysis of 1 – 4 with 1M aqueous HCl yielded D ‐glucose, which was identified by GC analysis after treatment with L ‐cysteine methyl ester hydrochloride. The structures of 1 – 4 were established by detailed spectroscopic analysis as (3β,6α,10α,16β,24E)‐3,6‐bis(acetyloxy)‐10,16‐dihydroxy‐12‐oxo‐9,19‐cyclo‐9,10‐secolanosta‐9(11),24‐dien‐26‐yl β‐D ‐glucopyranoside ( 1 ), (3β,6a,10α,24E)‐3,6‐bis(acetyloxy)‐10‐hydroxy‐12,16‐dioxo‐9,19‐cyclo‐9,10‐secolanosta‐9(11),24‐dien‐26‐yl β‐D ‐glucopyranoside ( 2 ), (3β,6α,9α,10α,16β,24E)‐3,6‐bis(acetyloxy)‐9,10,16‐trihydroxy‐9,19‐cyclo‐9,10‐secolanosta‐11,24‐dien‐26‐yl β‐D ‐glucopyranoside ( 3 ), and (3β,6α,10α,24E)‐3,6‐bis(acetyloxy)‐10‐hydroxy‐16‐oxo‐9,19‐cyclo‐9,10‐secolanosta‐9(11),24‐dien‐26‐yl β‐D ‐glucopyranoside ( 4 ).     

Furostane‐Type Steroidal Saponins from the Roots of Chlorophytum borivilianum

Four new furostanol steroid saponins, borivilianosides A–D ( 1 – 4 , resp.), corresponding to (3β,5α,22R,25R)‐26‐(β‐D ‐glucopyranosyloxy)‐22‐hydroxyfurostan‐3‐yl O‐β‐D ‐xylopyranosyl‐(1→3)‐O‐β‐D ‐glucopyranosyl‐(1→4)‐O‐[α‐L ‐rhamnopyranosyl‐(1→2)]‐β‐D ‐galactopyranoside ( 1 ), (3β,5α,22R,25R)‐ 26‐(β‐D ‐glucopyranosyloxy)‐22‐methoxyfurostan‐3‐yl O‐β‐D ‐xylopyranosyl‐(1→3)‐O‐β‐D ‐glucopyranosyl‐(1→4)‐O‐[α‐L ‐rhamnopyranosyl‐(1→2)]‐β‐D ‐galactopyranoside ( 2 ), (3β,5α,22R,25R)‐26‐(β‐D ‐glucopyranosyloxy)‐22‐methoxyfurostan‐3‐yl O‐β‐D ‐xylopyranosyl‐(1→3)‐O‐[β‐D ‐glucopyranosyl‐(1→2)]‐O‐β‐D ‐glucopyranosyl‐(1→4)‐β‐D ‐galactopyranoside ( 3 ), and (3β,5α,25R)‐26‐(β‐D ‐glucopyranosyloxy)furost‐20(22)‐en‐3‐yl O‐β‐D ‐xylopyranosyl‐(1→3)‐O‐[β‐D ‐glucopyranosyl‐(1→2)]‐O‐β‐D ‐glucopyranosyl‐(1→4)‐β‐D ‐galactopyranoside ( 4 ), together with the known tribuluside A and (3β,5α,22R,25R)‐26‐(β‐D ‐glucopyranosyloxy)‐22‐methoxyfurostan‐3‐yl O‐β‐D ‐xylopyranosyl‐(1→2)‐O‐[β‐D ‐xylopyranosyl‐(1→3)]‐O‐β‐D ‐glucopyranosyl‐(1→4)‐O‐[α‐L ‐rhamnopyranosyl‐(1→2)]‐β‐D ‐galactopyranoside were isolated from the dried roots of Chlorophytum borivilianum Sant and Fern . Their structures were elucidated by 2D ‐NMR analyses (COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry.