Distinct regulation of two flagella by calcium during chemotaxis of male gametes in the brown alga Mutimo cylindricus (Cutleriaceae, Tilopteridales)

Brown algal male gametes show chemotaxis to the sex pheromone that is released from female gametes. The chemotactic behavior of the male gametes is controlled by the changes in the beating of two flagella known as the anterior and posterior flagellum. Our previous study using Mutimo cylindricus showed that the sex pheromone induced an increment in both the deflection angle of the anterior flagellum and sustained unilateral bend of the posterior flagellum, but the mechanisms regulating these two flagellar waveforms were not fully revealed. In this study, we analyzed the changes in swimming path and flagellar waveforms with a high-speed recording system under different calcium conditions. The extracellular Ca2+ concentration at 10-3 M caused an increment in the deflection angle of the anterior flagellum only when ionomycin was absent. No sustained unilateral bend of the posterior flagellum was induced either in the absence or presence of ionomycin in extracellular Ca2+ concentrations below 10-2 M. Real-time Ca2+ imaging revealed that there is a spot near the basal part of anterior flagellum showing higher Ca2+ than in the other parts of the cell. The intensity of the spot slightly decreased when male gametes were treated with the sex pheromone. These results suggest that Ca2+-dependent changes in the anterior and posterior flagellum are regulated by distinct mechanisms and that the increase in the anterior flagellar deflection angle and sustained unilateral bend of the posterior flagellum may not be primarily induced by the Ca2+ concentration.

Syntheses and Biological Activities of Danicalipin A Derivatives

Synthesis of three derivatives of danicalipin A, tetrachloride, trisulfate and a fluorescent probe was achieved through Wittig reaction strategy. Toxicity of the derivatives against brine shrimp (Artemia salina) as also investigated to provide useful information for the biological activity; i) less chloride derivative showed similar toxicity to danicalipin A, ii) the amphiphilic property, a characteristic feature of danicalipin A, was crucial because trisulfate considerably decreased the toxicity and iii) fluorescent derivative kept brine shrimp toxicity of danicalipin A.

Scope and limitations of absolute configuration determination of allenic natural products using the CCC stretching VCD signal

The allene functional group in natural products isolated so far exists in a non-racemic form, but its axial chirality is difficult to elucidate. Allenes exhibit a characteristic antisymmetric CCC stretching mode at around 1950 cm^-1, and their VCD properties have not been studied in detail. This work, for the first time, applied VCD spectroscopy to allenic natural products and allenic molecules with other asymmetric centers focusing on the antisymmetric CCC stretching mode. This vibrational mode yielded a negligibly weak VCD signal for several molecules, but in the presence of electron-withdrawing and/or conjugating substituents, it generated a stronger one. Its sign was found to be influenced by the nature of substituents. These findings should deepen the understanding of the VCD properties of the allene functional group and should be useful for future studies of chiral allenes.

Nostosin G and Spiroidesin B from the Cyanobacterium Dolichospermum sp. NIES-1697

Chemical investigation of the cyanobacterium Dolichospermum sp. NIES-1697 afforded nostosin G (1), a linear tripeptide, spiroidesin B (2), and two known compounds, anabaenopeptins I (3) and J (4). Planar structures and absolute configurations for 1 and 2 were determined by 2D NMR, HRMS, Marfey's methodology, chiral-phase HPLC, and enzymatic degradation. Nostosin G (1) is a unique example of a linear peptide containing three subunits, 4-hydroxyphenyllactic acid (Hpla), homotyrosine (Hty), and argininal, with potent trypsin inhibitory properties. The biosynthetic gene clusters for nostosin G (1) and spiroidesin B (2) were investigated based on the genome sequence of Dolichospermum sp. NIES-1697.

Efficient synthesis of α,β-dichlorinated ketones from α,β-dichlorinated Weinreb amides through a simple work-up procedure

An efficient synthesis of α,β-dichlorinated ketones from α,β-dichlorinated Weinreb amides is described. Quenching with nonaqueous HCl avoided side reactions associated with typical work-up procedures. The amide reacted with various nucleophiles to give the corresponding ketones in high yields. A novel reactivity of the Weinreb amide is also discussed.

Assignment of Absolute Configuration of Bromoallenes by Vacuum-Ultraviolet Circular Dichroism (VUVCD)

A new application of vacuum-ultraviolet circular dichroism (VUVCD), which enables the measurement of CD spectra in the vacuum-ultraviolet region (140–200 nm), for the assignment of the absolute configurations of bromoallenes is described. Bromoallene moieties are found in natural products obtained from many marine organisms. To date, the absolute configuration of bromoallenes has been assigned almost exclusively with Lowe’s rule, which is based on specific rotation. However, exceptions to Lowe’s rule have been reported arising from the presence of other substituents with large specific rotations. For the unambiguous assignment of the absolute configuration of the bromoallene moiety with its characteristic absorption wavelength at 180–190 nm due to the π–π* transition, VUVCD was applied to four pairs of bromoallene diastereomers prepared by modifying the synthetic scheme of omaezallene. The VUVCD spectra clearly showed positive or negative Cotton effects around 180–190 nm according to the configuration of the bromoallene employed, revealing the potential of VUVCD for determining absolute stereochemistry.

Biosurfactants from Marine Cyanobacteria Collected in Sabah, Malaysia

Chemical investigation of the organic extract from Moorea bouillonii, collected in Sabah, Malaysia, led to the isolation of three new chlorinated fatty acid amides, columbamides F (1), G (2), and H (3). The planar structures of 1-3 were established by a combination of mass spectrometric and NMR spectroscopic analyses. The absolute configuration of 1 was determined by Marfey's analysis of its hydrolysate and chiral-phase HPLC analysis after conversion and esterification with Ohrui's acid, (1S,2S)-2-(anthracene-2,3-dicarboximido)cyclohexanecarboxylic acid. Compound 1 showed biosurfactant activity by an oil displacement assay. Related known fatty acid amides columbamide D and serinolamide C exhibited biosurfactant activity with critical micelle concentrations of about 0.34 and 0.78 mM, respectively.

Neighboring Effect of Intramolecular Chlorine Atoms on Epoxide Opening Reaction by Chloride Anions

We investigated the diastereoselectivity of ring openings for chloro vinyl epoxides with various chlorination reagents. In the chlorinolysis reactions using vinyl epoxides having an allyl alcohol, inversion:retention ratios varied depending on the chloride sources. In limited cases, the increase in retention ratio was consistent with the intervention of chloronium ions. In contrast, all vinyl epoxides bearing an α,β-unsaturated ester gave only the inversion products. These results suggest the electron-withdrawing property suppressed the chloronium ions.

A brown algal sex pheromone reverses the sign of phototaxis by cAMP/Ca2+-dependent signaling in the male gametes of Mutimo cylindricus (Cutleriaceae)

Male gametes of the brown alga Mutimo cylindricus show positive phototaxis soon after spawning in seawater but gradually change the sign of phototaxis with time. This conversion appears to need the decrease of intracellular Ca2+ concentration. In this study, we revealed that the conversion of male gamete phototactic sign, positive to negative, was accelerated by mixing with female gametes. The supernatant after the centrifugation of female gamete suspension showed the same activity to change the phototactic sign, suggesting that a factor released from female gametes was responsible for the reaction. A known brown algal sex pheromone, ectocarpene, induced chemotaxis of male gametes of M. cylindricus. The addition of this compound induced the change of phototactic sign, clearly indicating that a sex pheromone is essential for the reversal. An inhibitor of phosphodiesterase, theophylline, inhibited the chemotaxis and phototactic sign reversion by a factor released from female gametes and ectocarpene. Measurements of cyclic nucleotides showed that the increase in intracellular concentration of cAMP, not cGMP, was parallel to the change of phototactic sign. The inhibition of phototactic sign by theophylline was not observed in low Ca2+ sea water. These results suggest that a signaling pathway mediated by cAMP and Ca2+ concentrations drives the interconversion between two important behaviors of male gametes, phototaxis and chemotaxis.

Expression analysis of cellulose synthases that comprise the Type II complex in hybrid aspen

Gene duplication in plants occurs via several different mechanisms, including whole genome duplication, and the copied genes acquire various forms and types. The cellulose synthase (CesA) family functions in cellulose synthesis complex (CSC) formation, which is involved in the synthesis of primary and secondary cell walls in plants. In the genome of Populus, 17 CesA have been annotated, and some of them appeared through whole genome duplication. The nucleotide sequence of the duplicated genes changed during subsequent evolution, and functional differentiation of genes might have occurred. To gain insight into the evolutionary fate of the duplicated CesA, expression analysis with quantitative reverse transcription polymerase chain reactions and promoter-reporter assays was performed on three duplicated gene pairs whose products have been reported to form a single CSC. Changes in expression of each gene at different developmental stages were detected and divergent expression patterns in different organs and tissues observed between the gene pairs. Among the tested genes, expression of PttCesA3-C was apparently lower than that of its counterpart, PttCesA3-D. The results suggest that the six CesA are approaching sub-functionalisation or non-functionalisation. Furthermore, the level of functionalisation may vary among the three pairs of genes, and functional specialisation of each CesA should have been achieved, at least partially, through differences in expression of genes.

Synthesis and Structure-Activity Relationship of Omaezallene Derivatives

Omaezallene derivatives (nor-bromoallene, nor-bromodiene, and bromoenynes) were successfully synthesized. Their antifouling activity and toxicity to the cypris larvae of the barnacle Amphibalanus amphitrite and ecotoxicity to the marine crustacean Tigriopus japonicus were studied. It was revealed that the two side chains of omaezallene were essential to its antifouling activity because the activities of nor-bromoallene and nor-bromodiene were significantly diminished. The bromoenyne was found to exhibit potent antifouling activities comparable to omaezallene with low toxicity and ecotoxicity. Preparation of bromoenyne framework is much easier than that of bromodiene moiety in omaezallene. Based on the antifouling activities of the bromoenynes, the synthesis of fluorescent probes and evaluation of their biological activities were also carried out.

Antioxidants from the Brown Alga Dictyopteris undulata

An investigation of anti-oxidative compounds from the brown alga Dictyopteris undulata has led to the isolation and identification of isozonarol, isozonarone, chromazonarol, zonaroic acid and isozonaroic acid. Their structures were identified by comparison of MS and NMR spectra. Full NMR assignment and absolute configuration of isozonaroic acid are described. Isozonarol showed the most potent 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity among the compounds isolated.

Total synthesis and biological activity of dolastatin 16

The total synthesis of dolastatin 16, a macrocyclic depsipeptide first isolated from the sea hare Dolabella auricularia as a potential antineoplastic metabolite by Pettit et al., was achieved in a convergent manner. Dolastatin 16 was reported by Tan to exhibit strong antifouling activity, and thus shows promise for inhibiting the attachment of marine benthic organisms such as Amphibalanus amphitrite to ships and submerged artificial structures. Therefore, dolastatin 16 is a potential compound for a new, environmentally friendly antifouling material to replace banned tributyltin-based antifouling paints. The synthesis of dolastatin 16 involved the use of prolinol to prevent formation of a diketopiperazine composed of l-proline and N-methyl-d-valine during peptide coupling. This strategy for the elongation of peptide chains allowed the efficient and scalable synthesis of one segment, which was subsequently coupled with a second segment and cyclized to form the macrocyclic framework of dolastatin 16. The synthetic dolastatin 16 exhibited potent antifouling activity similar to that of natural dolastatin 16 toward cypris larvae of Amphibalanus amphitrite.

Serinolamides and Lyngbyabellins from an Okeania sp. Cyanobacterium Collected from the Red Sea

NMR- and MS-guided fractionation of an extract of an Okeania sp. marine cyanobacterium, collected from the Red Sea, led to the isolation of four new metabolites, including serinolamides C (1) and D (2) and lyngbyabellins O (3) and P (4), together with the three known substances lyngbyabellins F (5) and G (6) and dolastatin 16 (7). The planar structures of the new compounds were determined using NMR and MS analyses. The absolute configurations of 1 and 2 were determined by Marfey's analysis of their hydrolysates. The absolute configuration of 3 was ascertained by chiral-phase chromatography of degradation products, while that of 4 was determined by comparison to 3 and 5. The cytotoxic and antifouling activities of these compounds were evaluated using MCF7 breast cancer cells and Amphibalanus amphitrite larvae, respectively. Compounds 3, 4, and 7 exhibited strong antifouling activity, and 3 and 7 were not cytotoxic. A structure-activity relationship was observed for the cytotoxicity of the lyngbyabellins with the presence of a side chain (4 is more active than 3) leading to greater activity. For the antifouling activity, the acyclic form without a side chain (3) was the most active.

Total synthesis of (-)-kainic acid and (+)-allo-kainic acid through SmI2-mediated intramolecular coupling between allyl chloride and an α,β-unsaturated ester

A 3,4-disubstituted pyrrolidine ring was effectively cyclized through SmI₂-mediated reductive coupling between allyl chloride and an α,β-unsaturated ester, although little has been reported about SmI₂-promoted C-C bond formation of an allyl chloride with an α,β-unsaturated ester. Selection of either the 3,4-cis- or 3,4-trans-selective cyclization can be accomplished simply by changing the additives from NiI₂ to HMPA during reductive cyclization conducted in H₂O-THF. Total synthesis of (-)-kainic acid and (+)-allo-kainic acid, which are pyrrolidine alkaloids used in neuroscience and neuropharmacology as useful molecular probes, was successfully achieved by using the stereo-complementary ring closure reactions promoted by SmI₂ for the construction of the 2,3,4-trisubsituted pyrrolidine scaffold of kainoids.

cDNA cloning and characterization of vanadium-dependent bromoperoxidases from the red alga Laurencia nipponica

The marine red alga genus Laurencia is one of the richest producers of unique brominated compounds in the marine environment. The cDNAs for two Laurencia nipponica vanadium-dependent bromoperoxidases (LnVBPO1 and LnVBPO2) were cloned and expressed in Escherichia coli. Enzyme assays of recombinant LnVBPO1 and LnVBPO2 using monochlorodimedone revealed that they were thermolabile but their Km values for Br− were significantly lower than other red algal VBPOs. The bromination reaction was also assessed using laurediol, the predicted natural precursor of the brominated ether laurencin. Laurediol, protected by trimethylsilyl at the enyne, was converted to deacetyllaurencin by the LnVBPOs, which was confirmed by tandem mass spectrometry. Native LnVBPO partially purified from algal bodies was active, suggesting that LnVBPO is functional in vivo. These results contributed to our knowledge of the biosynthesis of Laurencia brominated metabolites.

Omaezallene from red alga Laurencia sp.: structure elucidation, total synthesis, and antifouling activity

Natural antifouling products have been the subject of considerable attention. We screened marine algae for antifouling activity and discovered omaezallenes, the new bromoallene-containing natural products isolated from the red alga Laurencia sp. Described is the isolation, structure elucidation, and total syntheses of omaezallenes. The relative and absolute configurations of natural omaezallenes were unambiguously established through total synthesis. The antifouling activities and ecotoxicity of omaezallenes were also evaluated.

Confirmation of the configuration of 10-isothiocyanato-4-cadinene diastereomers through synthesis

The marine sponge metabolite 10-isothiocyanato-4-cadinene (1) was first isolated by Garson et al. from Acanthella cavernosa in 2000. The same structure 1 was later reported by Wright et al. from the nudibranch Phyllidiella pustulosa and its sponge diet, but with different NMR data. The syntheses of both enantiomers of 1 were accomplished through the isothiocyanation of 10-isocyano-4-cadinene (2) previously synthesized by our group. The correct spectroscopic data and specific rotation value of the structure 1 were determined on the basis of the syntheses. The NMR data of synthetic 1 matched those of the isothiocyanate isolated by Garson and differed from those reported by Wright. The spectroscopic data and specific rotation values of 10-epi-10-isothiocyanato-4-cadinene (6) and di-1,6-epi-10-isothiocyanato-4-cadinene (8) were also established through the syntheses of these diastereomers. Structure 6 has been reported as a natural product by Mitome et al., but the NMR data for the synthetic sample of 6 differ from those of the natural isolate.

Thrombin inhibitors from the freshwater cyanobacterium Anabaena compacta

Bioassay-guided investigation of the cyanobacterium Anabaena compacta extracts afforded spumigin J (1) and the known thrombin inhibitor spumigin A (2). The absolute configuration of 1 was analyzed by advanced Marfey's methodology. Compounds 1 and 2 inhibited thrombin with EC(50) values of 4.9 and 2.1 μM, and 0.7 and 0.2 μM in the cathepsin B inhibitory assay, respectively. The MM-GBSA methodology predicted spumigin A with 2S-4-methylproline as the better thrombin inhibitor.

Synthesis and biological activity of kalkitoxin and its analogues

Total syntheses of kalkitoxin, isolated from the Caribbean Lyngbya majuscula, and its analogues, 3-epi-, 7-epi-, 8-epi-, 10-epi-, 10-nor-, and 16-nor-kalkitoxin, were achieved via oxazolidinone-based diastereoselective 1,4-addition reaction of a methyl group and efficient TiCl(4)-mediated thiazoline ring formation as the key steps. The biological activities of synthetic kalkitoxin and its analogues were evaluated with brine shrimp.

Total synthesis of 10-isocyano-4-cadinene and its stereoisomers and evaluations of antifouling activities

The first enantioselective total synthesis of 10-isocyano-4-cadinene, a marine sesquiterpene isolated from nudibranchs of the family Phyllidiidae, and determination of its absolute stereochemistry were achieved. 10-Isocyano-4-cadinene is expected to be a novel nontoxic antifouling agent. In the synthesis, intermolecular Diels-Alder reaction and samarium diiodide induced Barbier-type cyclization were employed as key steps. The absolute configuration of 10-isocyano-4-cadinene was determined as (1S,6S,7R,10S) by comparison of the optical rotations between natural and synthetic samples. In addition, the authors successfully synthesized 10-epi- and di-1,6-epi-10-isocyano-4-cadinene through the same synthetic pathway. Antifouling activities against Balanus amphitrite with the cadinenes were also evaluated.

Asymmetric total synthesis of danicalipin A and evaluation of biological activity

Asymmetric total synthesis of danicalipin A was achieved. The synthesis was characterized by diastereoselective introduction of chlorine atoms. Biological activities with synthetic danicalipin A, its enantiomer, and racemate were also evaluated toward brine shrimp. Both enantiomers of danicalipin A showed almost the same activity.

Synthesis of the QRSTU domain of maitotoxin and its 85-epi- and 86-epi-diastereoisomers

A devised synthetic strategy toward the QRSTU ring system 4 of the marine-derived biotoxin maitotoxin (1) delivered, in addition to 4, its diastereoisomers 85-epi-QRSTU and 86-epi-QRSTU ring systems 5 and 6. The convergent route to these maitotoxin fragments involved coupling of UT and Q building blocks 9 (obtained from 2-deoxy-D-ribose) and 10 (obtained from D-ribose) followed by ring-closing metathesis to afford enol ether 8, whose elaboration to the targeted QRSTU ring system 4 required its conversion to hydroxy ketone 7. The latter compound (7) was transformed to the final product through a hydroxy dithioketal cyclization, followed by oxidation/methylation of the resulting O,S-mixed ketal to install the last of the five methyl groups contained within the target molecule (4). (13)C NMR spectroscopic analysis of synthesized fragments 4, 5, and 6 and comparisons with maitotoxin provided strong support for the originally assigned structure of the QRSTU domain of the natural product.

Chemical Synthesis of the GHIJKLMNO Ring System of Maitotoxin

As the largest secondary metabolite to be discovered as of yet, the polyether marine neurotoxin maitotoxin constitutes a major structural and synthetic challenge. After its originally proposed structure ( 1) had been questioned on the basis of biosynthetic considerations, we provided computational and experimental support for structure 1. In an effort to provide stronger experimental evidence of the molecular architecture of maitotoxin, its GHIJKLMNO ring system 3 was synthesized. The (13)C NMR chemical shifts of synthetic 3 matched closely those corresponding to the same domain of the natural product providing strong evidence for the correctness of the originally proposed structure of maitotoxin ( 1).

Total Synthesis of (−)-5,6,11-Trideoxytetrodotoxin and Its 4-Epimer

[reaction: see text] The first total synthesis of 5,6,11-trideoxytetrodotoxin (1) and its 4-epimer were achieved. The synthesis is characterized by the stereoselective construction of the quaternary amino carbon center at C8a by an asymmetric transferring Strecker synthesis and the highly efficient conversion of cyanohydrin 4 to 1 via intramolecular cyclization reactions.

A case of undifferentiated glioma in a 70-year-old woman

The present case involved a 70-year-old woman who was diagnosed with a right cerebral hemorrhage. Excisional surgery of the hematoma was performed. Grossly, a whitish, solid tumor (1 x 1 x 0.8 cm in size) was recognized in the hematoma. Histologically, the tumor was composed of large, polygonal cells and small undifferentiated cells in a jumbled architectural arrangement with a cartilage component. The large, polygonal cell component was conspicuous and somewhat rhabdoid in appearance and appeared to be an astrocytic tumor showing glial differentiation. The small, undifferentiated cell component resembled tumor cells of a primitive neuroectodermal tumor (PNET). Clinical follow-up of the patient for 2 months after the first operation revealed recurrence with rapid growth. A second operation was performed, but the patient died 8 months after the first operation (2 months after the second). Immunohistochemically, the tumor cells suggesting glial differentiation were positive for glial fibrillary acidic protein (GFAP), S-100, neuron-specific enolase (NSE), and vimentin. PNET-like components in the primary tumor were positive for NSE, GFAP, and S-100, and weakly positive for vimentin and synaptophysin. Each tumor cell was negative for epithelial membrane antigen (EMA), keratin, desmin, actin, myoglobin, neurofilament (NF), and MIC2 protein. The recurrent tumor revealed predominantly PNET-like components; however, only a few tumor cells were positive for GFAP. This appearance suggested that this brain tumor might originate from a common multipotential stem cell. Considering its histopathological and immunohistochemical characteristics, the primary tumor was finally regarded as an undifferentiated glioma with dedifferentiation of the glial component in the recurrent tumor.

Progress of lignification mediated by intercellular transportation of monolignols during tracheary element differentiation of isolated Zinnia mesophyll cells

Tracheary element (TE) differentiation is a typical example of programmed cell death (PCD) in higher plants, and maturation of TEs is completed by degradation of all cell contents. However, lignification of TEs progresses even after PCD. We investigated how and whence monolignols are supplied to TEs which have undergone PCD during differentiation of isolated Zinnia mesophyll cells into TEs. Higher densities of cell culture induced greater lignification of TEs. Whereas the continuous exchanging of culture medium suppressed lignification of TEs, further addition of coniferyl alcohol into the exchanging medium reduced the suppression of lignification. Analysis of the culture medium by HPLC and GC-MS showed that coniferyl alcohol, coniferaldehyde, and sinapyl alcohol accumulated in TE inductive culture. The concentration of coniferyl alcohol peaked at the beginning of secondary wall thickening, decreased rapidly during secondary wall thickening, then increased again. These results indicated that lignification on TEs progresses by supply of monolignols from not only TEs themselves but also surrounding xylem parenchyma-like cells through medium in vitro.

The last step of syringyl monolignol biosynthesis in angiosperms is regulated by a novel gene encoding sinapyl alcohol dehydrogenase

Cinnamyl alcohol dehydrogenase (CAD; EC 1.1.1.195) has been thought to mediate the reduction of both coniferaldehyde and sinapaldehyde into guaiacyl and syringyl monolignols in angiosperms. Here, we report the isolation of a novel aspen gene (PtSAD) encoding sinapyl alcohol dehydrogenase (SAD), which is phylogenetically distinct from aspen CAD (PtCAD). Liquid chromatography-mass spectrometry-based enzyme functional analysis and substrate level-controlled enzyme kinetics consistently demonstrated that PtSAD is sinapaldehyde specific and that PtCAD is coniferaldehyde specific. The enzymatic efficiency of PtSAD for sinapaldehyde was approximately 60 times greater than that of PtCAD. These data suggest that in addition to CAD, discrete SAD function is essential to the biosynthesis of syringyl monolignol in angiosperms. In aspen stem primary tissues, PtCAD was immunolocalized exclusively to xylem elements in which only guaiacyl lignin was deposited, whereas PtSAD was abundant in syringyl lignin-enriched phloem fiber cells. In the developing secondary stem xylem, PtCAD was most conspicuous in guaiacyl lignin-enriched vessels, but PtSAD was nearly absent from these elements and was conspicuous in fiber cells. In the context of additional protein immunolocalization and lignin histochemistry, these results suggest that the distinct CAD and SAD functions are linked spatiotemporally to the differential biosynthesis of guaiacyl and syringyl lignins in different cell types. SAD is required for the biosynthesis of syringyl lignin in angiosperms.

The last step of syringyl monolignol biosynthesis in angiosperms is regulated by a novel gene encoding sinapyl alcohol dehydrogenase

Cinnamyl alcohol dehydrogenase (CAD; EC 1.1.1.195) has been thought to mediate the reduction of both coniferaldehyde and sinapaldehyde into guaiacyl and syringyl monolignols in angiosperms. Here, we report the isolation of a novel aspen gene (PtSAD) encoding sinapyl alcohol dehydrogenase (SAD), which is phylogenetically distinct from aspen CAD (PtCAD). Liquid chromatography-mass spectrometry-based enzyme functional analysis and substrate level-controlled enzyme kinetics consistently demonstrated that PtSAD is sinapaldehyde specific and that PtCAD is coniferaldehyde specific. The enzymatic efficiency of PtSAD for sinapaldehyde was approximately 60 times greater than that of PtCAD. These data suggest that in addition to CAD, discrete SAD function is essential to the biosynthesis of syringyl monolignol in angiosperms. In aspen stem primary tissues, PtCAD was immunolocalized exclusively to xylem elements in which only guaiacyl lignin was deposited, whereas PtSAD was abundant in syringyl lignin-enriched phloem fiber cells. In the developing secondary stem xylem, PtCAD was most conspicuous in guaiacyl lignin-enriched vessels, but PtSAD was nearly absent from these elements and was conspicuous in fiber cells. In the context of additional protein immunolocalization and lignin histochemistry, these results suggest that the distinct CAD and SAD functions are linked spatiotemporally to the differential biosynthesis of guaiacyl and syringyl lignins in different cell types. SAD is required for the biosynthesis of syringyl lignin in angiosperms.

Influence of natural and synthetic compounds on cell surface expression of cell adhesion molecules, ICAM-1 and VCAM-1

Various natural and synthetic compounds including alkaloids, terpenoids and phenolics were tested for inhibition of the cell surface expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), both of which are crucial in the regulation of immune response and inflammation. Of 40 compounds tested, two compounds significantly downregulated the expression of VCAM-1 on murine endothelial cells (F-2) and ten compounds that of ICAM-1 on mouse myeloid leukemia cells (M1). Sanguinarine chloride (5) and isoliquiritigenin (13) were capable of lowering the levels of both ICAM-1 and VCAM-1. The structure-activity relationships study on chalcone and flavone derivatives related to 13 suggested that the inhibitory activity of the chalcone derivatives is attributable to the 4-hydroxy group as well as the possible coplanarity between the phenyl ring and the adjacent conjugated ketone.

Comparisons of the pharmacokinetics and the leukopenia and thrombocytopenia grade after administration of irinotecan and 5-fluorouracil in combination to rats

BACKGROUND

Irinotecan (CPT-11) has been used recently for the treatment of several cancers in combination with 5-fluorouracil (5-FU). Preliminary data on this combination therapy in humans demonstrated no drug interactions between CPT-11 (or its metabolite, SN-38) and 5-FU however, because there is so little information on the combination, the possibility for an interaction still exists.

MATERIAL AND METHODS

CPT-11 and 5-FU were injected intravenously into rats and the pharmacokinetics of CPT-11 and SN-38 and alternations in blood cell count were investigated.

RESULTS

In the group of rats administered 5-FU prior to CPT-11, the area under the concentration-time curve (AUC) of CPT-11 was approximately eight-fold larger compared with the group administered CPT-11 prior to 5-FU. On the other hand, the grade of leukocytopenia or thrombocytopenia was not significantly different among the two groups.

CONCLUSION

In rats, the conversion of CPT-11 into SN-38 is possibly delayed by prior administration of 5-FU.

5-hydroxyconiferyl aldehyde modulates enzymatic methylation for syringyl monolignol formation, a new view of monolignol biosynthesis in angiosperms

S-Adenosyl-L-methionine-dependent caffeate O-methyltransferase (COMT, EC 2.1.1.6) has traditionally been thought to catalyze the methylation of caffeate and 5- hydroxyferulate for the biosynthesis of syringyl monolignol, a lignin constituent of angiosperm wood that enables efficient lignin degradation for cellulose production. However, recent recognition that coniferyl aldehyde prevents 5-hydroxyferulate biosynthesis in lignifying tissue, and that the hydroxylated form of coniferyl aldehyde, 5-hydroxyconiferyl aldehyde, is an alternative COMT substrate, demands a re-evaluation of the role of COMT during monolignol biosynthesis. Based on recombinant aspen (Populus tremuloides) COMT enzyme kinetics coupled with mass spectrometry analysis, this study establishes for the first time that COMT is in fact a 5-hydroxyconiferyl aldehyde O-methyltransferase (AldOMT), and that 5-hydroxyconiferyl aldehyde is both the preferred AldOMT substrate and an inhibitor of caffeate and 5-hydroxyferulate methylation, as measured by K(m) and K(i) values. 5-Hydroxyconiferyl aldehyde also inhibited the caffeate and 5-hydroxyferulate methylation activities of xylem proteins from various angiosperm tree species. The evidence that syringyl monolignol biosynthesis is independent of caffeate and 5-hydroxyferulate methylation supports our previous discovery that coniferyl aldehyde prevents ferulate 5-hydroxylation and at the same time ensures a coniferyl aldehyde 5-hydroxylase (CAld5H)-mediated biosynthesis of 5-hydroxyconiferyl aldehyde. Together, our results provide conclusive evidence for the presence of a CAld5H/AldOMT-catalyzed coniferyl aldehyde 5-hydroxylation/methylation pathway that directs syringyl monolignol biosynthesis in angiosperms.