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Biomedical subjects

R J Nash

Publications and source records attributed to R J Nash.

At least 19 recordsLinked to original sources
PubMed2002

Plasma metabolites indicate energy metabolism disruption during the preclinical phase of bovine spongiform encephalopathy infection.

During the preclinical phase of bovine spongiform encephalopathy (BSE), significantly increased concentrations of lactic acid were measured in the blood of infected dairy cows. Other plasma metabolites, including alanine, leucine, serine, and glutamic acid, also showed significantly altered concentrations in the preclinical BSE animals compared to a control group. This appears consistent with the exaggerated stress response observed in clinical BSE, and precedes the development of clinical signs and overt behavioural changes. A number of other plasma metabolites including other amino acids and components of the plasma fatty acid content showed no association with BSE status.

Amino Acids↗
PubMed2001

Polyhydroxylated alkaloids -- natural occurrence and therapeutic applications.

Over one hundred polyhydroxylated alkaloids have been isolated from plants and micro-organisms. These alkaloids can be potent and highly selective glycosidase inhibitors and are arousing great interest as tools to study cellular recognition and as potential therapeutic agents. However, only three of the natural products so far have been widely studied for therapeutic potential due largely to the limited commercial availability of the other compounds.

Alkaloids↗
PubMed2001

Dihydroxynortropane alkaloids from calystegine-producing plants.

Three dihydroxynortropanes, 2alpha,7beta-dihydroxynortropane, 2alpha,3beta-dihydroxynortropane, and 3alpha,7beta-dihydroxynortropane, were isolated from calystegine-producing plants in the families Convolvulaceae and Solanaceae. 2alpha,7beta-Dihydroxynortropane was isolated from six species in the Convolvulaceae whereas only Calystegia soldanella contained it and 2alpha,3beta-dihydroxynortropane. Although neither of these were detectable in three species tested in the Solanaceae, 3alpha,7beta-dihydroxynortropane was, however, isolated from Duboisia leichhardtii.

Alkaloids↗
PubMed2001

Lignans from Strophanthus gratus.

Three lignans, pinoresinol (1), 8-hydroxypinoresinol (2) and olivil (3) have been isolated from the leaves of Strophanthus gratus by reversed-phase HPLC.

Chromatography, High Pressure Liquid↗
PubMed2001

Polyhydroxylated alkaloids isolated from mulberry trees (Morusalba L.) and silkworms (Bombyx mori L.).

New polyhydroxylated alkaloids, (2R,3R,4R)-2-hydroxymethyl-3,4-dihydroxypyrrolidine-N-propionamide from the root bark of Morus alba L., and 4-O-alpha-D-galactopyranosyl-calystegine B(2) and 3 beta,6 beta-dihydroxynortropane from the fruits, were isolated by column chromatography using a variety of ion-exchange resins. Fifteen other polyhydroxylated alkaloids were also isolated. 1-Deoxynojirimycin, a potent alpha-glucosidase inhibitor, was concentrated 2.7-fold by silkworms feeding on mulberry leaves. Some alkaloids contained in mulberry leaves were potent inhibitors of mammalian digestive glycosidases but not inhibitors of silkworm midgut glycosidases, suggesting that the silkworm has enzymes specially adapted to enable it to feed on mulberry leaves. The possibility of preventing the onset of diabetes and obesity using natural dietary supplements containing 1-deoxynojirimycin and other alpha-glucosidase inhibitors in high concentration is of great potential interest.

Alkaloids↗
PubMed2001

Age-related autoantibody production in a nonhuman primate model.

Autoantibody production increases with ageing. However, the pathological significance of this increase as well as the corresponding underlying mechanisms are poorly understood. To further our understanding of the role that ageing plays in the development of autoantibody responses, we used a novel nonhuman primate model consisting of healthy baboons of ages representing the entire lifespan of this animal species. Results from this study indicate that production of antinuclear antibodies, anticell extract antibodies and natural autoantibodies gradually and significantly increases from young age to old age without a corresponding increase in neither serum immunoglobulin concentration nor in levels of selected markers of immune dysregulation (sTNF-RI, sTNF-RII, IL-2 sR alpha and IFN-gamma). Therefore, in the baboon model, autoantibodies may be produced in absence of recognizable pathological conditions of the ageing immune system.

Aging↗
PubMed2001

Novel alpha-L-fucosidase inhibitors from the bark of Angylocalyx pynaertii (Leguminosae).

The extract of bark of Angylocalyx pynaertii (Leguminosae) was found to potently inhibit mammalian alpha-L-fucosidases. A thorough examination of the extract resulted in the discovery of 15 polyhydroxylated alkaloids, including the known alkaloids from seeds of this plant, 1,4-dideoxy-1,4-imino-D-arabinitol (DAB), 1-deoxymannojirimycin (DMJ) and 2,5-imino-1,2,5-trideoxy-D-mannitol (6-deoxy-DMDP). Among them, eight sugar-mimic alkaloids showed the potent inhibitory activity towards bovine epididymis alpha-L-fucosidase and their Ki values are as follows: 6-deoxy-DMDP (83 microM), 2,5-imino-1,2,5-trideoxy-L-glucitol (0.49 microM), 2,5-dideoxy-2,5-imino-D-fucitol (17 microM), 2,5-imino-1,2,5-trideoxy-D-altritol (3.7 microM), DMJ (4.7 microM), N-methyl-DMJ (30 microM), 6-O-alpha-L-rhamnopyranosyl-DMJ (Rha-DMJ, 0.06 microM), and beta-L-homofuconojirimycin (beta-HFJ, 0.0053 microM). We definitively deduced the structural requirements of inhibitors of alpha-L-fucosidase for the piperidine alkaloids (DMJ derivatives). The minimum structural feature of alpha-L-fucosidase inhibitors is the correct configuration of the three hydroxyl groups on the piperidine ring corresponding to C2, C3 and C4 of L-fucose. Furthermore, the addition of a methyl group in the correct configuration to the ring carbon atom corresponding to C5 of L-fucose generates extremely powerful inhibition of alpha-L-fucosidase. The replacement of the methyl group of beta-HFJ by a hydroxymethyl group reduced its inhibitory potential about 80-fold. This suggests that there may be a hydrophobic region in or around the active site. The existence or configuration of a substituent group on the ring carbon atom corresponding to the anomeric position of L-fucose does not appear to be important for the inhibition. Interestingly, Rha-DMJ was a 70-fold more potent inhibitor of alpha-L-fucosidase than DMJ. This implies that the lysosomal alpha-L-fucosidase may have subsites recognizing oligosaccharyl structures in natural substrates.

1-Deoxynojirimycin↗
PubMed2000

Homonojirimycin analogues and their glucosides from Lobelia sessilifolia and Adenophora spp. (Campanulaceae).

2,6-Dideoxy-7-O-(beta-D-glucopyranosyl) 2,6-imino-D-glycero-L-gulo- heptitol (7-O-beta-D-glucopyranosyl-alpha-homonojirimycin, 1) was isolated from the 50% methanol extract of the whole plant of Lobelia sessilifolia (Campanulaceae), which was found to potently inhibit rice alpha-glucosidase. Adenophorae radix, roots of Adenophora spp. (Campanulaceae), yielded new homonojirimycin derivatives, adenophorine (2), 1-deoxyadenophorine (3), 5-deoxyadenophorine (4), 1-C-(5-amino-5-deoxy-beta-D-galactopyranosyl)butane (beta-1-C-butyl-deoxygalactonojirimycin, 5), and the 1-O-beta-D-glucosides of 2 (6) and 4 (7), in addition to the recently discovered alpha-1-C-ethylfagomine (8) and the known 1-deoxymannojirimycin (9) and 2R,5R-bis(hydroxymethyl)-3R,4R- dihydroxypyrrolidine (DMDP, 10). Compound 4 is a potent inhibitor of coffee bean alpha-galactosidase (IC50 = 6.4 microM) and a reasonably good inhibitor of bovine liver beta-galactosidase (IC50 = 34 microM). Compound 5 is a very specific and potent inhibitor of coffee bean alpha-galactosidase (IC50 = 0.71 microM). The glucosides 1 and 7 were potent inhibitors of various alpha-glucosidases, with IC50 values ranging from 1 to 0.1 microM. Furthermore, 1 potently inhibited porcine kidney trehalase (IC50 = 0.013 microM) but failed to inhibit alpha-galactosidase, whereas 7 was a potent inhibitor of alpha-galactosidase (IC50 = 1.7 microM) without trehalase inhibitory activity.

1-Deoxynojirimycin↗
PubMed2000

A sesquiterpene acid and flavonoids from Polygonum viscosum.

4-Isobutyl-6-methyl-5-oxo-3a,4,5,7a-tetrahydro-1H-inden-13-oic acid (named viscosumic acid) and quercetin 3-O-(6"-feruloyl)-beta-D-galactopyranoside, and the known 3',5-dihydroxy-3,4',5',7-tetramethoxyflavone have been isolated from Polygonum viscosum. The structures of these isolates were determined primarily on the basis of extensive 1D and 2D NMR spectral analyses, notably, 13C PENDANT, COSY45, TOCSY, GOESY, NOESY, HMQC and HMBC.

Flavonoids↗
PubMed2000

Polyhydroxylated pyrrolidine and piperidine alkaloids from Adenophora triphylla var. japonica (Campanulaceae).

Adenophora triphylla var. japonica (Campanulaceae) yielded two new alkaloids, the 6-C-butyl derivative of 2R,5R-bis(hydroxymethyl)-3R,4R-dihydroxypyrrolidine (DMDP) and alpha-1-C-ethyl-fagomine, together with the known alkaloids 1,4-dideoxy-1,4-imino-D-arabinitol, 1-deoxynojirimycin, and 1-deoxymannojirimycin. 6-C-Butyl-DMDP showed inhibitory activity toward almond beta-glucosidase (IC50 = 68 microM), whereas alpha-1-C-ethyl-fagomine inhibited bovine liver beta-galactosidase (IC50 = 29 microM).

Alkaloids↗
PubMed2000

Constituents of Cassia laevigata.

Calendin (1), cinnamic acid (2), 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one (3), 2,3-dihydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one (4), 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)-propan-1-one (5), syringic acid (6) and vanillic acid (7) have been isolated from a dichloromethane extract of the leaves and branches of Cassia laevigata.

Humans↗
PubMed2000

Pyranoisoflavones from Rinorea welwitschii.

Reversed-phase HPLC analysis of a dichloromethane extract of the stem-barks of Rinorea welwitschii has afforded two pyranoisoflavones, alpinumisoflavone (1) and di-O-methylalpinumisoflavone (2).

Chromatography, High Pressure Liquid↗
PubMed2000

Alkaloids from Balanites aegyptiaca.

High performance liquid chromatographic (HPLC) analysis of a dichloromethane extract of the stem-barks of Balanites aegyptiaca has yielded two known alkaloids, N-trans-feruloyltyramine (1) and N-cis-feruloyltyramine (2), and three common metabolites, vanillic acid, syringic acid and 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-1-propanone.

Alkaloids↗
PubMed1999

Polyhydroxylated pyrrolidine and pyrrolizidine alkaloids from Hyancinthoides non-scripta and Scilla campanulata.

Aqueous ethanol extracts from the immature fruits and stalks of bluebell (Hyacinthoides non-scripta) were subjected to various ion-exchange column chromatographic steps to give 1,4-dideoxy-1,4-imino-D-arabinitol (1),2(R),5(R)-bis(hydroxymethyl)-3(R),4(R)-dihydroxypyrrolidine (DMDP) (2), 6-deoxy-6-C-(2,5-dihydroxyhexyl)-DMDP (3),2,5-dideoxy-2,5-imino-DL-glycero-D-manno-heptitol (homoDMDP)(4),homoDMDP-7-O-apioside (5), homoDMDP-7-O-beta-D-xylopyranoside (6), (1S*,2R*,3R*,5R*,7aR*)-1,2-dihydroxy-3,5- dihydroxymethylpyrrolizidine (7), and (1S*,2R*,3R*,5R*,6R*,7R*,7aR*)-3-hydroxymethyl-5-methyl-1,2,6,7 tetrahydroxypyrrolizidine (8). Bulbs of Scilla campanulata (Hyacinthaceae) yielded (1S*,2R*,3R*,5S*,7aR*)-1,2-dihydroxy-3,5-dihydroxy-methylpyrrol izidine (9) in addition to compounds 1-7. Compounds 3,6,7,8, and 9 are new natural products. Compound 4 is a potent competitive inhibitor with K(i) values of 1.5 microM for Caldocellum saccharolyticum beta-glucosidase and 2.2 microM for bovine liver beta-galactosidase. The 7-O-beta-D xyloside 6 was a stronger competitive inhibitor than 4 of C saccharolyticum beta-glucosidase and rat intestinal lactase, with K(i) values of 0.06 and 0.07 microM, respectively, but a weaker inhibitor of bovine liver beta-galactosidase. Furthermore, compound 4 is also a competitive inhibitor (K(i) = 1.8 microM) of porcine kidney trehalase, but 6 was inactive against this enzyme.

Alkaloids↗
PubMed1998

Homonojirimycin isomers and N-alkylated homonojirimycins: structural and conformational basis of inhibition of glycosidases.

A series of natural epimers of alpha-homonojirimycin and its N-alkylated derivatives have been prepared to investigate the contribution of the different chiral centers and conformation of the specificity and potency of inhibition of glycosidases. These epimers and N-alkylated derivatives are alpha-homonojirimycin (1), beta-homonojirimycin (2), alpha-homomannojirimycin (3), beta-homomannojirimycin (4), alpha-3,4-di-epi-homonojirimycin (5), beta-4,5-di-epi-homonojirimycin (6), N-methyl-alpha-homonojirimycin (7), and N-butyl-alpha-homonojirimycin (8). Compound 1 was a potent inhibitor of a range of alpha-glucosidases with IC50 values of 1 to 0.01 microM. Compounds 2, 3, and 4 were surprisingly inactive as inhibitors of beta-glucosidase and alpha- and beta-mannosidases but were moderately good as inhibitors of rice and some mammalian alpha-glucosidases. Compound 4 was active in the micromolar range toward all alpha-glucosidases tested. Furthermore, compound 4, which superimposes well on beta-l-fucose, was a 10-fold more effective inhibitor of alpha-l-fucosidase than 1-deoxymannojirimycin (12) and 3, with a Ki value of 0.45 microM. Only compounds 5 and 6 showed inhibitory activity toward alpha- and beta-galactosidases (6with an IC50 value of 6.4 microM against alpha-galactosidase). The high-resolution structure of 1 has been determined by X-ray diffraction and showed a chair conformation with the C1 OH (corresponding to the C6 OH in 1-deoxynojirimycin) predominantly equatorial to the piperidine ring in the crystal structure. This preferred (C1 OH equatorial) conformation was also corroborated by 1H NMR coupling constants. The coupling constants for 7 suggest the axial orientation of the C1 OH, while in 8 the C1 OH axial conformation was not observed. The C1 OH axial conformation appears to be responsible for more potent inhibition toward processing alpha-glucosidase I than alpha-glucosidase II. It has been assumed that the anti-HIV activity of alkaloidal glycosidase inhibitors results from the inhibition of processing alpha-glucosidase I, but 1, 7, and 8 were inactive against HIV-1 replication at 500 microg/mL as measured by inhibition of virus-induced cytopathogenicity in MT-4 cells. In contrast, the EC50 value for N-butyl-1-deoxynojirimycin (11), which also inhibits processing alpha-glucosidase I, was 37 microg/mL. Compound 7 has been shown to be a better inhibitor of alpha-glucosidase I than 1 and 8 both in vitro and in the cell culture system. These data imply that inhibition of HIV by glycosidase inhibitors can be due to factors other than simply inhibition of processing alpha-glucosidase I.

1-Deoxynojirimycin↗
PubMed1998

Nitrogen-containing furanose and pyranose analogues from Hyacinthus orientalis.

Aqueous methanol extracts from the bulbs of Hyacinthusorientalis were subjected to various ion-exchange column chromatographic steps to give 2(R),5(R)-bis(hydroxymethyl)-3(R),4(R)-dihydroxypyrrolidine (DMDP) (1), 2,5-dideoxy-2,5-imino-dl-glycero-d-manno-heptitol (homoDMDP) (2), 2,5-imino-2,5,6-trideoxy-d-manno-heptitol (6-deoxy-homoDMDP) (3), 2,5-imino-2,5,6-trideoxy-d-gulo-heptitol (4), 1-deoxynojirimycin (5), 1-deoxymannojirimycin (6), alpha-homonojirimycin (7), beta-homonojirimycin (8), alpha-homomannojirimycin (9), beta-homomannojirimycin (10), and 7-O-beta-d-glucopyranosyl-alpha-homonojirimycin (MDL 25,637) (11). The structures of the new natural products 3 and 4 were determined by spectroscopic analysis, including extensive 1D and 2D NMR studies. Compound 2 was found to be a potent inhibitor of bacterial beta-glucosidase, mammalian beta-galactosidases, and mammalian trehalases, while 3 was a potent inhibitor of rice alpha-glucosidase and rat intestinal maltase. Compound 4 was observed to be a good inhibitor of alpha-l-fucosidase.

Alkaloids↗
PubMed1997

Enzymatic synthesis of the glycosides of calystegines B1 and B2 and their glycosidase inhibitory activities.

Several glycosides of calystegines B1 and B2 were synthesized by use of rice alpha-glucosidase and the whole cells of Rhodotorula lactosa, and their glycosidase inhibitory activities were investigated. Incubation of mixture of calystegine B1 and maltose with rice alpha-glucosidase gave 3-O-alpha-D-glucopyranosylcalystegine B1 (2, 11.3%). An enzymatic beta-transglucosylation reaction of calystegines B1 or B2 with cellobiose using the whole cells of R. lactosa gave 3-O-beta-D-glucopyranosylcalystegine B1 (1) (0.9%) or 4-O-beta-D-glucopyranosylcalystegine B2 (3, 11.2%), respectively, while similar beta-transgalactosylation of calystegine B2 from lactose gave 4-O-beta-D-galactopyranosylcalystegine B2 (4, 10.1%). The glycosylation of calystegines B1 and B2 markedly decreased or abolished their inhibition against beta-glucosidase, alpha- or beta-galactosidase. Compound 4 however retained more or less the potency of calystegine B2 against trehalase. Interestingly, compound 1 was a noncompetitive inhibitor of rice alpha-glucosidase, with a Ki value of 0.9 +/- 0.1 microM.

Animals↗