Inhibitory effect of rhetsinine isolated from Evodia rutaecarpa on aldose reductase activity

Aldose reductase inhibitors have considerable potential for the treatment of diabetic complications, without increased risk of hypoglycemia. Search for components inhibiting aldose reductase led to the discovery of active compounds contained in Evodia rutaecarpa Bentham (Rutaceae), which is the one of the component of Kampo-herbal medicine. The hot water extract from the E. rutaecarpa was subjected to distribution or gel filtration chromatography to give an active compound, N2-(2-methylaminobenzoyl)tetrahydro-1H-pyrido[3,4-b]indol-1-one (rhetsinine). It inhibited aldose reductase with IC(50) values of 24.1 microM. Furthermore, rhetsinine inhibited sorbitol accumulation by 79.3% at 100 microM. These results suggested that the E. rutaecarpa derived component, rhetsinine, would be potentially useful in the treatment of diabetic complications.

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.

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.

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.

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.

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.

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.

Application of gradient-enhanced nuclear Overhauser effect spectroscopy GOESY) in the structure elucidation of plant secondary metabolites

Gradient enhanced nuclear Overhauser effect spectroscopy (GOESY) has been applied in the structural elucidation of five plant secondary metabolites: eucalyptin, arctigenin, 5-geranyloxy-7-methoxycoumarin, 2,6-dihydroxy-4-methoxyisovalerophenone and N-feruloyltyramine. The importance and sensitivity of this technique in structure elucidation of plant secondary metabolites are discussed.

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.

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.

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).

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.

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.

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).

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.

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.

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.

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.

The effects of calystegines isolated from edible fruits and vegetables on mammalian liver glycosidases

The polyhydroxylated nortropane alkaloids called calystegines occur in many plants of the Convolvulaceae, Solanaceae, and Moraceae families. Certain of these alkaloids exhibit potent inhibitory activities against glycosidases and the recently demonstrated occurrence of calystegines in the leaves, skins, and sprouts of potatoes (Solanum tuberosum), and in the leaves of the eggplant (S. melongena), has raised concerns regarding the safety of these vegetables in the human diet. We have surveyed the occurrence of calystegines in edible fruits and vegetables of the families Convolvulaceae, Solanaceae, and Moraceae by GC-MS. Calystegines A3, B1, B2, and C1 were detected in all the edible fruits and vegetables tested; sweet and chili peppers, potatoes, eggplants, tomatoes, Physalis fruits, sweet potatoes, and mulberries. Calystegines B1 and C1 were potent competitive inhibitors of the bovine, human, and rat beta-glucosidase activities, with Ki values of 150, 10, and 1.9 microM, respectively for B1 and 15, 1.5, and 1 microM, respectively, for C1. Calystegine B2 was a strong competitive inhibitor of the alpha-galactosidase activity in all the livers. Human beta-xylosidase was inhibited by all four nortropanes, with calystegine C1 having a Ki of 0.13 microM. Calystegines A3 and B2 selectively inhibited the rat liver beta-glucosidase activity. The potent inhibition of mammalian beta-glucosidase and alpha-galactosidase activities in vitro raises the possibility of toxicity in humans consuming large amounts of plants that contain these compounds.

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.

Specific alpha-galactosidase inhibitors, N-methylcalystegines--structure/activity relationships of calystegines from Lycium chinense

An examination of the roots of Lycium chinense (Solanaceae) has resulted in the discovery of 14 calystegines, a cycloheptane bearing an amino group and three hydroxyl groups, and two polyhydroxylated piperidine alkaloids. Calystegines A7 and B5, in addition to the previously known calystegines A3, A5, A6, B1, B2, B3, B4, C1, C2 and N1, were isolated and determined as 1alpha,2beta,4alpha-trihydroxy-nortropane and 1alpha,2alpha,4alpha,7alpha-tetrahydroxy-nort ropane, respectively. L. chinense also had two polyhydroxytropanes bearing a methyl group on the nitrogen atom, unlike the previously reported nortropane alkaloids. They were established as N-methylcalystegines B2 and C1, and their N-methyl groups were found to be axially oriented from NOE experiments. 1Beta-amino-3beta,4beta,5alpha-trihydroxycyclohepta ne was also present in L. chinense and may be a biosynthetic precursor of the calystegines that occur in this plant. Two polyhydroxypiperidine alkaloids, fagomine and 6-deoxyfagomine, were isolated. Calystegine B2 is a potent competitive inhibitor of almond beta-glucosidase (Ki = 1.9 microM) and coffee bean alpha-galactosidase (Ki = 0.86 microM), while N-methylcalystegine B2 was a more potent competitive inhibitor of the latter enzyme (Ki = 0.47 microM) than the parent compound but showed a marked lack of inhibitory activities towards most other glycosidases. Since this compound is a very specific inhibitor of alpha-galactosidase and inhibits rat liver lysosomal alpha-galactosidase with a Ki of 1.8 microM, it may provide a useful experimental model for the lysosomal storage disorder, Fabry's disease. The addition of a hydroxyl group at C6exo, as in calystegines B1 and C1, enhances the inhibitory potential towards beta-glucosidase and beta-galactosidase but markedly lowers or abolishes inhibition towards alpha-galactosidase. Hence, the N-methylation of calystegine C1 did not enhance its inhibition of alpha-galactosidase. The chemical N-methylation of calystegines A3 and B4 markedly enhanced inhibition of coffee bean alpha-galactosidase, with Ki values of 5.2 microM and 36 microM, respectively, but almost eliminated their inhibitory potential towards beta-glucosidase and trehalase, respectively. Thus, methylation of the nitrogen atom significantly altered the specificity of the inhibitors.

Homonojirimycin and N-methyl-homonojirimycin inhibit N-linked oligosaccharide processing

Homonojirimycin (HNJ) and N-methylhomonojirimycin (MHNJ) were tested as inhibitors of the purified glycoprotein processing enzymes, glucosidase I and glucosidase II. MHNJ was a reasonably good inhibitor of glucosidase I (Ki = 1 x 10(-6) M) and was about three times as effective on this enzyme as was HNJ. On the other hand, HNJ inhibited glucosidase II with a Ki of about 1 x 10(-6) M, whereas MHNJ was three times less effective (Ki = 3 x 10(-5) M). However, the butyl derivative of HNJ had very low activity toward these two processing glucosidases. HNJ and its methyl derivative were also tested in vivo using influenza virus-infected MDCK cells, and measuring the inhibition of N-linked oligosaccharide processing of the viral envelope glycoproteins. With 100 micrograms/ml of MHNJ in the medium, essentially all of the N-linked oligosaccharide chains of the virus were of the "high-mannose" type with the major structure being characterized as Glc3Man9(GlcNAc)2. Similar results were obtained with HNJ although this compound was less effective in vivo as well as in vitro. These results are in keeping with these inhibitors being effective at the glucosidase I step. Both inhibitors were also tested in MDCK cell cultures to determine whether they affected the in vivo synthesis of proteins, or of lipid-linked saccharides. In contrast to deoxynojirimycin, which has been reported to inhibit the formation of lipid-linked saccharides, no effects were seen on either the incorporation of mannose into lipid-linked saccharides or the incorporation of leucine into protein.

Stability of a perturbed Leslie model

A small perturbation introduced in the stochastic Leslie model leads to a long-lived stable population in a region or parameter space where the stochastic model predicts the demise of the population. This somewhat surprising result is understood by considering a related model with a density-dependent sex ratio which exhibits similar features.

Calystegine B4, a novel trehalase inhibitor from Scopolia japonica

GLC-MS analysis has been developed for screening plants of the family Solanaceae for new calystegines. GLC-MS analyses of the extract of Scopolia japonica showed the presence of a new tetrahydroxy-nor-tropane alkaloid in addition to the known calystegines A3, A5, B1, B2, B3, and C1. We gave this new alkaloid the trivial name calystegine B4. The structure of calystegine B4 was determined as 1 alpha, 2 beta, 3 alpha, 4 alpha-tetrahydroxy-nor-tropane from a variety of NMR spectral data. Calystegines B1, B2, and C1 are potent competitive inhibitors with Ki values ranging from 10(-6) to 10(-7) M for almond beta-glucosidase, while calystegine B4 inhibited this enzyme in a competitive manner, with a Ki value of 7.3 microM. Calystegine B2 is also a potent inhibitor of green coffee bean alpha-galactosidase, whereas calystegine B4 exhibited no significant activity for this enzyme. Among rat intestinal glycosidases, only trehalase was potently inhibited by calystegine B4, with an IC50 value of 9.8 microM. Furthermore, calystegine B4 potently inhibited pig kidney trehalase in a competitive manner, with a Ki value of 1.2 microM, but it was almost inactive against yeast and fungal trehalases.

Antiviral activity and metabolism of the castanospermine derivative MDL 28,574, in cells infected with herpes simplex virus type 2

The 6-O-butanoyl derivative of castanospermine (MDL 28,574: BUCAST), an inhibitor of glycoprotein processing, blocked the growth of herpes simplex virus type-2 with the effect markedly enhanced by exposure of cells to the compound pre- as well as post-infection. The effectiveness of the derivative corresponded to an increased uptake with greatest accumulation after virus infection. Gas chromatography/mass spectrometry identified the predominant component in MDL 28,574 treated cells as castanospermine, an inhibitor of alpha-glucosidase 1. The effects of this compound on the synthesis of viral glycoprotein, gB, was determined with the increased molecular weight of the mannose-rich precursor evidence for the modulation of glycoprotein processing.

The effect of oral treatment with 6-O-butanoyl castanospermine (MDL 28,574) in the murine zosteriform model of HSV-1 infection

Oral treatment of mice, cutaneously infected with herpes simplex virus type 1 (HSV-1) (strain SC16), with the alpha-glucosidase 1 inhibitor 6-O-butanoyl castanospermine (MDL 28,574) produced a significant delay in lesion development and reduced the amount of virus recovered from the brain. Virus load in the brains of mice, whose treatment started 2 days prior to infection, was reduced approximately 100-fold when compared to untreated controls. Treatment initiated at the time of infection, while less effective than pre-treatment, nevertheless reduced virus recovery from the brain by 10-fold. Consistent with its antiviral activity, orally administered MDL 28,574 was rapidly incorporated by brain tissue and mice fed with compound over extended periods maintained relatively high levels of drug at this site.

Alzheimer's patients should be included in phase I clinical trials to evaluate compounds for Alzheimer's disease

Dosage and tolerance are critical issues in successful drug therapy for patients with Alzheimer's disease (AD). A clear distinction among patient populations and AD patient subpopulations is necessary to ensure a thorough assessment of new central nervous system-active compounds. Phase I inpatient trials, in which tolerance and safety are evaluated under double-blind conditions in the target population, provide valuable information for use in planning multicenter outpatient trials. In similar studies, even those involving the elderly, tolerance and safety outcomes in healthy volunteers are not always predictable. An early trial of the effects of velnacrine in healthy, elderly, male volunteers was followed by a trial in the target population. A group of volunteers, aged 60 to 74 years who did not have AD, received 300 mg of velnacrine each day. This dosage was well tolerated for 28 days. Diarrhea, generally of moderate severity, was the only reported adverse effect. No subjects were required to discontinue taking velnacrine. In contrast, a similar trial showed a dosage of 300 mg of velnacrine each day intolerable among patients with AD. Adverse reactions to dosages greater than 225 mg/day included dizziness, fainting, nausea and/or vomiting, headache, and severe diarrhea. A velnacrine dosage of 225 mg/day appeared to be safe and well tolerated in a small population of healthy patients with AD. Based on the inpatient experience with AD subjects, a maximum dose of 225 mg/day was adopted for outpatient studies. Although factors that may contribute to drug sensitivity in patients with AD vary beyond conclusive parameters, the observed sensitivity within the target AD group may indicate a safety/tolerance study as a worthwhile antecedent to multicenter efficacy trials.

Implications of the study population in the early evaluation of anticholinesterase inhibitors for Alzheimer's disease

OBJECTIVE

Velnacrine testing for tolerance and safety in both normal elderly subjects and patients with Alzheimer's disease (AD) is reviewed to illustrate the importance of Phase I trials in the target group as more predictive of safety and tolerance for subsequent multicenter trials than those conducted in healthy elderly subjects.

DESIGN

Both a single-dose and a randomized, double-blind, placebo-controlled, ascending, multiple-dose study were performed with healthy, elderly men. In the multiple-dose study, the subjects were randomized to four groups of 14, with 10 subjects receiving velnacrine and 4 receiving placebo. The doses were velnacrine 25 (group 1), 50 (group 2), and 100 mg (group 3), respectively, administered twice daily; group 4 received 100 mg three times daily for 28 days. Blood and urine were collected serially for the pharmacokinetic assessment. With AD patients, 24 subjects were randomly assigned to receive either placebo or velnacrine for 10 days in a double-blind, sequential escalation study in a hospital setting. There were three groups of 8 subjects. Six patients in each group received velnacrine and 2 placebo. The three groups received respective dosages of 450, 300, and 225 mg/d three times daily. Adverse events were closely monitored and recorded.

PATIENTS/PARTICIPANTS

The multiple-dose test in healthy elderly men included 56 men, aged 60-74 years. Rigorous screening for any potential complications that could affect absorption, distribution, metabolism, or excretion preceded patient entry in the AD patient study. Patients with a history of major psychiatric, neurologic, and cardiovascular disorders were excluded. The patients ranged in age from 56 to 89 years, and were equally distributed between gender.

INTERVENTION

Velnacrine was administered in various doses.

MAIN OUTCOME MEASURES

We emphasize the extreme adverse effects encountered in the AD patient group compared with the healthy group. Plasma concentrations of velnacrine over time in both groups are given, as well as the drug's half-life and excretion rates.

RESULTS

The tolerable dosage predicted by studies performed in healthy elderly subjects was 300 mg/d. This dosage was not tolerable among the AD patients. A dosage as high as 450 mg/d resulted in a tonic seizure in one patient. The predicted dosage of 300 mg/d produced an adverse effect profile in AD patients that included dizziness, nausea and/or vomiting, headaches, and severe diarrhea. AD patients tolerated a dosage of 225 mg/d.

CONCLUSIONS

A velnacrine dosage of 300 mg/d that was tolerated in healthy elderly subjects was not tolerated by AD patients.

Phenylethylamine and piperidine alkaloids in aloe species

Of the approximately 300 species of ALOE (Liliaceae) native to Africa and Arabia, leaf extracts of 224 species have been examined chromatographically for alkaloids using ninhydrin, Dragendorff's reagent, nitroprusside, and iodoplatinate as revealing agents. From these, 48 (21%) species contained compounds giving a strong colorimetric reaction with at least one of these reagents. Tyramine derivatives were identified in 18 species and piperidine derivatives in a further 6 species. The other coloured zones remain unidentified but often appeared to represent common amino acids. Some taxonomic correlations are suggested. The presence of the toxic hemlock alkaloids in aloes readily available for potential medicinal use by local inhabitants sounds a note of caution against the unthinking use of these otherwise useful plants.

Evaluation of HP 029 (velnacrine maleate) in Alzheimer's disease

HP 029 (1,2,3,4-tetrahydro-9-aminoacridin-1-ol-maleate) is a cholinesterase inhibitor and one of a series of compounds synthesized at Hoechst-Roussel Pharmaceuticals Inc. (HRPI) as a potential therapeutic agent for senile dementia of the Alzheimer type (SDAT). An ongoing clinical development program for HP 029 (velnacrine maleate) reflects a rational, traditional progression from therapeutic concept through clinical evaluation. Prior to the initiation of outpatient studies, sufficient data had been obtained from normal volunteers and hospitalized patients to support the following conclusions: the pharmacokinetic profile of HP 029 in young and elderly normal men is predictable; tolerance and safety data for HP 029 using normal volunteers poorly correlates with experience in patients with SDAT; patients with SDAT exhibit marked intersubject variability in tolerance within a suspected therapeutic dose range; mandatory endpoints for drug discontinuation for outpatients can be reliably established in an inpatient environment. Subsequently, Protocol 201 was initiated as a multicenter, multistage investigation of HP 029 in patients with probable SDAT (NINCDS-ADRDA criteria). A dose-ranging component determined patient eligibility for a subsequent dose-replication phase based upon explicit safety and efficacy criteria defined within protocol. One a priori specified interim analysis was conducted by the sponsor (HRPI) for administrative purposes after completing approximately 50% of the planned sample (September 1989). Results suggested that (1) beneficial effects of HP 029 existed on key and secondary measures for the approximately 30% of enrolled patients; (2) interim results would provide an accurate reflection of the results at the conclusion of the study (1991); (3) HP 029-induced hepatocellular injury appeared to be a reversible, predominantly dose-related event; and (4) cholinergically mediated adverse events are infrequent and clinically inconsequential at dosages less than or equal to 225 mg/day. Post hoc hypotheses based on the interim dataset suggest that: (1) carry-over effects of HP 029 exist within a dose-ranging/dose-replication paradigm that militate against the utility of an "enriched population" design; (2) beneficial effects are more robust on initial exposure to HP 029 with effects discerned on both memory and arousal; (3) patient characteristics associated with toxicity or response are not identified; (4) dosage reduction in subsequent efficacy trials may reduce hepatocellular injury and yield clinically unimportant differences in overall efficacy results.

Synthesis of the enantiomers of 6-epicastanospermine and 1,6-diepicastanospermine from D- and L-gulonolactone

The synthesis of the enantiomers of 6-epicastanospermine and of 1,6-diepicastanospermine from the enantiomeric gulonolactones is reported and the structure of the former is established as (1S,6R,7R,8R,8aR)-1,6,7,8-tetrahydroxyoctahydroindolizine. The inhibitory activities of the diastereomers against the amyloglucosidase-catalysed hydrolysis of p-nitrophenyl alpha-D-glucopyranoside were investigated, and the effects of 6-epicastanospermine and of 1,6-diepicastanospermine on 14 human liver glycosidases are reported.

The structural basis of the inhibition of human glycosidases by castanospermine analogues

A series of epimers and deoxy derivatives of castanospermine has been synthesized to investigate the contribution of the different chiral centres to the specificity and potency of inhibition of human liver glycosidases. Castanospermine inhibits all forms of alpha- and beta-D-glucosidases, but alteration to any of the five chiral centres in castanospermine markedly decreases the inhibition. 6-Epicastanospermine, which is related to D-pyranomannose in the same way as castanospermine is to D-pyranoglucose, does not inhibit lysosomal (acidic) alpha-mannosidase, but is a good inhibitor of the cytosolic or neutral alpha-mannosidase. Conversely, 1-deoxy-6-epicastanospermine inhibits acidic alpha-mannosidase strongly, but not the neutral alpha-mannosidase. An explanation of this different inhibition based on preferential recognition of different configurations of mannose by the different forms of alpha-mannosidase is postulated. All derivatives of 6-epicastanospermine also have the minimum structural feature for the inhibition of alpha-L-fucosidase, but those with a beta-anomeric substituent do not inhibit the enzyme, or do so very weakly. 1-Deoxy-6,8a-diepicastanospermine, which has four chiral centres identical with alpha-L-fucose, is, however, a potent inhibitor of alpha-L-fucosidase (Ki 1.3 microM).

Clinical safety, tolerance, and plasma levels of the oral anticholinesterase 1,2,3,4-tetrahydro-9-aminoacridin-1-oL-maleate (HP 029) in Alzheimer's disease: preliminary findings

HP 029 (1,2,3,4-tetrahydro-9-aminoacridin-1-oL-maleate), an oral anticholinesterase, enhances memory in rodents and may be useful in treating Alzheimer's disease (AD). To assess adverse events in relation to dosage and plasma drug levels, 24 hospitalized AD subjects were randomly assigned to receive placebo or HP 029 for 10 days in a double-blind, sequential escalation study. Maximum daily dosages were 450 mg (group 1), 300 mg (group 2), and 225 mg (group 3), divided into three doses per day. The group 1 trial was discontinued on day 5 because one subject, 6 hours following the second of three scheduled 150-mg doses, had a tonic seizure after protracted vomiting and hyperventilation; adverse events in other patients included nausea, vomiting, abdominal cramps, diarrhea, dizziness, and syncope. Adverse events were generally less severe in group 2, but only two of six HP 029 subjects could complete the trial at 300 mg/day. All group 3 subjects completed the trial at 225 mg/day with drug related, mild adverse events (nausea, vomiting, lacrimation, rhinorrhea) in only two subjects. Although mean plasma drug levels were related to adverse events across dosage groups, they did not adequately predict the occurrence or severity of adverse events in individual subjects. The 225 mg/day dose appears to be safe for use in multicenter outpatient trials of HP 029 efficacy in AD. Further patient studies are ongoing to determine the relation of specific subject characteristics to the metabolic profile of HP 029 and biological response.

Loss of cytomegalovirus infectivity after treatment with castanospermine or related plant alkaloids correlates with aberrant glycoprotein synthesis

Many plants contain polyhydroxyalkaloids which are potent inhibitors of glucosidases, enzymes involved in oligosaccharide trimming. These are important in determining the final configuration of specific glycoproteins. Human cytomegalovirus (CMV) encodes a number of glycoproteins, some of which ultimately reside in the outer envelope of the mature virion and are important for virus infectivity. Treatment with three polyhydroxyalkaloids, castanospermine (CAST), deoxynojirimycin (DNJ) and 2R,5R-dihydroxymethyl-3R,4R-dihydroxypyrrolidine (DMDP) blocked the growth of infectious virus, as determined by yield reduction and plaque reduction assays. However, in the presence of CAST, CMV infected cells continued to shed virions into the extracellular medium, as determined by electron microscopy. Envelope glycoproteins of virions produced after treatment with CAST (2.5 mM) were immunoprecipitated with a monoclonal antibody (F5) specific for the gcI family of glycoproteins. Analysis by PAGE-SDS showed an absence of gcI complex 2 (gp52 disulphide-linked to gp130) with a proportional increase in gcI complex 1 (gp52 disulphide-linked to gp95). The results indicated that gp130 alone, or linked to gp52, was important for CMV infectivity. As well as being potential targets for antiviral agents against CMV, inhibitors of glycoprotein trimming reactions may define components of the virion surface important for infectivity.

Inhibition of mammalian digestive disaccharidases by polyhydroxy alkaloids

Several polyhydroxy alkaloids, including the eight presently known to occur in plants, have been compared as inhibitors of mouse gut digestive disaccharidases. The indolizidine castanospermine inhibited all activities tested, but others showed a selectivity which could be of value in studies of carbohydrate digestion and errors of metabolism.

Hemlock Alkaloids in Aloes. Occurrence and Distribution of gamma-Coniceine

The hemlock alkaloid gamma-coniceine was identified in a number of ALOE species, namely A. GILLILANDII, Reynolds A. BALLYI Reynolds, A. RUSPOLIANA Baker, A. IBITIENSIS Perrier and A. DELTOIDEODONTA Baker. Coniine was identified in A. VIGUIERI Perrier. The levels of gamma-coniceine are higher than those found in CONIUM MACULATUM L. Some species also contained trace amounts of conhydrinone and pseudoconhydrin. Three of the species are Madagascan endemics, one is restricted to Arabia, while the rest are remote from each other in East Africa. Some of the species are loosely related but there is no overall taxonomic affinity between them.

An overview of side effects and long-term experience with nomifensine from United States clinical trials

During the clinical development of nomifensine maleate (Merital), 1319 depressed patients received nomifensine (average doses of 150 mg/day) in 4-6 week trials; treatment was continued for at least 2 months in 170 patients and at least 6 months in 53. Comparison data were provided by 593 patients who received placebo and 612 given the tricyclic antidepressant imipramine HCl (average doses of 150 mg/day). The relationship of therapeutic gain to interfering side effects (the therapeutic index) was rated by the investigators and nomifensine received a more favorable therapeutic index rating than did imipramine. Side effect information was collected at each visit. Nomifensine produced less sedating, anticholinergic, and other discomforting side effects than imipramine and was able to sustain clinical benefit with minimal side effects in patients treated up to 6 months.

Psychomotor changes during initial day of benzodiazepine medication

1 The detracting psychomotor effects of diazepam (5 mg three times daily) and clobazam (an investigational 1,5-benzodiazepine) were compared with placebo effects over the course of the initial day of medication. Tests were administered at hourly intervals and the data were analyzed from the standpoint of contrasts at each session and from the standpoint of trends that accrued during the course of the day. 2 It is concluded that among normal volunteers diazepam 5 mg three times daily may be near the threshold for detracting psychomotor consequences during the initial day and that clobazam seems to be without detracting consequences and may have some enhancing effects.

A comparison of the effect of imipramine, nomifensine, and placebo on the psychomotor performance of normal males

Imipramine (50 mg), nomifensine (50 mg) or placebo was administered early morning, late morning, and mid-afternoon to normal volunteers. The program of hourly tests included: the Digit Symbol Substitution, Perceptual Reversal, Time Estimation Test, and Simple and Complex Continuous Performances tests both of which required recognition of briefly exposed letters of the alphabet. It was found that relative to placebo or nomifensine, imipramine had a clearly detracting effect on most of the tests. Drowsiness was reported more often in the imipramine group than in the placebo and nomifensine groups combined.