Alkaloids from trunk bark of Hernandia nymphaeifolia

Six new alkaloids, (+)-ovigerdimerine, 4-methoxyoxohernandaline, 7-formyldehydrohernangerine, 5,6-dimethoxy-N-methylphthalimide, 7-hydroxy-6-methoxy-1-methylisoquinoline and (+)-vateamine-2′-β-N-oxide, along with one new dialdehyde, hernandial, have been isolated and characterized from the trunk bark of Hernandia nymphaeifolia. The structures of these compounds were elucidated by spectral analyses.     

N′-isopropylnornicotine: Its formation from nicotine in aged leaves of Nicotiana tabacum

An aqueous solution of nicotine-[2′-¹⁴C] was painted on the leaves of 4-month-old tobacco plants (Nicotiana tabacum) which were harvested 3 weeks later. This tracer was similarly applied to excised tobacco leaves which were allowed to dry in air for 4 weeks. The alkaloids, were extracted with the addition of N′-isopropylnornicotine, a compound which has been previously isolated from air-cured tobacco. Radioactive nicotine and nornicotine were isolated from the intact plants with only minute activity in the N′-isopropylnornicotine. All three of these alkaloids were radioactive from the air-cured leaves, and degradation of the labelled N'-isopropylnornicotine indicated that all the activity was located at the C-2′ position. A higher level of activity was found in N′-isopropylnornicotine which was obtained from excised leaves which were fed the nicotine- [2′- ¹⁴C] in aqueous acetone, and were treated on subsequent days with aqueous acetone. These results are consistent with the hypothesis that N′-isopropylnornicotine is produced in the curing of tobacco leaves by reaction of nornicotine (formed by the demethylation of nicotine) with acetoacetate, followed by decarboxylation and reduction. The ¹³C NMR chemical shifts of the methyl groups of N′-isopropylnornicotine and related 1-isopropylpyrrolidines which have chirality at the α-position of the pyrrolidine ring, are significantly different (up to 7.5 ppm).     

Norlittorine and norhyoscyamine identified as products of littorine and hyoscyamine metabolism by 13C-labeling in Datura innoxia hairy roots

The presence of two compounds, norlittorine and norhyoscyamine, has been reported in leaves and roots of Datura innoxia; however their metabolic origin in the tropane alkaloid pathway has remained unknown. Precise knowledge of this pathway is a necessary pre-requisite to optimize the production of hyoscyamine and scopolamine in D. innoxia hairy root cultures. The exact structure of norlittorine and norhyoscyamine was confirmed by LC–MS/MS and NMR analyses. Isotopic labeling experiments, using [1-¹³C]-phenylalanine, [1′-¹³C]-littorine and [1′-¹³C]-hyoscyamine, combined with elicitor treatments, using methyl jasmonate, coronalon and 1-aminocyclopropane-1-carboxylic acid, were used to investigate the metabolic origin of the N-demethylated tropane alkaloids. The results suggest that norlittorine and norhyoscyamine are induced under stress conditions by conversion of littorine and hyoscyamine. We propose the N-demethylation of tropane alkaloids as a mechanism to detoxify cells in overproducing conditions.     

Stereochemistry of tropane alkaloid formation in Datura

Five-month-old Datura innoxia plants were fed via the roots with either d(+)-hygrine-[2′-¹⁴C] or l(?)-hygrine-[2′-¹⁴C]. After 7 days the root alkaloids 3α,6β-ditigloyloxytropane, 3α,6β-ditigloyloxytropan-7β-ol, hyoscine, hyoscyamine and cuscohygrine were isolated from both groups of plants. d(+) but not l(?)-hygrine acts as a precursor for the tropane alkaloids whereas both enantiomers appeared to serve equally well in the biosynthesis of cuscohygrine.     

New diacylglyceryltrimethylhomoserines from the marine microalga Nannochloropsis granulata and their nitric oxide inhibitory activity

Chemical investigation of polar lipids from the marine eustigmatophyte microalga Nannochloropsis granulata led to the isolation of six betaine lipid diacylglyceryltrimethylhomoserine (DGTS), namely, (2S)-1,2-bis-O-eicosapentaenoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (1), (2S)-1-O-eicosapentaenoyl-2-O-arachidonoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (2), (2S)-1-O-eicosapentaenoyl-2-O-myristoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (3), (2S)-1-O-eicosapentaenoyl-2-O-palmitoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (4), (2S)-1-O-eicosapentaenoyl-2-O-palmitoleoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (5), and (2S)-1-O-eicosapentaenoyl-2-O-linoleoylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (6). Structures of the isolated DGTSs were elucidated based on both spectroscopic technique and degradation methods. This is the first report of isolation of 1 in pure state, and 2–6 are all new compounds. The isolated betaine lipids showed dose-dependent nitric oxide (NO) inhibitory activity against lipopolysaccharide-induced nitric oxide production in RAW264.7 macrophage cells. Further study suggested that these betaine lipids (1–6) inhibit NO production in RAW264.7 macrophage cells through downregulation of inducible nitric oxide synthase expression, indicating the possible use as an anti-inflammatory agent. This is the first report of DGTS with anti-inflammatory activity.     

Biosynthetic relations between protoberberine-, benzo(C)phenanthridine- and B-secoprotoberberine type alkaloids in Corydalis incisa

The biosynthetic relations between protoberberine-, benzo[C]phenanthridine- and B-secoprotoberberine type alkaloids were demonstrated by use of (±)-tetrahydrocoptisine-[8,14-³H HCl, (±)-tetrahydrocorysamine-[8,14-³H]HCl and corynoline-[6-³H]HCl in Corydalis incisa, and the following results were presented. (±)-Tetrahydrocoptisine was converted to corynoline, corydalic acid methyl ester and corydamine hydrochloride. (±)-Tetrahydrocorysamine was converted to corynoline and corydalic acid methyl ester. Evidence that N-methyl-3-[6′-(3′,4′-methylenedioxyphenethylalcohol)]-4-methyl-7,8-methylenedioxy-1,2,3,4-tetrahydroisoquinoline-[α-³H] HCl was incorporated into corynoline-[11-³H] indicates the occurrence of the ring fission at C₆-N followed by linking ofthe C₆ and C₁₃ positions in (±)-tetrahydrocoptisine and (±)-tetrahydrocorysamine, and suggests the participation of one of two possible intermediates in the biosynthesis of these alkaloids.     

Four new N-acetylnoraporphine alkaloids from Liriodendron tulipifera

Four new naturally occurring N-acetylnoraporphine alkaloids were obtained from the heartwood of Liriodendron tulipifera; (?)-N-acetylanonaine, (?)-N-acetylnornuciferine, (?)-N-acetylasimilobine, and (?)-tuliferoline. Structure determination was accomplished by physical and chemical methods.     

Preliminary SAR analysis of novel antiproliferative N6,5′-bis-ureidoadenosine derivatives

A preliminary library of novel N⁶,5′-bis-ureidoadenosine analogs and related derivatives was prepared and tested for activity against the NCI 60 panel of human cancers. A 2′-O-TBS group was found to be necessary, but not sufficient, for optimal antiproliferative activity. Neither the N⁶- nor 5′-ureido substituents were sufficient to achieve significant antiproliferative effects when present in the absence of the other. The 2′-O-TBS, and N⁶,5′-bis-ureido substitution patterns were found to be necessary for optimal antiproliferative activity.     

Preparations of 2-epi-fortimicins A from 2-epi-fortimicin B by intramolecular base-catalyzed 2-O-acylation of 1,2′,6′-tri-N-benzyloxycarbonyl-2-epi-fortimicin B

Preparations of 2-epi-fortimicin A (4) from 2-epi-fortimicin B (3) are described. In contrast to the previously reported, selective 4-N-acylation of 1,2′,6′-tri-N-benzyloxycarbonylfortimicin B (8) with N-(N-benzyloxycarbonylglycyloxy)succinimide, 1,2′,6′-tri-N-benzyloxycarbonyl-2-epi-fortimicin B (5) underwent predominant 2-O,4-N-diacylation under similar conditions. Proof of the structure of the diacylated product is presented, with evidence that the diacylated product is formed by initial intramolecular, base-catalyzed 2-O-acylation. The in vitro antibacterial activities of 2-epi-fortimicin A (4), 2-O-glycyl-2-epi-fortimicin A (11), 1-N-glycyl-2-epi-fortimicin A (12), and 5-deoxy-2-epi-fortimicin A (13) are reported.     

(−)-Epilamprolobine and its N-oxide,lupin alkaloids from Sophora tomentosa

From the fresh leaves of Sophora tomentosa, three new lupin alkaloids, (?)-epilamprolobine, (+)-epilamprolobine N-oxide and 5-(3′-methoxycarbonylbutyroyl)aminomethyl-trans-quinolizidine N-oxide, have further been isolated along with (+)-matrine, (+)-matrine N-oxide, (+)-sophocarpine N-oxide, (?)-anagyrine, (?)- baptifoline, (?)-cytisine, (?)-N-methylcytisine, (?)-N-formylcytisine, (?)-N-acetylcytisine and (±)-ammodendrine. The absolute configurations of (+)-epilamprolobine N-oxide (1R:5R:6S) and (?)-epilamprolobine (5R:6S) have also been established by spectroscopic data and by comparison with synthetic (+)-epilamprolobine (5S:6R)derived from (?)-lupinine (5R:6R). (?)-Epilamprolobine is a diastereomer of (+)-lamprolobine (5R:6R) in Lamprolobium fruticosum and 5-(3′-methoxycarbonylbutyroyl) aminomethyl-trans-quinolizidine N-oxide is presumed to be an artefact. A biosynthetic pathway for the formation of (?)-epilamprolobine is also proposed.     

New alkaloids from Aegle marmelos

Four new alkaloids, O-(3,3-dimethylallyl)-halfordinol, N-2-ethoxy-2-(4-methoxyphenyl)ethylcinnamamide, N-2-methoxy-2-[4-(3′,3′-dimethyl     

Biosynthesis of tropane ester alkaloids in Datura

Datura meteloides plants were fed via the roots with [1″,2′-¹⁴C]tigloyl hygroline and as a control, [2′-¹⁴C]hygrine. After a week the alkaloids were isolated and degraded. Despite hydrolysis of the putative precursor it was possible, by label ratio, to show that esterification occurs after, and not before, the tropane ring has been synthesized. Hygroline is proposed as a possible intermediate.     

Biosynthesis of alpinigenine by way of tetrahydroprotoberberine and protopine intermediates

In the biosynthesis of the benzazepine alkaloid alpinigenine a N-methylation step followed by hydroxylation α to nitrogen has now been shown more conclusively to be involved in the transformation of a N-heterocyclic ring system. After feeding Papaver bracteatum plants both the precursors (±)-tetrahydropalmatine-[8,13,14-³H] and (±)-tetrahydropalmatine methiodide-[8,13,14-³H;8-⁴C] an identical mode of abstraction of tritium was observed including a complete loss of the isotope from C-14. The next member in the biogenetic chain, muramine-[8-¹⁴C], was incorporated into alpinigenine very efficiently. Furthermore, using structurally different precursors not utilized for normal alkaloid formation, e.g. 2′-hydroxymethyl-laudanosine-[¹⁴CH₂OH], 13-hydroxymuramine-[8-¹⁴C], the specificity of alkaloid metabolism was examined in the whole plant. Tracer dilution technique was applied to confirm the occurrence in the plant of three established intermediates. Chemical syntheses of four of the alkaloids used during these investigations were developed.     

Novel amide alkaloids from the roots of Piper guineense

Two novel amide alkaloids, wisanine and wisanidine, have been isolated from the petroleum-extract of the roots of Piper guineense, and found to be N-piperidyl-5 (2-methoxy-4,5-methylenedioxyphenyl)-trans-2-trans-4-pentadienamide and N-pyrrolidyl-5-(2-methoxy-4, 5-methylenedioxyphenyl)-trans-2-trans-4-pentadienamide respectively. The structure of wisanidine has been confirmed by synthesis. N-Isobutyl)-trans-2-trans-4-eicosadienamide, recently reported to be present in the fruits of the plant as well as Piperine and Δ^α,β-dihydropiperine have also been found to be major constituents of the roots.     

Alkaloids of stem and rootbark of Tabernaemontana dichotoma

During chemical investigation for compounds possessing biological activity in the stem and rootbark of Tabernaemontana dichotoma, 22 alkaloids were isolated. Ten monomeric alkaloids were identified, viz. (?)-apparicine, coronaridine, 3-oxocoronaridine, 3-ketopropylcoronaridine, 19R-heyneanine, 3-ketopropyl-19R-heyneanine, ibogamine, isomethuenine, perivine and vobasine. Two of the monomeric alkaloids isolated were new, one was identified as 3,19R-oxidocoronaridine and the other one is not yet identified. The other ten alkaloids isolated were dimeric compounds, three were identified as tabernamine, voacamine and 3′R/S-hydroxyvoacamine. Five of the dimers were new alkaloids related to tabernamine and ervahanine type structures and identified as 3′R/S-hydroxytabernamine, 3′R/S-hydroxy-N₄-demethyltabernamine, N₄-demethyltabernamine and 3′R/S-hydroxy-N₄-demethytervahanine A and B. The remaining two alkaloids are partially characterized.     

Synthesis and characterization of modified nucleotides in the 970 hairpin loop of Escherichia coli 16S ribosomal RNA

The synthesis of the 6-O-DPC-2-N-methylguanosine (m²G) nucleoside and the corresponding 5′-O-DMT-2′-O-TOM-protected 6-O-DPC-2-N-methylguanosine phosphoramidite is reported [DPC, diphenyl carbamoyl; DMT, 4,4′-dimethoxytrityl; TOM, [(triisopropylsilyl)oxy]methyl]. The availability of the phosphoramidite allows for syntheses of hairpin RNAs with site-selective incorporation of 2-N-methylguanosine modification. Four 18-nt hairpin RNA analogues representing the 970-loop region (helix 31 or h31; U960–A975) of Escherichia coli 16S rRNA were synthesized with and without modifications in the loop region. Subsequently, stabilities and conformations of the singly and doubly modified RNAs were examined and compared with the corresponding unmodified RNA. Thermodynamic parameters and circular dichroism spectra are presented for the four helix 31 RNA analogues. Surprisingly, methylations in the loop region of helix 31 slightly destabilize the hairpin, which may have subtle effects on ribosome function. The hairpin construct is suitable for future ligand-binding experiments.     

Biosynthesis of Camptotheca acuminata alkaloids

Tracer feeding experiments with Camptotheca acuminata plants show that [1′-¹⁴C]L-tryptophan, [Ar-³H₄]L-tryptophan, [Ar-³H₄,1′-¹⁴C]tryptophan, [1′-¹⁴C]-tryptamine, [2-¹⁴C]DL-mevalonate, and [2-¹⁴C]geraniol-[2-¹⁴C]nerol are incorporated into camptothecin. Direct stem injection of the labeled precursors into C. acuminata plants resulted in a substantial increase in the activity of isolated Camptotheca alkaloids as compared to root feeding of the same tracer.     

Phenylpropanoid amides from Alisma orientalis and their protective effects against H2O2-induced damage in SH-SY5Y cells

Five new phenylpropanoid amides, including N-trans-feruloyl-N′-cis-feruloyl-cadaverine (1), N,N′-trans-diferuloyl-3-oxo-cadaverine (2), N-trans-feruloyl-N′-cis-feruloyl-3-hydroxy-cadaverine (3), N,N′-cis-diferuloyl-3-hydroxy-cadaverine (4), N-trans-p-coumaroyl-N′-trans-feruloyl-3-hydroxy-cadaverine (5), were isolated from Alisma orientalis together with four known analogues. Their structural elucidations were conducted by using 1D and 2D NMR and HRESIMS spectroscopic analyses. The isolated compounds were assayed for their inhibitory activities against HCE-2, anti-oxidant effects, and their protective effects on H₂O₂-induced damage in human dopaminergic neuroblastoma cells (SH-SY5Y). Compounds 3, 6, and 7 displayed moderate anti-oxidant activities with IC₅₀ values in the range of 36.9–40.7 μM. Compound 5 showed significant protective activity, while compounds 1, 2, 4, 7, and 8 showed moderate protective activities.     

Addition of 1-nitroalkanes to methyl 2,3-O-isopropylidene-β-d-ribo-pentodialdo-1,4-furanoside and N6-benzoyl-2′,3′-O-isopropylideneadenosine-5′-aldehyde

Various 1-nitroalkanes reacted with methyl 2,3-O-isopropylidene-β-d-ribo-pentodialdo-1,4-furanoside to yield methyl 6-alkyl-6-deoxy-2,3-O-isopropylidene-6-nitro-β-d-ribofuranosides in 64–79% yield. Similarly, nitromethane and 1-nitropentane reacted with N⁶-benzoyl-2′,3′-O-isopropylideneadenosine-5′-aldehyde, to yield the corresponding 9-[6-alkyl-6-deoxy-2,3-O-isopropylidene-6-nitro-α-l-talo(β-d-allo)furanosyl]-N⁶-benzoyladenines in 74 and 44% yield, respectively. The potential utility of this nitroalkane addition for the synthesis of nucleosides having a C-5′C-6′ bond is discussed.     

Nicotine N-oxides

Nicotine-1-N-oxide, trans and cis isomers of nicotine-1′-N-oxide and of nicotine-1,1′-di-N-oxide have been prepared and characterised by NMR, MS and reduction to nicotine. The trans and cis isomers of nicotine-1′-N-oxide have been identified in leaves, stems and roots of Nicotiana tabacum, N. affinis and N. sylvestris.