Alkaloid Methyllycaconitine Research Articles

Studying the Alkaloids Content in Delphinium oreophilum Huth

Research relevance: plant alkaloids are important in pharmacology based on their high physiological activity, as well as wide range of practical valuable medicinal properties. Most of plants necessary for conservation, cultivation and rational use of each type of plant resources in traditional and medical practice remains an urgent task. Kyrgyzstan is a favorable region for growth of medicinal herbs that is why flora research and study is of great importance. Research objectives: search of the biologically active content of methyllicaconitine alkaloids in roots and aerial parts of the Delphinium oreophilum plant growing in the territory of the Kyrgyz Republic. Research methods: diterpenoid alkaloids methyl lycaconitine, anthranoillicoctonine, lycoctonine, eldelin, eldelidine were obtained by separating the sum of alkaloids. Resulting compounds were analyzed by IR, NMR, Mass spectroscopy. A mixed melt test of the isolated perchlorate with a true sample of methyl lycaconitine perchlorate confirmed compounds identity. Research results: the sum of alkaloids obtained from the roots and aerial parts of Delphinium oreophilum plants collected in the southern and northern slopes of the Kichi Alai ridge. Conclusions: the content of total alkaloids in the roots and aerial parts of the plant growing in the southern slopes was 1.8% and 1% of the weight of the dry plant. The samples collected in the northern slopes contained 0.8% and 0.7% of the total alkaloids, respectively.

Serum toxicokinetics after intravenous and oral dosing of larkspur toxins in goats

Poisoning of cattle by larkspur plants (Delphinium spp.) is a concern for cattle ranchers in western North America. Previous research studies have evaluated the toxicokinetic profile of multiple larkspur toxins in several livestock species. However, those studies were all performed by orally dosing plant material. Consequently some toxicokinetic parameters could not be definitively determined. In this study, we compared the serum toxicokinetic profile of the larkspur alkaloids methyllycaconitine (MLA) and deltaline in goats dosed both IV and via oral gavage. The results from this study indicate that the toxic alkaloids in larkspurs undergo flip-flop kinetics, meaning the rate of absorption of the alkaloids is slower than the rate of elimination. The implications of flip-flop kinetics in treating animals poisoned by larkspur is discussed.

RP-HPLC Analysis of an Alkaloid–Methyllycaconitine from Mutagenic Delphinium malabaricum (Huth) Munz

A systematic search of some phytochemicals in Delphinium malabaricum will be undertaken to evaluate the therapeutic quality of D. malabaricum. The populations of D. malabaricum were subjected to analysis of alkaloids by Reversed phase HPLC technique. Among the various alkaloids present in Delphinium species methyllycaconitine is a principle alkaloid. Therefore, the populations of D. malabaricum were assessed for Methyllycaconitine (MLA) content in the mutants and their control. The results revealed that the MLA content was highest with 0.01% concentration of EMS (0.78 mg/g plant material) as compared to the control (0.76 mg/g plant material). The concentration of MLA decreased with an increase in dose/concentration of the mutagens. Less concentration of MLA in the roots of D. malabaricum indicates that it is less toxic and a further decrease in concentration after mutagenic treatment minimizes its toxic effects. As these populations are growing in the same environmental and edaphic conditions, observed variability can be related to genetic makeup altered due to mutation. The RP-HPLC analysis results could form the basis of a more detailed study of root alkaloids and any marked similarity/dissimilarity in their alkaloid pattern may draw reasonable conclusions of the difference between the mutants and the parent cultivar.

Norditerpenoid Alkaloids from Delphinium flexuosum Bieb.

Delphiniflexine, a new norditerpenoid alkaloid, together with the three known norditerpenoid alkaloids methyllycaconitine, ajadine, and acoseptrigenine were isolated from the aerial parts of Delphinium flexuosum. The structure of delphiniflexine was established on the basis of 1H, 13C, DEPT, homonuclear 1H COSY, NOESY, HSQC, and HMBC NMR studies.

ChemInform Abstract: A Double Mannich Approach to the Synthesis of Substituted Piperidones—Application to the Synthesis of Substituted E‐Ring Analogues of Methyllycaconitine.

AbstractA set of E‐ring analogues (X) of the delphinium alkaloid methyllycaconitine (XI) is prepared from title compounds (VII) using established transformations.

Synthesis of AE and BE Ring Analogues of the Alkaloid Methyllycaconitine

AbstractThe synthesis of AE and BE analogues of the alkaloid methyllycaconitine is reported. The analogues contain two key pharmacophores: a 2‐(2‐methylmaleimido)benzoate ester and a homocholine motif formed from a tertiary N‐(3‐phenylpropyl)amine incorporated into either a 3‐azabicyclo[3.3.1]nonane (AE) or octahydroquinoline (BE) ring system. An additional aromatic group is introduced into the AE bicyclic system using a Horner–Wadsworth–Emmons reaction. The BE analogues are synthesised by a one‐pot cyclisation using ethyl α‐(bromomethyl)acrylate, a primary amine and cyclohexanone leading to an efficient assembly of an octahydroquinoline ring system that mimics the BE‐rings of methyllycaconitine. In both the AE and BE analogues, the key 2‐(2‐methylsuccinimido)benzoate ester pharmacophore is introduced by esterification of the alcohol precursors with 2‐(2‐methylmaleimido)benzoic acid (10) under Steglich conditions followed by hydrogenation over palladium on charcoal.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

HPLC‐MS analysis of toxic norditerpenoid alkaloids: refinement of toxicity assessment of low larkspurs (Delphinium spp.)

The low larkspurs (Delphinium nuttallianum and D. andersonii) are two toxic plant species that are often fatally ingested by cattle on western USA rangelands. To assess the potential toxicity of the plants, methods are needed to identify and quantify the toxic N-methylsuccinimidoanthranoyllycacontine type alkaloids in the plant. To compare normal-phase and reverse-phase HPLC-MS methods of analysis for detection and identification of toxic alkaloids in two species of toxic larkspur plants and to define the toxic alkaloids found in Delphinium nuttallianum and D. andersonii collected from several sites in the western USA. The major toxic alkaloids found in the low larkspurs included methyllycaconitine, nudicauline, 14-deacetylnudicauline and geyerline. Other toxic alkaloids detected at lower concentrations included 16-deacetylgeyerline, grandiflorine, bearline, 14-acetylbearline, barbinine, 16-demethylnudicauline and three additional isomers of bearline. Total toxic alkaloid concentrations ranged from 0.72 mg/g (d.w.) to 7.02 mg/g determined by reverse-phase HPLC-MS. The low larkspurs contain a number of toxic alkaloids in addition to the alkaloid methyllycaconitine that need to be assessed when considering the toxicity of the plant. Both normal-phase and reverse-phase HPLC methods are adequate to detect and quantify the alkaloids. The reverse-phase separation may be preferred due to readily available columns, reduced solvent use and simplicity of the electrospray ionisation source.

Diastereoselective synthesis of a highly substituted cis-decahydroquinoline via a Knoevenagel condensation

A diastereoselective approach to 3,7,8-trisubstituted cis-decahydroquinolines is described. This ring system forms the core of rings B and E of the norditerpenoid alkaloid methyllycaconitine. This approach starts with a known disubstituted cyclohexene. The remaining carbons are attached via a Knoevenagel condensation followed by an intramolecular lactam formation. The stereochemistry of the substituents is controlled by the cis-substitution of the starting cyclohexene ring.

Synthesis of N‐(3‐Phenylpropyl)‐Substituted Tricyclic ABE Ring Analogues of the Alkaloid Methyllycaconitine

AbstractThe synthesis of several ABE tricyclic analogues 5, 31 and 32 of the alkaloid methyllycaconitine (1) is reported. The analogues contain two key pharmacophores: a tertiary N‐(3‐phenylpropyl) substituent attached to a 3‐azabicyclo[3.3.1]nonane ring system and a 2‐(3‐methyl‐2,5‐dioxopyrrolidin‐1‐yl)benzoate ester. Double Mannich reaction of the cyclic β‐keto esters 6 and 17 with the bis(aminol) ether 7 using methyltrichlorosilane as an activating agent provided an efficient method for the construction of the 3‐azabicyclo[3.3.1]nonanes 8 and 18. Ring‐closing metathesis of the derived dienes 11, 19, and 20 afforded the tricyclic ethers 12, 21, and 22, respectively, the C‐8 ester of which was reduced to a hydroxymethyl group to form the ABE tricyclic analogues 13, 23, and 24. Conversion of the alcohol 13 to the anthranilate ester 14 using N‐(trifluoroacetyl)anthranilic acid followed by fusion with methylsuccinic anhydride afforded the analogue 5 containing the key N‐(methylsuccinimido)anthranilate pharmacophore. In the case of the alcohols 23 and 24 the 2‐(3‐methyl‐2,5‐dioxopyrrolidin‐1‐yl)benzoate ester pharmacophore was appended by direct esterification with unsaturated acid 28 followed by hydrogenation to the ABE tricyclic compounds 33 and 34. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A Review of Advances in the Synthesis of Analogues of the Delphinium Alkaloid Methyllycaconitine

AbstractFor Abstract see ChemInform Abstract in Full Text.

Uraline, a New Norditerpenoid Alkaloid from Aerial Parts of Delphinium uralense Nevski

Uraline, a new norditerpenoid alkaloid, was isolated from aerial parts of Delphinium uralense. The structure of 1alpha,7,8-trihydroxy-6beta,14alpha,16beta-trimethoxy-18-N-(2-methyl)succinylanthranoyloxyaconane was ascribed to the new compound on the basis of 1H and 13C NMR, IR, and mass spectra. The known alkaloids methyllycaconitine and delcorine were also isolated from the plant.

Efficient Synthesis of the Azabicyclo[3.3.1]nonane Ring System in the Alkaloid Methyllycaconitine Using Bis(alkoxymethyl)alkylamines as Aminoalkylating Agents in a Double Mannich Reaction

AbstractThe double Mannich reaction of cyclic β‐keto esters with bis(alkoxymethyl)alkylamines provides an efficient and versatile method for the construction of azabicyclo[3.3.1]nonanes and azabicyclo[3.2.1]octanes. The optimum conditions for efficient reaction involve use of the activator trichloromethylsilane in acetonitrile as solvent at ambient temperature. The utility of this synthetic method is further demonstrated by the facile synthesis of several AE ring analogues 39, 42 of the alkaloid methyllycaconitine by appendage of the key N‐(methylsuccininimido)anthranilate pharmacophore to the N‐(3‐phenylpropyl)‐substituted double Mannich adducts 18, 27. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Use of bis-(aminol) ethers derived from N-( S)-(−)-α-methylbenzylamine in reactions with resorcinarenes and double Mannich reactions

The synthesis of some chiral bis-(aminol)ethers are described. Reaction of a solution of the resorcin[4]arene derived from propanal with N, N-bis(methoxymethyl)- N-( S)-(−)-α-methylbenzylamine in toluene at 85 °C initially afforded a 1:1 mixture of two diastereoisomeric tetrakis(benzoxazines). Further, heating of this mixture under reflux in ethanol for 24 h afforded the crystalline (α S),( S)-diastereoisomer in 77% yield. N, N-bis(ethoxymethyl)- N-( S)-(−)-α-methylbenzylamine and N, N-bis(ethoxymethyl)- N-( R)-(+)-α-methylbenzylamine were reacted with β keto esters to afford a 1:1 mixture of the diastereoisomeric double Mannich adducts. Two of the double Mannich adducts were converted into tricyclic ABE analogues of the alkaloid methyllycaconitine 1 .

Synthesis of Simple Analogues of Methyllycaconitine — An Efficient Method for the Preparation of the N‐Substituted Anthranilate Pharmacophore.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of simple analogues of methyllycaconitine—an efficient method for the preparation of the N-substituted anthranilate pharmacophore

The synthesis of several A and AE ring analogues of the alkaloid methyllycaconitine is reported. The key 2-(2″-methylsuccinimido)benzoate ester pharmacophore is introduced using an efficient two step procedure. Esterification of the alcohol precursors with N-(trifluoroacetyl)anthranilic acid under Steglich conditions followed by sodium borohydride mediated cleavage of the trifluoroacetyl group affords the anthranilate esters. Subsequent fusion with methylsuccinic anhydride affords the N-substituted anthranilate derivatives containing the key pharmacophore present in a range of commonly occurring Delphinium and Aconitum alkaloids.

Structure activity studies of ring E analogues of methyllycaconitine. Part 2: Synthesis of antagonists to the α3β4* nicotinic acetylcholine receptors through modifications to the ester

The development of novel agents for the differentiation of neuronal nicotinic acetylcholine receptors (nAChRs) is important for the treatment of a variety of pathological conditions. We have prepared and evaluated a number of simpler analogues of the norditerpeniod alkaloid methyllycaconitine (MLA) in an effort to understand molecular determinants of nAChR•small molecule interactions. We have previously reported the synthesis and evaluation of a series of ring E analogues of MLA. We report here the optimization of the α3β4* functional activity of this series of compounds through modification of the ester.

Synthesis of tricyclic analogues of methyllycaconitine using ring closing metathesis to append a B ring to an AE azabicyclic fragment.

The synthesis of several ABE tricyclic analogues of the alkaloid methyllycaconitine 1 is reported. The analogues contain two key pharmacophores: a homocholine motif formed from a tertiary N-ethyl amine in a 3-azabicyclo[3.3.1]nonane ring system and a 2-(3-methyl-2,5-dioxopyrrolidin-1-ly)benzoate ester 4. The synthesis of the ABE tricyclic analogues of MLA 1 began with selective allylation at C-3 of 3 to produce allyl beta-keto ester 4. Double Mannich reaction of 4 with ethylamine and formaldehyde produced bicyclic amine 5 The C-9 ketone of bicyclic amine 5 was selectively reduced to form bicyclic alcohols 6 and 7 which were subsequently allylated to form dienes 8 and 9. Ring closing metathesis of dienes 8 and 9 afforded tricyclic ethers 11 and 12, respectively, the C-8 ester of which was reduced to a hydroxymethyl group to form ABE tricyclic analogues 13 and 14. Addition of allylmagnesium bromide to the C-9 ketone of 20 afforded dienes 21 and 22, which underwent ring closing metathesis to form tricyclic esters 23 and 24, respectively. Reduction of the C-8 ethyl ester of 23 and 24 to a hydroxymethyl group afforded diols 25 and 26 respectively. The 2-(3-methyl-2,5-dioxopyrrolin-1-ly)benzoate ester was introduced by conversion of alcohols 13, 14, 25 and 26, to the anthranilate esters 16, 17, 27 and 28 using N-(trifluoroacetyl)anthranilic acid 15 followed by fusion with methylsuccinic anhydride to afford the substituted anthranilates 18, 19, 29 and 30 containing the key 2-(3-methyl-2,5-dioxopyrrolidin-1-ly)benzoate ester pharmacophore.

16-Demethoxymethyllycaconitine, a new norditerpenoid alkaloid from Delphinium cuneatum

A new norditerpenoid alkaloid has been isolated from the roots of Delphinium cuneatum. On the basis of 1H, 13C NMR, IR, and mass spectra, the structure of the alkaloid was established as 1α,6β,14α-trimethoxy-7,8-dihydroxy-18-(2″-methyl)succinylanthranoyloxyaconane (16-demethoxymethyllycaconitine). The roots of Delphinium cuneatum also contain the known alkaloid methyllycaconitine and N,N"-di(methoxycarbonyl)-3,4-diaminotoluene.

Methyllycaconitine is a potent antagonist of alpha-conotoxin-MII-sensitive presynaptic nicotinic acetylcholine receptors in rat striatum.

The plant alkaloid methyllycaconitine (MLA) is considered to be a selective antagonist of the alpha7 subtype of neuronal nicotinic acetylcholine receptor (nAChR). However, 50 nM MLA partially inhibited (by 16%) [(3)H]dopamine release from rat striatal synaptosomes stimulated with 10 microM nicotine. Other alpha7-selective antagonists had no effect. Similarly, MLA (50 nM) inhibited [(3)H]dopamine release evoked by the partial agonist (2-chloro-5-pyridyl)-9-azabicyclo[4.2.1]non-2-ene (UB-165) (0.2 microM) by 37%. In both cases, inhibition by MLA was surmountable with higher agonist concentrations, indicative of a competitive interaction. At least two subtypes of presynaptic nAChR can modulate dopamine release in the striatum, and these nAChR are distinguished by their differential sensitivity to alpha-conotoxin-MII (alpha-CTx-MII). MLA was not additive with a maximally effective concentration of alpha-CTx-MII (100 nM) in inhibiting [(3)H]dopamine release elicited by 10 microM nicotine or 0.2 microM UB-165, suggesting that both toxins act at the same site. This was confirmed in quantitative binding assays with (125)I-alpha-CTx-MII, which displayed saturable specific binding to rat striatum and nucleus accumbens with B(max) values of 9.8 and 16.5 fmol/mg of protein, and K(d) values of 0.63 and 0.83 nM, respectively. MLA fully inhibited (125)I-alpha-CTx-MII binding to striatum and nucleus accumbens with a K(i) value of 33 nM, consistent with the potency observed in the functional assays. We speculate that MLA and alpha-CTx-MII interact with a presynaptic nAChR of subunit composition alpha3/alpha6beta2beta3* on dopamine neurons. The use of MLA as an alpha7-selective antagonist should be exercised with caution, especially in studies of nAChR in basal ganglia.

Synthesis of ABE tricyclic analogues of methyllycaconitine using a Wacker oxidation–aldol strategy to append the B ring to the AE fragment

The synthesis of ABE tricyclic analogues 18 of the alkaloid methyllycaconitine 1 is described. The analogues contain the key pharmacophore reputed to be responsible for the biological activity of methyllycaconitine 1, namely, a homocholine motif formed from a tertiary N-ethylamine in a 3-azabicyclo[3.3.1]nonane ring system and a 2-(3-methyl-2,5-dioxopyrrolin-1-yl)benzoate ester side chain. The 3-azabicyclo[3.3.1]nonane ring system 10 was assembled via a double Mannich reaction of ethyl 3-(but-3′-enyl)-2-oxocyclohexane-1-carboxylate 9 with ethylamine and formaldehyde. Attempts to append a B ring to this AE ring system via McMurray coupling of dialdehyde 5 were hampered by the inability to effect conversion of the C-9 ketone 10 to vinyl ether 6. Wittig methylenation of ketone 10 afforded diene 7, however, subsequent attempts to effect double hydroboration–oxidation of diene 7 failed to realise diol 11enroute to the key dialdehyde precursor 5 required for the McMurray coupling. Wacker oxidation of the homoallyl group of 10 afforded methyl ketone 12 which underwent intramolecular aldol condensation to form enone 13. After selective reduction of the ketone and methylation, the resultant methyl ethers 15 underwent reduction of the ester sidechain affording neopentyl substituted alcohols 16. Finally, the 2-(3-methyl-2,5-dioxopyrrolin-1-yl)benzoate ester sidechain was appended by treatment of alcohols 16 with N-(trifluoroacetyl)anthranilic acid followed by fusion of the resultant anthranilates 17 with methylsuccinic anhydride.