Directed biosynthesis of unnatural alkaloids in Dolichothele sphaerica

Using appropriate precursors, the two unnatural alkaloids 4(5)-[N-isocaproylaminomethyl]imidazole and 3-[2-N-isovalerylaminoethyl]pyrazole were produced by Dolichothele sphaerica. The former compound represents an unnatural alkaloid formed by the simultaneous introduction of two unnatural precursors, namely isocaproic acid and 4(5)-aminomethylimidazole. The latter compound represents an aberrant alkaloid formed by the introduction of a precursor of different heterocyclic entity, 3-aminoethylpyrazole.     

δ-N-Methylornithine: a natural constituent of Atropa belladonna

δ-N-Methylornithine, a tropane alkaloid precursor, is shown for the first time to be a natural plant constituent; it was isolated in radioactive form after feeding [5-¹⁴C]- and [5-³H]ornithine to Atropa belladonna. This finding supports the deduced role of δ-N-methylornithine in tropane alkaloid biosynthesis.     

Melovinone,an open chain analogue of melochinone from Melochia tomentosa

Melovinone, a new alkaloid isolated from the roots of Melochia tomentosa has been characterized as 3,7,8-trimethoxy-2-methyl-5(5′-phenylpentyl)-4-quinolinone.     

Production of pilocarpine in callus of jaborandi (<Emphasis Type="Italic">pilocarpus microphyllus</Emphasis> stapf)

Summary Jaborandi (Pilocarpus microphyllus) is the only known source of pilocarpine, and although this alkaloid is the only natural compoud used to treat glaucoma, very little is known about its metabolism. Calluses obtained from petioles of P. microphyllus leaves were partially immersed in MS (Murashige and Skoog) liquid medium containing different pH levels (4.8, 5.8, and 6.8), nutrient concentration (MS normal basal medium concentration, absence of N, P, and K and three times normal concentrations), histidine and threonine (0.05, 0.15 and 0.75 mM) NaCl (25 and 75 mM) and polyethylene glycol (5 and 15%). Exposure to methyljasmonic acid (MJ) vapor was also investigated. The calluses were subjected to these conditions for 4 and 8d under gentle agitation in the dark. Some calluses were also kept under continuous light. Pilocarpine was identified in the liquid medium by liquid chromatography-mass spectrometry/mass spectrometry. The alkaloid quantifications in the media and cells were carried out by high performance liquid chromatography (HPLC). The calluses maintained in the dark released the greatest quantities of pilocarpine into the medium. Methyljasmonate inhibited the release of pilocarpine in the medium. High pH (6.8), absence and excess of N, excess of P, and 0.75 mM of histidine and threonine induced the highest production of the alkaloid.     

Origin of nitrogen in the biosynthesis of solanidine by Veratrum grandiflorum

Veratrum plants accumulate verazine as the major alkaloid in the rhizome during the dormant stage 4 months after cold treatment. The quantitative c     

Lycopodium Alkaloids from Huperzia serrata and Their Anti-acetylcholinesterase Activities

One new fawcettimine-type alkaloid ( 1 ), one new miscellaneous-type alkaloid ( 2 ), four new lycodine-type alkaloids ( 3 – 6 ), and eight known ones ( 7 – 14 ) were isolated from the whole plants of Huperzia serrata. Their structures and absolute configurations were elucidated based on spectroscopic data, X-ray diffraction, ECD calculation and Mosher's method. Compound 1 was a rare C₁₈N₂-type Lycopodium alkaloid, possessing serratinine skeleton with an amide side chain in C-5. The absolute configuration of the 18-OH of compounds 4 – 6 were first determined by Mosher's method. Moreover, compounds 1 – 14 were assayed anti-acetylcholinesterase effect in vitro, and compound 7 showed significant anti-acetylcholinesterase activity with an IC₅₀ value of 16.18±1.64 μM.     

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.     

Synthesis of [3-14C]-2′-methylreticuline and its incorporation into alkaloid fractions of Papaver somniferum

[3-¹⁴C]-2′-Methylreticuline has been synthesized by standard methods. This modified opium alkaloid precursor is efficiently incorporated by aberrant biosynthesis into alkaloid fractions of Papaver somniferum, particularly into a highly purified codeine fraction.     

A new dimeric carbazole alkaloid from Murraya koenigii (L.) leaves with α-amylase and α-glucosidase inhibitory activities

A new dimeric carbazole alkaloid, 3,3′,5,5′,8-pentamethyl-3,3′-bis(4-methylpent-3-en-1-yl)-3,3′,11,11′-tetrahydro-10,10′-bipyrano[3,2-a]carbazole, was isolated from the hexane extract of leaves of Murraya koenigii (L.) Sprengel. (Family: Rutaceae). The structure was elucidated based on ¹³C and ¹H NMR, High-Resolution Mass Spectrometry (HRMS), and 2D NMR data. The in vitro antidiabetic activity of the new dimer was investigated in terms of α-amylase and α-glucosidase enzyme inhibition assays. The dimer exhibited significant α-amylase inhibitory activity (IC₅₀ = 30.32 ± 0.34 ppm) and α-glucosidase inhibitory activity (IC₅₀ = 30.91 ± 0.36 ppm).     

Alkaloid distribution and catabolism in Cephalotaxus harringtonia

Cephalotaxus harringtonia produces a variety of antitumor alkaloids that are distributed throughout the tree. In a young plant grown in a controlled environment, the concentration of free alkaloids (homoerythrina alkaloids and cephalotaxine) did not increase with age, whereas the concentration of cephalotaxine esters (harringtonine, deoxyharringtonine, isoharringtonine and homoharringtonine) increased roughly 5-fold. Total alkaloid concentrations increased in the older leaves of the plant and decreased in the older stems. Physiological stress (pruning) causes hydrolysis of part of the stored alkaloid esters to free cephalotaxine within one week. In 4 out of 5 field-grown trees environmental factors caused complete ester hydrolysis and, in addition, the oxidation of cephalotaxine to 11-hydroxycephalotaxine and drupacine and of homoerythrina alkaloid to its epoxy derivative. This shows that the alkaloids in this perennial tree are not inert storage products, but are under metabolic control.     

Bioactive aporphine alkaloids from the stems of Dasymaschalon rostratum

Three undescribed aporphine alkaloids dasymaroine A (1), 3-methoxyoxoputerine N-oxide (2), and dasymaroine B (3), along with nine known analogues (4–12) were isolated from the stems of Dasymaschalon rostratum Merr. The structures were elucidated using spectroscopic methods and by comparison with published NMR spectroscopic data. Compound 1 is a rarely reported nitro aporphine alkaloid and its absolute configuration was defined based on negative specific rotation and single-crystal X-ray diffraction. Compound 2 represents the first example of oxoaporphine alkaloid N-oxide. All compounds were evaluated for their activities of six pathogenic bacteria, 1 exhibited significant inhibition against Escherichia coli and Saphylococcus aureus with MIC values of 1.2 and 2.5 μM, respectively. As well as compounds 1–5, 7, 10, 12 were evaluated for their anti-HIV activities with EC₅₀ ranged from 1.93 to 9.70 μM.     

Efficient synthesis of jusbetonin, an indolo[3,2-b]quinoline glycoside, and its derivatives

Jusbetonin, an indolo[3,2-b]quinoline alkaloid glycoside originally isolated from Justicia betonica, and its derivatives were synthesized. The key steps in the synthetic strategy were the construction of indolo[3,2-b]quinoline skeleton and efficient coupling with the saccharides, in which the α-d-glycopyranosyl bromides were shown to be effective donors. Primary screening showed that all synthesized compounds possessed moderate proliferation inhibitory activity.     

Micropropagation of Corydalis ambigua through embryogenesis of tuber sections and chemical evaluation of the ramets

Corydalis ambigua, a perennial herb of the family Papaveraceae, was micropropagated through somatic embryogenesis starting from sliced tubers. Somatic embryos were proliferated on Linsmaier and Skoog medium of a half strength containing 2% sucrose and 0.1 M indole-3-acetic acid or indole-3-butyric acid solidified with 0.2% Gelrite. Somatic embryos were germinated and grew on plant growth regulator-free White's medium supplemented with 2% sucrose and 0.8% agar in the dark at 0–4°C for 6 months to give rise to microtubers that could be potted out of culture tubes. Three strains of micropropagated plants cultivated outdoors for 5 years gave different tetrahydroprotoberberine-type alkaloids pattern, respectively. The variation of tetrahydroprotoberberine-type alkaloid (corybulbine, corydaline and cavidine) content within a strain was not significantly different from that of the corresponding alkaloid in the wild plants.     

Iridoids,monoterpenoid glucoindole alkaloids and flavonoids from Vinca major

A new secoiridoid glucoside, vinmajoroside (1), was isolated from the leaves of Vinca major L. along with 11 known compounds belonging to the secoiridoid ((7α)-7-O-methylmorroniside, 2), iridoid (loganin, loganic acid and 7-O-p-coumaroylloganin), monoterpenoid glucoindole alkaloid (5 (S)-5-carboxyvincoside and strictosamide), flavonoid (rutin, kaempferol 3-O-rutinoside and robinin), lignan (syringaresinol 4-O-β-glucopyranoside) and phenolic acid (chlorogenic acid) groups. The structure elucidation of the isolates was accomplished by extensive 1D and 2D-NMR experiments as well as ESI-MS. Secoiridoids and lignan were encountered for the first time in the genus Vinca.     

Pyrrolizidine alkaloids from Canarian endemic plants and their biological effects

Pyrrolizidine alkaloid (PA) producing plants belonging to the Boraginaceae (Echium wildpretti) and Asteraceae (Canariothamnus palmensis, Kleinia neriifolia, Pericallis appendiculata, Pericallis echinata, Pericallis hansenii, Pericallis multiflora, Pericallis steetzii and Senecio bollei) were selected to study their alkaloidal composition and the defensive properties (antifeedant and phytotoxic effects) of their ethanolic and alkaloidal extracts plus their isolated PAs against insects (Spodoptera littoralis, Leptinotarsa decemlineata, the aphids Myzus persicae and Rhopalosiphum padi) and Lactuca sativa seeds. We also tested the selective cytotoxic effects of these PAs on insect-derived Sf9 and mammalian CHO cells. Most of the insect antifeedant effects were found in the ethanolic extracts. The isolated PAs had species- and structure-dependent antifeedant effects and all of them decreased L. sativa radicle growth, suggesting a specific mode of action against insects and a generalized one against plants. Given the relatively low alkaloid content of these species, we assume that their herbivore defenses are not only alkaloid-based.     

Lupin alkaloids from flowers of Echinosophora koreensis

(?)-Methyl 12-cytisineacetate (2) was isolated from methanol extracts of fresh flowers of Echinosophora koreensis together with seven known lupin alkaloids. Ethyl 12-cytisineacetate (3) was also isolated from ethanol extracts of the same flowers. Compounds 2 and 3 were artifacts and (?)-12-cytisineacetic acid (4) is assumed to be the principal source of 2 and 3. The variations in alkaloid content during growth of the flowers and the seedlings were also examined.     

Translocation and accumulation of nicotine via distinct spatio-temporal regulation of nicotine transporters in Nicotiana tabacum

In plants, secondary metabolites play important roles in adaptation to the environment. Nicotine, a pyridine alkaloid in Nicotiana tabacum, functions as chemical barrier against herbivores. Nicotine produced in the root undergoes long-distance transport and accumulates mainly in the leaves. Since production of such defensive compounds is costly, plants must regulate the allocation of the products to their tissues; however, the molecular mechanism of nicotine translocation remains unclear. Our recent studies identified a novel multidrug and toxic compound extrusion (MATE)-type nicotine transporter, JAT2 (jasmonate-inducible alkaloid transporter 2). This transporter is specifically expressed in leaves, localizes to the tonoplast, and transports nicotine as its substrate. The specific induction of JAT2 expression in leaves by methyl jasmonate (MeJA) treatment suggests that this transporter plays an important role in nicotine distribution to leaves, especially under herbivore attack, by transporting nicotine into the vacuole. Considering JAT2, together with the previously identified MATE transporters JAT1, MATE1, and MATE2, and the PUP (purine permease) transporter NUP1 (nicotine uptake permease1), we show a model of nicotine translocation and accumulation via distinct spatio-temporal regulation of nicotine transporter expression. Furthermore, we discuss the possible role of nicotine transporters in determining outcrossing rates and seed production.     

Effect of 2-chloroethylphosphonic acid on capsule formation and alkaloid content in Papaver somniferum

Application of different concentrations of ethephon (2-chloroethylphosphonic acid) to Papaver somniferum L. at the times of stem elongation, bud, and capsule formation produced different effects. Ethephon (10^-2 M ) retarded growth of the plant and inhibited capsule formation during stem elongation, significantly reduced capsule size during the flowering period, but did not alter capsule development during capsule formation. When applied during the period of stem elongation, ethephon (10^-3 M and 10^-4 M ) reduced capsule size; alkaloid accumulation was reduced by ethephon at a concentration of 10^-3 M , but slightly increased by 10^-4 M . Ethephon (10^-3 M and 10^-4 M ) did not alter capsule development or alkaloid content significantly when applied during bud formation, but stimulated capsule size and alkaloid content when applied during capsule formation. Pretreating the plants with Ag⁺ (silver nitrate) did not reverse the ethephon effect. The results suggest that capsule maturation and alkaloid accumulation in P. somniferum are modified by ethylene, which is produced as a result of exogenous ethephon treatment.