Quantification of Anti‐Addictive Alkaloids Ibogaine and Voacangine in In Vivo‐ and In Vitro‐Grown Plants of Two Mexican Tabernaemontana Species

Tabernaemontana alba and Tabernaemontana arborea are Apocynaceae species used in Mexican traditional medicine for which little phytochemical information exists. In this study, preliminary gas chromatography/mass spectrometry analyses of different organs obtained from wild plants of both species identified a total of 10 monoterpenoid indole alkaloids (MIAs) and one simple indole alkaloid, nine of which were reported for the first time in these species. Furthermore, callus cultures were established from T. alba leaf explants and regeneration of whole plants was accomplished via somatic embryogenesis. The anti‐addictive MIAs ibogaine and voacangine were then quantified by gas chromatography with flame ionization detection in wild plants of both species, as well as greenhouse‐grown plants, in vitro‐grown plantlets and embryogenic callus of T. alba. Ibogaine and voacangine were present in most samples taken from the whole plants of both species, with stem and root barks showing the highest concentrations. No alkaloids were detected in callus samples. It was concluded that T. alba and T. arborea are potentially viable sources of ibogaine and voacangine, and that these MIAs can be produced through somatic embryogenesis and whole plant regeneration of T. alba. Approaches to increase MIA yields in whole plants and to achieve alkaloid production directly in cell cultures are discussed.     

Beilschglabrines A and B: Two new bioactive phenanthrene alkaloids from the stem bark of Beilschmiedia glabra

Two new phenanthrene alkaloids, beilschglabrines A (1) and B (2) were isolated from the stem bark of Beilschmiedia glabra, together with lupeol, taraxerol, and 24-methylenelanosta-7,9-diene-3β-15α-diol. The structures of the isolated compounds were elucidated by extensive spectroscopic data analysis and comparison with respective literature data. The compounds were tested for DPPH radical scavenging, acetylcholinesterase and lipoxygenase inhibitory activities. Compound 1 displayed considerable activity in the acetylcholinesterase (IC₅₀ 50.4 μM), the DPPH radical scavenging (IC₅₀ 115.9 μM) and the lipoxygenase (IC₅₀ 32.8 μM) assays.     

Metabolic engineering for the production of plant isoquinoline alkaloids

Several plant isoquinoline alkaloids (PIAs) possess powerful pharmaceutical and biotechnological properties. Thus, PIA metabolism and its fascinating molecules, including morphine, colchicine and galanthamine, have attracted the attention of both the industry and researchers involved in plant science, biochemistry, chemical bioengineering and medicine. Currently, access and availability of high‐value PIAs [commercialized (e.g. galanthamine) or not (e.g. narciclasine)] is limited by low concentration in nature, lack of cultivation or geographic access, seasonal production and risk of overharvesting wild plant species. Nevertheless, most commercial PIAs are still extracted from plant sources. Efforts to improve the production of PIA have largely been impaired by the lack of knowledge on PIA metabolism. With the development and integration of next‐generation sequencing technologies, high‐throughput proteomics and metabolomics analyses and bioinformatics, systems biology was used to unravel metabolic pathways allowing the use of metabolic engineering and synthetic biology approaches to increase production of valuable PIAs. Metabolic engineering provides opportunity to overcome issues related to restricted availability, diversification and productivity of plant alkaloids. Engineered plant, plant cells and microbial cell cultures can act as biofactories by offering their metabolic machinery for the purpose of optimizing the conditions and increasing the productivity of a specific alkaloid. In this article, is presented an update on the production of PIA in engineered plant, plant cell cultures and heterologous micro‐organisms.     

Cytotoxic monoterpenoid indole alkaloids from the leaves and twigs of Tabernaemontana bovina

Phytochemical investigation of the leaves and twigs of Tabernaemontana bovina led to the isolation of 10 monoterpenoid indole alkaloids, including two new taberbovinines A (1) and B (2) along with eight known analogs: mehranine (3), 14α,15β-dihydroxy-N-methylaspidospermidine (4), (16S*)− 15-epi-E-isositsirikine (5), (16R*)− 15-epi-E-isositsirikine (6), 16 R*-19,20-E-isositsirikine acetate (7), hecubine (8), voafinidine (9), and voacangarine (10). Taberbovinine B (2) represents the first case of an unusual ring C/D cleavage among the natural Corynanthe-type alkaloids. Compounds 2 and 8 exhibited weak cytotoxicity against five human cancer cell lines, including SK-LU-1, HepG2, MCF-7, SK-Mel-2, and LNCaP, with IC₅₀ values ranging from 42.9 to 66.3 μM, whereas compounds 4 − 6 and 9 were cytotoxic toward MCF-7, SK-LU-1 and LNCaP cells, with IC₅₀ values in a range of 51.6–93.3 μM.     

Spatial and temporal distribution of the alkaloid sanguinarine in Sanguinaria canadensis L. (Bloodroot)

Acclimated and non-acclimated potted plants of Sanguinaria canadensis L. were harvested at early and late dormancy, anthesis, and immature and mature fruiting stages. Sanguinarine content and concentration were determined for rhizomes (distal, proximal, and middle sections), roots, leaves, flower, and fruit. Rhizomes had highest sanguinarine content and concentrations, and exhibited decreasing concentration gradients from the distal to proximal third. Concentrations in roots were a tenth of rhizome concentration. Concentrations in leaves, flowers, and fruit were one-thousandth of rhizome Sanguinarine content in whole acclimated plants was constant. Content in whole nonacclimated plants increased as the plant became physiologically active, but was constant during fruit maturation: content in roots, leaves, and fruit did not change. The substantial increase in whole-plant dry weight coupled with the unchanging sanguinarine content during fruit maturation suggests either a shift in photosynthate allocation from defense to growth, or a constant turnover of sanguinarine.     

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.     

4-Deoxyraputindole C induces cell death and cell cycle arrest in tumor cell lines

Several molecules extracted from natural products exhibit different biological activities, such as ion channel modulation, activation of signaling pathways, and anti-inflammatory or antitumor activity. In this study, we tested the antitumor ability of natural compounds extracted from the Raputia praetermissa plant. Among the compounds tested, an alkaloid, here called compound S4 (4-Deoxyraputindole C), showed antitumor effects against human tumor lineages. Compound S4 was the most active against Raji, a lymphoma lineage, promoting cell death with characteristics that including membrane permeabilization, dissipation of the mitochondrial potential, increased superoxide production, and lysosomal membrane permeabilization. The use of cell death inhibitors such as Z-VAD-FMK (caspase inhibitor), necrostatin-1 (receptor-interacting serine/threonine-protein kinase 1 inhibitor), E-64 (cysteine peptidases inhibitor), and N-acetyl- L -cysteine (antioxidant) did not decrease compound S4-dependent cell death. Additionally, we tested the effect of cellular activity on adherent human tumor cells. The highest reduction of cellular activity was observed in A549 cells, a lung carcinoma lineage. In this lineage, the effect on the reduction of the cellular activity was due to cell cycle arrest, without plasma membrane permeabilization, loss of the mitochondrial potential or lysosomal membrane permeabilization. Compound S4 was able to inhibit cathepsin B and L by a nonlinear competitive (negative co-operativity) and simple-linear competitive inhibitions, respectively. The potency of inhibition was higher against cathepsin L. Compound S4 promoted cell cycle arrest at G ₀ and G ₂ phase, and increase the expression of p16 and p21 proteins. In conclusion, compound S4 is an interesting molecule against cancer, promoting cell death in the human lymphoma lineage Raji and cell cycle arrest in the human lung carcinoma lineage A549.     

(-)-Amarbellisine, a lycorine-type alkaloid from Amaryllis belladonna L. growing in Egypt

A new lycorine-type alkaloid, named (-)-amarbellisine, was isolated from the bulbs of Egyptian Amaryllis belladonna L. together with the well known alkaloids (-)-lycorine, (-)-pancracine, (+)-vittatine, (+)-11-hydroxyvittatine, and (+)-hippeastrine. The new alkaloid, containing the pyrrolo[de]phenanthridine ring system, was essentially characterised by spectroscopic and optical methods, and proved to be the 2-methoxy-3a,4,5,7,11b,11c-hexahydro-1H-[1,3]dioxolo[4,5-j]pyrrolo[3,2,1-de]phenanthridinol. By using HPTLC technique we also carried out a comparative study of the relative and total alkaloidal content at two different stages of plant growth. Finally, the antimicrobial activity of the isolated alkaloids was assayed.     

Alkaloid accumulation in Catharanthus roseus cell suspension cultures fed with stemmadenine

Feeding stemmadenine to Catharanthus roseus cell suspension culture resulted in the accumulation of catharanthine, tabersonine and condylocarpine. Condylocarpine is not an intermediate in the pathway to catharanthine or tabersonine when it is fed to the cultures. The results support the hypothesis that stemmadenine is an intermediate in the pathway to catharanthine and tabersonine.     

Effects of phytosulfokine-α on growth and tropane alkaloid production in transformed roots of Atropa belladonna

Phytosulfokine (PSK)- is a sulphated pentapeptide, isolated fromthe medium of cultured Asparagus officinalis mesophyllcells, that promotes cell proliferation. It is a putative key factor inconditioned medium required for the growth of low-density plant cell cultures.The present study investigates the effect of PSK- on growth and tropanealkaloid production in Atropa belladonna hairy rootstransformed with Agrobacterium rhizogenes (MAFF 03-01724). Although the growth rates ofhairy roots cultured in medium with orwithout PSK- for 4 weeks did not show any differences, the productivityof tropane alkaloids, especially of hyoscyamine, was enhanced by10^–7 or 10^–8 M PSK-. Inaddition, the content of tropane alkaloids in transformed roots treated withPSK- was 1.4 times higher than that of untreated roots after 4 weeks ofculture. The time course of growth and tropane alkaloid production inAtropa belladonna transformed roots suggested thatPSK- influenced the growth of transformed roots during the activegrowingphase, but not tropane alkaloid production.