Biosíntesis de alcaloides bencilisoquinolínicos / Benzylisoquinoline alkaloid biosynthesis / Biossíntese de alcalóides benzilisoquinolinas

Los alcaloides bencilisoquinolínicos (ABI) son metabolitos especializados con una distribución filogenética antigua pero conservadatodavía en clados modernos. Varios de ellos, como la morfina, sanguinerina y berberina tienen importancia en la medicina moderna. Enesta revisión se analizan los aspectos más sobresalientes del estado actual de la biosíntesis de ABI. Se han realizado estudios que hanpermitido conocer la biosíntesis de 22 de estos metabolitos nitrogenados. En su formación participan 43 enzimas agrupadas en oxidoreductasas,transferasas y liasas, que en algunos casos representan ejemplos atípicos de la forma en la que se originó la diversificación delmetabolismo secundario, entre ellos proteínas citocromo P450 (CYP450) con actividades catalíticas para la ruta de los ABI, o la enzimanorcoclaurina sintasa (NCS) que esta emparentada con proteínas alergénicas de defensa. Así mismo, hay avances genéticos en los quese ha podido caracterizar 30 enzimas, permitiendo conocer procesos de regulación. Otro aspecto interesante es la compartimentaciónde los sitios de biosíntesis y acumulación de ABI ya que en varios casos están separados espacialmente y en distintas especies o en lamisma pueden participar varios tipos de células. Ello ha sugerido el transporte intra e intercelular de los alcaloides, los precursores yde las enzimas, se ha documentado el transporte de berberina entre el citoplasma y las vacuolas del almacenamiento. El panorama de labiosíntesis de ABI se ha construido con los estudios de ejemplares de importancia farmacológica...

The benzylisoquinoline alkaloids (BIA) are specialized metabolites with an ancient phylogeneticdistribution, but still preserved in modern clades. Some of them, such as morphine, sanguinerine or berberine, are important for modernmedicine. This review discusses the highlights of the current state of the biosynthesis of BIA. There have been studies that show thebiosynthesis of 22 of these nitrogenous metabolites. In their formation there are 43 enzymes grouped into oxidoreductases, transferasesand lyases, which in some cases represent atypical examples of the manner in which the secondary metabolism diversification wasoriginated. Two of these examples are the cytochrome proteins P450 (P450), with catalytic activities for ABI route, or the norcoclaurinesynthase enzyme (NCS), which share substantial identity with defense allergenic proteins. Likewise, there are genetic advances thathave produced the characterization of 30 enzymes, allowing knowledge of regulatory processes. Another interesting aspect is thecompartmentation of the biosynthesis sites and accumulation of BIA, since in several cases they are spatially separated and in differentspecies, or in the same species several types of cells may be involved. This has suggested intra and intercellular transport of alkaloids,precursors and enzymes, and it has been documented berberine transport between the cytoplasm and the vacuoles of storage. The picturefor the biosynthesis of BIA has been constructed with exemplary studies of alkaloids with pharmacological importance...

Os alcalóides benzilisoquinolinas (ABI) são metabólitos especializados com umadistribuição filogenética antiga, mas ainda preservada em clados modernos. Vários deles, como a morfina, sanguinarina e berberina sãoimportantes na medicina moderna. Neste artigo, se analisam os aspectos mais destacados do estado atual da biossíntese de ABI; há estudosque tem permitido conhecer a biossíntese de 22 desses metabólitos nitrogenados. Na sua síntese participam 43 enzimas agrupadas emoxidoreductases, transferases, liases e, em alguns casos, representam exemplos atípicos da forma pela qual se originou a diversificaçãodo metabolismo secundário, incluindo as proteínas do citocromo P450 (CYP450), com atividades catalíticas para a rota dos ABI, ou aenzima norcoclaurina sintase (NCS), que está relacionada com proteínas alergênicas de defesa. Da mesma forma, há avanços genéticosna caracterização de 30 enzimas, permitindo conhecer processos de regulação. Outro aspecto interessante é a compartimentalização dossítios de biossíntese e acumulação de ABI uma vez que em muitos casos estão separados espacialmente e em diferentes espécies, ou namesma podem participar vários tipos de células. Isto há sugerido o transporte intra e intercelular de alcalóides, precursores das enzimas;tem sido documentado o transporte de berberina entre o citoplasma e os vacúolos de armazenamento. A perspectiva na biossíntese deABI foi construída com os estudos de exemplares de importância farmacológica...

Impact of cadmium and lead on Catharanthus roseus--a phytoremediation study.

The Madagascar Periwinkle, Catharanthus roseus (L.) G. Don (a valued medicinal plant) was exposed to different concentrations ofheavymetals like, CdCl, and PbCl, with a view to observe their bioaccumulation efficiency. Germination was inhibited by both the heavy metals in the seeds previously imbibed in GA, and KNO, for 24 hr. EC50 (the effective concentration which inhibits root length by 50%) was recorded as 180 microM for CdCl2, and 50 microM for PbCl2. Both alpha-amylase and protease activity were reduced substantially on treatment of seeds with increasing concentrations of CdCl2, and PbCl2. Malondialdehyde (MDA) a product of lipoxigenase (LOX) activity also increased due to the treatment of both CdCl, and PbCl2. When two-months-old plants grown in normal soil were transferred to soils containing increasing amounts of these two heavy metals, senescence of lower leaves and extensive chlorosis were noticed after four days of transfer However, plants gradually acclimatized and after 20 days the chlorophyll content was almost comparable to normal. Plants receiving CdCl2 treatment (250 microg g(-1) and less) became acclimatized after two weeks and started normal growth. But PbCl2 of 432 microg g(-1) and less could not affect the plant growth throughout, after a preliminary shock was erased. In case of CdCl2 treatment, a stunted growth with reduced leaf area, reduced biomass and sterility were recorded after six months, while plants show normal growth and flowering in case of PbCl2 treatment. Total alkaloid was also found to be decreased in the roots of CdCl2 treated plants. No change was observed in case of PbCl2. GA3 treatments to the CdCl2 treated plants show internode elongation and increase in leaf area with relatively elongated leaves and thinning of stem diameter AAS analyses of leaves of treated plants exhibited 5-10% accumulation of cadmium, but there was no accumulation of lead at all.

Antibacterial and antidiarrhoeal effects of alkaloids of Holarrhena antidysenterica WALL.

The alkaloids from the ethanolic extract of H. antidysenterica seeds were evaluated for their antibacterial activity against clinical isolates of enteropathogenic Escherichia coli (EPEC) in vitro, and their antidiarrhoeal activity on castor oil-induced diarrhoea in rats, in vivo. The plasmid DNA, whole cell lysate and outer membrane protein profile of a clinical isolate of EPEC was determined in presence of alkaloids of H. antidysenterica. The disc diffusion and agar well diffusion methods were used to evaluate the antibacterial efficacy. The alkaloids showed strong antibacterial activity against EPEC strains. In castor oil-induced diarrhoea, alkaloids reduced the diarrhoea with decrease in the number of wet faeces in pretreated rats at a dose of 200-800 mg/kg. The loss of plasmid DNA and suppression of high molecular weight proteins were observed on alkaloids treatment. Taking into account the multiple antibiotic resistance of EPEC, the results suggest usefulness of alkaloids of H. antidysenterica seeds as antibacterial and antidiarrhoeal agents.

Polyamines and plant alkaloids.

Naturally occurring alkaloids are nitrogenous compounds that constitute the pharmacogenically active basic principles of flowering plants. Alkaloids are classified into several biogenically related groups. Tobacco alkaloids are metabolised from polyamines and diamines putrescine and cadaverine. N-methyl transferase is the first enzyme in alkaloid biosynthetic pathway which drives the flow of nitrogen away from polyamine biosynthesis to alkaloid biosynthesis. Arginine decarboxylase has been suggested to be primarily responsible for providing putrescine for nicotine synthesis. Tryptophan is the precursor of indole alkaloids. However, the biosynthetic pathway of tropane and isoquinoline alkaloids are not clear. Genes for several key biosynthetic enzymes like arginine decarboxylase, ornithine decarboxylase, putrescine N-methyl transferase and spermidine synthase, hyoscyamine 6 beta hydroxylase,tryptophan decarboxylase etc have been cloned from different plant species. These genes are regulated by plant hormones, light, different kinds of stress and elicitors like jasmonates and their strong expression is primarily in the cultured roots. In view of this, the axenic hairy root cultures induced by Agrobacterium rhizogenes have been utilised to synthesise secondary metabolites. The current development in the knowledge of alkaloid biosynthesis, particularly molecular analysis, has been discussed in this review that may help to open up new avenues of investigation for the researchers.

1H NMR investigation of the interaction of berberine and sanguinarine with DNA.

Interaction of the alkaloids, berberine and sanguinarine with calf thymus DNA has been studied by 1H NMR. All proton resonances of the two compounds have been assigned using 2D-COSY, NOESY and ROESY spectra. Berberine has been found to partially intercalate into DNA, while sanguinarine shows normal intercalation and also binds more firmly to DNA. The NMR experiments indicate that sanguinarine is more potent than berberine in its activity.

Changes in phospholipids, fatty acids, oxidative enzymes, phenolics and protein levels during growth of normal and habituated tissues of Cocculus pendulus.

Cultures of C. pendulus were maintained on hormone free and hormone supplemented (NAA 1.0 mg/l and kinetin 0.5 mg/l) Murashige and Skoog medium. During the growth period, hormone free cultures had higher phenolic content, polyphenol oxidase activity and less protein content, peroxidase and IAA oxidase activity. Activity of all the three oxidising enzymes and phenolic content were high at 16 days growth. Total lipid content was higher (2.7-folds at 15 days) in hormone free cultures. Phospholipid content of both cultures was not markedly dissimilar except PC and DGDG contents. Thus it is evidenced that both the tissues were similar metabolically.