Stereoselective enzymatic O-methylation of tetrahydropapaveroline and tetrahydroxyberbine alkaloids (original) (raw)
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Phytochemistry, 1972
Three labelled N-ace@ ammes have been syntheszed and tested as precursors of tetrahydro-flcarbolme and tetrahydrmsoqumolme alkaloids These are N-114Gacetyltryptamme, N-l-14C-acetyl-3-hydroxy4methoxyphenylethylamme and N-l-'*C-acetyl-3,4-dImethoxy-5-hydroxyphenylethykunme which were tested as precursors for eleagmne m Elaeagnus angustrfoha, salsolme m Echmocereus merkerl and anhalomdme m Lophophoru wdhamszr, respectively Under conditions when the plants were syntheslzmg these alkaloids from other precursors none of these amldes was mcorporated
Journal of Pharmacology and Experimental Therapeutics, 2003
The psychotropic β-carboline alkaloids, showing high affinity for 5-hydroxytryptamine (5-HT), dopamine, benzodiazepine and imidazoline receptors and the stimulation of locus coeruleus neurons, are formed endogenously from tryptophan-derived indolealkylamines through the Pictet-Spengler condensation with aldehydes in both plants and mammals. Cytochromes P450 (CYP) 1A1 (18.5), 1A2 (20) and 2D6 (100) catalyzed the Odemethylation of harmaline, and CYP1A1 (98.5), CYP1A2 (35), CYP2C9 (16), CYP2C19 (30) and CYP2D6 (115) that of harmine (relative activities). The dehydrogenation/aromatization of harmaline to harmine was not carried out by aromatase (CYP19), CYP1A2, CYP2C9, CYP2D6, CYP3A4, pooled recombinant P450s, or by human liver microsomes (HLM). Kinetic parameters were calculated for the Odemethylations mediated by each isozyme and by pooled HLM. K cat (min-1) and K m (µM) values for harmaline were CYP1A1 (10.
Inhibition of human drug metabolizing cytochrome P450 enzymes by plant isoquinoline alkaloids
Phytomedicine, 2011
The human cytochrome P450 (CYP) enzymes play a major role in the metabolism of endobiotics and numerous xenobiotics including drugs. Therefore it is the standard procedure to test new drug candidates for interactions with CYP enzymes during the preclinical development phase. The purpose of this study was to determine in vitro CYP inhibition potencies of a set of isoquinoline alkaloids to gain insight into interactions of novel chemical structures with CYP enzymes. These alkaloids (n = 36) consist of compounds isolated from the Papaveraceae family (n = 20), synthetic analogs (n = 15), and one commercial compound. Their inhibitory activity was determined towards all principal human drug metabolizing CYP enzymes: 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6 and 3A4. All alkaloids were assayed in vitro in a 96-well plate format using pro-fluorescent probe substrates and recombinant human CYP enzymes. Many of these alkaloids inhibited the CYP3A4 form, with 30/36 alkaloids inhibiting CYP3A4 with at least moderate potency (IC 50 < 10 M) and 15/36 inhibiting CYP3A4 potently (IC 50 < 1 M). Among them corydine, parfumine and 8-methyl-2,3,10,11-tetraethoxyberbine were potent and selective inhibitors for CYP3A4. CYP2D6 was inhibited with at least moderate potency by 26/34 alkaloids. CYP2C19 was inhibited by 15/36 alkaloids at least moderate potently, whereas CYP1A2, CYP2B6, CYP2C8, and CYP2C9 were inhibited to a lesser degree. CYP2A6 was not significantly inhibited by any of the alkaloids. The results provide initial structure-activity information about the interaction of isoquinoline alkaloids with major human xenobiotic-metabolizing CYP enzymes, and illustrate potential novel structures as CYP form-selective inhibitors.
Proceedings of the Japan Academy Ser B Physical and Biological Sciences
O-Methyltransferases, which catalyze the production of small molecules in plants, play a crucial role in determining biosynthetic pathways in secondary metabolism because of their strict substrate specificity. Using three O-methyltransferase (OMT) cDNAs that are involved in berberine biosynthesis, we investigated the structure that was essential for this substrate specificity and the possibility of creating a chimeric enzyme with novel substrate specificity. Since each OMT has a relatively well-conserved C-terminal putative S-adenosyl-L-methionine-binding domain, we first exchanged the N-terminal halves of different OMTs. Among the 6 combinations that we tested for creating chimeric OMTs, 5 constructs produced detectable amounts of recombinant proteins, and only one of these with an N-terminal half of 6-OMT and a C-terminal half of 4′-OMT (64′-OMT) showed methylation activity with isoquinoline alkaloids as a substrate. Further enzymological analysis of 64′-OMT reaction product indicated that 64′-OMT retained the regiospecificity of 6-OMT. Further examination of the N-terminal region of 64′-OMT showed that about 90 amino acid residues in the N-terminal half were critical for reaction specificity. The creation of OMTs with novel reactivity is discussed.
Phosphate mediated biomimetic synthesis of tetrahydroisoquinoline alkaloids
Chemical Communications, 2011
All reagents were obtained from commercial sources and used as received unless otherwise stated. TLC was performed on Kieselgel 60 F 254 precoated plastic plates and compounds visualised by exposure to UV light, potassium permanganate, phosphomolybdic acid (PMA) or ninhydrin. Flash column chromatography was carried out using silica gel (particule size 40-63 µm). Both analytical and preparative HLPC were performed on a Varian Prostar instrument equipped with an autosampler, a UV-visible detector and a DiscoveryBIO wide Pore C18-10 Supelco column (25 × 0.46 cm for analytical scale work and 25 × 2.12 cm for preparative scale). Elutions were monitored at 280 nm and carried out according to either of the following gradients. Gradient 1: 5% to 40% of acetonitrile/water (0.1% TFA) and gradient 2: 5% to 90% of acetonitrile/water (0.1% TFA). Diasteromeric excesses were calculated by HPLC chromatography following gradient method 1 or 2. 1 H and 13 C NMR specta were recorded at 298 K at the field indicated using Bruker AMX 300, AMX 400, Avance 500 and Avance 600 machines. Coupling constants were measured in Hertz (Hz) and referenced to the deuterated solvent used. Infrared spectra were recorded on Perkin Elmer Spectrum 100 FTIR spectrometer. Optical rotations were recorded on a Perkin Elmer model 343 polarimeter at 589 nm, quoted in deg cm 2 g-1 and conc (c) in g/100 mL. Mass spectra were recorded on Thermo Finnegan MAT 900XP and Micro Mass Quattro LC electrospray mass spectrometers VG ZAB 2SE. Procedure A. Pictet-Spengler biomimetic reaction Amine (1 eq.) and aldehyde (1.2 eq.) were added to 10 mL of a 1:1 mixture of acetonitrile/potassium phosphate buffer (0.1 M solution at pH 6). The resulting solution was stirred at 50 ºC for 12 h. The crude product was extracted with dichloromethane (3 × 20 mL) which was evaporated in vacuo, then purified by preparative HPLC (by either gradient 1 or 2) and fractions containing the desired product were combined, concentrated and co-evaporated with methanol (3 × 20 mL). 4-Hydroxyphenylacetaldehyde 1 (2). The reaction was carried out under anhydrous conditions. To a solution of 2-(4-hydroxyphenyl)ethanol (500 mg, 3.62 mmol) in DMSO (5 mL) was added diisopropylethylamine (1.30 mL, 7.46 mmol) and then a solution of
Steric course of the N-methylation in the biosynthesis of ergot alkaloids byClaviceps purpurea
Journal of Basic Microbiology, 1991
Using the chiral methyl group methodology, the methylation step in the biosynthesis of ergot alkaloids catalyzed by the enzyme AdoMet:dimethylallyltryptophan N-methyltransferase was found to proceed with net inversion of methyl group configuration. The enzyme thus conforms to the majority of methyltransferases studied which mediate a direct SN2 transfer of the methyl group from AdoMet2) to the acceptor nucleophile in a ternary enzyme substrate complex.
Biophysical Reviews, 2015
The putative anticancer alkaloids berberine, palmatine, jatrorrhizine, and sanguinarine are known to bind to nucleic acids. To develop them as potential drugs for therapeutic use, their binding affinity to functional proteins and mode of transport in the circulatory system need to be clearly understood. Towards this, many studies on their binding aspects to proteins have been reported and a considerable amount of data, mostly of biophysical nature, exists in the literature. The importance of these natural isoquinoline alkaloids and the recent literature on their interaction phenomena with functional proteins, serum albumins, hemoglobin, and lysozyme are presented in this review.
The New β-D-Glucosidase in Terpenoid-Isoquinoline Alkaloid Biosynthesis in Psychotria ipecacuanha
Journal of Biological Chemistry, 2008
Ipecac alkaloids produced in the medicinal plant Psychotria ipecacuanha such as emetine and cephaeline possess a monoterpenoid-tetrahydroisoquinoline skeleton, which is formed by condensation of dopamine and secologanin. Deglucosylation of one of the condensed products N-deacetylisoipecoside (1␣(S)-epimer) is considered to be a part of the reactions for emetine biosynthesis, whereas its 1(R)-epimer N-deacetylipecoside is converted to ipecoside in P. ipecacuanha. Here, we isolated a cDNA clone Ipeglu1 encoding Ipecac alkaloid -D-glucosidase from P. ipecacuanha. The deduced protein showed 54 and 48% identities to raucaffricine -glucosidase and strictosidine -glucosidase, respectively. Recombinant IpeGlu1 enzyme preferentially hydrolyzed glucosidic Ipecac alkaloids except for their lactams, but showed poor or no activity toward other substrates, including terpenoid-indole alkaloid glucosides. Liquid chromatography-tandem mass spectrometry analysis of deglucosylated products of N-deacetylisoipecoside revealed spontaneous transitions of the highly reactive aglycons, one of which was supposed to be the intermediate for emetine biosynthesis. IpeGlu1 activity was extremely poor toward 7-Omethyl and 6,7-O,O-dimethyl derivatives. However, 6-O-methyl derivatives were hydrolyzed as efficiently as non-methylated substrates, suggesting the possibility of 6-O-methylation prior to deglucosylation by IpeGlu1. In contrast to the strictosidine -glucosidase that stereospecifically hydrolyzes 3␣(S)-epimer in terpenoid-indole alkaloid biosynthesis, IpeGlu1 lacked stereospecificity for its substrates where 1(R)-epimers were preferred to 1␣(S)-epimers, although ipecoside (1(R)) is a major alkaloidal glucoside in P. ipecacuanha, suggesting the compartmentalization of IpeGlu1 from ipecoside. These facts have significant implications for distinct physiological roles of 1␣(S)-and 1(R)-epimers and for the involvement of IpeGlu1 in the metabolic fate of both of them. Psychotria ipecacuanha Stokes (Rubiaceae) is a medicinal plant that is native to South and Central America. Its roots and