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PubMed1992

HIV-1 and HIV-2 reverse transcriptases: a comparative study of sensitivity to inhibition by selected natural products.

One hundred and fifty six pure natural products, which had previously been tested against HIV-1 reverse transcriptase, were evaluated for HIV-2 reverse transcriptase inhibitory activity. Compounds that lacked effect in the HIV-1 reverse transcriptase system were found also to be inactive against HIV-2 reverse transcriptase. However, compounds belonging to the benzophenanthridine and protoberberine classes of alkaloids, certain flavonoids, the iridoid, fulvoplumierin, and the ansamycin antibiotic, daunomycin, exhibited similar potencies in both enzyme systems. In contrast, HIV-2 reverse transcriptase was observed to be four-fold more sensitive toward the inhibitory effects of the ipecac alkaloids, O-methylpsychotrine sulfate heptahydrate and psychotrine dihydrogen oxalate. Such differences in susceptibilities to inhibitors may indicate subtle dissimilarities in enzyme structure and function.

Alkaloids↗
PubMed1996

Elicitation of dihydrobenzophenanthridine oxidase in Sanguinaria canadensis cell cultures.

Dihydrobenzophenanthridine (DHBP) oxidase catalyses the last step in the biogenesis of the benzo[c]phenanthridine alkaloid sanguinarine. Addition of autoclaved fungal preparations or putative plant defence signalling intermediates (jasmonic acid (JA), methyl jasmonate (MeJ), acetylsalicylic acid (ASA)) to Sanguinaria canadensis cell suspension cultures elicited an increase in the activity of DHBP oxidase. MeJ and ASA were better inducers of oxidase activity than were the fungal elicitor and JA. Enzyme-specific activity could be induced in a dose- and time-dependent manner up to 4- to 14-fold, respectively, when cells were treated with MeJ or with ASA. A change in total enzyme activity in cultured cells was observed only at the highest concentration of MeJ and not at any level of ASA tested. The results suggest that MeJ and ASA may play a role in the S. canadensis defence against pathogens by eliciting the enzymes involved in the synthesis of the phytoalexin benzophenanthridine alkaloids.

Cells, Cultured↗
PubMed1999

A redox-dependent, G-protein-coupled phospholipase A of the plasma membrane is involved in the elicitation of alkaloid biosynthesis in Eschscholtzia californica.

In cultured cells of California poppy formation of benzophenanthridine alkaloids can be triggered by a yeast elicitor preparation independently of the hypersensitive reaction. A plasma membrane (PM) bound phospholipase A (PLA) is likely to play a role in the signalling process: PLA activity was detectable in individual cells, cell suspensions and PM vesicles with the fluorogenic phospholipid bis-BODIPY FL C11-PC and was sensitive to known inhibitors of PLA2. In microscopic assays, enzyme activity increased after elicitor contact of cells that were pretreated with non-saturating concentrations of PLA2 inhibitors. In PM vesicles a PLA2-like protein as well as G alpha- and G beta-proteins were detected immunologically. Anti-G alpha or anti-G beta antisera or mastoparan stimulated PLA activity thus indicating a G-protein-controlled enzyme. Elicitation of alkaloid production was sensitive to aristolochic acid and enhanced by PLA2 products such as lysophosphatidylcholine and linolenic acid. Pretreatment of the cells with the artificial electron acceptors hexabromoiridate(V) or ferricyanide(III) reversibly abolished the effect of subsequent elicitation and reduced the activity of PLA both in intact cells and in PM vesicles. It appears, therefore, that PLA2 is a point of interference of redox control with the signal path.

Alkaloids↗
PubMed2002

The evaluation of forty-three plant species for in vitro antimycobacterial activities; isolation of active constituents from Psoralea corylifolia and Sanguinaria canadensis.

Extracts from forty-three plant species were selected on account of reported traditional uses for the treatment of TB and/or leprosy. These were assayed for antimycobacterial activities. A simple in vitro screening assay was employed using two model species of mycobacteria, M. aurum and M. smegmatis. Crude methanolic extracts from three of the plants, C. mukul, P. corylifolia and S. canadensis, were found to have significant antimycobacterial activity against M. aurum only (MIC=62.5 microg/ml). Bioassay guided fractionation led to the isolation of two known benzophenanthridine alkaloids, sanguinarine (1) and chelerythrine (2), from the roots S. canadensis and the known phenolic meroterpene, bakuchiol (3) from the seeds of P. corylifolia. The fractionation of the resin of C. mukul lead to a decrease in antimycobacterial activity and hence further work was not pursued. Compound (2) was the most active against M. aurum and M. smegmatis (IC(50)=7.30 microg/ml [19.02 microM] and 29.0 microg/ml [75.56 microM], respectively). M. aurum was the most susceptible organism to all three compounds. No significant difference in antimycobacterial activity was observed when the two alkaloids were tested for activity in media of differing pH values. The activities of the pure compounds against M. aurum were comparable with those against M. bovis BCG with compound (2) being the most active (M. bovis BCG, IC(50)=14.3 microg/ml [37.3 microM]). These results support the use of these plants in traditional medicine.

Antitubercular Agents↗
PubMed1999

Two antimicrobial alkaloids from Bocconia arborea.

Two alkaloid constituents of Bocconia arborea showed considerable antimicrobial activity against gram-positive and gram-negative bacteria and Candida albicans. Bioactivity-guided fractionation with thin-layer bioautography led to the isolation of the two known benzophenanthridine alkaloids, dihydrochelerythrine and dihydrosanguinarine. The minimal inhibitory concentration was determined for each compound using a twofold serial dilution assay. The structures of these compounds were determined by 1H and 13C NMR analyses.

Alkaloids↗
PubMed2002

Molecular modeling of 3-arylisoquinoline antitumor agents active against A-549. A comparative molecular field analysis study.

A series of 58 3-arylisoquinoline antitumor agents were investigated for defining the pharmacophore model using comparative molecular field analysis (CoMFA) program. The studied compounds related to bioisostere of benzophenanthridine alkaloid were synthesized and evaluated for antitumor cytotoxicity against human lung tumor cell (A 549). In order to perform the systematic molecular modeling study of these compounds, the conformational search was carried out based on the single X-ray crystallographic structure of 7,8-dimethoxy-3-phenylisoquinolin-(2H)-one (2). Interestingly, two types of structures having different dihedral angles between the isoquinoline ring and 3-aryl ring were found in the crystals. Therefore, CoMFA was performed two different, overlapping ways. The alignments of the structures were based on the common isoquinoline ring and 3-aryl ring. The 3-D-quantitative structure-activity relationship study resulted in significant cross-validated, conventional r(2) values equal to 0.715 and 0.927, respectively.

Antineoplastic Agents↗
PubMed1997

Further definition of the D1 dopamine receptor pharmacophore: synthesis of trans-6,6a,7,8,9,13b-hexahydro-5H-benzo[d]naphth[2,1-b]azepines as rigid analogues of beta-phenyldopamine.

In an effort to define further the active geometry of the beta-phenyldopamine pharmacophore of certain dopamine D1 agonists, the title compounds have been synthesized as conformationally restricted homologues of the potent benzophenanthridine dopamine D1 agonist dihydrexidine 4a. The dihydroxy secondary amine 5b was evaluated as a potential agonist, whereas the N-methyl compounds 5a and 5c were hypothesized to be antagonists. Surprisingly, none of the three compounds had high affinity for dopamine D1 or D2 receptors. A comparison of the low-energy conformations of these molecules shows that the pendant phenyl ring of 5b is twisted about 28 degrees relative to that of the corresponding ring of 4a. Further, the additional methylene used to expand the C ring of 5b projects toward the alpha face of the molecule, perhaps suggesting that steric protrusion in this region of the molecule is not tolerated. Finally, the phenethylamine fragment incorporated into these molecules deviates about 30 degrees from the antiperiplanar conformation postulated to be necessary for agonist activity. On the other hand, the potential antagonist molecules 5a and 5c were compared with the dopamine D1 antagonist SCH 39166 2. The conformations of the former two structures differ quite dramatically from that of 2. The most notable differences lie in the relative orientations of the pendant phenyl rings in the two series, as well as the fact that the ethylamine fragment in 2 approximates a gauche conformation, while the comparable orientation in 5a and 5c more nearly approaches an antiperiplanar conformation. These findings will be used to refine further the model of the dopamine D1 agonist receptor that we have previously developed.

Animals↗
PubMedDate not supplied

The alkaloids of Corydalis meifolia.

Six tetrahydroprotoberberines, (+)-sinactine, apocavidine, stylopine, (+)-cavidine, cheilanthifoline, and dehydrocavidine; two spirobenzylisoquinolines, yenhusomine and yenhusomidine; one phthalideisoquinoline, corlumine; one benzophenanthridine, dihydrosanguinarine and protopine, have been isolated from the leaves and stems of Corydalis meifolia Wall. Of these alkaloids, dehydrocavidine was a new base. The remaining alkaloids, although known, were isolated for the first time for this plant. (+)-Cavidine, protopine, corlumine, yenhusomine, and dehydrocavidine exhibited spasmolytic activity.

Alkaloids↗
PubMedDate not supplied

The alkaloids of Corydalis meifolia.

Six tetrahydroprotoberberines, (+)-sinactine, apocavidine, stylopine, (+)-cavidine, cheilanthifoline, and dehydrocavidine; two spirobenzylisoquinolines, yenhusomine and yenhusomidine; one phthalideisoquinoline, corlumine; one benzophenanthridine, dihydrosanguinarine and protopine, have been isolated from the leaves and stems of Corydalis meifolia Wall. Of these alkaloids, dehydrocavidine was a new base. The remaining alkaloids, although known, were isolated for the first time for this plant. (+)-Cavidine, protopine, corlumine, yenhusomine, and dehydrocavidine exhibited spasmolytic activity.

Alkaloids↗
PubMedDate not supplied

Evaluation of natural products as inhibitors of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase.

Inhibition of human immunodeficiency virus reverse transcriptase is currently considered a useful approach in the prophylaxis and intervention of acquired immunodeficiency syndrome (AIDS), and natural products have not been extensively explored as inhibitors of this enzyme. We currently report that the reverse transcriptase assay developed for the detection of the enzyme in virions involving polyadenylic acid.oligodeoxythymidylic acid (poly rA.oligo dT) and radiolabeled thymidine 5'-triphosphate (TTP), can be applied as a simple method for screening the human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) inhibitory potential of natural products. As reported herein, 156 pure natural products have been examined in this system. Benzophenanthridine alkaloids such as faragaronine chloride [1] and nitidine chloride, which are known inhibitors of avian myeloblastosis virus reverse transcriptase, demonstrated potent activity in the HIV-1 RT system, and 1 (IC50 10 micrograms/ml) was adopted as a positive-control substance. Additional inhibitors found were columbamine iodide [2] and other protoberberine alkaloids, the isoquinoline alkaloid O-methylpsychotrine sulfate [3], and the iridoid fulvoplumierin [4]. A number of indolizidine, pyrrolizidine, quinolizidine, indole, and other alkaloids, as well as compounds of many other structural classes, were tested and found to be inactive. A total of 100 plant extracts have also been evaluated, and 15 of these extracts showed significant inhibitory activity. Because tannins and other polyphenolic compounds are potent reverse transcriptase inhibitors, methods were evaluated for the removal of these from plant extracts prior to testing. Polyphenolic compounds were found to be responsible for the activity demonstrated by the majority of plant extracts. After appropriate tannin removal procedures were established, the bioassay system was shown to be generally applicable to both pure natural products and plant extracts. The method also proved useful in directing an isolation procedure with Plumeria rubra to yield fulvoplumierin [4] as an active compound (IC50 45 micrograms/ml).

Antiviral Agents↗
PubMed1998

Isolation and analysis of a gene bbe1 encoding the berberine bridge enzyme from the California poppy Eschscholzia californica.

A genomic clone, bbe1 was isolated that encodes the methyl jasmonate-inducible berberine bridge enzyme of antimicrobial benzophenanthridine alkaloid biosynthesis in the California poppy Eschscholzia californica. Genomic DNA gel blot analysis indicates that two genes are present in the E. californica genome that code for the berberine bridge enzyme reading frame. Each coding region is apparently preceeded by a unique promoter sequence. The bbe1 gene contains no introns and one transcriptional start site. A 41 nucleotide region between -496 and -455 of the 5'-flanking region appears to be essential for promoter activity in E. californica. The promoter displayed an unexpectedly high species specificity, being active in only E. californica and Thalictrum bulgaricum, out of 28 cell suspension cultures tested.

Amino Acid Sequence↗
PubMed2001

Elevational trends in defense chemistry, vegetation, and reproduction in Sanguinaria canadensis.

Evaluation of biotic interactions along geographic gradients reveals that pressure on plant populations by herbivores and pathogens increases as latitude decreases, and is accompanied by a parallel increase in the number and toxicity of alkaloid-bearing plants. We compared rhizome alkaloid content with plant reproductive and vegetative characters in Sanguinaria canadensis (Papaveraceae) along an elevational gradient over two growing seasons to ascertain 1) if alkaloid production in bloodroot varies among populations and systematically with elevation, and 2) if there exists a correlation between isoquinoline alkaloid, vegetative and reproductive production. In general, alkaloid content in bloodroot rhizomes declines with elevation, increases with rhizome water content, varies by site, and fluctuates seasonally with plant growth and reproduction. Alkaloid content was positively correlated with vegetative and reproductive effort with few exceptions. Analysis of total protopine and benzophenanthridine alkaloid concentrations revealed generally similar patterns as those of individual alkaloid concentrations, although significant differences did appear between individual alkaloid concentrations.

Adaptation, Physiological↗
PubMed2001

Chemopreventive activity of isoquinoline alkaloids from Corydalis plants.

Eighteen isoquinoline alkaloids including protoberberines (1-12), benzophenanthridines (13-16) and an aporphine (17) isolated from plants of Corydalis species (Fumariaceae) were tested for inhibitory effects on Epstein-Barr virus early antigen activation induced by 12-O-tetradecanoylphorbol 13-acetate in Raji cells. In a primary screening test, all of the isoquinoline alkaloids showed inhibitory activity with the IC50 values being in the range of 140-410 mol ratio/32 pmol TPA. The data demonstrate that these isoquinoline alkaloids might be valuable as anti-tumor promoters.

Alkaloids↗
PubMed2003

Antibacterial alkaloids from Zanthoxylum rhoifolium.

Two new dihydrobenzophenanthridine-type alkaloids, 6-methoxy dioxolo[4',5':4,5]benzo[c] dioxolo[4,5- j]phenanthridine (1) and 2,3,13-trimethoxy-5,11a-dihydro dioxolo[4',5':4,5]benzo[c]phenanthridine (2) were isolated from the stem bark of Zanthoxylum rhoifolium, together with four other previously known benzophenanthridine alkaloids, 6-acetonyldihydronitidine (3) [= 8-acetonyldihydronitidine], 6-acetonyldihydroavicine (4) [= 8-acetonyldihydroavicine], 6-acetonyldihydrochelerythrine (5) and xanthoxyline (6). The structures were elucidated mainly by spectroscopic methods, including 1D and 2D NMR spectroscopy. For alkaloids 1 and 2 we propose the trivial names rhoifolines A and B. The crude plant extracts and the alkaloids 3, 4 and 6 showed activity against Gram (+/-) bacteria, while the new alkaloids 1 and 2 were inactive.

Alkaloids↗
PubMed1998

Plant-derived leading compounds for chemotherapy of human immunodeficiency virus (HIV) infection.

Many compounds of plant origin have been identified that inhibit different stages in the replication cycle of human immunodeficiency virus (HIV): 1) virus adsorption: chromone alkaloids (schumannificine), isoquinoline alkaloids (michellamines), sulphated polysaccharides and polyphenolics, flavonoids, coumarins (glycocoumarin, licopyranocoumarin) phenolics (caffeic acid derivatives, galloyl acid derivatives, catechinic acid derivatives), tannins and triterpenes (glycyrrhizin and analogues, soyasaponin and analogues); 2) virus-cell fusion: lectins (mannose- and N-acetylglucosamine-specific) and triterpenes (betulinic acid and analogues); 3) reverse transcription; alkaloids (benzophenanthridines, protoberberines, isoquinolines, quinolines), coumarins (calanolides and analogues), flavonoids, phloroglucinols, lactones (protolichesterinic acid), tannins, iridoids (fulvoplumierin) and triterpenes; 4) integration: coumarins (3-substituted-4-hydroxycoumarins), depsidones, O-caffeoyl derivatives, lignans (arctigenin and analogues) and phenolics (curcumin); 5) translation: single chain ribosome inactivating proteins (SCRIP's); 6) proteolytic cleavage (protease inhibition): saponins (ursolic and maslinic acids), xanthones (mangostin and analogues) and coumarins; 7) glycosylation: alkaloids including indolizidines (castanospermine and analogues), piperidines (1-deoxynojirimicin and analogues) and pyrrolizidines (australine and analogues); 8) assembly/release: naphthodianthrones (hypericin and pseudohypericin), photosensitisers (terthiophenes and furoisocoumarins) and phospholipids. The target of action of several anti-HIV substances including alkaloids (O-demethyl-buchenavianine, papaverine), polysaccharides (acemannan), lignans (intheriotherins, schisantherin), phenolics (gossypol, lignins, catechol dimers such as peltatols, naphthoquinones such as conocurvone) and saponins (celasdin B, Gleditsia and Gymnocladus saponins), has not been elucidated or does not fit in the proposed scheme. Only a very few of these plant-derived anti-HIV products have been used in a limited number of patients suffering from AIDS viz. glycyrrhizin, papaverine, trichosanthin, castanospermine, N-butyl-1-deoxynojirimicin and acemannan.

Alkaloids↗
PubMed1997

Inhibition of eukaryote protein kinases by isoquinoline and oxazine alkaloids.

The aporphine isoquinoline alkaloid apomorphine is a potent inhibitor of the catalytic subunit (cAK) of rat liver cyclic AMP-dependent protein kinase (PKA), myosin light chain kinase (MLCK), and Ca(2+)- and phospholipid-dependent protein kinase C (PKC) (IC50 values 1, 11, and 8 microM, respectively). However, a number of O-methylated analogues of apomorphine are inactive or poor inhibitors of cAK. The benzophenanthridine isoquinoline alkaloid sanguinarine is a potent inhibitor of cAK but is a relatively poor inhibitor of PKC (IC50 values 6 and 217 microM respectively). However a number of methylated analogues of sanguinarine are inactive as cAK inhibitors. The aporphine isoquinoline alkaloids (+)-boldine and bulbocapnine are non-competitive inhibitors of MLCK with respect to both peptide substrate and ATP. The inhibition of cAK, MLCK, and PKC by apomorphine and sanguinarine is competitive with respect to ATP as substrate. The oxazine alkaloids darrow red, nile blue A, and oxazine 170 are variously effective as inhibitors of cAK, MLCK, PKC, and CDPK (IC50 values 4-65 microM). Ca2+ binds to apomorphine and (+)-boldine which, together with nile blue A and oxazine 170, are potent inhibitors of calmodulin (CaM)-dependent MLCK (IC50 values 11, 12, 4, and 7 microM, respectively), and interact with dansyl-CaM.

Alkaloids↗
PubMed2006

Biochemical evidence that berberine bridge enzyme belongs to a novel family of flavoproteins containing a bi-covalently attached FAD cofactor.

Berberine bridge enzyme (BBE) is involved in the transformation of (S)-reticuline to (S)-scoulerine in benzophenanthridine alkaloid biosynthesis of plants. In this report, we describe the high level expression of BBE encoded by the gene from Eschscholzia californica (California poppy) in the methylotrophic yeast Pichia pastoris employing the secretory pathway of the host organism. Using a two-step chromatographic purification protocol, 120 mg of BBE could be obtained from 1 liter of fermentation culture. The purified protein exhibits a turnover number for substrate conversion of 8.2 s(-1). The recombinant enzyme is glycosylated and carries a covalently attached FAD cofactor. In addition to the previously known covalent attachment of the 8alpha-position of the flavin ring system to a histidine (His-104), we could also demonstrate that a covalent linkage between the 6-position and a thiol group of a cysteine residue (Cys-166) is present in BBE. The major evidence for the occurrence of a bi-covalently attached FAD cofactor is provided by N-terminal amino acid sequencing and mass spectrometric analysis of the isolated flavin-containing peptide. Furthermore, it could be shown that anaerobic photoirradiation leads to cleavage of the linkage between the 6-cysteinyl group yielding 6-mercaptoflavin and a peptide with the cysteine residue replaced by alanine due to breakage of the C-S bond. Overall, BBE is shown to exhibit typical flavoprotein oxidase properties as exemplified by the occurrence of an anionic flavin semiquinone species and formation of a flavin N(5)-sulfite adduct.

Amino Acid Sequence↗
PubMed1986

Subcellular Localization of Alkaloids and Dopamine in Different Vacuolar Compartments of Papaver bracteatum.

Fractionation of Papaver bracteatum Arya II Lindl. latex on Renografin step gradients revealed that 43% of the dopamine was compartmentalized along with alpha-mannosidase (40%) in vacuoles sedimenting in the 2% fraction. Twenty-two percent of the dopamine was in the supernatant, but a corresponding amount (18%) of alpha-mannosidase was also present suggesting vacuole breakage during isolation. By subcellular fractionation of protoplasts from cultured P. bracteatum cells, the 1,000g sedimenting organelles have been identified as the major site of accumulation of the morphinan alkaloid, thebaine (99+/-0.8%), and the benzophenanthridine alkaloid, sanguinarine (96+/-3%). Although the 1,000g pellet also contained 33+/-4% of the total alkaloid precursor, dopamine, and half of the total vacuolar marker enzyme, alpha-mannosidase, 62+/-10% of the amine was localized in the 100,000g supernatant. A differential distribution of the alkaloids was discovered upon resolution of the lysed protoplasts on Renografin step gradients. Over 40% of the dopamine was in the supernatant with 15% in a 2% Renografin band. The remainder was evenly distributed in denser fractions of the gradient. The 4 to 8% interface, previously found to contain the largest amount of thebaine and small amounts of sanguinarine and dopamine, has been shown to be enriched in vacuoles by electron microscopy. Using a histofluorescence method, dopamine compartmentation in vacuoles of intact cultured cells was corroborated. In summary, dopamine, sanguinarine, and thebaine occur in vacuoles of different densities. A large fraction of the total dopamine in cultured cells was found in the 100,000g supernatant along with 37% of the alpha-mannosidase suggesting that the amine may be sequestered in more fragile vacuoles than the alkaloids. The possibility that some dopamine may be cytosolic cannot be ruled out.

Journal Article↗