Modulation of CYPs, P-gp, and PXR by Eschscholzia californica (California Poppy) and Its Alkaloids.

Eschscholzia californica, a native US plant, is traditionally used as a sedative, analgesic, and anxiolytic herb. With the rapid rise in the use of herbal supplements together with over-the-counter and prescription drugs, the risk for potential herb-drug interactions is also increasing. Most of the clinically relevant pharmacokinetic drug interactions occur due to modulation of cytochrome P450 enzymes (CYPs), P-glycoprotein, and the pregnane X receptor by concomitantly used herbs. This study aimed to determine the effects of an EtOH extract, aqueous extract (tea), basic CHCl3 fractions, and isolated major alkaloids, namely protopine (1), escholtzine (2), allocryptopine (3), and californidine (4), of E. californica on the activity of cytochrome P450s, P-glycoprotein and the pregnane X receptor. The EtOH extract and fractions showed strong time-dependent inhibition of CYP 3A4, CYP 2C9, and CYP 2C19, and reversible inhibition of CYP 2D6. Among the alkaloids, escholtzine (2) and allocryptopine (3) exhibited time-dependent inhibition of CYP 3A4, CYP 2C9, and CYP 2C19 (IC50 shift ratio > 2), while protopine (1) and allocryptopine (3) showed reversible inhibition of CYP 2D6 enzyme. A significant activation of the pregnane X receptor (> 2-fold) was observed with the EtOH extract, basic CHCl3 fraction, and alkaloids (except protopine), which resulted into an increased expression of mRNA and the activity of CYP 3A4 and CYP 1A2. The expression of P-glycoprotein was unaffected. However, aqueous extract (tea) and its main alkaloid californidine (4) did not affect cytochrome P450s, P-glycoprotein, or the pregnane X receptor. This data suggests that EtOH extract of E. californica and its major alkaloids have a potential of causing interactions with drugs that are metabolized by cytochrome P450s, while the tea seems to be safer.

Molecular cloning and characterization of a cytochrome P450 in sanguinarine biosynthesis from Eschscholzia californica cells.

Benzophenanthridine alkaloids, such as sanguinarine, are produced from reticuline, a common intermediate in benzylisoquinoline alkaloid biosynthesis, via protopine. Four cytochrome P450s are involved in the biosynthesis of sanguinarine from reticuline; i.e. cheilanthifoline synthase (CYP719A5; EC 1.14.21.2.), stylopine synthase (CYP719A2/A3; EC 1.14.21.1.), N-methylstylopine hydroxylase (MSH) and protopine 6-hydroxylase (P6H; EC 1.14.13.55.). In this study, a cDNA of P6H was isolated from cultured Eschscholzia californica cells, based on an integrated analysis of metabolites and transcript expression profiles of transgenic cells with Coptis japonica scoulerine-9-O-methyltransferase. Using the full-length candidate cDNA for P6H (CYP82N2v2), recombinant protein was produced in Saccharomyces cerevisiae for characterization. The microsomal fraction containing recombinant CYP82N2v2 showed typical reduced CO-difference spectra of P450, and production of dihydrosanguinarine and dihydrochelerythrine from protopine and allocryptopine, respectively. Further characterization of the substrate-specificity of CYP82N2v2 indicated that 6-hydroxylation played a role in the reaction.

Identification of pavinane alkaloids in the genera Argemone and Eschscholzia by GC-MS.

The genera Eschscholtzia and Argemone (Papaveraceae) represent a rich source of pavinane alkaloids, the identification of which in alkaloid extracts is generally problematic without standards. The alkaloid extracts of three Argemone and four Eschscholtzia species were analyzed using GC-MS. The alkaloids were identified based on comparison of their mass spectra with commercial libraries, with reported data in the literature and with spectra of reference compounds. A total of 23 alkaloids of six structural types (pavinane, protopine, benzylisoquinoline, benzophenanthridine, aporphine and protoberberine) were identified. The fragmentation pathway of pavinane alkaloids was used for their identification. O-Methylneocaryachine has been reported for the first time from a natural sources and the alkaloid pattern of Eschscholzia pulchella has been analyzed and described for the first time.

Acetylcholinesterase and butyrylcholinesterase inhibitory compounds from Eschscholzia californica (Papaveraceae).

The roots and aerial parts of Eschscholzia californica Cham. (Papaveraceae) were extracted with ethanol. Repeated column chromatography, preparative TLC, and crystallization led to the isolation of fourteen isoquinoline alkaloids, the structures of which were determined on the basis of spectroscopic techniques and by comparison with literature values. One of the compounds isolated, 1-(3-hydroxy-4-methoxybenzyl)-2-methyl-6,7-methylenedioxy-1,2,3,4-tetrahydroisoquinoline (14), has not previously been isolated from a natural source. All isolated compounds were tested for human blood acetylcholinesterase (HuAChE) and human plasma butyrylcholinesterase (HuBuChE) inhibition activity. None of the compounds isolated significantly inhibited both HuAChE and HuBuChE, but the two benzylisoquinoline alkaloids, reticuline 9 and 14, showed promising inhibitory activity against HuBuChE.

Antifungal activity of the alkaloids from Eschscholzia californica.

The isoquinoline alkaloids hunnemanine and norsanguinarine have been isolated from methanolic extract of the whole plant of Eschscholzia californica. These two alkaloids were checked for their antifungal activity against phytopathogenic fungi Alternaria melongenae, A. brassicola, A. brassicae, Curvularia lunata, C. maculans, Helminthosporium pennisetti, H. oryzae, H. turcicum, Fusarium undum and F. lini. Hunnemanine exhibited 100 % inhibition of spore germination of A. brassicae, H. pennisetti and F. lini at 1000 ppm whereas norsanguinarine exhibited 100 % inhibition of A. brassicicola and C. maculans at this concentration.

Berberine bridge enzyme catalyzes the six electron oxidation of (S)-reticuline to dehydroscoulerine.

Berberine bridge enzyme catalyzes the stereospecific oxidation and carbon-carbon bond formation of (S)-reticuline to (S)-scoulerine. In addition to this type of reactivity the enzyme can further oxidize (S)-scoulerine to the deeply red protoberberine alkaloid dehydroscoulerine albeit with a much lower rate of conversion. In the course of the four electron oxidation, no dihydroprotoberberine species intermediate was detectable suggesting that the second oxidation step leading to aromatization proceeds at a much faster rate. Performing the reaction in the presence of oxygen and under anoxic conditions did not affect the kinetics of the overall reaction suggesting no strict requirement for oxygen in the oxidation of the unstable dihydroprotoberberine intermediate. In addition to the kinetic characterization of this reaction we also present a structure of the enzyme in complex with the fully oxidized product. Combined with information available for the binding modes of (S)-reticuline and (S)-scoulerine a possible mechanism for the additional oxidation is presented. This is compared to previous reports of enzymes ((S)-tetrahydroprotoberberine oxidase and canadine oxidase) showing a similar type of reactivity in different plant species.

Differential induction of protein expression and benzophenanthridine alkaloid accumulation in Eschscholtzia californica suspension cultures by methyl jasmonate and yeast extract.

Methyl jasmonate (MJ) and yeast extract (YE) induce protein expression and benzophenanthridine alkaloid accumulation in Eschscholtzia californica suspension cell cultures. One hundred microM MJ primarily induced dihydrosanguinarine 509.0+/-7.4 mg/l); 0.2 g/l YE induced sanguinarine (146.8+/- 3.8 mg/l) and an unknown compound. These results occur because dihydrobenzophenanthridine oxidase (DHBO) is induced by YE and not by MJ. YE and chitin (CHI) had similar effects on sanguinarine production and DHBO expression. Differential induction of secondary metabolites was shown in E. californica suspension cultures and the expression of proteins confirmed the metabolite results. Furthermore, treatment by various oligosaccharides helped us to understand the elicitation effect of YE in signal transduction pathways.

Analysis of secondary metabolites from eschscholtzia californica by high-performance liquid chromatography.

A rapid and precise analytical HPLC method has been developed for screening the major benzophenanthridine alkaloids produced by cell cultures of Eschscholtzia califomica, namely, sanguinarine, chelirubine, macarpine, chelerythrine and chelilutine. Separation was achieved on a C18, reversed-phase column with gradient elution using acetonitrile and 50 mM phosphoric acid. Detection was performed by both fluorescence (lambda(ex) 330 nm, lambda(em) 570 nm) and photodiode array, leading to good selectivity and precision in determining peak purity. A simple and quick sample preparation protocol was elaborated involving a methanolic extraction for the measurement of intracellular concentrations of the alkaloids and a solid phase extraction for their quantification in culture medium. Owing to the non-availability of commercially standards, a method for the purification of chelirubine, macar pine and chelilutine by semi-preparative HPLC was developed. Coupled together, the isolation method and the analytical method were highly reliable for screening the alkaloids of interest produced by E. califomica.

Alkaloids from Eschscholzia californica and their capacity to inhibit binding of [3H]8-Hydroxy-2-(di-N-propylamino)tetralin to 5-HT1A receptors in Vitro.

A 70% ethanol extract of California poppy (Eschscholzia californica) was able to bind to 5-HT(1A) and 5-HT(7) receptors at 100 mug/mL. The subsequent isolation procedure yielded the known alkaloids californidine (1), escholtzine (2), N-methyllaurotetanine (3), caryachine (4), and O-methylcaryachine (5), along with a new pavine alkaloid, 6S,12S-neocaryachine-7-O-methyl ether N-metho salt (7). The structure of 7 was determined by spectroscopic data interpretation, while the absolute stereochemistry was determined by means of circular dichroism. From the results obtained from the radioligand-binding assay of the pure compounds, including the commercially available protopine (6), it was evident that the activity on the 5-HT(1A) receptor was at least partly due to the presence of the aporphine alkaloid 3, which showed the highest inhibition of [(3)H]8-hydroxy-2-(di-N-propylamino)tetralin ([(3)H]8-OH-DPAT) binding with an EC(50) value of 155 nM and a K(i) of 85 nM.

Intracellular pH signals in the induction of secondary pathways--the case of Eschscholzia californica.

Transient peaks of the cytoplasmic pH are essential elements in a number of signal cascades that activate environmental responses or developmental processes in plant cells but little is known about the mechanisms of their generation. In many plant cells, elicitation of the hypersensitive response is preceded by a perturbation of the ionic balance at the plasma membrane including the inhibition of the proton pump and the influx of H+ from the apoplast. A basically different mechanism of cytoplasmic acidification that is fed by vacuolar protons has been discovered in cell suspensions of the California Poppy (Eschscholzia californica). These cells react to a yeast glycoprotein elicitor with the overproduction of benzophenanthridine alkaloids. Low elicitor concentrations trigger the biosynthesis of these phytoalexins without invoking elements of the hypersensitive response. Accumulated data support the existence of a signal path that includes the following steps: Links between the above events that connect them within a distinct signal path are substantiated by the phenotypes of transformed cell lines that either display lowered Galpha levels due to antisense transformation or express Galpha-binding antibodies in the cytoplasm. All of these cell lines lack the elicitor-activation of PLA2 and of vacuolar proton fluxes and show an impaired phytoalexin response to low elicitor concentrations. High elicitor concentrations trigger alkaloid biosynthesis via an increase of jasmonate at a pH-independent signal path.

Critical influence of Eschscholzia californica cells nutritional state on secondary metabolite production.

In this study, we investigated the influence of initial internal nutrient concentrations at the time of elicitation on the ability of Eschscholzia californica (EC) cells to produce alkaloids. Three EC cell suspensions cultivated in culture media differing in their PO4(3-) and NO3- contents were sampled daily for 12 days and analyzed for extracellular and intracellular nutrient concentrations. The ability of the cells to produce alkaloids was tested along the three cell suspension cultures. Sampled cells were then further cultured for 7 days in a production medium containing the elicitor and an extraction resin. The alkaloid production of the cells was measured 7 days post-elicitation. In the low-N medium, starch, glucose, and phosphate contents in the biomass was increased by 470, 1624 and 70%, respectively, 10 days after inoculation compared to the control culture in standard B5 medium. Cell concentration was significantly reduced from 10.3 to 8.6 millions cell/mL on this low-N medium compared to the control, nevertheless alkaloid production was multiplied by 39 at day 10 when cells were elicited. Cells grown on the low-N or low-P media accumulated 83% and 188% more carbon, respectively, than control cells at the end of the culture. This intracellular C was mainly stored in the form of starch in low-P medium and both in the form of starch and glucose in the low-N medium. The ability of EC cells to produce alkaloids upon elicitation was shown to be strongly dependent on the initial intracellular C and P content at the time of elicitation. This suggests that reproducibility and productivity during EC cell culture could be enhanced by manipulating the intracellular C and P content at the time of elicitation.

In situ extraction strategy affects benzophenanthridine alkaloid production fluxes in suspension cultures of Eschscholtzia californica.

The effect of contact between cells and extractive phase on secondary metabolite production was investigated in two-phase suspension cultures of Eschscholtzia californica. A system was designed to extract benzophenanthridine alkaloids from the cell culture, without contact between XAD-7 resins and the cells: only medium was recirculated through a column packed with the extractive phase. This strategy was compared to the classic method of addition of resins directly into the cell suspension. Removal of the product directly from the medium enabled important increases in production of alkaloids, namely a 20-fold increase in sanguinarine production and a 10-fold increase in chelerythrine, with high recovery in the resin. The recirculation strategy greatly simplified the production process since the resins are easily recovered from the cell culture and enable harvest of product without termination of culture. However, due to limited flow rate, the recirculation strategy was slightly less effective than direct addition of resins into the cell suspension. In addition to enabling increased production, removal of secondary metabolites from the medium changed metabolic flux distribution, testifying to a complex control mechanism of production.

Studies on the metabolism and toxicological detection of the Eschscholtzia californica alkaloids californine and protopine in urine using gas chromatography-mass spectrometry.

Eschscholtzia californica preparations are in use as phytopharmaceuticals and as herbal drugs. Studies are described on the metabolism and the toxicological analysis of the Eschscholtzia californica alkaloids californine and protopine in rat urine using gas chromatography-mass spectrometry. The identified metabolites indicated that californine is extensively metabolized by N-demethylation and/or single or double demethylenation with consecutive catechol-O-methylation of one of the hydroxy groups. Protopine, however, only undergoes extensive demethylenation of the 2,3-methylenedioxy group followed by catechol-O-methylation. All phenolic hydroxy metabolites were found to be partly conjugated. The authors' systematic toxicological analysis procedure using full-scan gas chromatography-mass spectrometry after acid hydrolysis, liquid-liquid extraction and microwave-assisted acetylation allowed the detection of the main metabolites of californine and protopine in rat urine after a dose which should correspond to that of drug users. Therefore, use of Eschscholtzia californica preparations should also be detectable in human urine by the authors' systematic toxicological analysis procedure.