Dechlorodauricumine from cultured roots of Menispermum dauricum

Identification of nuclear factor-κB inhibitors in the folk herb Rhizoma Menispermi via bioactivity-based ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry analysis

BACKGROUND

Rhizoma Menispermi (RM) is the dried root of Menispermum dauricum DC, which is traditionally used to treat swelling and pain for sore throat, enteritis and rheumatic arthralgia in the clinic, but its bioactive compounds remain unclear.

METHODS

In this study, RM extract was administered orally to ICR mice followed by challenging with an intratracheal Pseudomonas aeruginosa suspension. Then mortality, histological features of lung, and inflammatory cytokines were evaluated. RM treatment significantly ameliorated Pseudomonas aeruginosa-induced acute lung inflammation and reduced levels of inflammatory mediators. To screen for potential anti-inflammatory constituents of the RM extract, a simple and rapid method based on ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF MS) coupled with a luciferase reporter assay system to detect nuclear factor-κB (NF-κB) activity was established.

RESULTS

Using this system, seven potential NF-κB inhibitors were detected, including sinomenine, norsinoacutin, N-norsinoacutin-β-D-glucopyranoside, 6-O-methyl-laudanosoline-13-O-glucopyranoside, magnoflorine, laurifloline and dauricinoline. Furthermore, IL-6 and IL-8 assays confirmed the anti-inflammatory effects of these potential NF-κB inhibitors, in which norsinoacutin, 6-O-methyl-laudanosoline-13-O-glucopyranoside laurifloline, dauricinoline and N-norsinoacutin-β-D-glucopyranoside were revealed as new NF-κB inhibitors.

CONCLUSION

This method of UPLC-Q/TOF coupled with the luciferase reporter assay system was initially applied to the study of RM and was demonstrated to represent a simple, rapid and practical approach to screen for anti-inflammatory compounds. This study provided useful results for further investigation on the anti-inflammatory mechanism of RM.

Substrate-modified functional group reactivity: hasubanan and acutumine alkaloid syntheses

Functional group taxonomy provides a powerful conceptual framework to classify and predict the chemical reactivity of molecular structures. These principals are most effective in monofunctional settings, wherein individual functional groups can be analyzed without complications. In more complex settings, the predictive value of these analyses decreases as alternative reaction pathways, promoted by neighboring substituents and aggregate molecular properties, emerge. We refer to this phenomenon as substrate-modified functional group reactivity. In this Perspective, we explain how substrate-modified functional group reactivity molded our synthetic routes to the hasubanan and acutumine alkaloids. These investigations underscore the potential for discovery and insight that can only be gained by studying the reactivity of complex multifunctional structures.

Total synthesis of the congested propellane alkaloid (-)-acutumine

The enantioselective total synthesis of (-)-acutumine is described. The synthetic strategy was inspired by the premise that the cyclohexenone ring could be derived from an aromatic precursor. After successful construction of a propellane model system, an initial attempt to prepare the spirocyclic subunit was thwarted by incorrect regioselectivity in a radical cyclization. A second-generation approach involving a radical-polar crossover reaction was successful, and the chemistry developed in the aforementioned model system was then applied to synthesize the natural product. Key reactions included a phenolic oxidation, a diastereoselective ketone allylation utilizing Nakamura's chiral allylzinc reagent, an anionic oxy-Cope rearrangement, an acid-promoted cyclization of a secondary amine onto an α,β-unsaturated ketal, and a regioselective methyl enol etherification of a 1,3-diketone.

A method for the selective hydrogenation of alkenyl halides to alkyl halides

A general method for the selective hydrogenation of alkenyl halides to alkyl halides is described. Fluoro, chloro, bromo, iodo, and gem-dihaloalkenes are viable substrates for the transformation. The selectivity of the hydrogenation is consistent with reduction by a hydrogen atom transfer pathway.

The Hasubanan and Acutumine Alkaloids

Research in the hasubanan and acutumine alkaloid fields up to 1970 was discussed under "morphine alkaloids" in Volume 13 of this chapter. Advances in the field of hasubanan alkaloids from 1971 to 1975 were reviewed in Volume 16 and from 1976 to 1986 in Volume 33. This chapter extends the information in the three preceding reviews to hasubanan alkaloid literature published from 1987 to June 2013. This chapter covers acutumine alkaloid literature since (-)-acutumine (3) was isolated in 1929. This chapter includes occurrence and physical constants, new alkaloids, synthesis, biosynthesis, and pharmacology. Section 1 introduces the foremost alkaloids, (-)-hasubanonine (1) and (-)-acutumine (3), and the numbering systems of the hasubanan (2) and acutumine (4) skeletons. Section 2 details the occurrence and physical constants of 29 new hasubanan and 15 acutumine alkaloids. The isolation and structural determination of these new alkaloids are described in Section 3. Section 4 summarizes total syntheses and synthetic studies toward hasubanan and acutumine alkaloids. Completed syntheses of the hasubanan alkaloids (+)-cepharamine (ent-71), (-)-hasubanonine (1), (-)-runanine (8), (-)-delavayine (6), (+)-periglaucine B (19), and (-)-8-demethoxyrunanine (12) are reviewed. Completed syntheses of (-)-acutumine (3) and (-)-dechloroacutumine (52) are also described. Section 5 details biosyntheses of (-)-acutumine (3) advanced by Barton, Wipf, and Sugimoto. Section 6 summarizes pharmacological studies of hasubanan and acutumine alkaloids. Opioid receptor affinity, anti-HBV activity, and antimicrobial activity of hasubanan alkaloids are reported. Antiamnesic properties, cytotoxicity, and anti-HBV activity of acutumine alkaloids are described.

Development of enantioselective synthetic routes to the hasubanan and acutumine alkaloids

We describe a general strategy to prepare the hasubanan and acutumine alkaloids, a large family of botanical natural products that display antitumor, antiviral, and memory-enhancing effects. The absolute stereochemistry of the targets is established by an enantioselective Diels-Alder reaction between 5-(trimethylsilyl)cyclopentadiene (36) and 5-(2-azidoethyl)-2,3-dimethoxybenzoquinone (24). The Diels-Alder adduct 38 is transformed to the tetracyclic imine 39 by a Staudinger reduction-aza-Wittig sequence. The latter serves as a universal precursor to the targets. Key carbon-carbon bond constructions include highly diastereoselective acetylide additions to the N-methyliminium ion derived from 39 and Friedel-Crafts and Hosomi-Sakurai cyclizations to construct the carbocyclic skeleton of the targets. Initially, this strategy was applied to the syntheses of (-)-acutumine (4), (-)-dechloroacutumine (5), and four hasubanan alkaloids (1, 2, 3, and 8). Herein, the synthetic route is adapted to the syntheses of six additional hasubanan alkaloids (12, 13, 14, 15, 18, and 19). The strategic advantage of 5-(trimethylsilyl)cyclopentadiene Diels-Alder adducts is demonstrated by site-selective functionalization of distal carbon-carbon π-bonds in the presence of an otherwise reactive norbornene substructure. Evaluation of the antiproliferative properties of the synthetic metabolites revealed that four hasubanan alkaloids are submicromolar inhibitors of the N87 cell line.

Enantioselective total synthesis of (-)-acutumine

An account of the total synthesis of the tetracyclic alkaloid (-)-acutumine is presented. A first-generation approach to the spirocyclic subunit was unsuccessful as a result of incorrect regioselectivity in a radical cyclization. However, this work spawned a second-generation strategy in which the spirocycle was fashioned via a radical-polar crossover reaction. This process merged an intramolecular radical conjugate addition with an enolate hydroxylation and created two stereocenters with excellent diastereoselectivity. The reaction was promoted by irradiation with a sunlamp, and a ditin reagent was required for aryl radical formation. These facts suggest that the substrate may function as a sensitizer, thereby facilitating homolytic cleavage of the ditin reagent. The propellane motif of the target was then installed via annulation of a pyrrolidine ring onto the spirocycle. The sequence of reactions used included a phenolic oxidation, an asymmetric ketone allylation mediated by Nakamura's chiral allylzinc reagent, an anionic oxy-Cope rearrangement, a one-pot ozonolysis-reductive amination, and a Lewis acid promoted cyclization of an amine onto an alpha,beta-unsaturated dimethyl ketal. Further studies of the asymmetric ketone allylation demonstrated the ability of the Nakamura reagent to function well in a mismatched situation. A TiCl(4)-catalyzed regioselective methyl enol etherification of a 1,3-diketone completed the synthesis.

Conversion of dechlorodauricumine into miharumine by a cell-free preparation from cultured roots of Menispermum dauricum

Dechlorodauricumine (5) and dechloroacutumine (6) were converted to miharumine (7) and dechloroacutumidine (8), respectively, by a cell-free preparation from cultured roots of Menispermum dauricum in the presence of FAD. The structures of 7 and 8 were elucidated on the basis of spectroscopic analyses and chemical conversion.

Conversion of dechlorodauricumine into chlorinated alkaloids in Menispermum dauricum root culture

(15)N-Labeled dechlorodauricumine and dechloroacutumine were isolated from Menispermum dauricum roots cultured in a chloride-deficient medium, in which nitrogen-containing macro-components K(14)NO(3) and ((14)NH(4))(2)SO(4) were replaced by K(15)NO(3) and ((15)NH(4))(2)SO(4), respectively. These (15)N-labeled substrates were supplied independently to the roots cultured in a chloride-enriched medium. LC-ESI-MS analysis of alkaloids extracted from the roots, harvested 5 and 10 days after administering the (15)N-labeled substrates, revealed that the (15)N derived from dechlorodauricumine was much more effectively incorporated into chlorinated alkaloids than that derived from dechloroacutumine. These findings suggest that dechlorodauricumine is the principal precursor of the chlorinated alkaloids produced by M. dauricum roots.