13C NMR of flavonolignans from Hydnocarpus wightiana

Parthasarathy, M. R.; Ranganathan, Krishnakumar; Sharma, Dimpy

doi:10.1016/s0031-9422(00)81905-6

Cited by 29 publications

(15 citation statements)

References 7 publications

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“…Theoretically, 3-coupled products (like b-coupled products from normal monolignols) are possible, but they have not been shown here in either the biomimetic coupling reactions or in the polymers of the natural samples we examined, notwithstanding the report of compound 20 (Fig. 3) in the literature (Parthasarathy et al, 1979;Wenzig et al, 2005). All of these theoretical products would have very different NMR characteristics from those noted here.…”

Section: Tricin Initiates Lignin Chainsmentioning

confidence: 57%

“…A dimer (compound 20a in Fig. 3) containing a flavonoid moiety (C 3 ) connected to a monolignol-derived unit (C b ) that has the appearance of deriving from 3-b cross coupling was isolated from oat and Hydnocarpus wightiana (Parthasarathy et al, 1979;Wenzig et al, 2005). This type of structure could not be identified among the radical coupling products examined in this study, either by NMR or LC-MS analysis.…”

Section: Radical Coupling Reactions Between Tricin and Monolignolsmentioning

confidence: 75%

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Tricin, a Flavonoid Monomer in Monocot Lignification

et al. 2015

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Tricin was recently discovered in lignin preparations from wheat (Triticum aestivum) straw and subsequently in all monocot samples examined. To provide proof that tricin is involved in lignification and establish the mechanism by which it incorporates into the lignin polymer, the 49-Ob-coupling products of tricin with the monolignols (p-coumaryl, coniferyl, and sinapyl alcohols) were synthesized along with the trimer that would result from its 49-O-b-coupling with sinapyl alcohol and then coniferyl alcohol. Tricin was also found to cross couple with monolignols to form tricin-(49-O-b)-linked dimers in biomimetic oxidations using peroxidase/hydrogen peroxide or silver (I) oxide. Nuclear magnetic resonance characterization of gel permeation chromatography-fractionated acetylated maize (Zea mays) lignin revealed that the tricin moieties are found in even the highest molecular weight fractions, ether linked to lignin units, demonstrating that tricin is indeed incorporated into the lignin polymer. These findings suggest that tricin is fully compatible with lignification reactions, is an authentic lignin monomer, and, because it can only start a lignin chain, functions as a nucleation site for lignification in monocots. This initiation role helps resolve a long-standing dilemma that monocot lignin chains do not appear to be initiated by monolignol homodehydrodimerization as they are in dicots that have similar syringyl-guaiacyl compositions. The term flavonolignin is recommended for the racemic oligomers and polymers of monolignols that start from tricin (or incorporate other flavonoids) in the cell wall, in analogy with the existing term flavonolignan that is used for the lowmolecular mass compounds composed of flavonoid and lignan moieties.Lignin, a complex phenylpropanoid polymer in the plant cell wall, is predominantly deposited in the cell walls of secondary-thickened cells (Vanholme et al., 2010). It is synthesized via oxidative radical coupling reactions from three prototypical monolignols, p-coumaryl, coniferyl, and sinapyl alcohols, differentiated by their degree of methoxylation ortho to the phenolic hydroxyl group. Considered within the context of the entire polymer, the main structural features of lignin can be defined in terms of its p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units, derived respectively from these three monolignols (Ralph, 2010). Several novel monomers, all deriving from the monolignol biosynthetic pathway, have been found to incorporate into lignin in wild-type and transgenic plants. For example, monolignol acetate, p-hydroxybenzoate, and p-coumarate ester conjugates have all been shown to incorporate into lignin polymers and are the source of naturally acylated lignins (Ralph et al., 2004;Lu and Ralph, 2008); lignins derived solely from caffeyl alcohol were found in the seed coats of both monocot and dicot plants (Chen et al., 2012a(Chen et al., , 2012b; lignins derived solely from 5-hydroxyconiferyl alcohol were found in a cactus (for example, in a member of the genera Astrop...

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Section: Tricin Initiates Lignin Chainsmentioning

confidence: 57%

Section: Radical Coupling Reactions Between Tricin and Monolignolsmentioning

confidence: 75%

Tricin, a Flavonoid Monomer in Monocot Lignification

et al. 2015

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“…Material from the active fractions was subjected to further separation on silica gel columns with chloroform͞ethyl acetate͞acetone͞acetic acid, 7:1:2:0.1, and͞or on reverse-phase silica gel columns by using acetonitrile͞water, 70:30, with addition of a drop of diluted acetic acid. Structure determination was by NMR, UV light, and MS in comparison with literature values (13,14). …”

mentioning

confidence: 99%

Synergy in a medicinal plant: Antimicrobial action of berberine potentiated by 5′-methoxyhydnocarpin, a multidrug pump inhibitor

Stermitz

Lorenz

Tawara

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

651

461

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Multidrug resistance pumps (MDRs) protect microbial cells from both synthetic and natural antimicrobials. Amphipathic cations are preferred substrates of MDRs. Berberine alkaloids, which are cationic antimicrobials produced by a variety of plants, are readily extruded by MDRs. Several Berberis medicinal plants producing berberine were found also to synthesize an inhibitor of the NorA MDR pump of a human pathogen Staphylococcus aureus. The inhibitor was identified as 5-methoxyhydnocarpin (5-MHC), previously reported as a minor component of chaulmoogra oil, a traditional therapy for leprosy. 5-MHC is an amphipathic weak acid and is distinctly different from the cationic substrates of NorA. 5-MHC had no antimicrobial activity alone but strongly potentiated the action of berberine and other NorA substrates against S. aureus. MDR-dependent efflux of ethidium bromide and berberine from S. aureus cells was completely inhibited by 5-MHC. The level of accumulation of berberine in the cells was increased strongly in the presence of 5-MHC, indicating that this plant compound effectively disabled the bacterial resistance mechanism against the berberine antimicrobial.multidrug resistance ͉ efflux inhibitor B acteria have evolved numerous defenses against antimicrobial agents, and drug-resistant pathogens are on the rise (1). A general and effective defense is conferred by ubiquitous multidrug resistance pumps (MDRs), membrane translocases that extrude structurally unrelated toxins from the cell (2-5). Preferred substrates of most MDRs are synthetic hydrophobic cations such as quaternary ammonium antiseptics (6, 7). We have identified a group of cationic berberine alkaloids as natural substrates of MDR pumps (6). We suggested that berberine alkaloids represent a possibly larger group of cationic toxins that fueled the evolution of MDRs (7). Considering that microbial MDRs can render berberine alkaloids essentially ineffective, we reasoned that plants would benefit from making an MDR inhibitor. Here we show that Berberis fremontii, a berberine producer (8) used in Native American traditional medicine (9, 10), synthesizes a potent MDR inhibitor. Structural determination identified the substance as 5Ј-methoxyhydnocarpin (5Ј-MHC). Efflux of berberine from pathogenic Staphylococcus aureus expressing the NorA MDR pump that confers resistance to quinolones and antiseptics (6,11,12) was inhibited completely by 5Ј-MHC. This is a clear example of synergy between components of a medicinal plant described at a molecular level. Materials and MethodsCell Culturing and Susceptibility Testing. S. aureus 4222 parent strain and the norA mutant KLE 820 (6) were cultured in Mueller-Hinton (MH) broth. Cells (10 5 ͞ml) were inoculated into MH broth and dispensed at 0.2 ml͞well in microtiter plates. All tests were done in triplicate by following National Center for Clinical Laboratory Standards recommendations. Briefly, minimal inhibitory concentrations (MIC) were determined by serial 2-fold dilution of test compounds. MIC was defined as a concentr...

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“…Its molecular formula was established as C 25 H 20 O 9 from its positive HR-ESI-MS at m/z 487.1012 [M þ Na] þ . The UV spectrum of 1 exhibited absorption maxima at 281 and 339 nm characteristic of a flavone [4]. The 1 H-and 13 C-NMR spectral data of 1 (Table 1) were similar to those of isohydnocarpin [5], implying 1 to be a flavonolignan analog.…”

Section: Resultsmentioning

confidence: 77%

Anti-inflammatory flavonolignans fromHydnocarpus anthelminthicaseeds

Wang

Yin

Zhou

et al. 2011

Journal of Asian Natural Products Research

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A new flavonolignan, anthelminthicol A (1), together with four known compounds, was isolated from the EtOAc extracts of the seeds of Hydnocarpus anthelminthica. Their structures were elucidated using extensive spectroscopic techniques. Bioassay showed that compounds 3-5 could inhibit nitric oxide production in LPS-stimulated RAW 264.7 macrophage cell lines, with IC(50) values of 7.81, 9.38, and 10.55 μM, respectively.

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13C NMR of flavonolignans from Hydnocarpus wightiana

Cited by 29 publications

References 7 publications

Tricin, a Flavonoid Monomer in Monocot Lignification

Tricin, a Flavonoid Monomer in Monocot Lignification

Synergy in a medicinal plant: Antimicrobial action of berberine potentiated by 5′-methoxyhydnocarpin, a multidrug pump inhibitor

Anti-inflammatory flavonolignans fromHydnocarpus anthelminthicaseeds

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