Extractives from Guttiferae. Part XXII. The isolation and structure of four novel biflavanones from the heartwoods of Garcinia buchananii Baker and G. eugeniifolia Wall

Jackson, B.; Locksley, H. D.; Scheinmann, F.; Wolstenholme, W. A.

doi:10.1039/j39710003791

Cited by 38 publications

(33 citation statements)

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“…The spectral complexity at the dimeric level was observed in both measurements. At 90°C in Pyridine-d 6 , the 13 C-NMR spectra were also a single set of signals. These observations suggested that the solvents had no significant effect on its rotameric behavior.…”

Section: Resultsmentioning

confidence: 99%

“…In the same way, the remaining four doublets at dϭ5.54, 5.01, 4.53, and 4.43 for one proton each with Jϭ11.2 Hz were indicated to be H-2, H-2Љ, H-3, H-3Љ, respectively. In the 13 C-NMR spectrum, ten indicative lowfield signals out of twenty-six were assigned to two carbonyl carbons, six hydroxylated carbons, and two aromatic carbons bearing oxygen-bridge to the pyran rings of the benzopyran moieties. Similarly, the signals at dϭ82.4, 81.2, 71.7, and 47.3 were assigned to C-2Љ, C-2, C-3Љ, and C-3, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…It was identified as 3Љ,4Ј,4ٞ,5,5Љ,7,7Љ-heptahydroxy-3,8Љ-biflavanone (GB1) by 1 H-, 13 C-, and 2D NMR data recorded at 90°C in DMSO-d 6 . The 1 H-NMR spectra recorded at 90°C showed four signals for five exchangeable OH protons, two at low field with dϭ12.08 and 11.62, two in the range from dϭ9.20 to 8.80 and one upfield at dϭ5.94 (Table 1).…”

Section: Resultsmentioning

confidence: 99%

“…Additionally, the effects of solvents were also investigated. At 21°C, the 13 C-NMR spectra were measured in DMSO-d 6 , and acetone-d 6 , respectively. The spectral complexity at the dimeric level was observed in both measurements.…”

Section: Resultsmentioning

confidence: 99%

“…[4][5][6][7][8][9][10][11][12] The confusing signals due to its rotameric behavior (atropisomerism) collapse with increasing rotation around 3/8Љ bond at higher temperature like 100°C to a single set of signals. 13) This phenomenon indicated a characteristic of this kind of 3,8Љ-linked biflavanoids. 14) We compared its NMR data obtained at different temperatures including Ϫ50°C, Ϫ30°C, 21°C, 70°C, and 90°C, and in different solvents such as acetone, pyridine, and dimethyl sulfoxide (DMSO).…”

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confidence: 99%

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Complete NMR Assignments of the Antibacterial Biflavonoid GB1 from Garcinia kola

Han

Lee

Qiao

et al. 2005

CHEMICAL & PHARMACEUTICAL BULLETIN

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From the antibacterial fraction of the roots of Garcinia kola, 3؆,4,4ٟ,5,5؆,7,7؆-heptahydroxy-3,8؆-biflavanone (GB1) was isolated as the major constituent, whose interesting conformations were studied on the basis of its 1D and 2D NMR spectra obtained at different temperatures and in different solvents. GB1 showed antibacterial activities against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) with MIC of 32 and 128 m mg/ml, respectively.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Complete NMR Assignments of the Antibacterial Biflavonoid GB1 from Garcinia kola

Han

Lee

Qiao

et al. 2005

CHEMICAL & PHARMACEUTICAL BULLETIN

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Complete NMR assignments of bioactive rotameric (3 → 8) biflavonoids from the bark of Garcinia hombroniana

Jamila

Khairuddean

Khan

et al. 2014

Magnetic Reson in Chemistry

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The genus Garcinia is reported to possess antimicrobial, anti-inflammatory, anticancer, hepatoprotective and anti-HIV activities. Garcinia hombroniana in Malaysia is used to treat itching and as a protective medicine after child birth. This study was aimed to isolate the chemical constituents from the bark of G. hombroniana and explore their possible pharmacological potential. Ethyl acetate extract afforded one new (1) and six (2-7) known 3 → 8 rotameric biflavonoids. Their structures were elucidated by UV, IR and NMR (1D and 2D) spectroscopy together with electron ionization/ESI mass spectrometric techniques and were identified as (2R, 3S) volkensiflavone-7-O-rhamnopyranoside (1), volkensiflavone (2), 4″-O-methyl-volkensiflavone (3), volkensiflavone-7-O-glucopyranoside (4), morelloflavone (5), 3″-O-methyl-morelloflavone (6) and morelloflavone-7-O-glucopyranoside (7). The absolute configuration of compound 1 was assigned by circular dichroism spectroscopy as 2R, 3S. The coexistence of conformers of isolated biflavonoids in solution at 25 °C in different solvents was confirmed by variable temperature NMR studies. At room temperature (25 °C), compounds 1-7 exhibited duplicate NMR signals, while at elevated temperature (90 °C), a single set of signals was obtained. Compound 5 showed significant in vitro antioxidant activities against 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azino-bis-3-ethyl benzthiazoline-6-sulfonic acid radicals. The antibacterial studies showed that compounds 5 and 6 are the most active against Staphylococcus aureus, Bacillus subtilis and Escherichia coli. Compounds 3 and 6 also showed moderate antituberculosis activity against H38 Rv. Based on the research findings, G. hombroniana could be concluded as a rich source of flavanone-flavone (3 → 8) biflavonoids that exhibit rotameric behaviour at room temperature and display significant antioxidant and antibacterial activities.

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A new NMR approach for structure determination of thermally unstable biflavanones and application to phytochemicals from Garcinia buchananii

Stark

Lösch

Salger

et al. 2015

Magnetic Reson in Chemistry

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Previous activity-guided phytochemical studies on Garcinia buchananii stem bark, which is traditionally used in Africa to treat various gastrointestinal and metabolic illnesses, revealed xanthones, polyisoprenylated benzophenones, flavanone-C-glycosides, biflavonoids, and/or biflavanones as bioactive key molecules. Unequivocal structure elucidation of biflavonoids and biflavanones by means of NMR spectroscopy is often complicated by the hindered rotation of the monomers around the C-C axis (atropisomerism), resulting in a high spectral complexity. In order to facilitate an unrestricted rotation, NMR spectra are usually recorded at elevated temperatures, commonly over 80 °C, which effects in a single set of resonance signals. However, under these conditions, one of the target compounds of this investigation, (2R,3S,2″R,3″R)-manniflavanone (1), undergoes degradation. Therefore, we demonstrated in the present study that the 1,1-ADEQUATE could be successfully used as a powerful alternative approach to confirm the C-C connectivities in 1, avoiding detrimental conditions. However, a moderate increase in temperature up to 50 °C was sufficient to deliver sharp signals in the proton NMR experiment of (2R,3S,2″R,3″R)-isomanniflavanone (2) and (2″R,3″R)-preussianone (3). In addition, two new compounds could be isolated, namely (2R,3S,2″R,3″R)-GB-2 7″-O-β-D-glucopyranoside (4) and (2R,3S,2″R,3″R)-manniflavanone-7″-O-β-D-glucopyranoside (5), and whose structures were elucidated by spectroscopic analysis including 1D and 2D NMR and mass spectrometry methods. The absolute configurations were determined by a combination of NMR and electronic circular dichroism (ECD) spectroscopy. The aforementioned compounds exhibited high anti-oxidative capacity in the H2O2 scavenging, hydrophilic Trolox equivalent antioxidant capacity (H-TEAC) and hydrophilic oxygen radical absorbance capacity (H-ORAC) assays.

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Extractives from Guttiferae. Part XXII. The isolation and structure of four novel biflavanones from the heartwoods of Garcinia buchananii Baker and G. eugeniifolia Wall

Abstract: ax1(1) R1 = H, 1.' = OH, R3 = H (GB-1)together with a small quantity of GB-2a (4). Further separation and purification of each GB constituent was achieved by preparative t.1.c. on silica gel.

Cited by 38 publications

References 0 publications

Complete NMR Assignments of the Antibacterial Biflavonoid GB1 from Garcinia kola

Complete NMR Assignments of the Antibacterial Biflavonoid GB1 from Garcinia kola

Complete NMR assignments of bioactive rotameric (3 → 8) biflavonoids from the bark of Garcinia hombroniana

A new NMR approach for structure determination of thermally unstable biflavanones and application to phytochemicals from Garcinia buchananii

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