¹³C nuclear magnetic resonance analysis of two prenyl flavonols from platanus acerifolia buds

Abstract

The carbon nuclear magnetic resonance (NMR) data of the acetyl derivatives of 8‐(1,1‐dimethyl‐2‐propen‐1‐y1) galangin and 8‐(1,1‐dimethyl‐2‐propen‐1‐yl) kaempferide, isolated from Platanus acerifolia buds, have been reassigned unambiguously by HETCOR and COLOC experiments on synthetic compounds. The carbon NMR data for the naturally occurring 8‐(1,1‐dimethyl‐2‐propen‐1‐yl) kaempferide is reported for the first time.

On-line (HPLC-NMR) and Off-line Phytochemical Profiling of the Australian Plant, Lasiopetalum macrophyllum

“…This structure revision was immediately recognized as being necessary on the basis of the downfield assignments allocated to the meta coupled aromatic protons (δ 6.50 and δ 6.68) of the flavonoid moiety. In comparison with literature NMR data for closely related metabolites, these 1 H NMR chemical shifts are not consistent with two hydroxy moieties being substituted at positions 5 and 7 (δ 6.15 and δ 6.40) [46,47]. Without an authentic sample of the compound incorrectly reported as kaempferol 4′-methyl ether 3-O-β-D-(6-O-trans-p-coumaroyl) glucopyranoside, only a tentative re-assignment can be proposed for this compound.…”

“…On the basis of a comparison of the NMR data obtained for 18 in CD 3 OD to that reported for these two compounds, it was concluded that both literature structures had been assigned incorrectly. A 1 H NMR comparison of the meta coupled protons to literature NMR data for compounds 22, 23, 24, 25 and 26, indicated that a substitution at the C4' and C3 positions only has a small effect on the chemical shifts of the meta coupled aromatic protons, whereas substitution at the C7 position has a significant effect on these protons (see Figure 3) [44,46]. In considering the reported 2D NMR HMBC correlations for the compound reported as kaempferol 4′methyl ether 3-O-β-D-(6-O-trans-p-coumaroyl) glucopyranoside, the anomeric proton of the sugar moiety showed a correlation to a quaternary carbon at 133.6 ppm.…”

On-line (HPLC-NMR) and Off-line Phytochemical Profiling of the Australian Plant, Lasiopetalum macrophyllum

“…This structure revision was immediately recognized as being necessary on the basis of the downfield assignments allocated to the meta coupled aromatic protons (δ 6.50 and δ 6.68) of the flavonoid moiety. In comparison with literature NMR data for closely related metabolites, these 1 H NMR chemical shifts are not consistent with two hydroxy moieties being substituted at positions 5 and 7 (δ 6.15 and δ 6.40) [46,47]. Without an authentic sample of the compound incorrectly reported as kaempferol 4′-methyl ether 3-O-β-D-(6-O-trans-pcoumaroyl) glucopyranoside, only a tentative reassignment can be proposed for this compound.…”

“…A 1 H NMR comparison of the meta coupled protons to literature NMR data for compounds 22, 23, 24, 25 and 26, indicated that a substitution at the C4' and C3 positions only has a small effect on the chemical shifts of the meta coupled aromatic protons, whereas substitution at the C7 position has a significant effect on these protons (see Figure 3) [44,46]. In considering the reported 2D NMR HMBC correlations for the compound reported as kaempferol 4′-methyl ether 3-O-β-D-(6-O-trans-pcoumaroyl) glucopyranoside, the anomeric proton of the sugar moiety showed a correlation to a quaternary carbon at 133.6 ppm.…”

Correlation between the Affinity of Flavonoids Binding to the Cytosolic Site of Leishmania tropica Multidrug Transporter and Their Efficiency To Revert Parasite Resistance to Daunomycin

“…Commercial flavonoids were from either Aldrich (galangin, 7-hydroxyflavone), Sigma (chrysin, naringenin, quercetin, rutin) or Extrasynthe `se, Genay, France (acacetin, apigenin, 3-hydroxyflavone, genistein, kaempferide). The 8-(1,1-dimethylallyl) derivatives of chrysin (25), apigenin (26), and kaempferide (27) were synthesized as described.…”