An Efficient Method for Determining the Relative Configuration of Furofuran Lignans by ¹H NMR Spectroscopy

An efficient ¹H NMR spectroscopic approach for determining the relative configurations of lignans with a 7,9′:7′,9-diepoxy moiety has been established. Using the chemical shift differences of H₂-9 and H₂-9′ (Δδ_H‑9 and Δδ_H‑9′), the configurations of 8-H and 8-OH furofuran lignans can be rapidly and conveniently determined. The rule is applicable for data acquired in DMSO-<i>d</i>₆, methanol-<i>d</i>₄, or CDCl₃. Notably, the rule should be applied carefully when the C-2 or C-6 substituent of the aromatic rings may alter the dominant conformers of the furofuran moiety

New Butyrolactone Type Lignans from Arctii Fructus and Their Anti-inflammatory Activities

Arctiidilactone (<b>1</b>), a novel rare butyrolactone lignan with a 6-carboxyl-2-pyrone moiety, and 11 new butyrolactone lignans (<b>2</b>–<b>12</b>) were isolated from the fruits of Arctium lappa L., together with 5 known compounds (<b>13</b>–<b>17</b>). Their structures were elucidated by interpretation of their spectroscopic data (1D and 2D NMR, UV, IR, ORD, and HRESIMS) and comparison to literature data. The absolute configurations of compounds <b>1</b>–<b>12</b> were determined by a combination of rotating-frame nuclear Overhauser effect spectroscopy (ROESY), circular dichroism (CD) spectroscopy, and Rh₂(OCOCF₃)₄-induced CD spectroscopy. All of the compounds were tested for their anti-inflammatory properties in terms of suppressing the production of NO in lipopolysaccharide-induced BV2 cells. Compounds <b>1</b>, <b>6</b>, <b>8</b>, and <b>10</b> exhibited stronger anti-inflammatory effects than the positive control curcumin, particularly <b>1</b>, which exhibited 75.51, 70.72, and 61.17% inhibition at 10, 1, and 0.1 μM, respectively

Dibenzoyl and Isoflavonoid Glycosides from <i>Sophora flavescens</i>: Inhibition of the Cytotoxic Effect of d‑Galactosamine on Human Hepatocyte HL-7702

Twelve new dibenzoyl derivatives sophodibenzoside A–L (<b>1</b>–<b>12</b>) and five new isoflavone glycosides (<b>13</b>–<b>17</b>) have been isolated from the roots of Sophora flavescens together with eight known compounds (<b>18</b>–<b>25</b>). Notably, the use of acetic acid-<i>d</i>₄ was required to enable identification of the dibenzoyl glycoside structures. Compounds <b>1</b>, <b>2</b>, <b>13</b>, <b>14</b>, and <b>19</b> exhibited weak inhibition of the cytotoxic effect of d-galactosamine on the human hepatic cell line HL-7702

An Efficient Method for Determining the Relative Configuration of Furofuran Lignans by ¹H NMR Spectroscopy

An efficient ¹H NMR spectroscopic approach for determining the relative configurations of lignans with a 7,9′:7′,9-diepoxy moiety has been established. Using the chemical shift differences of H₂-9 and H₂-9′ (Δδ_H‑9 and Δδ_H‑9′), the configurations of 8-H and 8-OH furofuran lignans can be rapidly and conveniently determined. The rule is applicable for data acquired in DMSO-<i>d</i>₆, methanol-<i>d</i>₄, or CDCl₃. Notably, the rule should be applied carefully when the C-2 or C-6 substituent of the aromatic rings may alter the dominant conformers of the furofuran moiety

Hepatoprotective Activity of Twelve Novel 7′-Hydroxy Lignan Glucosides from Arctii Fructus

Twelve novel 7′-hydroxy lignan glucosides (<b>1</b>–<b>12</b>), including two benzofuran-type neolignans, two 8-<i>O</i>-4′ neolignans, two dibenzylbutyrolactone lignans, and six tetrahydrofuranoid lignans, together with six known lignan glucosides (<b>13</b>–<b>18</b>), were isolated from the fruit of Arctium lappa L. (Asteraceae), commonly known as Arctii Fructus. Their structures were elucidated using spectroscopy (1D and 2D NMR, MS, IR, ORD, and UV) and on the basis of chemical evidence. The absolute configurations of compounds <b>1</b>–<b>12</b> were confirmed using rotating frame nuclear overhauser effect spectroscopy (ROESY), the circular dichroic (CD) exciton chirality method, and Rh₂(OCOCF₃)₄-induced CD spectrum analysis. All of the isolated compounds were tested for hepatoprotective effects against d-galactosamine-induced cytotoxicity in HL-7702 hepatic cells. Compounds <b>1</b>, <b>2</b>, <b>7</b>–<b>12</b>, and <b>17</b> showed significantly stronger hepatoprotective activity than the positive control bicyclol at a concentration of 1 × 10^–5 M

NMR Solution Structure Study of the Representative Component Hydroxysafflor Yellow A and Other Quinochalcone C‑Glycosides from <i>Carthamus tinctorius</i>

Hydroxysafflor yellow A (HSYA), a representative component of <i>Carthamus tinctorius</i>, has attracted much attention because of its remarkable cardiovascular activities. Its structure was originally reported in 1993 and has been widely cited to date. In our experiments, its solution structure was studied using NMR techniques in different solvents, including DMSO-<i>d</i>₆, pyridine-<i>d</i>₅, and CD₃OH. The results indicate that the structure of HSYA is different than the previously described <b>1b</b>, with 3-enol-1,7-diketo form. The structure has two keto–enol tautomers (<b>2a</b> and <b>2b</b>), and <b>2a</b>, with the 1-enol-3,7-diketo form, is the preferred tautomer. On the basis of this finding, other published quinochalcone C-glycoside structures were revised. Furthermore, a trend in the ¹³C NMR data of the (<i>E</i>)-olefinic carbons of quinochalcone C-glycosides is summarized, and a hypothesis is proposed for the relationship between the features of the molecular structure and the preferred keto–enol tautomer

Direct Assignment of the <i>Threo</i> and <i>Erythro</i> Configurations in Polyacetylene Glycosides by ¹H NMR Spectroscopy

An approach for discriminating the <i>threo</i> and <i>erythro</i> configurations of polyacetylene glycosides by ¹H NMR spectroscopy was developed. Using acetic acid-<i>d</i>₄/D₂O as the solvent, a relatively larger ³<i>J</i>_HH value (7.0 Hz) for the acyclic vicinal diol group was unambiguously assigned to the <i>threo</i> configuration, whereas the smaller value (3.5 Hz) was assigned to the <i>erythro</i> configuration. This convenient method requires no hydrolysis or derivatization and is suitable for micromolar concentrations of polyacetylene glycosides. The underlying mechanism is discussed via visualized conformations

An Approach for Determining the Absolute Configuration of C‑2 in 2‑Oxygenated Phenylethanoid Glycosides by ¹H NMR Spectroscopy

The absolute configurations of 2-oxygenated phenylethanoid glycosides were conveniently determined by ¹H NMR spectroscopy. A comparison of the chemical shift differences (Δδ) of the diastereotopic methylene protons (H-1) demonstrate that a large chemical shift difference corresponds to an <i>R</i> configuration and a small chemical shift difference indicates <i>S</i> for the 2<b>-</b>alkoxy form. However, the situation is contrary to that of the 2-hydroxy form. Furthermore, the mechanism underlying this result is discussed based on the visualized conformations of such compounds

Bioactive Sesquiterpenoid and Polyacetylene Glycosides from <i>Atractylodes lancea</i>

Nine new sesquiterpenoids (<b>1</b>–<b>9</b>), five new polyacetylenes (<b>10</b>–<b>14</b>), and six known compounds were isolated from the rhizomes of <i>Atractylodes lancea</i>. These new chemical structures were established using NMR, MS, and ECD data. Notably, compounds <b>3</b>–<b>5</b>, the aglycone of which possesses two stereogenic centers (C-5 and C-7), exhibited similar ECD spectra to compounds <b>1</b> and <b>2</b>, the aglycone of which possesses one stereogenic center (C-7). Such a difference was supported by the experimental and calculated ECD data and single-crystallographic analyses of <b>3a</b>. In addition, compound <b>3</b> inhibited lipopolysaccharide-induced NO production in BV2 cells with an IC₅₀ value of 11.39 μM (positive control curcumin, IC₅₀ = 4.77 μM); compound <b>4</b> showed better hepatoprotective activity against <i>N</i>-acetyl-<i>p</i>-aminophenol-induced HepG2 cell injury than the positive drug (bicyclol) at a concentration of 10 μM (<i>p</i> < 0.001)

Bioactive Sesquiterpenoid and Polyacetylene Glycosides from <i>Atractylodes lancea</i>

Nine new sesquiterpenoids (<b>1</b>–<b>9</b>), five new polyacetylenes (<b>10</b>–<b>14</b>), and six known compounds were isolated from the rhizomes of <i>Atractylodes lancea</i>. These new chemical structures were established using NMR, MS, and ECD data. Notably, compounds <b>3</b>–<b>5</b>, the aglycone of which possesses two stereogenic centers (C-5 and C-7), exhibited similar ECD spectra to compounds <b>1</b> and <b>2</b>, the aglycone of which possesses one stereogenic center (C-7). Such a difference was supported by the experimental and calculated ECD data and single-crystallographic analyses of <b>3a</b>. In addition, compound <b>3</b> inhibited lipopolysaccharide-induced NO production in BV2 cells with an IC₅₀ value of 11.39 μM (positive control curcumin, IC₅₀ = 4.77 μM); compound <b>4</b> showed better hepatoprotective activity against <i>N</i>-acetyl-<i>p</i>-aminophenol-induced HepG2 cell injury than the positive drug (bicyclol) at a concentration of 10 μM (<i>p</i> < 0.001)