Phenylpropanoids and lignans from Prunus tomentosa seeds as efficient β-amyloid (Aβ) aggregation inhibitors

Alzheimer’s disease (AD) is characterized by the progressive accumulation of extracellular β-amyloid (Aβ) aggregates. Recently, lignans and phenylpropanoids are attracting increasing attention to discovery useful agents of inhibition on Aβ aggregation. In the present study, to develop potential agents for slowing the progression of AD, Prunus tomentosa seeds were selected as a raw material for bioactive compounds, which led to the separation of two pairs of new enantiomeric lignans and phenylpropanoids using chiral HPLC. The planar structures of these compounds were elucidated by spectroscopic data analyses. And their absolute configurations were determined by comparing of experimental and calculated electronic circular dichroism (ECD). The biosynthesis pathway was also discussed. Additionally, the inhibitory activity on Aβ aggregation of all optical pure compounds was tested by thioflavin T (ThT) assay. The isolates (1a, 1b, 2a and 2b) showed more potent inhibitory activity than positive control curcumin with inhibitory rate of 73.89 ± 3.41% 78.69 ± 1.50%, 63.25 ± 2.68%, and 67.13 ± 0.90% at 20 μM, respectively. More importantly, the inhibition profiles were explained by molecular dynamics and docking simulation studies.     

Dibenzylbutane and aryltetralone lignans from seeds of Virola sebifera

Two lignans rel-(8R, 8'R)-3,4:3',4'-bis-(methylenedioxy)-7.7'-dioxo-lignan and (7'R,8'S,8S)-2'-hydroxy-3,4:4',5'-bis-(methylenedioxy)-7-oxo-2,7'-cyclolignan were isolated from seeds of Virola sebifera. The cyclolignan showed two atropisomers as determined by 1H NMR spectroscopy at low temperature.     

Two highly oxygenated eudesmanes and 10 lignans from Achillea holosericea

Two new highly oxygenated eudesmanes and 10 known lignans were isolated from the aerial parts of Achillea holosericea. Their structures were elucidated by extensive application of one- and two-dimensional 1H and 13C NMR spectroscopy.     

HPLC method with fluorescence detection for the quantitative determination of flaxseed lignans

We report a rapid and simple HPLC method with fluorescence detection for the quantification of the major flaxseed lignan, secoisolarisiresinol diglucoside (SDG) and its major metabolites. The method is specific for SDG, secoisolarisiresinol (SECO), enterodiol (ED) and entrolactone (EL) in rat serum. The assay procedure involves chromatographic separation using a Waters Symmetry C₁₈ reversed-phase column (4.6 mm × 150 mm, 5 μm) and mobile phase gradient conditions consisting of acetonitrile (0.1% formic acid) and water (0.1% formic acid). SDG extraction from serum requires the use of Centrifuge filters while SECO, ED and EL are extracted with diethyl ether. The organic layer is evaporated and reconstituted in 100 μL of mobile phase and 50 μL of reconstituted sample or filtrate is injected onto the column. Total run time is 25 min. Calibration curves are linear (r² ≥ 0.997) from 0.05 to 10 μg/mL for SDG and EL and 0.01–10 μg/mL for SECO and ED. Precision and accuracy are within USFDA specified limits. The stability of all lignans is established in auto-injector, bench-top, freeze–thaw and long-term stability at −80 °C for 30 days. The method's reasonable sensitivity and reliance on more widely available HPLC technology should allow for its straightforward application to pharmacokinetic evaluations of lignans in animal model systems such as the rat.     

Phenolic compounds from Selaginella moellendorfii

Chemical investigation of the leaves and roots of Selaginella moellendorfii Hieron has resulted in the isolation and characterization of two new flavone glucosides, 7‐O‐(β‐glucopyranosyl(1→2)‐[β‐glucopyranosyl(1→6)]‐β‐glucopyranosyl)flavone‐3′,4′,5,7‐tetraol ( 1 ) and 7‐O‐(β‐glucopyranosyl(1→2)‐[β‐glucopyranosyl(1→6)]‐β‐glucopyranosyl)flavone‐4′,5,7‐triol ( 2 ), two new biflavonoids, 2,3‐dihydroflavone‐5,7,4′‐triol‐(3′→8″)‐flavone‐5″,6″,7″,4′′′‐tetraol ( 3 ) and 6‐methylflavone‐5,7,4′‐triol‐(3′→O→4′′′)‐6″‐methylflavone‐5″,7″‐diol ( 4 ), two new lignans, (7′E)‐3,5,3′,5′‐tetramethoxy‐8 : 4′‐oxyneolign‐7′‐ene‐4,9,9′‐triol ( 5 ) and 3,3′‐dimethoxylign‐8′‐ene‐4,4′,9‐triol ( 6 ), together with two known monolignans, four known lignans, and four known biflavonoids. Their structures were established by spectroscopic means and by comparison with literature values.     

Furanofuran lignans from Vitex negundo seeds

A new furanofuran lignan, vitelignin A (1), together with eight known lignan derivatives, were isolated from the seeds of Vitex negundo. Their structures were identified as (+)-4-oxo-8-hydroxy-2,6-di(3,4-methylenedioxy)phenyl-3,7-dioxabicyclo[3.3.0]octane (1), 4-oxosesamin (2), (+)-sesamin (3), (+)-paulownin (4), 4-hydroxysesamin (5), 4,8-dihydroxysesamin (6), 4-oxopaulownin (7), (+)-2-(3-methoxy-4-hydroxyphenyl)-6-(3,4-methylenedioxy)phenyl-3,7-dioxabicyclo[3.3.0]octane (8), and (+)-pinoresinol (9), respectively, based on extensive NMR and MS spectroscopic studies. Compounds 1, 2, and 7 showed moderate antifungal activity in vitro.     

白粉藤的木脂素和三萜成分

从白粉藤（Cissus repens Lank）地上部分分离得到5个木脂素和8个三萜,其中一个木脂素是新化合物,它的结构通过波谱分析和碱水解的方法鉴定为：（＋）-异落叶松树脂醇-9′-（2-对-香豆酰）-O-β-D-吡喃木糖苷（1）。其余化合物分别是：（＋）-异落叶松树脂醇-9′-O-β-D-吡喃木糖苷（2）,（＋）-Lyoniside（3）,（—）-开环异落叶松树脂醇-9-O-β-D-吡喃木糖苷（4）,（7′R,8′S）-4′-hydroxy-3′,5-dimethoxy-7,8′-dihydrobenzofuran-1-propanolneolignan-9′-O-β-D-xylopyranoside（5）,木栓酮（6）,表木栓醇（7）,蒲公英赛醇乙酸酯（8）,熊果酸（9）,2α-羟基乌索酸（10）,积雪草酸（11）,Niga-ichigoside F1（12）,羽扇豆醇（13）。这些化合物都是首次从该植物中分离得到。