Naturally occurring biflavonoids with amyloid β aggregation inhibitory activity for development of anti-Alzheimer agents

Amyloid β (Aβ) aggregation plays an essential role in promoting the progression of Alzheimer’s disease (AD). Therefore, the inhibition of Aβ aggregation is a potential therapeutic approach for AD. Herein, twenty-seven biflavonoids with different inter-flavonyl linkages and methoxy substitution patterns were isolated from several plants, and their Aβ₄₀ aggregation inhibitory activity was evaluated by the thioflavin-T fluorescence assay. Amentoflavone (1) and its monomethoxy derivatives (2, 3, and 5) exhibited the most potent inhibitory activity, with IC₅₀ values of approximately 5 μM. It was clarified that increasing the number of methoxy substituents on the biflavonoid structures attenuated the inhibitory activity. Moreover, the linkage and the methoxy substitution pattern had a marked influence on the inhibitory activity. Our investigation strongly supports that biflavonoids can be considered a new type of anti-Alzheimer agents that may be successfully developed for AD patients.     

Interactions of the monomeric and dimeric flavones apigenin and amentoflavone with the plasma membrane of L929 cells; a fluorescence study

Flavonoids are ubiquitous polyphenolic compounds, found in vascular plants, which are endowed with a large variety of biological effects. Some of these effects have been assumed to result from interactions with the cell plasma membrane. In order to investigate the nature of these interactions a fluorescence study was performed with two flavonoids, currently used in one of the laboratories: apigenin and its homologous dimer amentoflavone. After preliminary assays with DPH in several types of phospholipid liposomes, the effects of these flavonoids on the membrane of mouse L929 fibroblasts were compared, using the non-permeant probe TMA-DPH. Amentoflavone, unlike apigenin, induced a static quenching effect, which denoted an important, but reversible, association of the molecule with the plasma membrane. In addition, amentoflavone treatment induced a dose-dependent increase in TMA-DPH fluorescence anisotropy, which could be interpreted as an increase in membrane lipidic order. For apigenin, the effect was much less important. Moreover, exploiting the capacity of TMA-DPH to label endocytic compartments, it was shown that, after association with the membrane, amentoflavone is not internalized into the cell. Possible correlations of these membrane effects with other biological properties are discussed.     

Biflavonoid constituents of Campylospermum mannii

Air dried leaves and stem bark of Campylospermum mannii used in the south of Cameroon by the Baka pigmies to remedy heart and stomach disorders have been examined for their photochemical content. Three biflavonoid, amentoflavone, robustaflavone and chamaejasmin were characterized alongside with two new biflavonoids, campylospermones A and B. The structures of isolated compounds were established from complete analysis of their spectroscopic data (MS, IR, ¹H and ¹³C NMR). These results place the Ochnaceae family among the sources of the rare class of 5-deoxyflavonoids.     

Biflavonoids from Brazilian pine Araucaria angustifolia as potentials protective agents against DNA damage and lipoperoxidation

A biflavonoid fraction (BFF) obtained from Araucaria angustifolia needles was effective to quench singlet oxygen (1O2), to protect plasmid DNA against single strand break (ssb) caused by 1O2 or Fenton reaction and to inhibit Fenton or UV radiation-induced lipoperoxidation in phosphatidylcholine liposomes. The activity of the biflavonoid fraction (BFF) was compared with quercetin, rutin (flavonoids), ginkgetin, amentoflavone (biflavonoids), alpha-tocopherol and Trolox. The BFF displayed a higher quenching rate constant compared to flavonoids and biflavonoids and protected against ssb induced by 1O2. Although the BFF was not as efficient as either flavonoids, alpha-tocopherol or Trolox in protection against ssb induced by Fenton-reaction or lipoperoxidation, these scavenging properties suggest that BFF is still an excellent candidate for successful employment as an antioxidant and photoprotector.     

星点设计-效应面法优化杉木枝叶中双黄酮的提取工艺

采用星点设计-效应面法优化杉木枝叶中穗花杉双黄酮和金松双黄酮的提取工艺.以乙醇体积分数、料液比、提取时间为自变量,穗花杉双黄酮和金松双黄酮转移率的归一化值为因变量,通过对自变量与因变量的二次多项式拟合,采用效应面法选取较优的工艺条件,并进行预测分析.最终确定穗花杉双黄酮和金松双黄酮的最佳提取工艺为:乙醇体积分数为50％,料液比为1∶13,超声提取3次,每次提取60 min,最佳工艺验证结果与模型预测值相差-2.55％.结果表明:星点设计-效应面法优选的穗花杉双黄酮和金松双黄酮的提取工艺,方法简便、可靠.