A New Antimicrobial Flavonol Glycoside from Alchornea Davidii

A new flavonol glycoside,isorhamnetin-3-O- β-D-xyloside,was isolated from the extract of leaves and twigs of Alchornea davidii (Euphorbiaceae).Its structure was established on the basis of the spectral analysis and chemical degradation.Antimicrobial assay showed that it moderately inhibited the growth of test bacteria (Staphylocoocu aureus,Bacillus subtilis and Pseudomonas fluorescens)and fungi (Candida albicans,Aspergillus niger and Trichophyton rubrum) with MICs at 50μg/ml.     

A Flavonol Glycoside from Smilax glabra

A new flavonol glycoside,named neosmitibin was isolated the rhizome of Smilax glabra. Its structure and absolute configuration were elucidated on the basis of spectroscopic studies.     

HPLC-ESI-MS/MS识别蓝莓提取物中的花青素和黄酮醇

用高效液相色谱-电喷雾离子化串联质谱联用技术(HPLC-ESI-MS/MS)对蓝莓提取物中的黄酮类物质进行了分析, 可以快速地鉴定其主要成分为花青素和黄酮醇. 结构上的不同导致花青素和黄酮醇在紫外-可见光谱吸收、离子化以及裂解方式上都存在差异. 尽管花青素和黄酮醇在270 nm处都有吸收, 但两者分别在530和372 nm附近有特征吸收. 负离子模式下, 黄酮醇可以生成负离子和自由基负离子, 而正离子型的花青素则几乎不产生质谱信号, 这一显著差异可用以区别花青素和黄酮醇. 花青素与黄酮醇在串联质谱中分别拥有各自的特征产物离子更进一步证实了其结构存在差别. 该研究对于蓝莓提取物的质量分析与控制很有帮助.     

银杏叶黄酮糖苷精制工艺的研究

银杏叶用5倍重的70%乙醇水溶液回流提取4次,每次30min,银杏叶黄酮糖苷的平均浸出率为93.8%,不同型号大孔吸附树脂的精制效果研究表明,在确定的精制条件下制备的银杏叶提取物,其得率为2.50%～2.92%,黄酮糖苷含量25.7%～34.6%．     

Synthesis and Structure of Borane Complexes with 3-Hydroxyflavone

Conclusions have been made regarding the structure of the complexes formed between flavonol and boranes of different structures on the basis of the analysis of their ¹H, ¹³C, and ¹¹B NMR spectra, IR and electronic spectra, and also from the results of quantum-chemical calculations. In all of the complexes, independently of the structure and acceptor properties of the boranes, it was found that the donor acceptor bond is formed between the boron atoms and the oxygen of the carbonyl group in the flavonol. Despite the lowered electron-donor ability of the carbonyl group oxygen atom after the formation of the bond to the boron atom it is likely that the hydrogen bond between the carbonyl and the 3-hydroxy group of the flavonol is retained. It was found that the carbonyl group of the flavonol has a lower electron-donor ability than the analogous group of aliphatic and aromatic ketones.     

Two New Flavonol Glycosides from Knoxia corymbosa

Two new flavonol glycosides (1 and 2) together with two known flavonoides (3 and 4),were isolated from the whole plant of Knoxia corymbosa willd. The structures of I and 2 were elucidated as kaempferol-7-O-α-L-arabinosyl-3-O-β-D-6“-acetylglucopyranoside and kaempferol -7-O-α-L-arabinosyl-3-O-β-D-3″,6″-diacetylglucopyranoside respectivedly.     

Visconata: A rare flavonol having long chain fatty acid from Dodonaea viscosa which inhibits Human neutrophil elastase (HNE)

A series of flavonoids were isolated from Dodonaea Viscosa and tested for inhibition of human neutrophil elastase (HNE), enzyme involved in inflammatory disorders. Isolated compounds were identified as a novel flavonol (1) along with eight known flavonoids (2–9). Novel flavonol, visconata (1) has a very rare skeleton having odd numbered long chain (C19) fatty acid, which was completely identified by mass fragmentation and 2D NMR analysis. All compounds (1–9) inhibited HNE in dose dependent manner with IC₅₀s ranging between 2.4 and 150 μM. Visconata (1) emerged to be the most potent compound with 2.4 μM of IC₅₀. In kinetic studies, compound (1) was observed to be reversible, noncompetitive inhibitor having K_i = 1.8 μM, whereas other flavonoids (2–9) displayed mixed type inhibition.     

Target profiling of flavonol glycosides in the extract of Ginkgo biloba leaf and their pharmacokinetics in rat plasma by ultra-high-performance liquid chromatography with tandem mass spectrometry

The extract of Ginkgo biloba leaf is a popular herbal product or dietary supplement in the world to treat various diseases, and flavonol glycosides are considered as the main bioactive constituents. In this study, 37 flavonol glycosides were rapidly screened out by precursor ion scanning in positive ion mode with production ions at m/z 287.05, 303.05, and 317.06. Subsequently, a reliable and sensitive ultra-high-performance liquid chromatography coupled with triple quadrupole-linear ion trap mass spectrometry approach was established and validated to quantify the 20 prototype flavonol glycosides in rat plasma. Calibration curves showed good linearity (R² ≥ 0.9894) over the corresponding concentration range. The precision, accuracy, extraction recovery, matrix effect, and stability were also satisfactory. The validated method was successfully applied to a pharmacokinetic study of prototype flavonol glycosides in rat after oral administration of the extract of G. biloba leaf. As a result, the T_max of flavonol glycosides was short at 0.11–0.60 h. Quercetin-3-O-(2“,6″-di-O-rhamnosyl)-glucoside, kaempferol-3-O-(2′',6′'-di-O-rhamnosyl)-glucoside, quercetin-3-O-rutinoside, quercetin- 3-O-glucosyl-(1-2)-O-rhamnoside, and kaempferol-3-O-glucoside presented relatively high systemic exposure levels with AUC_0-∞ > 500 μg h/L and C_max > 100 μg/L. This study would provide the valuable information for further scientific research and clinical application of the extract of G. biloba leaf.     

7-羟基黄酮醇和7-羟基黄烷酮及其衍生物的合成

从2-羟基-4-甲氧甲氧基苯乙酮和3,5-二甲氧基苯甲醛出发,通过醛酮缩合、环化、Algar-Flynn-Oyamada反应、脱保护基、异戊烯基化反应等步骤,合成了5个未见文献报道的7-羟基黄酮醇和7-羟基黄烷酮及其衍生物,总收率22%~36%。其结构经1HNMR,13CNMR,IR和MS确证。     

槲皮素与桑色素ESI-MS裂解行为的比较分析

运用量子化学方法辅助解析并比较槲皮素与桑色素在电喷雾离子阱质谱(ESI-MS)负离子模式下的裂解行为。依据密度泛函理论(Density functional theory,DFT),在B3LYP/6-31G(d)水平,对槲皮素与桑色素的分子空间构型进行优化,确定稳定的几何构型与去质子化位点,在RB3LYP/6-31+G(2d,2p)水平,计算相对碎裂电压下的二级质谱中碎片离子处于稳定状态时的能量,通过比较准分子离子稳定构型并结合基组重叠误差(Basis set superposition error,BSSE)校正后的键解离能(Bond dissociation energy,BDE),推导了质谱碎裂过程。结果显示:槲皮素的稳定构型为A,B,C环处于同一平面,桑色素上的2'-OH使得B环与AC环之间翻转一定角度,二面角D(1,2,1',6')为-134.662 4°。槲皮素与桑色素的质谱裂解过程主要通过C环跨环裂解产生,且具有多种开裂方式,开裂先后顺序为:1,2开裂、0,2开裂、1,3开裂、1,4开裂与0,4开裂,分别生成碎片离子1,2A-,0,2A-,1,3A-,1,4A-与0,4A-,并逐步进行后续裂解,而2'-OH的存在促进了桑色素的裂解。该研究为进一步揭示黄酮醇类化合物的质谱裂解规律提供了理论依据。