Preparation and properties of rutin-hydrolyzing enzyme from tartary buckwheat seeds

A rutin hydrolyzing enzyme (RHE) was isolated from Fagopyrum tataricum Moench seeds by using ammonium sulphate fractionation, anion exchange and size exclusion chromatography. The purified RHE has an apparent molecular weight of about 70 kDa determined by SDS-PAGE, with an isoelectric point (pI) (determined by isoelectric focusing) of 6.7. RHE has a specific catalytic activity toward rutin when incubated together with rutin at 37 °C for 30 min in the presence of 20% ethanol, and its K_m value for rutin is 1.04 × 10⁻³ M. The RHE catalytic product analyzed by HPLC displayed high similarity with quercetin and this is confirmed by ¹H NMR spectroscopy and LC-ESI-MS/MS, suggesting that the RHE hydrolysis product is quercetin. These results suggest that the RHE from tartary buckwheat seeds is a specific rutin-hydrolyzing enzyme, providing a new enzymatic preparation method for quercetin.     

Preliminary separation and purification of rutin and quercetin from Euonymus alatus (Thunb.) Siebold extracts by macroporous resins

In this study, the performances of rutin and quercetin from Euonymus alatus (Thunb.) Siebold extracts on five macroporous resins with different physical and chemical properties were investigated. The results of static tests indicated that AB-8 resin was the most appropriate and its adsorption data were well fitted to the Langmuir and Freundlich isotherms. In order to optimize the separation process, different pH values of sample solution, different concentrations and pH values of ethanol solution also have been investigated. Column packed with AB-8 resin was used to perform dynamic adsorption and desorption experiments. After the treatment with AB-8 resin and optimal conditions, the contents of rutin and quercetin in the product were 8.45-fold and 13.14-fold increased with recovery yields of 63.1% and 72.3%, respectively. The results showed that the present method was suitable for large-scale preparation of rutin and quercetin from Euonymus alatus (Thunb.) Siebold or other herbal materials.     

Enzymatic de-glycosylation of rutin improves its antioxidant and antiproliferative activities

Bioavailability and biological properties of flavonoid glycosides can be improved after the enzymatic hydrolysis of specific glycosyl groups. In this study, we evaluate the antioxidant and antiproliferative potential of rutin after enzymatic hydrolysis performed by α-l-rhamnosidases (hesperidinase from Penicillium sp. and naringinase from Penicillium decumbens) previously heated at 70 °C for 30 min to inactivate the undesirable β-d-glucosidase activity. The highest in vitro antioxidant activity determined by DPPH radical scavenging was achieved with rutin hydrolyzed by hesperidinase. Rutin was predominantly bioconverted into quercetin-3-glucoside. There was no statistical difference between xanthine oxidase inhibition by rutin before and after hydrolysis. However, in vitro inhibitory activity against ten human tumor cell lines showed that hydrolyzed rutin exerted a more potent antiproliferative effect than quercetin and rutin on various cancer cell lines, specially glioma, and ovarian and breast adenocarcinomas. These results indicate that quercetin-3-glucoside could be a promising functional derivative obtained by rutin hydrolysis.     

Antiproliferative,proapoptotic and morphogenic effects of the flavonoid rutin on human glioblastoma cells

In this study, we investigated the effects of the flavonoid rutin (3,3′,4′,5,7-pentahydroxyflavone-3-rutinoside) on glioma cells, using the highly proliferative human cell line GL-15 as a model. We observed that rutin (50–100 μM) reduced proliferation and viability of GL-15 cells, leading to decreased levels of ERK1/2 phosphorylation (P-ERK1/2) and accumulation of cells in the G2 phase of the cell cycle. On the other hand, 87.4% of GL-15 cells exposed to 100 μM rutin entered apoptosis, as revealed by flow cytometry after AnnexinV/PI staining. Nuclear condensation and DNA fragmentation were also observed, further confirming that apoptosis had occurred. Moreover, the remaining cells that were treated with 50 μM rutin presented a morphological pattern of astroglial differentiation in culture, characterised by a condensed cell body and thin processes with overexpression of GFAP. Because of its capacity to induce differentiation and apoptosis in cultured human glioblastoma cells, rutin could be considered as a potential candidate for malignant gliomas treatment.     

RP-HPLC梯度洗脱法测定杏香兔耳风不同部位中绿原酸和芦丁的含量

目的：建立高效液相色谱法同时测定杏香兔耳风不同部位中绿原酸和芦丁的含量。方法：采用Kromasil C18柱（4．6mm×250him，5μm），以甲醇-水为流动相，梯度洗脱程序为0min（25：75）-13min（25：75）-14min（45：55）-30min（45：55）-40min（75：25）；流速0．8ml·min^-1；检测波长350nm；柱温25℃；光电二极管阵列检测器（PAD）。结果：绿原酸线性范围为0．430～3．870μg，r=0．9996，样品的平均加样回收率为98．9％（RSD=1．7％）；芦丁线性范围为0．252～2．268μg，r=0．9995，样品的平均加样回收率为97．6％（RSD=2．3％）。结论：方法快速简便，专属性强，重复性好，可作为杏香兔耳风中绿原酸和芦丁的定量分析方法。     

三种芦丁脂肪酸酯在空气/水界面的成膜性质

采用LB膜分析仪分别研究了芦丁硬脂酸酯(RS)、芦丁月桂酸酯(RL)和芦丁正己酸酯(RC)在空气/水界面的成膜性质,及亚相中的Al3+对3种芦丁脂肪酸酯成膜性质的影响.结果显示,3种芦丁脂肪酸酯的成膜性质与其疏水基的碳链长度、压膜速度和亚相性质有关.RS和RL能在水面铺展为液态扩张膜,RC则不能成膜.引入芦丁分子中的疏水基碳链越长,成膜越稳定.慢速压膜利于膜稳定性,膜的崩溃压大;较快速压膜能使更多膜分子保留在水表面,膜的平均分子面积大.选择适宜的压膜速度对得到比较稳定的芦丁脂肪酸酯膜很关键.当亚相中含Al3+时,RS、RL和RC均铺展成液态扩张膜,且RS膜和RL膜崩溃时的分子面积(acoll)大于它们在水表面铺展成膜的acoll.研究结果对从分子水平研究芦丁脂肪酸酯抗氧化活性的作用机制具有重要的参考价值.     

Reduction of rutin loss in buckwheat noodles and their physicochemical characterisation

Tartary buckwheat was subjected to hydrothermal treatments for minimising rutin loss in buckwheat-based foods by water addition. When native buckwheat flour was mixed with water for 60 min, the rutin content was distinctly reduced from 3.74 g/100 g to 0.31 g/100 g, increasing the amount of quercetin. However, the rutin content remained constant and quercetin was hardly detected in hydrothermally-treated buckwheat flour. Also, when noodles were prepared with wheat and buckwheat flours (7:3, w/w), the noodle samples containing hydrothermally-treated buckwheat flour, showed higher amounts of rutin (more than 0.83 g/100 g) than the control noodle with native buckwheat flour (0.27 g/100 g). In addition, the use of hydrothermally-treated buckwheat flour gave less pasting parameters and lower viscoelastic properties. The noodle dough with hydrothermally-treated buckwheat flour also had greater water absorption and development time during mixing while the elongation stress of the noodle dough was reduced.     

Cyclic voltammograms obtained from the optical signals: Study of the successive electro-oxidations of rutin

This paper describes a novel method of obtaining cyclic voltammograms (CVs) from optical signals. The obtained CVs correspond to the various specific species involved in the electrode process, which give more detailed information on the system under investigation than the common CV. For this purpose cyclic voltabsorptometry was used to investigate the successive oxidation processes of rutin on a graphite-wax electrode by using a long optical-path thin-layer electrochemical cell. The dynamic UV spectra of rutin showed the information on the structures of the oxidation products at different potentials. Cyclic voltabsorptiograms (CVAs) were measured in three potential ranges at the characteristic absorption wavelengths of rutin, 346, 254 and 296 nm, respectively. The CVs of three species in solution (rutin and its two products) were obtained from the derivative cyclic voltabsorptiograms (DCVAs). Based on this the redox mechanisms of rutin in different CV peaks were discussed.     

In vitro antioxidant properties of rutin

Much work has been carried out in recent years on the beneficial effect of phenolic compounds which act as natural antioxidants and help to neutralize free radicals. We analysed the antioxidant activity of the rutin (quercetin-3-rhamnosyl glucoside) using different assays including: total antioxidant activity and reducing power, hydroxyl radical scavenging assay, superoxide radical scavenging assay, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assay and lipid peroxidation assay which uses egg yolk as the lipid-rich source. Total antioxidant capacity was determined by the assay based on the decrease in absorbance of β-carotene by the sample. Rutin exhibited strong DPPH radical scavenging activity. At the concentration of 0.05 mg/ml, ascorbic acid (Vc), butylated hydroxytoluene (BHT) and rutin showed 92.8%, 58.8%, and 90.4% inhibition, respectively. In addition, rutin had effective inhibition of lipid peroxidation. Those various antioxidant activities were compared to standard antioxidants such as BHT and Vc.     

Antioxidant activity and quality of asparagus affected by microwave-circulated water combination and conventional sterilization

Green asparagus (Asparagus officinalis L.), as a healthy and perishable vegetable, is processed after harvest to minimize the deterioration of its physical and chemical quality. In our research, fresh asparagus was sterilized using several methods, including a pilot-scale 915 MHz microwave-circulated water combination (MCWC) heating system, pressured hot-water heating and steam-heating in a retort. Rutin content of asparagus processed by these methods did not show significant difference. But antioxidant activity of asparagus after MCWC treatment was significantly greater than that processed by other methods. Although the shear stress of asparagus spears was significantly decreased by eight times after sterilization, no significant difference existed among the textures of asparagus processed by these methods. Asparagus processed by MCWC showed greener colour with negative a* value and greater hue value (H⁰) than did hot water- and retort-treated asparagus. Therefore, asparagus sterilized by MCWC showed greater antioxidant activity and greener colour than did asparagus processed by the conventional methods.