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.     

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。     

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.     

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.     

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.     

Rutin content in buckwheat (Fagopyrum esculentum Moench) food materials and products

The rutin content of buckwheat products was compared to the rutin content in their raw materials, in order to evaluate their value for producing functional foods. There is much less rutin in noodles (78 mg/kg, d.w.b. – dry weight basis), than in the dark buckwheat flour (218 mg/kg, d.w.b.) from which they are produced. One of the possible explanations is the presence of the rutin degrading enzyme. In raw (uncooked) groats there is 230 mg/kg (d.w.b.) of rutin and in precooked groats, 88 mg/kg (d.w.b.). In buckwheat beer and vinegar there is a negligible content of rutin. Buckwheat leaf flour contains about 2700 mg/kg (d.w.b.) rutin, and is thus a suitable material for enriching functional foods, giving it the potential for preventive nutrition.     

Antioxidants in spring leaves of Oxalis acetosella L.

Oxalis acetosella L. is a common, edible wild plant native to the northern hemisphere. The contents of selected antioxidants, and the antioxidant capacity of young and old spring leaves of O. acetosella, were evaluated. The present study reports foliar contents of ascorbic acid, tocopherols, carotenoids, chlorophyll, flavonoids, phenolic acids and total phenolics, and compares the nutritional value of O. acetosella with other cultivated and wild plants. The composition of foliar antioxidants was found to depend on leaf age. On the other hand, the antioxidant capacity of old leaves were in the same range as young leaves. A comparison between O. acetosela with lettuce analysed in our study, and with numerous cultivated and wild edible plants from other studies, showed that O. acetosella is very rich in β-carotene, ascorbic acid, tocopherols and xanthophylls, and that it is one of the best sources of flavonoids (flavonol glycosides and flavan-3-ols), especially rutin. Therefore, O. acetosella is a potentially important dietary source of antioxidants.     

Phenolic content and antioxidant activity of extracts from whole buckwheat (Fagopyrum esculentum Möench) with or without microwave irradiation

The purpose of this study was to extract phenolic compounds and antioxidant activity from buckwheat with water, 50% aqueous ethanol, or 100% ethanol using microwave irradiation or a water bath for 15 min at various temperatures (23–150 °C). Phenolic content of extracts increased with increasing temperature. In general, phenolic contents in microwave irradiated extracts were higher than those heated with a water bath. The highest phenolic content, 18.5 ± 0.2 mg/g buckwheat, was observed in the extract that was microwave irradiated in 50% aqueous ethanol at 150 °C. The highest antioxidant activities, 5.61 ± 0.04–5.73 ± 0.00 μmol Trolox equivalents/g buckwheat, were found in the 100% ethanol extracts obtained at 100 and 150 °C, independent of heat source. These results indicate that microwave irradiation can be used to obtain buckwheat extracts with higher phenolic content and similar antioxidant activity as extracts heated in a water bath.     

Nucleic acid biosensor for DNA hybridization detection using rutin-Cu as an electrochemical indicator

The complex of rutin-Cu (C₈₁H₈₆Cu₂O₄₈, abbreviated by Cu₂R₃, R = rutin) was synthesized and characterized by elemental analysis and IR spectra. Cyclic voltammetry (CV) and fluorescence spectroscopy were used to investigate the interaction of Cu₂R₃ with salmon sperm DNA. It was revealed that Cu₂R₃ could interact with double-stranded DNA (dsDNA) by a major intercalation role. Using Cu₂R₃ as a novel electroactive indicator, an electrochemical DNA biosensor for the detection of specific DNA fragment was developed and its selectivity for the recognition with different target DNA was assessed by differential pulse voltammetry (DPV). The target DNA related to coliform virus gene could be quantified ranged from 1.62 × 10⁻⁸ mol L⁻¹ to 8.10 × 10⁻⁷ mol L⁻¹ with a good linearity (r = 0.9989) and a detection limit of 2.3 × 10⁻⁹ mol L⁻¹ (3σ, n = 7) was achieved by the constructed electrochemical DNA biosensor.     

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.