Electrooxidation of quercetin at glassy carbon electrode studied by a.c. impedance spectroscopy

The present paper reports cyclic voltammetry and a.c. impedance spectroscopy studies on adsorption and electrooxidation of quercetin (3,3′,4′,5,7-pentahydroxyflavone) compound at glassy carbon electrode surface in 0.1 M sodium acetate–acetic acid buffer in 90% methanol solution. The resulted information provided support for a cascade electrooxidation mechanism, which process commences with oxidation of catechol hydroxyl groups and involves strongly adsorbed reaction intermediate. The significance of each oxidation step is explained through associated charge-transfer resistance (derived for all individual oxidation steps and electrosorption of quercetin) and capacitance parameters. This work also presents an original way to regenerate the surface of glassy carbon electrode (after being blocked by quercetin oxidation products) through voltammetric cycling over the potential range negative to the hydrogen reversible potential. The above is realized by means of in situ evolved hydrogen, which species is capable of electrochemically reducing products formed during the cascade electrooxidation reaction of quercetin.     

高效液相色谱法测定胆立清胶囊中的槲皮素含量

目的：建立胆立清胶囊中的槲皮素含量的测定方法。方法：采用Lichrospher C18色谱柱,甲醇-0.4%磷酸（50：50）为流动相,检测波长为360nm。结果：槲皮素的回归方程：Y=7414.2X＋0.1162 r=0.9999,线性范围为1-16μg/mL;平均回收率为98.6%,RSD=2.00%（n=5）。结论：方法简便、专属、准确,能有效地控制胆立清胶囊的质量。     

桑寄生化学成分的研究广寄生叶中d-儿茶素及檞皮甙的分离和鉴定

桑寄生为常用中药,广寄生(Taxillus Chinensis(DC.)Danser)为桑寄生主流品种之一,中国药典各版均有收载。据文献报道叶中含广寄生甙(Avicullarin)及檞皮素(Quercetin)。作者从叶中分得二种结晶,理化鉴定及光谱分析证明晶Ⅰ为d-儿茶素(d-Catechin),晶Ⅱ为檞皮甙(Quercitrin),收率分别为0.013％和0.14％。为进一步考察广寄生叶中黄酮成分的组成,取夏季、冬季采收的广寄生及两种市售的寄生茶作叶的总黄丽层折鉴定,用檞皮甙、广寄生甙、d-儿茶素、槲皮素纯品对照,结果均含以上成分,但以檞皮甙为主,广寄生甙含量很低。     

东北不同产地野生罗布麻叶总黄酮含量及抗氧化性比较

目的 测定东北松嫩草原和辽河入海口野生罗布麻叶总黄酮和槲皮素含量,并对其抗氧化活性进行比较.方法 超声波辅助提取总黄酮,比色法和HPLC分别测定总黄酮和槲皮素含量,DPPH·和·OH清除法评价抗氧化活性.结果 松嫩草原和辽河入海口罗布麻叶总黄酮含量分别为10.593～11.001mg·g-1,11.203mg·g-1;槲皮素含量分别为5.507～5.753mg·g-1,5.218mg·g-1.松嫩草原罗布麻叶总黄酮抗氧化活性较强.结论 辽河入海口和松嫩草原野生罗布麻叶总黄酮、槲皮素含量差异不显著,松嫩草原野生罗布麻叶总黄酮具有较强的抗氧化活性.     

槲皮素对镉致大鼠急性肾损伤预防作用的研究

目的研究镉致急性肾损伤中肾脏的病理和临床改变及槲皮素的预防作用。方法雄性Wistar大鼠随机分成对照组和预防组。测定肾损伤指标:血尿素氮(BUN)、尿乙酰氨基葡糖苷酶(NAG)、尿γ-L-谷氨酰转肽酶(γ-GT)、尿蛋白含量。光镜及透射电镜下观察肾脏病理改变。结果槲皮素预防组与对照组相比,大鼠的一般状态较好。预防组与对照组相比,肾脏病理损伤相对减轻且肾损伤指标含量显著降低,各组间比较差异具有统计学意义(P<0.01)。结论镉能够导致肾损伤,槲皮素对镉性肾损伤具有一定的预防作用。     

正交试验优选复方青牛胆降糖胶囊的醇提取工艺

目的:筛选复方青牛胆降糖胶囊最佳醇提工艺。方法:采用L₉（3⁴）正交试验,以盐酸巴马汀、槲皮素提取率和干浸膏得率综合评分为指标,考察复方青牛胆降糖胶囊回流提取工艺中乙醇浓度、乙醇用量、提取时间、提取次数的影响。结果:最佳提取工艺为10倍量的90%乙醇,提取2次,每次0.5 h。结论:所建立的最佳提取方法稳定、可行,为进一步的工业生产提供理论依据。     

HPLC法测定紫花地丁中槲皮素、芹菜素、木犀草素含量

目的:建立高效液相色谱法测定紫花地丁中槲皮素、芹菜素和木犀草素的含量测定方法。方法:采用HPLC法对紫花地丁中的槲皮素、芹菜素、木犀草素进行含量测定。色谱条件为:C18柱(5μm,4.6 mm×250 mm),柱温30℃,流动相为乙腈-甲醇-0.2%磷酸水溶液梯度洗脱,流速0.8 mL.min-1,检测波长350 nm。结果:槲皮素、芹菜素和木犀草素色谱分离良好,浓度与峰面积呈良好线性关系,线性范围分别为槲皮素7.5~90.0 mg.L-1,r=0.999 9(n=6);芹菜素7.5~180.0 mg.L-1,r=0.999 8(n=6),木犀草素2.5~55.0 mg.L-1,r=0.999 9(n=6)。平均加样回收率分别为95.1%(n=9,RSD=1.0%)、95.7%(n=9,RSD=1.2%)、97.8%(n=9,RSD=0.7%)。结论:本方法测定了5批紫花地丁的槲皮素、芹菜素和木犀草素的含量,该方法分离度好、快速、简便、重现性好。     

高效液相色谱法测定乳舒片中槲皮素含量

目的建立测定乳舒片中槲皮素含量的高效液相色谱法。方法色谱柱：Agilent Eclipse XDB C18（4.6 mm×250 mm,5 μm）,流动相：甲醇－0.2%磷酸水溶液（45：55）,流速1 mL·min 1,检测波长370 nm。结果槲皮素进样量在0.03～0.30 μg范围内具有良好的线性关系（r＝0.999 9）,平均加样回收率99.65%,RSD为1.85%（n＝5）。结论该方法简便、准确,重复性好,可用于控制乳舒片的质量。     

Preparation of amino-modified active carbon cartridges and their use in the extraction of quercetin from Oldenlandia diffusa

Polyethyleneimine (PEI) and ethylenediamine (EDA) as modifiers were bonded on active carbon (AC) surface for specific selective extraction of quercetin from Oldenlandia diffusa. The characteristics of the modified AC materials that were obtained were investigated by field emission-scanning electron microscopy (FE-SEM) and Fourier transform infrared spectrometer (FT-IR). The interactions between quercetin and the AC materials were investigated by fitting the static adsorption data to four linear and nonlinear adsorption isotherm models. Of these four models, the Langmuir-Freundlich adsorption isotherm was proved the best for investigating quercetin on AC materials. Scatchard analysis was used to evaluate the binding properties of the AC materials for quercetin. Solvent extraction and solid-phase extraction (SPE) were optimized, and the effect of the mobile phase pH was investigated to improve the performance for the separation of quercetin on high performance liquid chromatography (HPLC). The results from the validation of the proposed analytical method demonstrated that the EDA-modified AC was the most suitable SPE cartridge for the purification of quercetin from O. diffusa.