Using multiwalled carbon nanotube modified electrodes for the adsorptive striping voltammetric determination of hesperidin

Hesperidin, a flavone glycoside found in the skins and juices of citrus fruits, can be detected using multiwalled carbon nanotube (MWCNT)-modified electrodes using the technique of adsorptive stripping voltammetry (AdSV) with accumulation at open circuit potential. This is relevant because hesperidin can be used as an indication of the citrus fruit juice's freshness. The oxidation mechanism to explain the observed voltammetry corresponds to the redox chemistry of the guaiacol sub-unit within the hesperidin molecular structure. Hesperidin could be detected over a linear range up to 30 μM, and with a detection limit of 0.61 μM and 7 nM, with less than 5% variation between different electrodes, using cyclic voltammetric or square wave adsorptive stripping techniques respectively. This methodology was extended to MWCNT-modified screen-printed electrodes (MWCNT-SPEs), allowing the development of a cheap, mass produced, disposable sensor that we show is capable of measuring the concentration of hesperidin in real orange juice samples, and be applied within the citrus fruit industry.     

Isolation of hesperidin from peels of thinned Citrus unshiu fruits by microwave-assisted extraction

Simultaneous extraction by microwave-irradiation and crystallisation were performed in the same pot of solvent of 70% (v/v) aqueous ethanol for isolation of hesperidin from thinned immature fruit peels of Citrus unshiu as refining of Citrus waste biomass. The hesperidin content in immature fruits peels was about 3.2-fold higher than that of mature fruit. After microwave-assisted extraction (MAE), the yield of hesperidin reached 58.6 mg/g, which was comparable to the amount obtained after extraction using DMSO:methanol (1:1, v/v) as a solvent for 30 min at room temperature. Heating temperature and time for isolation of hesperidin crystallites were optimised as 140 °C and 8 min by using response surface methodology. Under this optimal condition, 86.8% (47.7 mg/g) of total hesperidin was isolable by MAE and low-temperature storage (5 °C, 24 h).     

Comparative study of flavonoid and scoparone accumulation in different Citrus species and their susceptibility to Penicillium digitatum

Fungi of the genus Penicillium are responsible for substantial post-harvest losses in Citrus fruits. The results obtained following artificial inoculation of Citrus fruits with Penicillium digitatum showed that the degree of fungal development depended on the Citrus species. Thus, the mature fruit of Citrus paradisi were more susceptible to this fungus than the mature fruit of Citrus limon, Citrus sinensis,Citrus clementina Hort. ex Tan., and Citrus unshiu (mak) Marc. The results point to an inverse correlation between the degree of susceptibility of Citrus species to this fungus and the flavanone content – hesperidin in C. sinensis, C. clementina Hort. ex Tan. and C. unshiu (mak) Marc.; naringin in C. paradisi and the flavanone hesperidin and the flavone diosmin in C. limon. Thus, in C. sinensis,C. clementina Hort. ex Tan and C. unshiu (mak) Marc. the highest levels of the polymethoxyflavones, sinensetin, tangeretin, heptamethoxyflavone and nobiletin, were observed in the least susceptible varieties and viceversa. In the case of C. paradisi, no significant differences were detected in the polymethoxyflavone levels between varieties, while in C. limon, polymethoxyflavones were hardly detectable. The production of scoparone was observed in all the species and varieties studied after inoculation with the fungus, especially in C. limon fruits. Based on the evidence, it seems that flavanones, flavones, polymethoxyflavones (phytoanticipins) and scoparone (a phytoalexin) may well be involved in the defence mechanisms of Citrus fruits against P. digitatum. Depending on the Citrus species in question, the relative participation of one group of secondary compounds or another may vary.     

橙皮苷半合成香叶木苷及抑癌作用研究

本文首次研究了一种半合成香叶木苷的化学方法，并测定该合成产物对六种常见癌细胞的抗增殖活性。该方法以廉价的橙皮苷为原料，用DDQ作脱氢剂，氧化制备香叶木苷。经sephadex LH-20柱纯化后，HPLC-MS与1H-NMR鉴定确定该产物为香叶木苷，首次证实该转化方法对于黄酮苷类物质的合成是可行的。优化所得合成工艺为：原料质量比为1:0.4，反应温度为110℃（油浴温度），反应时间为6小时。本实验的研究结果为香叶木苷的合成与应用提供新的途径。     

橙皮甙的电化学行为研究

用单扫示波极谱法,橙皮甙在0.1mol/LKH_2PO_4缓冲溶液中(pH4.60)有一灵敏的二阶导数峰,25℃时峰电位为-1.43V(vs、SCE),峰电流与橙皮甙浓度在2.5×10~(-7)～4.0×1O~(-5)mol/L范围内有良好的线性关系,检测限为1.2×10~(-7)mol/L。用本法测定了中药陈皮中总黄酮的含量,其结果令人满意。实验证明橙皮甙的电极反应机理为双电子的不可逆过程。此外,还证明了H_2O_2和·OH自由基可催化该还原电流,并讨论了橙皮甙对超氧阴离子自由基的清除作用。     

Exploring the phytochemical content and the antioxidant potential of Citrus fruits grown in Cyprus

The physicochemical and phytochemical profile as well as the antioxidant properties of the most important Citrus fruits grown in Cyprus [orange (Citrus sinensis, cv. ‘Valencia’), grapefruit (Citrus paradisi, cvs. ‘White Marsh’, ‘Star Ruby’, ‘Rio Red’) and an interspecific hybrid (Citrus reticulata x Citrus sinensis, cv. ‘Mandora’)] were determined. ‘Valencia’ fruit exhibited the highest phenolic, flavonoid and ascorbic acid content, as well as a higher antioxidant potency, followed by ‘Mandora’ fruit and the three grapefruit cultivars. HPLC indicated significant diversity on flavanones among the examined fruits, while LC-MS analysis revealed the presence of hydroxycinnamic acid derivatives, polymethoxyflavones and a furocoumarin. Overall, this study provides supporting evidence for the superiority of ‘Valencia’ orange fruit as an excellent source of bioactive compounds. In addition, to the best of our knowledge, this is the first study thoroughly describing the phytochemical profile of ‘Mandora’ fruit, an interspecific hybrid cultivated in Cyprus.     

高效液相色谱法测定胃苏颗粒中橙皮苷和柚皮苷含量

目的：用高效液相色谱法测定胃苏颗粒中橙皮苷和柚皮苷的含量。方法：采用DiamonsilTMC18（4．6mm×150mm,5μm）色谱柱;乙腈一磷酸水（pH=3．5）（22：78,V/V）为流动相,流速为1．2mL／min;检测波长为283nm。结果：待测组分与其他组分分离度良好（R〉1．5）,橙皮苷和柚皮苷线性范围分别为0．25～1．49μg和0．093～0．56μg,橙皮苷和柚皮苷的平均回收率分别为99．2％,98．8％,RSD分别为1．6％,2．3％。结论：高效液相色谱法是测定胃苏颗粒中橙皮苷和柚皮苷成分的一种简便、有效的方法。     

RP—HPLC法测定不同产地枳实中的柚皮苷、橙皮苷及新橙皮苷

目的：建立同时测定枳实中柚皮苷、橙皮苷和新橙皮苷含量的方法。方法：采用反相高效液相色谱法分离检测柚皮苷、橙皮苷和新橙皮苷,色谱柱为HypersilODS2（250mm×4．6mm,5μm大连依利特公司）,流动相为乙腈-水（20：80）,流速为1．0mL／min,检测波长283nm,柱温为30℃。结果：柚皮苷、新橙皮苷在1．00～7．50μg,橙皮苷在0．40～3．00μg与峰面积呈良好的线性关系。柚皮苷、橙皮苷、新橙皮苷的平均回收率分别为100．56％（RSD：0．55％）、100．20％（RSD=1．00％）、101．14％（RSD=1．74％）。结论：该方法简便、准确、可靠、重复性好,可用于枳实药材的质量控制。     

Recovery of hesperidin and narirutin from waste Citrus unshiu peel using subcritical water extraction aided by pulsed electric field treatment

The objective of this study was to identify whether the efficacy of extracting hesperidin and narirutin from Citrus unshiu peel by-products can be increased by combining pulsed electric field (PEF) and subcritical water extraction (SWE). The samples were treated with a PEF at a strength of 3 kV/cm for 60 and 120 s. Subsequent SWE was conducted at extraction temperatures of 110–190 °C for 3–15 min. The concentration of hesperidin was highest at 46.96 ± 3.37 mg/g peel (dry basis) after PEF treatment at 120 s, combined with SWE at 150 °C for 15 min, while that of narirutin peaked at 8.76 ± 0.83 mg/g after PEF treatment at 120 s, integrated with SWE at 190 °C for 5 min. The concentrations of both hesperidin and narirutin increased with PEF treatment time. The PEF increased the amounts of hesperidin and narirutin extracted by 22.1% and 33.6%, respectively. This study demonstrate the potential of PEF pretreatment for enhancing the SWE of flavonoids from C. unshiu peel.