Department of Physical and Analytical Chemistry, University of Jaén, Campus Las Lagunillas s/n, 23071, Jaén, Spain.
Anal Bioanal Chem. 2011 Jan;399(2):965-72. doi: 10.1007/s00216-010-4261-z. Epub 2010 Oct 16.
Piceid (3,4',5-trihydroxystilbene-3-β-D: -glucoside) is a stilbene which occurs naturally in various families of plants and has been shown to protect lipoproteins from oxidative damage and to have cancer chemopreventive activity. This paper deals with the determination of piceid in cocoa-containing products by using photo-induced fluorescence and the aid of a multicommutated continuous-flow assembly which was provided with an on-line photoreactor. A strongly fluorescent photoproduct is generated from piceid when it is irradiated under UV light for 30 s, which is retained on Sephadex QAE A-25 and directly monitored on this active solid support at 257/382 nm (λ (exc)/λ (em), respectively). The pre-concentration of the photoproduct of piceid on the solid support greatly improves both sensitivity and selectivity. The influence of different experimental parameters, both chemical (pH, ionic strength) and hydrodynamic (irradiation time, flow rate, photoreactor length, sampling time), was tested. The sample pre-treatment included delipidation with toluene and cyclohexane, stilbene extraction with ethanol/water (80:20, v/v) and clean-up by solid-phase extraction on C(18) cartridges and methanol/water (40:20, v/v) as eluting solution. This procedure allowed the elimination of the aglycon of piceid, resveratrol and other potential interfering species and a recovery of about a 90% piceid. The method was applied to the analysis of piceid in cocoa powder, dark chocolate and milk chocolate. The quantification limits were 1.4, 1.1 and 0.09 mg kg(-1), respectively. Relative standard deviations ranged from 1.8% to 3.1%. This is the first reported non-chromatographic method for determination of piceid in these foods.
白皮杉醇（3,4',5-三羟基二苯乙烯-3-β-D：-葡萄糖苷）是一种天然存在于多种植物科中的二苯乙烯，已被证明可保护脂蛋白免受氧化损伤，并具有抗癌化学预防活性。本文涉及使用光致荧光和多切换连续流动组件（该组件配备有在线光反应器）来测定含可可产品中的白皮杉醇。当白皮杉醇在紫外光下辐照 30 秒时，会生成一种强荧光光产物，该产物在 Sephadex QAE A-25 上保留，并在该活性固体载体上直接在 257/382nm（分别为λ（激发）/λ（发射））处监测。光产物在固体载体上的预浓缩极大地提高了灵敏度和选择性。测试了不同的实验参数（化学参数（pH 值，离子强度）和流体动力学参数（辐照时间，流速，光反应器长度，采样时间））的影响。样品预处理包括用甲苯和环己烷进行脱脂，用乙醇/水（80:20，v/v）提取二苯乙烯，并通过 C（18）小柱固相萃取和甲醇/水（40:20，v/v）作为洗脱液进行净化。该程序允许消除白皮杉醇的糖苷配基，白藜芦醇和其他潜在的干扰物质，并回收约 90％的白皮杉醇。该方法用于分析可可粉，黑巧克力和牛奶巧克力中的白皮杉醇。定量限分别为 1.4、1.1 和 0.09mgkg(-1)。相对标准偏差范围为 1.8％至 3.1％。这是首次报道的用于测定这些食品中白皮杉醇的非色谱法。
