A Simple Approach to Analyze Sugar Nectar Composition in Flowers Using Capillary Electrophoresis and Enzymatic Assays

Despite the obvious importance of nectar, the composition of this solution remains surprisingly understudied to most of the flowers. Here we describe a simple, low-cost, and reliable methodology to analyze the three main sugars present in 210 nectar samples of Christmas Bellflowers using capillary electrophoresis (CE) and enzymatic assays. CE separation (-16 kV) was made using an electrolyte containing 36 mM NaOH pH 12, 15 mM sorbic acid, 0.5 mM hexadecyl trimethylammonium bromide (CTAB), and indirect UV detection. 72.9% of analyzed nectar samples were sucrose dominant; 13.3% sucrose rich only and 13.8% were fructose rich. The concentrations of fructose and glucose present in most of the samples were very similar, while the amount of sucrose varied considerably. The average amounts of fructose, glucose, sucrose and total sugar were 0.22, 0.21, 0.34 and 0.8 M, respectively. The nectar sample shows a pH average of 5. α-Glucosidase activity was observed in 65% of the samples with an average activity of 0.013 µU µL-1 providing a possible explanation for the similar concentrations of fructose and glucose in the samples. Under our knowledge, this is the first article that shows the analysis of sugars in nectar flowers using CE.

尽管花蜜的重要性不言而喻，但迄今为止绝大多数开花植物的花蜜组成仍未得到充分研究，这一点颇令人意外。本研究介绍了一种简便、低成本且可靠的分析方法，用于检测210份圣诞风铃草（Christmas Bellflowers）花蜜样品中的三种主要糖类，检测手段包括毛细管电泳（Capillary Electrophoresis，CE）与酶促分析法。该实验采用含36 mM氢氧化钠（pH 12）、15 mM山梨酸、0.5 mM十六烷基三甲基溴化铵（hexadecyl trimethylammonium bromide，CTAB）的电解质体系，以-16 kV电压进行毛细管电泳分离，并采用间接紫外检测法。在所有待测花蜜样品中，72.9%以蔗糖为主要糖类，13.3%仅蔗糖含量偏高，13.8%则以果糖为主要糖类。多数样品中果糖与葡萄糖的浓度十分相近，而蔗糖的含量则存在显著差异。果糖、葡萄糖、蔗糖与总糖的平均浓度分别为0.22、0.21、0.34和0.8 mol/L。待测花蜜样品的平均pH值为5。65%的样品中检测到α-葡萄糖苷酶（α-Glucosidase）活性，平均活性为0.013 µU·µL⁻¹，这为样品中果糖与葡萄糖浓度相近的现象提供了一种可能的解释。据我们所知，本研究是首个利用毛细管电泳（CE）对开花植物花蜜中的糖类进行分析的报道。