Department of Entomology, University of Wisconsin, 53706, Madison, Wisconsin.
J Chem Ecol. 1996 Apr;22(4):765-71. doi: 10.1007/BF02033584.
The chemistry of the plant family Salicaceae has been of interest to researchers as diverse as chemical ecologists, chemosystematists, and paper chemists. Continuing the debate on proper methods for preservation of plant material prior to analysis, vacuum-drying was recently advocated, because freeze-drying may cause degradation of phenolic glycosides. This study was conducted to clarify the consequences of freeze-drying for foliar secondary chemicals and to evaluate the consequences of vacuum-drying for primary compounds (protein and carbohydrates). Leaves of quaking aspen (Populus tremuloides) were flash-frozen in liquid nitrogen and freeze-dried or vacuum-dried at room temperature. We then analyzed samples for levels of salicortin and tremulacin (phenolic glycosides), condensed tannins, nitrogen, soluble protein, sugars, and starch. Freeze-drying did not alter the concentrations of phenolic glycosides or tannins, relative to vacuum-drying. Freeze-drying did cause a small and inexplicable decline in nitrogen and soluble protein. Vacuum-drying, however, reduced starch concentrations by 38%. We suggest that the vacuum-drying method be used in studies in which carbohydrates are of no interest. For studies measuring carbohydrates, however, freeze-drying is a better alternative, and should effect no changes in levels of secondary compounds if samples are not allowed to thaw during the drying process.
杨柳科的化学物质一直以来都引起了化学生态学家、化学分类学家和造纸化学家等不同领域研究人员的关注。最近，人们继续争论在分析之前保存植物材料的适当方法，提倡使用真空干燥，因为冷冻干燥可能会导致酚糖苷降解。本研究旨在阐明冷冻干燥对叶片次生化学物质的影响，并评估真空干燥对初生化合物（蛋白质和碳水化合物）的影响。颤杨（Populus tremuloides）的叶子在液氮中快速冷冻，然后在室温下进行冷冻干燥或真空干燥。然后，我们分析了样品中柳杉脂素和震颤素（酚糖苷）、缩合单宁、氮、可溶性蛋白质、糖和淀粉的含量。与真空干燥相比，冷冻干燥并没有改变酚糖苷或单宁的浓度。然而，冷冻干燥会使氮和可溶性蛋白质的含量莫名其妙地略有下降。然而，真空干燥会使淀粉浓度降低 38%。我们建议在对碳水化合物不感兴趣的研究中使用真空干燥法。但是，对于测量碳水化合物的研究，冷冻干燥是更好的选择，如果在干燥过程中不允许样品解冻，那么它不会对次生化合物的水平产生任何影响。
