School of Biological Science, Monash University, Melbourne 3800, Victoria, Australia.
J Sci Food Agric. 2012 Aug 30;92(11):2234-8. doi: 10.1002/jsfa.5752. Epub 2012 Jun 14.
Cyanogenic glucosides are common bioactive products that break down to release toxic hydrogen cyanide (HCN) when combined with specific β-glucosidases. In forage sorghum, high concentrations of the cyanogenic glucoside dhurrin lead to reduced productivity and sometimes death of grazing animals, especially in times of drought, when the dhurrin content of stunted crops is often higher. The aim of this study was to develop harvesting protocols suitable for sampling in remote areas.
Dhurrin concentration in air- and oven-dried leaves was the same as in fresh leaves, with no subsequent losses during storage. Dhurrin concentration was halved when leaves were freeze-dried, although activity of the endogenous dhurrinase was preserved. Direct measurement of dhurrin concentration in methanolic extracts using liquid chromatography/mass spectrometry (LC/MS) gave similar results to methods that captured evolved cyanide. A single freezing event was as effective as fine grinding in facilitating complete conversion of dhurrin to cyanide.
Direct measurement of dhurrin using LC/MS is accurate but expensive and not appropriate for fieldwork. Air drying provides an accurate, low-cost method for preparing tissue for dhurrin analysis, so long as the specific β-glucosidase is added. It is recommended that comparative studies like the one presented here be extended to other cyanogenic species.
氰苷是常见的生物活性产物，当与特定的β-葡萄糖苷酶结合时会分解释放出有毒的氢氰酸（HCN）。在饲料高粱中，氰苷苦杏仁苷的高浓度会导致生产力降低，有时甚至会导致放牧动物死亡，尤其是在干旱时期，此时矮化作物中的苦杏仁苷含量通常更高。本研究的目的是开发适用于偏远地区采样的收获方案。
空气干燥和烘箱干燥叶片中的苦杏仁苷浓度与新鲜叶片相同，在储存过程中没有随后的损失。虽然内源性苦杏仁酶的活性得以保留，但冷冻干燥会使苦杏仁苷浓度减半。使用液相色谱/质谱（LC/MS）直接测量甲醇提取物中的苦杏仁苷浓度与测量释放出的氰化物的方法得出的结果相似。单次冷冻事件与精细研磨一样有效，可促进苦杏仁苷完全转化为氰化物。
使用 LC/MS 直接测量苦杏仁苷虽然准确但昂贵，不适合野外工作。空气干燥是一种准确且低成本的方法，可用于为苦杏仁苷分析制备组织，只要添加了特定的β-葡萄糖苷酶。建议将像本文所展示的这种比较研究扩展到其他含氰化物的物种。
