School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia.
Phytochemistry. 2013 Sep;93:210-5. doi: 10.1016/j.phytochem.2013.03.004. Epub 2013 Apr 6.
The tyrosine-derived cyanogenic di-glucoside proteacin and related mono-glucoside dhurrin were identified as the cyanogens in foliage of the tropical tree species Polyscias australiana, present in the approximate ratio 9:1. To date cyanogenic glycosides have not been characterised from the Araliaceae or the Apiales. Concentrations of cyanogenic glycosides varied significantly between plant parts and with leaf age, with the highest concentrations in young emerging leaves (mean 2217.1 μg CN g(-1) dry wt), petioles (rachis; 1487.1 μg CN g(-1) dry wt) and floral buds (265.8 μg CN g(-1) dry wt). Between 2% and 10% of nitrogen in emerging leaves and petioles was present as cyanogenic glycosides. With the exception of floral buds, all tissues apparently lack a specific cyanogenic β-glucosidase to catalyse the first step in the breakdown of these cyanogenic glycosides. Only with the addition of emulsin, an exogenous non-specific β-glucosidase from almonds, were high concentrations of cyanogenic glycosides detected, as much as 20-fold greater than the low to negligible cyanogenic glycoside concentrations determined in the absence of exogenous enzyme. High concentrations of cyanogens in young tissues may confer protection, but may also be a nitrogen source during leaf expansion.
已鉴定出热带树种垂叶榕（Polyscias australiana）叶片中的酪氨酸衍生氰基二糖苷蛋白和相关的单糖苷滇乌头苷是氰化物的来源，其比例约为 9:1。迄今为止，还没有从五加科或伞形科中鉴定出氰苷。氰苷糖苷在植物各部分和叶片年龄之间的浓度存在显著差异，在幼嫩的新叶（平均 2217.1μg CN g(-1)干重）、叶柄（叶轴；1487.1μg CN g(-1)干重）和花芽（265.8μg CN g(-1)干重）中浓度最高。新叶和叶柄中 2%至 10%的氮以氰苷糖苷的形式存在。除了花芽，所有组织显然都缺乏一种特定的氰基β-葡萄糖苷酶来催化这些氰苷糖苷的第一步分解。只有加入苦杏仁酶（一种来自杏仁的外源非特异性β-葡萄糖苷酶），才能检测到高浓度的氰苷糖苷，其浓度比没有外源酶时测定的低至可忽略不计的氰苷糖苷浓度高 20 倍。年轻组织中氰化物的高浓度可能提供保护，但在叶片扩展期间也可能是氮源。
