Chikaraishi Yoshito, Suzuki Yaeko, Naraoka Hiroshi
Department of Chemistry, Tokyo Metropolitan University, 1-1, Minami-Ohsawa, Hachioji, Tokyo 192-0397, Japan.
Phytochemistry. 2004 Aug;65(15):2293-300. doi: 10.1016/j.phytochem.2004.06.030.
Compound-specific hydrogen isotopic compositions (deltaD) of saturated, monounsaturated and polyunsaturated fatty acids have been determined for natural marine macroalgae including two brown algae (Heterokontophyta) and two red algae (Rhodophyta). deltaD values of individual fatty acids from four macroalgae exhibit a wide variation ranging from -189% to +48%. Generally, stearic (18:0), arachidic (20:0) and behenic acids (22:0) are much more enriched in D by up to approximately 180% relative to myristic (14:0), palmitic (16:0), octatetraenoic [18:4(n-3)] and eicosapentaenoic acids [20:5(n-3)]. Other fatty acids such as oleic [18:1(n-9)], lenoleic [18:2(n-6)] and linolenic acids [18:3(n - 3)] fall isotopically between these fatty acids. This wide deltaD variation of fatty acids is probably explained by the hydrogen isotopic fractionation during desaturation being much larger than that during elongation in the network of polyunsaturated fatty acid biosynthesis. A large hydrogen isotopic fractionation during desaturation may cause D-enrichment in the remaining hydrogen of the residual fatty acids, which could be controlled by the relative flux into their desaturates.
已测定了包括两种褐藻（不等鞭毛藻门）和两种红藻（红藻门）在内的天然海洋大型藻类中饱和脂肪酸、单不饱和脂肪酸和多不饱和脂肪酸的化合物特异性氢同位素组成（δD）。四种大型藻类中各脂肪酸的δD值变化范围很大，从 -189‰ 到 +48‰。一般来说，相对于肉豆蔻酸（14:0）、棕榈酸（16:0）、十八碳四烯酸 [18:4(n-3)] 和二十碳五烯酸 [20:5(n-3)]，硬脂酸（18:0）、花生酸（20:0）和山嵛酸（22:0）的D含量要高得多，富集量高达约180‰。其他脂肪酸，如油酸 [18:1(n-9)]、亚油酸 [18:2(n-6)] 和亚麻酸 [18:3(n - 3)] 的同位素值则介于这些脂肪酸之间。脂肪酸这种较大的δD变化可能是由于在多不饱和脂肪酸生物合成网络中，去饱和过程中的氢同位素分馏比延长过程中的氢同位素分馏大得多。去饱和过程中较大的氢同位素分馏可能会导致残余脂肪酸中剩余氢的D富集，这可能受其去饱和产物相对通量的控制。
