Tang G W, Russell R M
USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111.
J Lipid Res. 1990 Feb;31(2):175-82.
The occurrence of 13-cis-retinoic acid as an endogenous component in human serum has been confirmed by cochromatography with standards in both normal-phase and reverse-phase high-performance liquid chromatographic (HPLC) system, by the lambda max of its UV spectrum recorded simultaneously with the HPLC run, and by chromatography of its methyl derivative. The method using solid-phase extraction followed by a gradient reverse-phase HPLC procedure with an internal standard and sensitive UV detector, provides an efficient and sensitive technique for the separation and quantification of serum 13-cis- and all-trans-retinoic acid. Serum levels of 13-cis- and all-trans-retinoic acid in 26 fasting volunteers ranged from 1.0 to 2.2 ng/ml (mean +/- SEM = 1.4 +/- 0.3 ng/ml) and from 1.1 to 1.9 ng/ml (mean +/- SEM = 1.4 +/- 0.2 ng/ml), respectively. The levels determined by a liquid-liquid double-phase extraction method were 90% higher in both 13-cis- and all- trans-retinoic acid than those from a solid-phase extraction. Human small intestine can isomerize all-trans-retinoic acid. 13-cis-Retinoic acid is the predominant cis isomer after incubation of intestinal mucosa homogenates with all-trans-retinoic acid. Moreover, the concentration of retinoic acid in serum is related to diet in that the level of total retinoic acid was 36% higher (n = 10) 2 h after a nonstandard breakfast than in fasting subjects.
通过在正相和反相高效液相色谱（HPLC）系统中与标准品共色谱分析、在HPLC运行时同时记录其紫外光谱的最大吸收波长以及对其甲基衍生物进行色谱分析，已证实13 - 顺式视黄酸是人体血清中的内源性成分。采用固相萃取，随后进行带有内标和灵敏紫外检测器的梯度反相HPLC程序的方法，为血清中13 - 顺式和全反式视黄酸的分离和定量提供了一种高效且灵敏的技术。26名空腹志愿者血清中13 - 顺式和全反式视黄酸的水平分别为1.0至2.2 ng/ml（平均值±标准误 = 1.4±0.3 ng/ml）和1.1至1.9 ng/ml（平均值±标准误 = 1.4±0.2 ng/ml）。通过液 - 液双相萃取法测定的13 - 顺式和全反式视黄酸水平比固相萃取法测定的水平高90%。人类小肠能够使全反式视黄酸异构化。在用全反式视黄酸孵育肠黏膜匀浆后，13 - 顺式视黄酸是主要的顺式异构体。此外，血清中视黄酸的浓度与饮食有关，即非标准早餐后2小时总视黄酸水平比空腹受试者高36%（n = 10）。
