菠菜中β-胡萝卜素在人体内转化为维生素A的效率

目的测定菠菜中β-胡萝卜素(β-C)在人体内转化为维生素A的效率。方法将菠菜培植在25%重水(2H2O)营养液,氘随机标记在类胡萝卜素分子上,其中全反式β-C同位素丰度分布的最高值出现在分子量547(2H10全反式β-C)。给予10名健康成年(43~56岁)男性5.8μmol(2.0mg)溶于油的13C10视黄醇醋酸酯,作为参考VA。7天后,每位受试者摄入100g蒸熟的菠菜(含有7.0μmol或3.8mgβ-C)。56天试验期内,从每位受试者采集血样40次,用HPLC,GC-ECNCI-MS和LC-APCI-MS分析视黄醇和β-C浓度及标记的视黄醇和β-C丰度。试验期间受试者维持低VA和类胡萝卜素膳食。结果标记视黄醇血清反应曲线显示,每1nmol菠菜β-C产生了(0.25±0.10)nmol视黄醇,以13C10视黄醇醋酸酯为参照,菠菜β-C转化为VA的效率是质量比(9.0±4.5)∶1。结论菠菜β-C可以在体内有效的转化为视黄醇,食用菠菜也提高了血清叶黄素的水平。

Vitamin A equivalence of spinach β-carotene in human body

OBJECTIVE: To determine the vitamin A equivalence of spinach beta-carotene (beta-C) in human body. METHODS: Spinach grown in 25 atom% 2H2O cultural solution was intrinsically labeled by deuterium. The highest enrichment of spinach trans-beta-C isotopomers was at the molecular mass of 547 (2H10 trans-beta-C). Ten healthy Chinese male adults (43-56y) were given a dose of 5.8 micromol 13C10 retinyl acetate as vitamin A reference dose. One week later, each subject was given 100g of steamed spinach (containing 7.0 micromol beta-C). Forty blood samples were collected over 56 days from each subject. A HPLC method was used to detect the concentrations of retinol and beta-C in serum, and a GC-MS method was used to detect the enrichment of the labeled retinol. Kinetic curves of the labeled retinol from the reference dose and the spinach beta-C were compared to determine the vitamin A equivalence of spinach beta-C. RESULTS: The results showed that 1 nmol spinach beta-C provided (0.25 +/- 0.10) nmol retinol. The mean conversion factor of spinach beta-C to vitamin A was (9.0 +/- 4.5) : 1 by weight. CONCLUSION: The bioconversion of spinach beta-C to vitamin A was determined in 10 Chinese male adults by stable isotope tracer and reference techniques, and the mean conversion factor was 9.0 to 1 on a weight basis.