Lindberg J S, Zobitz M M, Poindexter J R, Pak C Y
Center for Mineral Metabolism and Clinical Research, University of Texas, Southwestern Medical Center, Dallas 75235.
J Am Coll Nutr. 1990 Feb;9(1):48-55. doi: 10.1080/07315724.1990.10720349.
This study compared magnesium oxide and magnesium citrate with respect to in vitro solubility and in vivo gastrointestinal absorbability. The solubility of 25 mmol magnesium citrate and magnesium oxide was examined in vitro in solutions containing varying amounts of hydrochloric acid (0-24.2 mEq) in 300 ml distilled water intended to mimic achlorhydric to peak acid secretory states. Magnesium oxide was virtually insoluble in water and only 43% soluble in simulated peak acid secretion (24.2 mEq hydrochloric acid/300 ml). Magnesium citrate had high solubility even in water (55%) and was substantially more soluble than magnesium oxide in all states of acid secretion. Reprecipitation of magnesium citrate and magnesium oxide did not occur when the filtrates from the solubility studies were titrated to pH 6 and 7 to stimulate pancreatic bicarbonate secretion. Approximately 65% of magnesium citrate was complexed as soluble magnesium citrate, whereas magnesium complexation was not present in the magnesium oxide system. Magnesium absorption from the two magnesium salts was measured in vivo in normal volunteers by assessing the rise in urinary magnesium following oral magnesium load. The increment in urinary magnesium following magnesium citrate load (25 mmol) was significantly higher than that obtained from magnesium oxide load (during 4 hours post-load, 0.22 vs 0.006 mg/mg creatinine, p less than 0.05; during second 2 hours post-load, 0.035 vs 0.008 mg/mg creatinine, p less than 0.05). Thus, magnesium citrate was more soluble and bioavailable than magnesium oxide.
本研究比较了氧化镁和柠檬酸镁在体外溶解性和体内胃肠道吸收性方面的差异。在300毫升蒸馏水中，于含有不同量盐酸（0 - 24.2毫当量）的溶液中对25毫摩尔柠檬酸镁和氧化镁的溶解性进行体外检测，旨在模拟无胃酸分泌到胃酸分泌高峰的状态。氧化镁实际上不溶于水，在模拟胃酸分泌高峰（24.2毫当量盐酸/300毫升）时仅有43%可溶。柠檬酸镁即使在水中也具有高溶解性（55%），并且在所有胃酸分泌状态下都比氧化镁更易溶。当将溶解性研究的滤液滴定至pH 6和7以刺激胰腺碳酸氢盐分泌时，柠檬酸镁和氧化镁均未发生再沉淀。约65%的柠檬酸镁以可溶性柠檬酸镁络合物形式存在，而氧化镁体系中不存在镁络合现象。通过评估口服镁负荷后尿镁的升高情况，在正常志愿者体内测量了两种镁盐的镁吸收。柠檬酸镁负荷（25毫摩尔）后尿镁的增加显著高于氧化镁负荷后（负荷后4小时内，分别为0.22对0.006毫克/毫克肌酐，p < 0.05；负荷后第二个2小时内，分别为(0.035)对(0.008)毫克/毫克肌酐，p < 0.05）。因此，柠檬酸镁比氧化镁更易溶且生物利用度更高。
