Nadathur S R, Carney J R, Gould S J, Bakalinsky A T
Department of Food Science and Technology, Oregon State University, Corvallis 97331-6602, USA.
Mutat Res. 1996 Apr 4;359(3):179-89. doi: 10.1016/s0165-1161(96)90265-4.
We describe here the isolation and identification of palmitic acid as being responsible for significant anti-N-methyl-N'-nitro-N-nitroguanidine (MNNG) activity in yogurt. The Ames test (Salmonella typhimurium TA100) was used to direct fractionation of activity. Yogurt was freeze-dried and extracted with acetone to yield a crude extract. The crude extract was purified by normal phase silica gel, Sephadex LH-20, and reversed phase medium pressure liquid chromatographies. The major compound in the active medium pressure liquid chromatographic fractions was determined to be palmitic acid on GC and high pressure liquid chromatography (HPLC) systems, and by nuclear magnetic resonance (NMR) analysis. Other saturated straight chain and methyl branched fatty acids were detected by GC/MS and were later shown to possess anti-MNNG activity. Of the straight chain fatty acids, palmitic acid had the highest anti-MNNG activity. All omega - 1 methyl branched fatty acids tested were more active than their straight chain counterparts. A trace amount of isopalmitic acid (14-methyl pentadecanoic acid), a minor milk lipid, was detected in one of the active fractions, and was later shown to be five times more active than palmitic acid. Isopalmitic acid also inhibited mutagenesis induced 4-nitroquinoline-N-oxide (4NQO), and 7, 12-dimethyl benz[a]anthracene (DMBA), and was found to inhibit the metabolic activation of DMBA.
我们在此描述了棕榈酸的分离与鉴定，其被认为是酸奶中具有显著抗N-甲基-N'-硝基-N-亚硝基胍（MNNG）活性的成分。采用艾姆斯试验（鼠伤寒沙门氏菌TA100）来指导活性成分的分级分离。将酸奶冷冻干燥后用丙酮萃取，得到粗提物。粗提物通过正相硅胶、葡聚糖LH - 20和反相中压液相色谱进行纯化。在气相色谱（GC）、高压液相色谱（HPLC）系统以及核磁共振（NMR）分析的基础上，确定活性中压液相色谱馏分中的主要化合物为棕榈酸。通过GC/MS检测到了其他饱和直链脂肪酸和甲基支链脂肪酸，随后发现它们也具有抗MNNG活性。在直链脂肪酸中，棕榈酸具有最高的抗MNNG活性。所有测试的ω-1甲基支链脂肪酸比其直链对应物更具活性。在其中一个活性馏分中检测到微量的异棕榈酸（14-甲基十五烷酸），一种次要的乳脂成分，随后发现其活性比棕榈酸高五倍。异棕榈酸还抑制由4-硝基喹啉-N-氧化物（4NQO）和7,12-二甲基苯并[a]蒽（DMBA）诱导的诱变作用，并且发现它能抑制DMBA的代谢活化。
