Concentration And Distribution Of Nervonic Acid In Human Milk Fat And The Influence Of Maternal Diet

Nervonic acid?24:1 n-9,NA?is a very-long-chain monounsaturated fatty acid.It is reported that NA is beneficial for early myelination and nervous system development of infants.NA naturally occurs in human milk,and the content in human milk is much higher than that in infant formulae.However,the NA concentration and distribution in human milk and the influence factor is currently unclear.Thus,this study systematically analyzed the NA concentration and distribution in triacylglycerol and phospholipid of human milk fat,and investigated the influence of maternal diet.The main research contents were as follows:Firstly,a quantitative analysis method for NA in human milk was established which using tricosanic acid?23:0?as an internal standard by gas chromatography.The linear correlation coefficient of this method was 0.9944,the detection limit was 1.34?3.25?g/mL,the quantification limit was 3.11?5.36?g/mL,the standard recovery rate was 95%?103%,the precision of the retention time was less than 0.01%,the peak area precision was 0.02%?0.18%.This method met the requirements of quantitative analysis.Secondly,NA in triacylglycerol?TAG-NA?concentration in human milk fat which collected from eight mothers with full-term infants,six mothers with early preterm infants and four mothers with near full-term infants,were analyzed.The results showed that TAG-NA concentration decreased by 73%during the 3rd?15th lactation days which was the most pronounced,and then decreased slowly.The TAG-NA concentration in full-term,early preterm and near full-term human milk fat were 0.76±0.23 mg/g,1.11±0.12 mg/g and 0.74±0.27mg/g,respectively.The concentration in colostrum of early preterm human milk fat was significantly higher than that in full-term and near full-term human milk fat?p<0.05?,the difference gradually disappeared during lactation,however.The TAG-NA concentration in colostrum of full-term human milk fat was 6.91?12.67 times as that in infant formulae fat?n=119?and 12.56?25.33 times as that in cow's,goat's,camel's and yak's milk fat.Then,pancreatic lipase hydrolysis combined with thin-layer chromatography was used to detect the positional distribution of TAG-NA in milk fat and Acer truncatum Bunge oil.The results showed that the positional distribution of TAG-NA in human milk was similar to mammals'milk which mainly located at sn-2 position,with the content of 51.17%?70.55%and46.36%?70.49%,respectively.However,TAG-NA in Acer truncatum Bunge oil which was the main plant source of NA was located at sn-1,3 position.Then,thin-layer chromatography and BF₃-CH₃OH methyl esterification were used to detect NA in phospholipid?PL-NA?in full-term human milk fat.The results showed that PL-NA concentration changed slightly during the lactation,ranging from 0.02 mg/g to 0.08 mg/g.NA relative content in phospholipid fatty acid and triacylglycerol fatty acid was 0.45%?0.90%and 0.04%?0.21%,respectively.This meant that NA was more likely to bind to phospholipid.The PL-NA concentration in full-term human milk fat was 10.69?23.50 times as that in infant formulae oil and 5.47?28.32 times as that in four mammals'milk fat.Finally,24 hour dietary recall method was used to track the free diet of the eight mothers with full-term infants on the 3rd to 30th days after delivery to investigate the influence of maternal diet on NA concentration and distribution.Furtherly,Acer truncatum Bunge oil was added into the diet of two mothers with full-term infants to observe the influence on NA concentration and distribution.The results showed that the intake of NA of free-eating mothers was 0.05±0.01 g/d,and there was no significant difference in the intakes during different lactation stages?p>0.05?.The kinds of food and dietary n-9 series fatty acids had no significant impact on NA concentration and distribution?p>0.05?.It was speculated that under a low NA intake diet,NA in human milk was mainly synthesized in the body,and its concentration decreased during lactation was not caused by the diet.After maternal intaking Acer truncatum Bunge oil,the TAG-NA concentration was 6.17 times higher than that in the control group,and the PL-NA concentration increased significantly?p<0.05?.The sn-2 positional distribution of TAG-NA was not changed.It showed that high NA intake diet could increase NA concentration in human milk fat and NA could be resynthesized in the body and transformed from sn-1,3position into sn-2 position distribution which was beneficial to the digestion and absorption of infants.This article systematically studied the concentration and distribution of NA in human milk fat,clarified the variations features of NA in human milk fat during different lactation stages and gestational ages,and explored dietary influencing factors.It aimed to broaden the application of nervonic acid in infant formulae fat.